diff --git a/SUMMARY.md b/SUMMARY.md
index b7a592f6..ac2160af 100644
--- a/SUMMARY.md
+++ b/SUMMARY.md
@@ -33,7 +33,7 @@
 * [拡張\(Extensions\)](language-guide/extensions.md)
 * [プロトコル\(Protocols\)](language-guide/protocols.md)
 * [ジェネリクス\(Generics\)](language-guide/generics.md)
-* [Opaque 型\(Opaque Types\)](language-guide/opaque-types.md)
+* [Opaque 型とBox プロトコル型\(Opaque Types and Boxed Types\)](language-guide/opaque-types.md)
 * [自動参照カウント ARC\(Automatic Reference Counting\)](language-guide/automatic-reference-counting.md)
 * [メモリ安全性\(Memory Safety\)](language-guide/memory-safety.md)
 * [アクセスコントロール\(Access Control\)](language-guide/access-control.md)
diff --git a/language-guide/opaque-types.md b/language-guide/opaque-types.md
index ec59b6f5..25862eb5 100644
--- a/language-guide/opaque-types.md
+++ b/language-guide/opaque-types.md
@@ -1,11 +1,15 @@
-# Opaque 型\(Opaque Types\)
+# Opaque 型とBox 型\(Opaque Types and Boxed Types\)
 
-最終更新日: 2022/12/3  
+最終更新日: 2023/5/28  
 原文: https://docs.swift.org/swift-book/LanguageGuide/OpaqueTypes.html
 
 値の型に関する実装の詳細を隠す。
 
-戻り値に不透明な型\(以下_Opaque 型_\)を持つ関数またはメソッドは、その戻り値の型情報を隠します。関数の戻り値の型として具体的な型を提供する代わりに、準拠するプロトコルの観点から戻り値を記述します。型情報を隠すことで、戻り値の基になる型を private のままにすることができるため、モジュールとモジュールを呼び出すコードの間に境界を設けることに役立ちます。プロトコル型の値を返すのとは異なり、Opaque 型は具体的な型情報を保持し続けます。コンパイラは型情報にアクセスできますが、モジュールのクライアントはアクセスできません。
+Swift は値の型情報を隠すために 2 つの方法を提供します。不透明な型\(以下_Opaque 型_\)と Box 型です。
+型情報を隠すことで、戻り値の基になる型を private のままにすることができるため、モジュールとモジュールを呼び出すコードの間に境界を設けることに役立ちます。戻り値に Opaque 型を持つ関数またはメソッドは、その戻り値の型情報を隠します。関数の戻り値の型として具体的な型を提供する代わりに、準拠するプロトコルの観点から戻り値を記述します。
+コンパイラは型情報にアクセスできますが、モジュールのクライアントはアクセスできません。
+Box プロトコル型は、任意の型のインスタンスを格納することができます。Box プロトコル型は、与えられたプロトコルに準拠する任意の型のインスタンスを格納することができます。
+ボックス型プロトコル型は型の同一性を保持しません。つまり、値の特定の型は実行時までわからず、また、異なる値が保存されるため、時間の経過とともに変化する可能性があります。
 
 ## <a id="the-problem-that-opaque-types-solve">Opaque 型が解決する問題\(The Problem That Opaque Types Solve\)</a>
 
@@ -176,11 +180,52 @@ func `repeat`<T: Shape>(shape: T, count: Int) -> some Collection {
 
 この場合、戻り値の基になる型は `T` によって異なります。どの形状が渡されても、`repeat(shape:count:)` はその形状の配列を作成して返します。それにもかかわらず、戻り値は常に同じ `[T]` の基になる型のため、Opaque な戻り値の型を持つ関数は単一の型の値のみを返す必要があるという要件に従います。
 
+## Box プロトコル型\(Boxed Protocol Types\)
+
+Box プロトコル型は存在型とも呼ばれることがありますが、これは「`T` がプロトコルに準拠するような型 `T` が存在する」という表現に由来しています。Box プロトコル型を作るには、プロトコルの名前の前に `any` と書きます。以下はその例です:
+
+```swift
+struct VerticalShapes: Shape {
+    var shapes: [any Shape]
+    func draw() -> String {
+        return shapes.map { $0.draw() }.joined(separator: "\n\n")
+    }
+}
+
+let largeTriangle = Triangle(size: 5)
+let largeSquare = Square(size: 5)
+let vertical = VerticalShapes(shapes: [largeTriangle, largeSquare])
+print(vertical.draw())
+```
+
+上の例では、`VerticalShapes` は、`Shape` のタイプを `[any Shape]`、つまり Box  Shape 型要素の配列、と宣言しています。配列の各要素には、異なる型を入れることができ、それらの型の各々は、`Shape` プロトコルに準拠する必要があります。この実行時の柔軟性をサポートするために、Swift は必要なときに間接層を追加します。つまり、この間接的な存在は*ボックス*と呼ばれ、パフォーマンスコストがかかります。
+
+`VerticalShapes` 型の中で、コードは `Shape` プロトコルで必要とされるメソッド、プロパティ、およびサブスクリプトを使用することができます。例えば、`VerticalShapes` の `draw()` メソッドは、配列の各要素の `draw()` メソッドを呼び出します。`Shape` が `draw()` メソッドを要件にしているため、このメソッドを利用できます。これに対して、三角形の `size` プロパティや、`Shape` が要件していないプロパティやメソッドにアクセスしようとすると、エラーが発生します。
+
+`Shape` に使用できる 3 つのタイプを対比してみましょう:
+
+- `struct VerticalShapes<S: Shape>` と `var shapes: [S]` を書くことで、ジェネリクスを使い、ある特定の形状を要素とする配列を作り、その配列とやり取りをするすべてのコードから、その特定の型が識別できるようにする
+- Opaque 型を使用する場合、`var shapes:[some Shape]` と書くと、特定の形状を要素とする配列を作成し、その特定の型の識別は隠されます
+- Box プロトコル型を使って、`var shapes:[any Shape]` と書くと、異なる形状の要素を格納できる配列ができ、それらの型の識別は隠される
+
+この場合、Box プロトコル型は、`VerticalShapes` の呼び出し元が異なる種類の形状を一緒に混ぜることができる唯一のアプローチです。
+
+Box 値の基礎となる型がわかっている場合は、`as` キャストを使用することができます。例えば、以下のような感じです:
+
+```swift
+if let downcastTriangle = vertical.shapes[0] as? Triangle {
+    print(downcastTriangle.size)
+}
+// "5"
+```
+
+より詳細は[Downcasting\(ダウンキャスト\)](../language-guide/type-casting.md#downcasting)を参照ください。
+
 ## Opaque 型とプロトコルの違い\(Differences Between Opaque Types and Protocol Types\)
 
-Opaque 型を返すことは、プロトコル型を関数の戻り値の型として使用する場合と非常によく似ていますが、これら 2 種類の戻り値の型は、型情報を保持するかどうかが異なります。Opaque 型は 1 つの特定の型を参照しますが、関数の呼び出し側はどの型を参照するかはわかりません。プロトコル型は、プロトコルに準拠する任意の型を参照できます。一般に、プロトコル型では、格納する値の基になる型についてより柔軟に対応でき、Opaque 型を使用すると、基になる型についてより強力な保証を行うことができます。
+Opaque 型を返すことは、Box プロトコル型を関数の戻り値の型として使用する場合と非常によく似ていますが、これら 2 種類の戻り値の型は、型情報を保持するかどうかが異なります。Opaque 型は 1 つの特定の型を参照しますが、関数の呼び出し側はどの型を参照するかはわかりません。Box プロトコル型は、プロトコルに準拠する任意の型を参照できます。一般に、Box プロトコル型では、格納する値の基になる型についてより柔軟に対応でき、Opaque 型を使用すると、基になる型についてより強力な保証を行うことができます。
 
-例えば、Opaque 型の代わりにプロトコル型を戻り値の型として使用する、`flip(_:)` のバージョンを次に示します:
+例えば、Opaque 型の代わりに Box プロトコル型を戻り値の型として使用する、`flip(_:)` のバージョンを次に示します:
 
 ```swift
 func protoFlip<T: Shape>(_ shape: T) -> Shape {
@@ -210,11 +255,11 @@ protoFlippedTriangle == sameThing  // エラー
 
 この例の最終行のエラーは、いくつかの理由で発生します。当面の問題は、`Shape` のプロトコル要件に `==` 演算子が含まれていないことです。追加しようとすると、次に遭遇する問題は、`==` 演算子がその左辺と右辺の引数の型を知る必要があることです。この種の演算子は通常、`Self` 型の引数を取り、プロトコルに準拠する具体的な型に一致しますが、プロトコルに `Self` 要件を追加すると、プロトコルを型として使用することができなくなります。
 
-プロトコル型を関数の戻り値の型として使用すると、プロトコルに準拠する任意の型を柔軟に返すことができます。ただし、その柔軟性によって、返された値の一部の操作が犠牲になります。この例では、プロトコル型では保持されない特定の型情報に依存しているため、`==` 演算子が使用できないことを示しています。
+Box プロトコル型を関数の戻り値の型として使用すると、プロトコルに準拠する任意の型を柔軟に返すことができます。ただし、その柔軟性によって、返された値の一部の操作が犠牲になります。この例では、Box プロトコル型では保持されない特定の型情報に依存しているため、`==` 演算子が使用できないことを示しています。
 
-このアプローチのもう 1 つの問題は、形状変換をネストできないことです。三角形を反転した結果は、`Shape` 型の値で、`protoFlip(_:)` 関数は、`Shape` プロトコルに準拠した何らかの型の引数を取ります。ただし、プロトコル型はそのプロトコル自体に準拠しません。`protoFlip(_:)` によって返される値は `Shape` に準拠していません。これは、反転した形状が `protoFlip(_:)` の有効な引数ではないため、複数の変換を適用する `protoFlip(protoFlip(smallTriangle))` のようなコードが無効だということを意味します。
+このアプローチのもう 1 つの問題は、形状変換をネストできないことです。三角形を反転した結果は、`Shape` 型の値で、`protoFlip(_:)` 関数は、`Shape` プロトコルに準拠した何らかの型の引数を取ります。ただし、Box プロトコル型はそのプロトコル自体に準拠しません。`protoFlip(_:)` によって返される値は `Shape` に準拠していません。これは、反転した形状が `protoFlip(_:)` の有効な引数ではないため、複数の変換を適用する `protoFlip(protoFlip(smallTriangle))` のようなコードが無効だということを意味します。
 
-対照的に、Opaque 型は、基になる型情報を保持します。Swift は関連型を推論できるため、プロトコル型を戻り値として使用できない場所で Opaque 型な戻り値の型を使用できます。例えば、これは [Generics\(ジェネリクス\)](generics.md)の `Container` プロトコルの別のバージョンです:
+対照的に、Opaque 型は、基になる型情報を保持します。Swift は関連型を推論できるため、Box プロトコル型を戻り値として使用できない場所で Opaque 型な戻り値の型を使用できます。例えば、これは [Generics\(ジェネリクス\)](generics.md)の `Container` プロトコルの別のバージョンです:
 
 ```swift
 protocol Container {
diff --git a/language-guide/protocols.md b/language-guide/protocols.md
index c630189b..d1145f69 100644
--- a/language-guide/protocols.md
+++ b/language-guide/protocols.md
@@ -35,6 +35,11 @@ class SomeClass: SomeSuperclass, FirstProtocol, AnotherProtocol {
 }
 ```
 
+> NOTE: 
+> プロトコルは型のため、
+> Swiftの他の型に一致するように(`Int`、`String` や `Double` など)
+> 名前は大文字から始めてください。(`FullyNamed` や `RandomNumberGenerator` など)
+
 ## <a id="property-requirements">プロパティ要件\(Property Requirements\)</a>
 
 プロトコルは、特定の名前と型のインスタンスプロパティまたは型プロパティを要件にできます。プロトコルでは、格納プロパティか計算プロパティかを指定しません。必要なプロパティの名前と型を指定するだけです。また、プロトコルは、各プロパティが get のみか、get/set どちらも必要かどうかも指定します。
@@ -245,54 +250,16 @@ class SomeSubClass: SomeSuperClass, SomeProtocol {
 
 ## <a id="protocols-as-types">型としてのプロトコル\(Protocols as Types\)</a>
 
-プロトコルは、実際には機能を実装しません。それにもかかわらず、コード内で完全な型としてプロトコルを使用できます。プロトコルを型として使用することは、_存在型_と呼ばれることもあります。これは、「T がプロトコルに準拠するような型 T が存在する」というフレーズから来ています。
-
-次のような他の型が許可されている多くの場所でプロトコルを使用できます。
-
-* 関数、メソッド、またはイニシャライザのパラメータの型または戻り値の型として
-* 定数、変数、またはプロパティの型として
-* 配列、辞書、またはその他のコンテナ内のアイテムの型として
-
-> NOTE  
-> プロトコルは型であるため、他の型 \(`Int`、`String`、`Double` など\) と同じように名前を大文字で始めます。\(`FullyNamed` や `RandomNumberGenerator` など\)
-
-型として使用されるプロトコルの例を次に示します:
-
-```swift
-class Dice {
-    let sides: Int
-    let generator: RandomNumberGenerator
-    init(sides: Int, generator: RandomNumberGenerator) {
-        self.sides = sides
-        self.generator = generator
-    }
-    func roll() -> Int {
-        return Int(generator.random() * Double(sides)) + 1
-    }
-}
-```
-
-この例では、ボードゲームで使用する n 面のサイコロを表す `Dice` という新しいクラスを定義しています。`Dice` のインスタンスには、側面の数を表す `sides` と呼ばれる整数のプロパティと、ダイスの出目を作成するための乱数ジェネレータを提供する `generator` と呼ばれるプロパティがあります。
-
-`generator` プロパティの型は `RandomNumberGenerator` です。したがって、`RandomNumberGenerator` プロトコルに準拠する任意の型のインスタンスを設定できます。このプロパティに割り当てるインスタンスには、インスタンスが `RandomNumberGenerator` プロトコルに準拠する必要があることを除いて、他に何も必要ありません。型は `RandomNumberGenerator` なので、`Dice` クラス内のコードは、このプロトコルに準拠する `generator` のみを使用できます。つまり、その具体的なジェネレータの型で定義されているメソッドやプロパティを使用することはできません。ただし、[Downcasting\(ダウンキャスト\)](../language-guide/type-casting.md#downcasting)で説明されているように、スーパークラスからサブクラスにダウンキャストできるのと同じ方法で、プロトコル型から準拠した具体的な型にダウンキャストできます。
+プロトコルは、実際には機能を実装しません。
+それにもかかわらず、コード内で型としてプロトコルを使用できます。
 
-`Dice` には、初期状態を設定するためのイニシャライザもあります。このイニシャライザには、`RandomNumberGenerator` 型の `generator` と呼ばれるパラメータがあります。新しい `Dice` インスタンスを初期化するときに、このパラメータに `RandomNumberGenerator` に準拠する型の値を渡すことができます。
+プロトコルを型として使用する最も一般的な方法は、プロトコルをジェネリック制約として使用することです。ジェネリック制約を持つコードは、プロトコルに準拠する任意の型を扱うことができ、特定の型は API を使用する側のコードで選択されます。例えば、引数を取る関数を呼び出したとき、その引数の型がジェネリックであれば、呼び出し元がその型を選びます。
 
-`Dice` は、1 からサイコロの面の数までの整数値を返す 1 つのインスタンスメソッド、`roll` を提供しています。このメソッドは、ジェネレータの `random()` メソッドを呼び出して `0.0` から `1.0` の間の新しい乱数を作成し、この乱数を使用して正しい範囲内でサイコロの目を作成します。`generator` は `RandomNumberGenerator` に準拠することがわかっているため、呼び出すべき `random()` メソッドが存在していることは保証されています。
+Opaque 型を持つコードは、プロトコルに準拠した何らかの型を使って機能します。基本的な型はコンパイル時に判明し、API 実装はその型を選択しますが、その型の正体は API のクライアントから隠されています。例えば、ある関数の戻り値の型を隠し、その値があるプロトコルに準拠していることだけを保証します。
 
-`Dice` クラスを使用して、`LinearCongruentialGenerator` インスタンスを乱数ジェネレータとして使用して、6 面体のサイコロを作成する方法を次に示します:
+Box プロトコル型を持つコードは、プロトコルに準拠する、実行時に選択された任意の型で動作します。この実行時の柔軟性をサポートするために、Swift は必要なときに間接的なレイヤーを追加します。これは、*ボックス*として知られており、これはパフォーマンスコストを伴います。この柔軟性が理由で、Swift はコンパイル時に基礎となる型を知らなりません。つまり、プロトコルによって必要とされるメンバのみにアクセスできることを意味します。基礎となる型で定義された他の API にアクセスするには、実行時にキャストが必要です。
 
-```swift
-var d6 = Dice(sides: 6, generator: LinearCongruentialGenerator())
-for _ in 1...5 {
-    print("Random dice roll is \(d6.roll())")
-}
-// Random dice roll is 3
-// Random dice roll is 5
-// Random dice roll is 4
-// Random dice roll is 5
-// Random dice roll is 4
-```
+プロトコルをジェネリック制約として使用することについては、[ジェネリクス\(Generics\)](../language-guide/generics.md)を参照してください。Opaque 型と Box プロトコル型については、[Opaque 型とBox プロトコル型\(Opaque Types and Boxed Types\)](language-guide/opaque-types.md)を参照してください。
 
 ## <a id="delegation">委譲\(Delegation\)</a>
 
diff --git a/language-reference/summary-of-the-grammar.md b/language-reference/summary-of-the-grammar.md
index 7223a719..2bc6f482 100644
--- a/language-reference/summary-of-the-grammar.md
+++ b/language-reference/summary-of-the-grammar.md
@@ -1,872 +1,1676 @@
 # 文法のまとめ\(Summary of the Grammar\)
 
-最終更新日: 2023/5/27  
+最終更新日: 2023/5/28  
 原文: https://docs.swift.org/swift-book/ReferenceManual/zzSummaryOfTheGrammar.html
 
 ## Lexical Structure\(構文の構造\)
 
-> GRAMMAR OF WHITESPACE  
-> whitespace → [whitespace-item](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_whitespace-item) [whitespace](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_whitespace)<sub>opt</sub>  
-> whitespace-item → [line-break](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_line-break)  
-> whitespace-item → [inline-space](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_inline-space)  
-> whitespace-item → [comment](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_comment)  
-> whitespace-item → [multiline-comment](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_multiline-comment)  
-> whitespace-item → U+0000, U+000B, または U+000C  
-> line-break → U+000A  
-> line-break → U+000D  
-> line-break → U+000D に続く U+000A  
-> inline-spaces → [inline-space](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_inline-space) [inline-spaces](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_inline-spaces)<sub>opt</sub>  
-> inline-space → U+0009 または U+0020  
-> comment → `//` [comment-text](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_comment-text) [line-break](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_line-break)  
-> multiline-comment → `/*` [multiline-comment-text](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_multiline-comment-text) `*/`  
-> comment-text → [comment-text-item](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_comment-text-item) [comment-text](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_comment-text)<sub>opt</sub>  
-> comment-text-item → U+000A または U+000D を除く任意のUnicodeスカラ値  
-> multiline-comment-text → [multiline-comment-text-item](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_multiline-comment-text-item) [multiline-comment-text](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_multiline-comment-text)<sub>opt</sub>  
-> multiline-comment-text-item → [multiline-comment](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_multiline-comment)  
-> multiline-comment-text-item → [comment-text-item](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_comment-text-item)  
-> multiline-comment-text-item → `/*` または `*/` を除く任意のUnicodeスカラ値
-
-> GRAMMAR OF AN IDENTIFIER  
-> identifier → [identifier-head](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_identifier-head) [identifier-characters](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_identifier-characters)<sub>opt</sub>  
-> identifier → **\`** [identifier-head](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_identifier-head) [identifier-characters](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_identifier-characters)<sub>opt</sub> **\`**  
-> identifier → [implicit-parameter-name](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_implicit-parameter-name)  
-> identifier → [property-wrapper-projection](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_property-wrapper-projection)  
-> identifier-list → [identifier](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_identifier) \| [identifier](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_identifier) `,` [identifier-list](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_identifier-list)  
-> identifier-head → 大文字または小文字の A ~ Z  
-> identifier-head → `_`  
-> identifier-head → U+00A8, U+00AA, U+00AD, U+00AF, U+00B2–U+00B5, または U+00B7–U+00BA  
-> identifier-head → U+00BC–U+00BE, U+00C0–U+00D6, U+00D8–U+00F6, または U+00F8–U+00FF  
-> identifier-head → U+0100–U+02FF, U+0370–U+167F, U+1681–U+180D, または U+180F–U+1DBF  
-> identifier-head → U+1E00–U+1FFF  
-> identifier-head → U+200B–U+200D, U+202A–U+202E, U+203F–U+2040, U+2054, または U+2060–U+206F  
-> identifier-head → U+2070–U+20CF, U+2100–U+218F, U+2460–U+24FF, または U+2776–U+2793  
-> identifier-head → U+2C00–U+2DFF または U+2E80–U+2FFF  
-> identifier-head → U+3004–U+3007, U+3021–U+302F, U+3031–U+303F, または U+3040–U+D7FF  
-> identifier-head → U+F900–U+FD3D, U+FD40–U+FDCF, U+FDF0–U+FE1F, または U+FE30–U+FE44  
-> identifier-head → U+FE47–U+FFFD  
-> identifier-head → U+10000–U+1FFFD, U+20000–U+2FFFD, U+30000–U+3FFFD, または U+40000–U+4FFFD  
-> identifier-head → U+50000–U+5FFFD, U+60000–U+6FFFD, U+70000–U+7FFFD, または U+80000–U+8FFFD  
-> identifier-head → U+90000–U+9FFFD, U+A0000–U+AFFFD, U+B0000–U+BFFFD, または U+C0000–U+CFFFD  
-> identifier-head → U+D0000–U+DFFFD または U+E0000–U+EFFFD  
-> identifier-character → 数値 0 ~ 9  
-> identifier-character → U+0300–U+036F, U+1DC0–U+1DFF, U+20D0–U+20FF, または U+FE20–U+FE2F  
-> identifier-character → [identifier-head](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_identifier-head)  
-> identifier-characters → [identifier-character](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_identifier-character) [identifier-characters](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_identifier-characters)<sub>opt</sub>  
-> implicit-parameter-name → `$` [decimal-digits](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_decimal-digits)  
-> property-wrapper-projection → `$` [identifier-characters](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_identifier-characters)
-
-> GRAMMAR OF A LITERAL  
-> literal → [numeric-literal](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_numeric-literal) \| [string-literal](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_string-literal) \| [boolean-literal](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_boolean-literal) \| [nil-literal](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_nil-literal)  
-> numeric-literal → `-`<sub>opt</sub> [integer-literal](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_integer-literal) \| `-`<sub>opt</sub> [floating-point-literal](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_floating-point-literal)  
-> boolean-literal → `true` \| `false`  
-> nil-literal → `nil`
-
-> GRAMMAR OF AN INTEGER LITERAL  
-> integer-literal → [binary-literal](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_binary-literal)  
-> integer-literal → [octal-literal](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_octal-literal)  
-> integer-literal → [decimal-literal](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_decimal-literal)  
-> integer-literal → [hexadecimal-literal](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_hexadecimal-literal)  
-> binary-literal → `0b` [binary-digit](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_binary-digit) [binary-literal-characters](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_binary-literal-characters)<sub>opt</sub>  
-> binary-digit → 数値 0 または 1  
-> binary-literal-character → [binary-digit](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_binary-digit) \| `_`  
-> binary-literal-characters → [binary-literal-character](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_binary-literal-character) [binary-literal-characters](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_binary-literal-characters)<sub>opt</sub>  
-> octal-literal → `0o` [octal-digit](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_octal-digit) [octal-literal-characters](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_octal-literal-characters)<sub>opt</sub>  
-> octal-digit → 数値 0 ~ 7 octal-literal-character → [octal-digit](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_octal-digit) \| `_`  
-> octal-literal-characters → [octal-literal-character](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_octal-literal-character) [octal-literal-characters](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_octal-literal-characters)<sub>opt</sub>  
-> decimal-literal → [decimal-digit](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_decimal-digit) [decimal-literal-characters](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_decimal-literal-characters)<sub>opt</sub>  
-> decimal-digit → 数値 0 ~ 9  
-> decimal-digits → [decimal-digit](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_decimal-digit) [decimal-digits](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_decimal-digits)<sub>opt</sub>  
-> decimal-literal-character → [decimal-digit](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_decimal-digit) \| `_`  
-> decimal-literal-characters → [decimal-literal-character](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_decimal-literal-character) [decimal-literal-characters](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_decimal-literal-characters)<sub>opt</sub>  
-> hexadecimal-literal → `0x` [hexadecimal-digit](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_hexadecimal-digit) [hexadecimal-literal-characters](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_hexadecimal-literal-characters)<sub>opt</sub>  
-> hexadecimal-digit → 数値 0 ~ 9、 a ~ f、または A ~ F  
-> hexadecimal-literal-character → [hexadecimal-digit](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_hexadecimal-digit) \| `_`  
-> hexadecimal-literal-characters → [hexadecimal-literal-character](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_hexadecimal-literal-character) [hexadecimal-literal-characters](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_hexadecimal-literal-characters)<sub>opt</sub>
-
-> GRAMMAR OF A FLOATING-POINT LITERAL  
-> floating-point-literal → [decimal-literal](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_decimal-literal) [decimal-fraction](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_decimal-fraction)<sub>opt</sub> [decimal-exponent](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_decimal-exponent)<sub>opt</sub>  
-> floating-point-literal → [hexadecimal-literal](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_hexadecimal-literal) [hexadecimal-fraction](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_hexadecimal-fraction)<sub>opt</sub> [hexadecimal-exponent](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_hexadecimal-exponent)  
-> decimal-fraction → `.` [decimal-literal](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_decimal-literal)  
-> decimal-exponent → [floating-point-e](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_floating-point-e) [sign](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_sign)<sub>opt</sub> [decimal-literal](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_decimal-literal)  
-> hexadecimal-fraction → `.` [hexadecimal-digit](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_hexadecimal-digit) [hexadecimal-literal-characters](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_hexadecimal-literal-characters)<sub>opt</sub>  
-> hexadecimal-exponent → [floating-point-p](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_floating-point-p) [sign](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_sign)<sub>opt</sub> [decimal-literal](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_decimal-literal)  
-> floating-point-e → `e` \| `E`  
-> floating-point-p → `p` \| `P`  
-> sign → `+` \| `-`
-
-> GRAMMAR OF A STRING LITERAL  
-> string-literal → [static-string-literal](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_static-string-literal) \| [interpolated-string-literal](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_interpolated-string-literal)  
-> string-literal-opening-delimiter → [extended-string-literal-delimiter](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_extended-string-literal-delimiter)<sub>opt</sub> `"`  
-> string-literal-closing-delimiter → `"` [extended-string-literal-delimiter](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_extended-string-literal-delimiter)<sub>opt</sub>  
-> static-string-literal → [string-literal-opening-delimiter](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_string-literal-opening-delimiter) [quoted-text](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_quoted-text)<sub>opt</sub> [string-literal-closing-delimiter](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_string-literal-closing-delimiter)  
-> static-string-literal → [multiline-string-literal-opening-delimiter](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_multiline-string-literal-opening-delimiter) [multiline-quoted-text](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_multiline-quoted-text)<sub>opt</sub> [multiline-string-literal-closing-delimiter](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_multiline-string-literal-closing-delimiter)  
-> multiline-string-literal-opening-delimiter → [extended-string-literal-delimiter](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_extended-string-literal-delimiter) `"""`  
-> multiline-string-literal-closing-delimiter → `"""` [extended-string-literal-delimiter](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_extended-string-literal-delimiter)  
-> extended-string-literal-delimiter → `#` [extended-string-literal-delimiter](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_extended-string-literal-delimiter)<sub>opt</sub>  
-> quoted-text → [quoted-text-item](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_quoted-text-item) [quoted-text](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_quoted-text)<sub>opt</sub>  
-> quoted-text-item → [escaped-character](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_escaped-character)  
-> quoted-text-item → **"**、**\\**、 U+000A、または U+000D を除く任意のUnicodeスカラ値  
-> multiline-quoted-text → [multiline-quoted-text-item](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_multiline-quoted-text-item) [multiline-quoted-text](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_multiline-quoted-text)<sub>opt</sub>  
-> multiline-quoted-text-item → [escaped-character](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_escaped-character)  
-> multiline-quoted-text-item → **\\** を除く任意のUnicodeスカラ値  
-> multiline-quoted-text-item → [escaped-newline](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_escaped-newline)  
-> interpolated-string-literal → [string-literal-opening-delimiter](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_string-literal-opening-delimiter) [interpolated-text](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_interpolated-text)<sub>opt</sub> [string-literal-closing-delimiter](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_string-literal-closing-delimiter)  
-> interpolated-string-literal → [multiline-string-literal-opening-delimiter](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_multiline-string-literal-opening-delimiter) [multiline-interpolated-text](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_multiline-interpolated-text)<sub>opt</sub> [multiline-string-literal-closing-delimiter](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_multiline-string-literal-closing-delimiter)  
-> interpolated-text → [interpolated-text-item](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_interpolated-text-item) [interpolated-text](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_interpolated-text)<sub>opt</sub>  
-> interpolated-text-item → `\(` [expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_expression) `)` \| [quoted-text-item](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_quoted-text-item)  
-> multiline-interpolated-text → [multiline-interpolated-text-item](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_multiline-interpolated-text-item) [multiline-interpolated-text](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_multiline-interpolated-text)<sub>opt</sub>  
-> multiline-interpolated-text-item → `\(` [expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_expression) `)` \| [multiline-quoted-text-item](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_multiline-quoted-text-item)  
-> escape-sequence → `\` [extended-string-literal-delimiter](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_extended-string-literal-delimiter)  
-> escaped-character → [escape-sequence](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_escape-sequence) `0` \| [escape-sequence](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_escape-sequence) `\` \| [escape-sequence](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_escape-sequence) `t` \| [escape-sequence](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_escape-sequence) `n` \| [escape-sequence](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_escape-sequence) `r` \| [escape-sequence](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_escape-sequence) `"` \| [escape-sequence](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_escape-sequence) `'`  
-> escaped-character → [escape-sequence](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_escape-sequence) `u` `{` [unicode-scalar-digits](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_unicode-scalar-digits) `}`  
-> unicode-scalar-digits → 0 から 8 までの16進数  
-> escaped-newline → [escape-sequence](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_escape-sequence) [inline-spaces](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_inline-spaces)<sub>opt</sub> [line-break](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_line-break)
-
-> GRAMMAR OF OPERATORS  
-> operator → [operator-head](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_operator-head) [operator-characters](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_operator-characters)<sub>opt</sub>  
-> operator → [dot-operator-head](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_dot-operator-head) [dot-operator-characters](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_dot-operator-characters)  
-> operator-head → `/` \| `=` \| `-` \| `+` \| `!` \| `*` \| `%` \| `<` \| `>` \| `&` \| `|` \| `^` \| `~` \| `?`  
-> operator-head → U+00A1–U+00A7  
-> operator-head → U+00A9 または U+00AB  
-> operator-head → U+00AC または U+00AE  
-> operator-head → U+00B0–U+00B1  
-> operator-head → U+00B6, U+00BB, U+00BF, U+00D7, または U+00F7  
-> operator-head → U+2016–U+2017  
-> operator-head → U+2020–U+2027  
-> operator-head → U+2030–U+203E  
-> operator-head → U+2041–U+2053  
-> operator-head → U+2055–U+205E  
-> operator-head → U+2190–U+23FF  
-> operator-head → U+2500–U+2775  
-> operator-head → U+2794–U+2BFF  
-> operator-head → U+2E00–U+2E7F  
-> operator-head → U+3001–U+3003  
-> operator-head → U+3008–U+3020  
-> operator-head → U+3030  
-> operator-character → [operator-head](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_operator-head)  
-> operator-character → U+0300–U+036F  
-> operator-character → U+1DC0–U+1DFF  
-> operator-character → U+20D0–U+20FF  
-> operator-character → U+FE00–U+FE0F  
-> operator-character → U+FE20–U+FE2F  
-> operator-character → U+E0100–U+E01EF  
-> operator-characters → [operator-character](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_operator-character) [operator-characters](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_operator-characters)<sub>opt</sub>  
-> dot-operator-head → `.`  
-> dot-operator-character → `.` \| [operator-character](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_operator-character)  
-> dot-operator-characters → [dot-operator-character](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_dot-operator-character) [dot-operator-characters](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_dot-operator-characters)<sub>opt</sub>  
-> infix-operator → [operator](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_operator)  
-> prefix-operator → [operator](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_operator)  
-> postfix-operator → [operator](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_operator)
+> Grammar of whitespace:
+>
+> *whitespace* → *whitespace-item* *whitespace*_?_
+>
+> *whitespace-item* → *line-break*
+>
+> *whitespace-item* → *inline-space*
+>
+> *whitespace-item* → *comment*
+>
+> *whitespace-item* → *multiline-comment*
+>
+> *whitespace-item* → U+0000, U+000B, または U+000C
+>
+>
+>
+> *line-break* → U+000A
+>
+> *line-break* → U+000D
+>
+> *line-break* → U+000D followed by U+000A
+>
+>
+>
+> *inline-spaces* → *inline-space* *inline-spaces*_?_
+>
+> *inline-space* → U+0009 または U+0020
+>
+>
+>
+> *comment* → **`//`** *comment-text* *line-break*
+>
+> *multiline-comment* → **`/*`** *multiline-comment-text* **`*/`**
+>
+>
+>
+> *comment-text* → *comment-text-item* *comment-text*_?_
+>
+> *comment-text-item* → Any Unicode scalar value except U+000A または U+000D
+>
+>
+>
+> *multiline-comment-text* → *multiline-comment-text-item* *multiline-comment-text*_?_
+>
+> *multiline-comment-text-item* → *multiline-comment*
+>
+> *multiline-comment-text-item* → *comment-text-item*
+>
+> *multiline-comment-text-item* → Any Unicode scalar value except  **`/*`** または  **`*/`**
+
+> Grammar of an identifier:
+>
+> *identifier* → *identifier-head* *identifier-characters*_?_
+>
+> *identifier* → **`` ` ``** *identifier-head* *identifier-characters*_?_ **`` ` ``**
+>
+> *identifier* → *implicit-parameter-name*
+>
+> *identifier* → *property-wrapper-projection*
+>
+> *identifier-list* → *identifier* | *identifier* **`,`** *identifier-list*
+>
+>
+>
+> *identifier-head* → 大文字または小文字の A ~ Z
+>
+> *identifier-head* → **`_`**
+>
+> *identifier-head* → U+00A8, U+00AA, U+00AD, U+00AF, U+00B2–U+00B5, または U+00B7–U+00BA
+>
+> *identifier-head* → U+00BC–U+00BE, U+00C0–U+00D6, U+00D8–U+00F6, または U+00F8–U+00FF
+>
+> *identifier-head* → U+0100–U+02FF, U+0370–U+167F, U+1681–U+180D, または U+180F–U+1DBF
+>
+> *identifier-head* → U+1E00–U+1FFF
+>
+> *identifier-head* → U+200B–U+200D, U+202A–U+202E, U+203F–U+2040, U+2054, または U+2060–U+206F
+>
+> *identifier-head* → U+2070–U+20CF, U+2100–U+218F, U+2460–U+24FF, または U+2776–U+2793
+>
+> *identifier-head* → U+2C00–U+2DFF または U+2E80–U+2FFF
+>
+> *identifier-head* → U+3004–U+3007, U+3021–U+302F, U+3031–U+303F, または U+3040–U+D7FF
+>
+> *identifier-head* → U+F900–U+FD3D, U+FD40–U+FDCF, U+FDF0–U+FE1F, または U+FE30–U+FE44
+>
+> *identifier-head* → U+FE47–U+FFFD
+>
+> *identifier-head* → U+10000–U+1FFFD, U+20000–U+2FFFD, U+30000–U+3FFFD, または U+40000–U+4FFFD
+>
+> *identifier-head* → U+50000–U+5FFFD, U+60000–U+6FFFD, U+70000–U+7FFFD, または U+80000–U+8FFFD
+>
+> *identifier-head* → U+90000–U+9FFFD, U+A0000–U+AFFFD, U+B0000–U+BFFFD, または U+C0000–U+CFFFD
+>
+> *identifier-head* → U+D0000–U+DFFFD または U+E0000–U+EFFFD
+>
+>
+>
+> *identifier-character* → 数値 0 ~ 9
+>
+> *identifier-character* → U+0300–U+036F, U+1DC0–U+1DFF, U+20D0–U+20FF, または U+FE20–U+FE2F
+>
+> *identifier-character* → *identifier-head*
+>
+> *identifier-characters* → *identifier-character* *identifier-characters*_?_
+>
+>
+>
+> *implicit-parameter-name* → **`$`** *decimal-digits*
+>
+> *property-wrapper-projection* → **`$`** *identifier-characters*
+
+> Grammar of a literal:
+>
+> *literal* → *numeric-literal* | *string-literal* | *regular-expression-literal* | *boolean-literal* | *nil-literal*
+>
+>
+>
+> *numeric-literal* → **`-`**_?_ *integer-literal* | **`-`**_?_ *floating-point-literal*
+>
+> *boolean-literal* → **`true`** | **`false`**
+>
+> *nil-literal* → **`nil`**
+
+> Grammar of an integer literal:
+>
+> *integer-literal* → *binary-literal*
+>
+> *integer-literal* → *octal-literal*
+>
+> *integer-literal* → *decimal-literal*
+>
+> *integer-literal* → *hexadecimal-literal*
+>
+>
+>
+> *binary-literal* → **`0b`** *binary-digit* *binary-literal-characters*_?_
+>
+> *binary-digit* → 数値 0 または 1
+>
+> *binary-literal-character* → *binary-digit* | **`_`**
+>
+> *binary-literal-characters* → *binary-literal-character* *binary-literal-characters*_?_
+>
+>
+>
+> *octal-literal* → **`0o`** *octal-digit* *octal-literal-characters*_?_
+>
+> *octal-digit* → 数値 0 ~ 7
+>
+> *octal-literal-character* → *octal-digit* | **`_`**
+>
+> *octal-literal-characters* → *octal-literal-character* *octal-literal-characters*_?_
+>
+>
+>
+> *decimal-literal* → *decimal-digit* *decimal-literal-characters*_?_
+>
+> *decimal-digit* → 数値 0 ~ 9
+>
+> *decimal-digits* → *decimal-digit* *decimal-digits*_?_
+>
+> *decimal-literal-character* → *decimal-digit* | **`_`**
+>
+> *decimal-literal-characters* → *decimal-literal-character* *decimal-literal-characters*_?_
+>
+>
+>
+> *hexadecimal-literal* → **`0x`** *hexadecimal-digit* *hexadecimal-literal-characters*_?_
+>
+> *hexadecimal-digit* → 数値 0 ~ 9, a ~ f、または A ~ F
+>
+> *hexadecimal-literal-character* → *hexadecimal-digit* | **`_`**
+>
+> *hexadecimal-literal-characters* → *hexadecimal-literal-character* *hexadecimal-literal-characters*_?_
+
+> Grammar of a floating-point literal:
+>
+> *floating-point-literal* → *decimal-literal* *decimal-fraction*_?_ *decimal-exponent*_?_
+>
+> *floating-point-literal* → *hexadecimal-literal* *hexadecimal-fraction*_?_ *hexadecimal-exponent*
+>
+>
+>
+> *decimal-fraction* → **`.`** *decimal-literal*
+>
+> *decimal-exponent* → *floating-point-e* *sign*_?_ *decimal-literal*
+>
+>
+>
+> *hexadecimal-fraction* → **`.`** *hexadecimal-digit* *hexadecimal-literal-characters*_?_
+>
+> *hexadecimal-exponent* → *floating-point-p* *sign*_?_ *decimal-literal*
+>
+>
+>
+> *floating-point-e* → **`e`** | **`E`**
+>
+> *floating-point-p* → **`p`** | **`P`**
+>
+> *sign* → **`+`** | **`-`**
+
+> Grammar of a string literal:
+>
+> *string-literal* → *static-string-literal* | *interpolated-string-literal*
+>
+>
+>
+> *string-literal-opening-delimiter* → *extended-string-literal-delimiter*_?_ **`"`**
+>
+> *string-literal-closing-delimiter* → **`"`** *extended-string-literal-delimiter*_?_
+>
+>
+>
+> *static-string-literal* → *string-literal-opening-delimiter* *quoted-text*_?_ *string-literal-closing-delimiter*
+>
+> *static-string-literal* → *multiline-string-literal-opening-delimiter* *multiline-quoted-text*_?_ *multiline-string-literal-closing-delimiter*
+>
+>
+>
+> *multiline-string-literal-opening-delimiter* → *extended-string-literal-delimiter*_?_ **`"""`**
+>
+> *multiline-string-literal-closing-delimiter* → **`"""`** *extended-string-literal-delimiter*_?_
+>
+> *extended-string-literal-delimiter* → **`#`** *extended-string-literal-delimiter*_?_
+>
+>
+>
+> *quoted-text* → *quoted-text-item* *quoted-text*_?_
+>
+> *quoted-text-item* → *escaped-character*
+>
+> *quoted-text-item* → **`"`**,  **`\`**, U+000A、または U+000D を除く任意のUnicodeスカラ値
+>
+>
+>
+> *multiline-quoted-text* → *multiline-quoted-text-item* *multiline-quoted-text*_?_
+>
+> *multiline-quoted-text-item* → *escaped-character*
+>
+> *multiline-quoted-text-item* → **`\`** を除く任意のUnicodeスカラ値
+>
+> *multiline-quoted-text-item* → *escaped-newline*
+>
+>
+>
+> *interpolated-string-literal* → *string-literal-opening-delimiter* *interpolated-text*_?_ *string-literal-closing-delimiter*
+>
+> *interpolated-string-literal* → *multiline-string-literal-opening-delimiter* *multiline-interpolated-text*_?_ *multiline-string-literal-closing-delimiter*
+>
+>
+>
+> *interpolated-text* → *interpolated-text-item* *interpolated-text*_?_
+>
+> *interpolated-text-item* → **`\(`** *expression* **`)`** | *quoted-text-item*
+>
+>
+>
+> *multiline-interpolated-text* → *multiline-interpolated-text-item* *multiline-interpolated-text*_?_
+>
+> *multiline-interpolated-text-item* → **`\(`** *expression* **`)`** | *multiline-quoted-text-item*
+>
+>
+>
+> *escape-sequence* → **`\`** *extended-string-literal-delimiter*
+>
+> *escaped-character* → *escape-sequence* **`0`** | *escape-sequence* **`\`** | *escape-sequence* **`t`** | *escape-sequence* **`n`** | *escape-sequence* **`r`** | *escape-sequence* **`"`** | *escape-sequence* **`'`**
+>
+> *escaped-character* → *escape-sequence* **`u`** **`{`** *unicode-scalar-digits* **`}`**
+>
+> *unicode-scalar-digits* → Between one and eight hexadecimal digits
+>
+>
+>
+> *escaped-newline* → *escape-sequence* *inline-spaces*_?_ *line-break*
+
+> Grammar of a regular expression literal:
+>
+> *regular-expression-literal* → *regular-expression-literal-opening-delimiter* *regular-expression* *regular-expression-literal-closing-delimiter*
+>
+> *regular-expression* → Any regular expression
+>
+>
+>
+> *regular-expression-literal-opening-delimiter* → *extended-regular-expression-literal-delimiter*_?_ **`/`**
+>
+> *regular-expression-literal-closing-delimiter* → **`/`** *extended-regular-expression-literal-delimiter*_?_
+>
+>
+>
+> *extended-regular-expression-literal-delimiter* → **`#`** *extended-regular-expression-literal-delimiter*_?_
+
+> Grammar of operators:
+>
+> *operator* → *operator-head* *operator-characters*_?_
+>
+> *operator* → *dot-operator-head* *dot-operator-characters*
+>
+>
+>
+> *operator-head* → **`/`** | **`=`** | **`-`** | **`+`** | **`!`** | **`*`** | **`%`** | **`<`** | **`>`** | **`&`** | **`|`** | **`^`** | **`~`** | **`?`**
+>
+> *operator-head* → U+00A1–U+00A7
+>
+> *operator-head* → U+00A9 または U+00AB
+>
+> *operator-head* → U+00AC または U+00AE
+>
+> *operator-head* → U+00B0–U+00B1
+>
+> *operator-head* → U+00B6, U+00BB, U+00BF, U+00D7, または U+00F7
+>
+> *operator-head* → U+2016–U+2017
+>
+> *operator-head* → U+2020–U+2027
+>
+> *operator-head* → U+2030–U+203E
+>
+> *operator-head* → U+2041–U+2053
+>
+> *operator-head* → U+2055–U+205E
+>
+> *operator-head* → U+2190–U+23FF
+>
+> *operator-head* → U+2500–U+2775
+>
+> *operator-head* → U+2794–U+2BFF
+>
+> *operator-head* → U+2E00–U+2E7F
+>
+> *operator-head* → U+3001–U+3003
+>
+> *operator-head* → U+3008–U+3020
+>
+> *operator-head* → U+3030
+>
+>
+>
+> *operator-character* → *operator-head*
+>
+> *operator-character* → U+0300–U+036F
+>
+> *operator-character* → U+1DC0–U+1DFF
+>
+> *operator-character* → U+20D0–U+20FF
+>
+> *operator-character* → U+FE00–U+FE0F
+>
+> *operator-character* → U+FE20–U+FE2F
+>
+> *operator-character* → U+E0100–U+E01EF
+>
+> *operator-characters* → *operator-character* *operator-characters*_?_
+>
+>
+>
+> *dot-operator-head* → **`.`**
+>
+> *dot-operator-character* → **`.`** | *operator-character*
+>
+> *dot-operator-characters* → *dot-operator-character* *dot-operator-characters*_?_
+>
+>
+>
+> *infix-operator* → *operator*
+>
+> *prefix-operator* → *operator*
+>
+> *postfix-operator* → *operator*
+
+## Types\(型\)
+
+> Grammar of a type:
+>
+> *type* → *function-type*
+>
+> *type* → *array-type*
+>
+> *type* → *dictionary-type*
+>
+> *type* → *type-identifier*
+>
+> *type* → *tuple-type*
+>
+> *type* → *optional-type*
+>
+> *type* → *implicitly-unwrapped-optional-type*
+>
+> *type* → *protocol-composition-type*
+>
+> *type* → *opaque-type*
+>
+> *type* → *metatype-type*
+>
+> *type* → *any-type*
+>
+> *type* → *self-type*
+>
+> *type* → **`(`** *type* **`)`**
+
+> Grammar of a type annotation:
+>
+> *type-annotation* → **`:`** *attributes*_?_ **`inout`**_?_ *type*
+
+> Grammar of a type identifier:
+>
+> *type-identifier* → *type-name* *generic-argument-clause*_?_ | *type-name* *generic-argument-clause*_?_ **`.`** *type-identifier*
+>
+> *type-name* → *identifier*
+
+> Grammar of a tuple type:
+>
+> *tuple-type* → **`(`** **`)`** | **`(`** *tuple-type-element* **`,`** *tuple-type-element-list* **`)`**
+>
+> *tuple-type-element-list* → *tuple-type-element* | *tuple-type-element* **`,`** *tuple-type-element-list*
+>
+> *tuple-type-element* → *element-name* *type-annotation* | *type*
+>
+> *element-name* → *identifier*
+
+> Grammar of a function type:
+>
+> *function-type* → *attributes*_?_ *function-type-argument-clause* **`async`**_?_ **`throws`**_?_ **`->`** *type*
+>
+>
+>
+> *function-type-argument-clause* → **`(`** **`)`**
+>
+> *function-type-argument-clause* → **`(`** *function-type-argument-list* **`...`**_?_ **`)`**
+>
+>
+>
+> *function-type-argument-list* → *function-type-argument* | *function-type-argument* **`,`** *function-type-argument-list*
+>
+> *function-type-argument* → *attributes*_?_ **`inout`**_?_ *type* | *argument-label* *type-annotation*
+>
+> *argument-label* → *identifier*
+
+> Grammar of an array type:
+>
+> *array-type* → **`[`** *type* **`]`**
+
+> Grammar of a dictionary type:
+>
+> *dictionary-type* → **`[`** *type* **`:`** *type* **`]`**
+
+> Grammar of an optional type:
+>
+> *optional-type* → *type* **`?`**
+
+> Grammar of an implicitly unwrapped optional type:
+>
+> *implicitly-unwrapped-optional-type* → *type* **`!`**
+
+> Grammar of a protocol composition type:
+>
+> *protocol-composition-type* → *type-identifier* **`&`** *protocol-composition-continuation*
+>
+> *protocol-composition-continuation* → *type-identifier* | *protocol-composition-type*
+
+> Grammar of an opaque type:
+>
+> *opaque-type* → **`some`** *type*
+
+> Grammar of a boxed protocol type:
+>
+> *boxed-protocol-type* → **`any`** *type*
+
+> Grammar of a metatype type:
+>
+> *metatype-type* → *type* **`.`** **`Type`** | *type* **`.`** **`Protocol`**
+
+> Grammar of an Any type:
+>
+> *any-type* → **`Any`**
+
+> Grammar of a Self type:
+>
+> *self-type* → **`Self`**
+
+> Grammar of a type inheritance clause:
+>
+> *type-inheritance-clause* → **`:`** *type-inheritance-list*
+>
+> *type-inheritance-list* → *attributes*_?_ *type-identifier* | *attributes*_?_ *type-identifier* **`,`** *type-inheritance-list*
+
+## Expressions\(式\)
+
+> Grammar of an expression:
+>
+> *expression* → *try-operator*_?_ *await-operator*_?_ *prefix-expression* *infix-expressions*_?_
+>
+> *expression-list* → *expression* | *expression* **`,`** *expression-list*
+
+> Grammar of a prefix expression:
+>
+> *prefix-expression* → *prefix-operator*_?_ *postfix-expression*
+>
+> *prefix-expression* → *in-out-expression*
+
+> Grammar of an in-out expression:
+>
+> *in-out-expression* → **`&`** *identifier*
+
+> Grammar of a try expression:
+>
+> *try-operator* → **`try`** | **`try`** **`?`** | **`try`** **`!`**
+
+> Grammar of an await expression:
+>
+> *await-operator* → **`await`**
+
+> Grammar of an infix expression:
+>
+> *infix-expression* → *infix-operator* *prefix-expression*
+>
+> *infix-expression* → *assignment-operator* *try-operator*_?_ *prefix-expression*
+>
+> *infix-expression* → *conditional-operator* *try-operator*_?_ *prefix-expression*
+>
+> *infix-expression* → *type-casting-operator*
+>
+> *infix-expressions* → *infix-expression* *infix-expressions*_?_
+
+> Grammar of an assignment operator:
+>
+> *assignment-operator* → **`=`**
+
+> Grammar of a conditional operator:
+>
+> *conditional-operator* → **`?`** *expression* **`:`**
+
+> Grammar of a type-casting operator:
+>
+> *type-casting-operator* → **`is`** *type*
+>
+> *type-casting-operator* → **`as`** *type*
+>
+> *type-casting-operator* → **`as`** **`?`** *type*
+>
+> *type-casting-operator* → **`as`** **`!`** *type*
+
+> Grammar of a primary expression:
+>
+> *primary-expression* → *identifier* *generic-argument-clause*_?_
+>
+> *primary-expression* → *literal-expression*
+>
+> *primary-expression* → *self-expression*
+>
+> *primary-expression* → *superclass-expression*
+>
+> *primary-expression* → *conditional-expression*
+>
+> *primary-expression* → *closure-expression*
+>
+> *primary-expression* → *parenthesized-expression*
+>
+> *primary-expression* → *tuple-expression*
+>
+> *primary-expression* → *implicit-member-expression*
+>
+> *primary-expression* → *wildcard-expression*
+>
+> *primary-expression* → *key-path-expression*
+>
+> *primary-expression* → *selector-expression*
+>
+> *primary-expression* → *key-path-string-expression*
+
+> Grammar of a literal expression:
+>
+> *literal-expression* → *literal*
+>
+> *literal-expression* → *array-literal* | *dictionary-literal* | *playground-literal*
+>
+> *literal-expression* → **`#file`** | **`#fileID`** | **`#filePath`**
+>
+> *literal-expression* → **`#line`** | **`#column`** | **`#function`** | **`#dsohandle`**
+>
+>
+>
+> *array-literal* → **`[`** *array-literal-items*_?_ **`]`**
+>
+> *array-literal-items* → *array-literal-item* **`,`**_?_ | *array-literal-item* **`,`** *array-literal-items*
+>
+> *array-literal-item* → *expression*
+>
+>
+>
+> *dictionary-literal* → **`[`** *dictionary-literal-items* **`]`** | **`[`** **`:`** **`]`**
+>
+> *dictionary-literal-items* → *dictionary-literal-item* **`,`**_?_ | *dictionary-literal-item* **`,`** *dictionary-literal-items*
+>
+> *dictionary-literal-item* → *expression* **`:`** *expression*
+>
+>
+>
+> *playground-literal* → **`#colorLiteral`** **`(`** **`red`** **`:`** *expression* **`,`** **`green`** **`:`** *expression* **`,`** **`blue`** **`:`** *expression* **`,`** **`alpha`** **`:`** *expression* **`)`**
+>
+> *playground-literal* → **`#fileLiteral`** **`(`** **`resourceName`** **`:`** *expression* **`)`**
+>
+> *playground-literal* → **`#imageLiteral`** **`(`** **`resourceName`** **`:`** *expression* **`)`**
+
+> Grammar of a self expression:
+>
+> *self-expression* → **`self`** | *self-method-expression* | *self-subscript-expression* | *self-initializer-expression*
+>
+>
+>
+> *self-method-expression* → **`self`** **`.`** *identifier*
+>
+> *self-subscript-expression* → **`self`** **`[`** *function-call-argument-list* **`]`**
+>
+> *self-initializer-expression* → **`self`** **`.`** **`init`**
+
+> Grammar of a superclass expression:
+>
+> *superclass-expression* → *superclass-method-expression* | *superclass-subscript-expression* | *superclass-initializer-expression*
+>
+>
+>
+> *superclass-method-expression* → **`super`** **`.`** *identifier*
+>
+> *superclass-subscript-expression* → **`super`** **`[`** *function-call-argument-list* **`]`**
+>
+> *superclass-initializer-expression* → **`super`** **`.`** **`init`**
+
+> Grammar of a conditional expression:
+>
+> *conditional-expression* → *if-expression* | *switch-expression*
+>
+>
+>
+> *if-expression* → **`if`** *condition-list* **`{`** *statement* **`}`** *if-expression-tail*
+>
+> *if-expression-tail* → **`else`** *if-expression*
+>
+> *if-expression-tail* → **`else`** **`{`** *statement* **`}`** *if-expression-tail*
+>
+>
+>
+> *switch-expression* → **`switch`** *expression* **`{`** *switch-expression-cases* **`}`**
+>
+> *switch-expression-cases* → *switch-expression-case* *switch-expression-cases*_?_
+>
+> *switch-expression-case* → *case-label* *statement*
+>
+> *switch-expression-case* → *default-label* *statement*
+
+> Grammar of a closure expression:
+>
+> *closure-expression* → **`{`** *attributes*_?_ *closure-signature*_?_ *statements*_?_ **`}`**
+>
+>
+>
+> *closure-signature* → *capture-list*_?_ *closure-parameter-clause* **`async`**_?_ **`throws`**_?_ *function-result*_?_ **`in`**
+>
+> *closure-signature* → *capture-list* **`in`**
+>
+>
+>
+> *closure-parameter-clause* → **`(`** **`)`** | **`(`** *closure-parameter-list* **`)`** | *identifier-list*
+>
+> *closure-parameter-list* → *closure-parameter* | *closure-parameter* **`,`** *closure-parameter-list*
+>
+> *closure-parameter* → *closure-parameter-name* *type-annotation*_?_
+>
+> *closure-parameter* → *closure-parameter-name* *type-annotation* **`...`**
+>
+> *closure-parameter-name* → *identifier*
+>
+>
+>
+> *capture-list* → **`[`** *capture-list-items* **`]`**
+>
+> *capture-list-items* → *capture-list-item* | *capture-list-item* **`,`** *capture-list-items*
+>
+> *capture-list-item* → *capture-specifier*_?_ *identifier*
+>
+> *capture-list-item* → *capture-specifier*_?_ *identifier* **`=`** *expression*
+>
+> *capture-list-item* → *capture-specifier*_?_ *self-expression*
+>
+> *capture-specifier* → **`weak`** | **`unowned`** | **`unowned(safe)`** | **`unowned(unsafe)`**
+
+> Grammar of a implicit member expression:
+>
+> *implicit-member-expression* → **`.`** *identifier*
+>
+> *implicit-member-expression* → **`.`** *identifier* **`.`** *postfix-expression*
+
+> Grammar of a parenthesized expression:
+>
+> *parenthesized-expression* → **`(`** *expression* **`)`**
+
+> Grammar of a tuple expression:
+>
+> *tuple-expression* → **`(`** **`)`** | **`(`** *tuple-element* **`,`** *tuple-element-list* **`)`**
+>
+> *tuple-element-list* → *tuple-element* | *tuple-element* **`,`** *tuple-element-list*
+>
+> *tuple-element* → *expression* | *identifier* **`:`** *expression*
+
+> Grammar of a wildcard expression:
+>
+> *wildcard-expression* → **`_`**
+
+> Grammar of a key-path expression:
+>
+> *key-path-expression* → **`\`** *type*_?_ **`.`** *key-path-components*
+>
+> *key-path-components* → *key-path-component* | *key-path-component* **`.`** *key-path-components*
+>
+> *key-path-component* → *identifier* *key-path-postfixes*_?_ | *key-path-postfixes*
+>
+>
+>
+> *key-path-postfixes* → *key-path-postfix* *key-path-postfixes*_?_
+>
+> *key-path-postfix* → **`?`** | **`!`** | **`self`** | **`[`** *function-call-argument-list* **`]`**
+
+> Grammar of a selector expression:
+>
+> *selector-expression* → **`#selector`** **`(`** *expression* **`)`**
+>
+> *selector-expression* → **`#selector`** **`(`** **`getter:`** *expression* **`)`**
+>
+> *selector-expression* → **`#selector`** **`(`** **`setter:`** *expression* **`)`**
+
+> Grammar of a key-path string expression:
+>
+> *key-path-string-expression* → **`#keyPath`** **`(`** *expression* **`)`**
+
+> Grammar of a postfix expression:
+>
+> *postfix-expression* → *primary-expression*
+>
+> *postfix-expression* → *postfix-expression* *postfix-operator*
+>
+> *postfix-expression* → *function-call-expression*
+>
+> *postfix-expression* → *initializer-expression*
+>
+> *postfix-expression* → *explicit-member-expression*
+>
+> *postfix-expression* → *postfix-self-expression*
+>
+> *postfix-expression* → *subscript-expression*
+>
+> *postfix-expression* → *forced-value-expression*
+>
+> *postfix-expression* → *optional-chaining-expression*
+
+> Grammar of a function call expression:
+>
+> *function-call-expression* → *postfix-expression* *function-call-argument-clause*
+>
+> *function-call-expression* → *postfix-expression* *function-call-argument-clause*_?_ *trailing-closures*
+>
+>
+>
+> *function-call-argument-clause* → **`(`** **`)`** | **`(`** *function-call-argument-list* **`)`**
+>
+> *function-call-argument-list* → *function-call-argument* | *function-call-argument* **`,`** *function-call-argument-list*
+>
+> *function-call-argument* → *expression* | *identifier* **`:`** *expression*
+>
+> *function-call-argument* → *operator* | *identifier* **`:`** *operator*
+>
+>
+>
+> *trailing-closures* → *closure-expression* *labeled-trailing-closures*_?_
+>
+> *labeled-trailing-closures* → *labeled-trailing-closure* *labeled-trailing-closures*_?_
+>
+> *labeled-trailing-closure* → *identifier* **`:`** *closure-expression*
+
+> Grammar of an initializer expression:
+>
+> *initializer-expression* → *postfix-expression* **`.`** **`init`**
+>
+> *initializer-expression* → *postfix-expression* **`.`** **`init`** **`(`** *argument-names* **`)`**
+
+> Grammar of an explicit member expression:
+>
+> *explicit-member-expression* → *postfix-expression* **`.`** *decimal-digits*
+>
+> *explicit-member-expression* → *postfix-expression* **`.`** *identifier* *generic-argument-clause*_?_
+>
+> *explicit-member-expression* → *postfix-expression* **`.`** *identifier* **`(`** *argument-names* **`)`**
+>
+> *explicit-member-expression* → *postfix-expression* *conditional-compilation-block*
+>
+>
+>
+> *argument-names* → *argument-name* *argument-names*_?_
+>
+> *argument-name* → *identifier* **`:`**
+
+> Grammar of a postfix self expression:
+>
+> *postfix-self-expression* → *postfix-expression* **`.`** **`self`**
+
+> Grammar of a subscript expression:
+>
+> *subscript-expression* → *postfix-expression* **`[`** *function-call-argument-list* **`]`**
+
+> Grammar of a forced-value expression:
+>
+> *forced-value-expression* → *postfix-expression* **`!`**
+
+> Grammar of an optional-chaining expression:
+>
+> *optional-chaining-expression* → *postfix-expression* **`?`**
+
+## Statements\(文\)
+
+> Grammar of a statement:
+>
+> *statement* → *expression* **`;`**_?_
+>
+> *statement* → *declaration* **`;`**_?_
+>
+> *statement* → *loop-statement* **`;`**_?_
+>
+> *statement* → *branch-statement* **`;`**_?_
+>
+> *statement* → *labeled-statement* **`;`**_?_
+>
+> *statement* → *control-transfer-statement* **`;`**_?_
+>
+> *statement* → *defer-statement* **`;`**_?_
+>
+> *statement* → *do-statement* **`;`**_?_
+>
+> *statement* → *compiler-control-statement*
+>
+> *statements* → *statement* *statements*_?_
+
+> Grammar of a loop statement:
+>
+> *loop-statement* → *for-in-statement*
+>
+> *loop-statement* → *while-statement*
+>
+> *loop-statement* → *repeat-while-statement*
+
+> Grammar of a for-in statement:
+>
+> *for-in-statement* → **`for`** **`case`**_?_ *pattern* **`in`** *expression* *where-clause*_?_ *code-block*
+
+> Grammar of a while statement:
+>
+> *while-statement* → **`while`** *condition-list* *code-block*
+>
+>
+>
+> *condition-list* → *condition* | *condition* **`,`** *condition-list*
+>
+> *condition* → *expression* | *availability-condition* | *case-condition* | *optional-binding-condition*
+>
+>
+>
+> *case-condition* → **`case`** *pattern* *initializer*
+>
+> *optional-binding-condition* → **`let`** *pattern* *initializer*_?_ | **`var`** *pattern* *initializer*_?_
+
+> Grammar of a repeat-while statement:
+>
+> *repeat-while-statement* → **`repeat`** *code-block* **`while`** *expression*
+
+> Grammar of a branch statement:
+>
+> *branch-statement* → *if-statement*
+>
+> *branch-statement* → *guard-statement*
+>
+> *branch-statement* → *switch-statement*
+
+> Grammar of an if statement:
+>
+> *if-statement* → **`if`** *condition-list* *code-block* *else-clause*_?_
+>
+> *else-clause* → **`else`** *code-block* | **`else`** *if-statement*
+
+> Grammar of a guard statement:
+>
+> *guard-statement* → **`guard`** *condition-list* **`else`** *code-block*
+
+> Grammar of a switch statement:
+>
+> *switch-statement* → **`switch`** *expression* **`{`** *switch-cases*_?_ **`}`**
+>
+> *switch-cases* → *switch-case* *switch-cases*_?_
+>
+> *switch-case* → *case-label* *statements*
+>
+> *switch-case* → *default-label* *statements*
+>
+> *switch-case* → *conditional-switch-case*
+>
+>
+>
+> *case-label* → *attributes*_?_ **`case`** *case-item-list* **`:`**
+>
+> *case-item-list* → *pattern* *where-clause*_?_ | *pattern* *where-clause*_?_ **`,`** *case-item-list*
+>
+> *default-label* → *attributes*_?_ **`default`** **`:`**
+>
+>
+>
+> *where-clause* → **`where`** *where-expression*
+>
+> *where-expression* → *expression*
+>
+>
+>
+> *conditional-switch-case* → *switch-if-directive-clause* *switch-elseif-directive-clauses*_?_ *switch-else-directive-clause*_?_ *endif-directive*
+>
+> *switch-if-directive-clause* → *if-directive* *compilation-condition* *switch-cases*_?_
+>
+> *switch-elseif-directive-clauses* → *elseif-directive-clause* *switch-elseif-directive-clauses*_?_
+>
+> *switch-elseif-directive-clause* → *elseif-directive* *compilation-condition* *switch-cases*_?_
+>
+> *switch-else-directive-clause* → *else-directive* *switch-cases*_?_
+
+> Grammar of a labeled statement:
+>
+> *labeled-statement* → *statement-label* *loop-statement*
+>
+> *labeled-statement* → *statement-label* *if-statement*
+>
+> *labeled-statement* → *statement-label* *switch-statement*
+>
+> *labeled-statement* → *statement-label* *do-statement*
+>
+>
+>
+> *statement-label* → *label-name* **`:`**
+>
+> *label-name* → *identifier*
+
+> Grammar of a control transfer statement:
+>
+> *control-transfer-statement* → *break-statement*
+>
+> *control-transfer-statement* → *continue-statement*
+>
+> *control-transfer-statement* → *fallthrough-statement*
+>
+> *control-transfer-statement* → *return-statement*
+>
+> *control-transfer-statement* → *throw-statement*
+
+> Grammar of a break statement:
+>
+> *break-statement* → **`break`** *label-name*_?_
+
+> Grammar of a continue statement:
+>
+> *continue-statement* → **`continue`** *label-name*_?_
+
+> Grammar of a fallthrough statement:
+>
+> *fallthrough-statement* → **`fallthrough`**
+
+> Grammar of a return statement:
+>
+> *return-statement* → **`return`** *expression*_?_
+
+> Grammar of a throw statement:
+>
+> *throw-statement* → **`throw`** *expression*
+
+> Grammar of a defer statement:
+>
+> *defer-statement* → **`defer`** *code-block*
+
+> Grammar of a do statement:
+>
+> *do-statement* → **`do`** *code-block* *catch-clauses*_?_
+>
+> *catch-clauses* → *catch-clause* *catch-clauses*_?_
+>
+> *catch-clause* → **`catch`** *catch-pattern-list*_?_ *code-block*
+>
+> *catch-pattern-list* → *catch-pattern* | *catch-pattern* **`,`** *catch-pattern-list*
+>
+> *catch-pattern* → *pattern* *where-clause*_?_
+
+> Grammar of a compiler control statement:
+>
+> *compiler-control-statement* → *conditional-compilation-block*
+>
+> *compiler-control-statement* → *line-control-statement*
+>
+> *compiler-control-statement* → *diagnostic-statement*
+
+> Grammar of a conditional compilation block:
+>
+> *conditional-compilation-block* → *if-directive-clause* *elseif-directive-clauses*_?_ *else-directive-clause*_?_ *endif-directive*
+>
+>
+>
+> *if-directive-clause* → *if-directive* *compilation-condition* *statements*_?_
+>
+> *elseif-directive-clauses* → *elseif-directive-clause* *elseif-directive-clauses*_?_
+>
+> *elseif-directive-clause* → *elseif-directive* *compilation-condition* *statements*_?_
+>
+> *else-directive-clause* → *else-directive* *statements*_?_
+>
+> *if-directive* → **`#if`**
+>
+> *elseif-directive* → **`#elseif`**
+>
+> *else-directive* → **`#else`**
+>
+> *endif-directive* → **`#endif`**
+>
+>
+>
+> *compilation-condition* → *platform-condition*
+>
+> *compilation-condition* → *identifier*
+>
+> *compilation-condition* → *boolean-literal*
+>
+> *compilation-condition* → **`(`** *compilation-condition* **`)`**
+>
+> *compilation-condition* → **`!`** *compilation-condition*
+>
+> *compilation-condition* → *compilation-condition* **`&&`** *compilation-condition*
+>
+> *compilation-condition* → *compilation-condition* **`||`** *compilation-condition*
+>
+>
+>
+> *platform-condition* → **`os`** **`(`** *operating-system* **`)`**
+>
+> *platform-condition* → **`arch`** **`(`** *architecture* **`)`**
+>
+> *platform-condition* → **`swift`** **`(`** **`>=`** *swift-version* **`)`** | **`swift`** **`(`** **`<`** *swift-version* **`)`**
+>
+> *platform-condition* → **`compiler`** **`(`** **`>=`** *swift-version* **`)`** | **`compiler`** **`(`** **`<`** *swift-version* **`)`**
+>
+> *platform-condition* → **`canImport`** **`(`** *import-path* **`)`**
+>
+> *platform-condition* → **`targetEnvironment`** **`(`** *environment* **`)`**
+>
+>
+>
+> *operating-system* → **`macOS`** | **`iOS`** | **`watchOS`** | **`tvOS`** | **`Linux`** | **`Windows`**
+>
+> *architecture* → **`i386`** | **`x86_64`** | **`arm`** | **`arm64`**
+>
+> *swift-version* → *decimal-digits* *swift-version-continuation*_?_
+>
+> *swift-version-continuation* → **`.`** *decimal-digits* *swift-version-continuation*_?_
+>
+> *environment* → **`simulator`** | **`macCatalyst`**
+
+> Grammar of a line control statement:
+>
+> *line-control-statement* → **`#sourceLocation`** **`(`** **`file:`** *file-path* **`,`** **`line:`** *line-number* **`)`**
+>
+> *line-control-statement* → **`#sourceLocation`** **`(`** **`)`**
+>
+> *line-number* → A decimal integer greater than zero
+>
+> *file-path* → *static-string-literal*
+
+> Grammar of a compile-time diagnostic statement:
+>
+> *diagnostic-statement* → **`#error`** **`(`** *diagnostic-message* **`)`**
+>
+> *diagnostic-statement* → **`#warning`** **`(`** *diagnostic-message* **`)`**
+>
+>
+>
+> *diagnostic-message* → *static-string-literal*
+
+> Grammar of an availability condition:
+>
+> *availability-condition* → **`#available`** **`(`** *availability-arguments* **`)`**
+>
+> *availability-condition* → **`#unavailable`** **`(`** *availability-arguments* **`)`**
+>
+> *availability-arguments* → *availability-argument* | *availability-argument* **`,`** *availability-arguments*
+>
+> *availability-argument* → *platform-name* *platform-version*
+>
+> *availability-argument* → **`*`**
+>
+>
+>
+> *platform-name* → **`iOS`** | **`iOSApplicationExtension`**
+>
+> *platform-name* → **`macOS`** | **`macOSApplicationExtension`**
+>
+> *platform-name* → **`macCatalyst`** | **`macCatalystApplicationExtension`**
+>
+> *platform-name* → **`watchOS`** | **`watchOSApplicationExtension`**
+>
+> *platform-name* → **`tvOS`** | **`tvOSApplicationExtension`**
+>
+> *platform-version* → *decimal-digits*
+>
+> *platform-version* → *decimal-digits* **`.`** *decimal-digits*
+>
+> *platform-version* → *decimal-digits* **`.`** *decimal-digits* **`.`** *decimal-digits*
+
+## DeclarDeclarations\(宣言\)ations
+
+> Grammar of a declaration:
+>
+> *declaration* → *import-declaration*
+>
+> *declaration* → *constant-declaration*
+>
+> *declaration* → *variable-declaration*
+>
+> *declaration* → *typealias-declaration*
+>
+> *declaration* → *function-declaration*
+>
+> *declaration* → *enum-declaration*
+>
+> *declaration* → *struct-declaration*
+>
+> *declaration* → *class-declaration*
+>
+> *declaration* → *actor-declaration*
+>
+> *declaration* → *protocol-declaration*
+>
+> *declaration* → *initializer-declaration*
+>
+> *declaration* → *deinitializer-declaration*
+>
+> *declaration* → *extension-declaration*
+>
+> *declaration* → *subscript-declaration*
+>
+> *declaration* → *operator-declaration*
+>
+> *declaration* → *precedence-group-declaration*
+>
+> *declarations* → *declaration* *declarations*_?_
+
+> Grammar of a top-level declaration:
+>
+> *top-level-declaration* → *statements*_?_
+
+> Grammar of a code block:
+>
+> *code-block* → **`{`** *statements*_?_ **`}`**
+
+> Grammar of an import declaration:
+>
+> *import-declaration* → *attributes*_?_ **`import`** *import-kind*_?_ *import-path*
+>
+>
+>
+> *import-kind* → **`typealias`** | **`struct`** | **`class`** | **`enum`** | **`protocol`** | **`let`** | **`var`** | **`func`**
+>
+> *import-path* → *identifier* | *identifier* **`.`** *import-path*
 
-## Types\(型\)
+> Grammar of a constant declaration:
+>
+> *constant-declaration* → *attributes*_?_ *declaration-modifiers*_?_ **`let`** *pattern-initializer-list*
+>
+>
+>
+> *pattern-initializer-list* → *pattern-initializer* | *pattern-initializer* **`,`** *pattern-initializer-list*
+>
+> *pattern-initializer* → *pattern* *initializer*_?_
+>
+> *initializer* → **`=`** *expression*
 
-> GRAMMAR OF A TYPE  
-> type → [function-type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_function-type)  
-> type → [array-type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_array-type)  
-> type → [dictionary-type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_dictionary-type)  
-> type → [type-identifier](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type-identifier)  
-> type → [tuple-type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_tuple-type)  
-> type → [optional-type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_optional-type)  
-> type → [implicitly-unwrapped-optional-type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_implicitly-unwrapped-optional-type)  
-> type → [protocol-composition-type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_protocol-composition-type)  
-> type → [opaque-type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_opaque-type)  
-> type → [metatype-type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_metatype-type)  
-> type → [any-type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_any-type)  
-> type → [self-type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_self-type)  
-> type → `(` [type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type) `)`
-
-> GRAMMAR OF A TYPE ANNOTATION  
-> type-annotation → `:` [attributes](https://docs.swift.org/swift-book/ReferenceManual/Attributes.html#grammar_attributes)<sub>opt</sub> **inout**<sub>opt</sub> [type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type)
-
-> GRAMMAR OF A TYPE IDENTIFIER  
-> type-identifier → [type-name](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type-name) [generic-argument-clause](https://docs.swift.org/swift-book/ReferenceManual/GenericParametersAndArguments.html#grammar_generic-argument-clause)<sub>opt</sub> \| [type-name](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type-name) [generic-argument-clause](https://docs.swift.org/swift-book/ReferenceManual/GenericParametersAndArguments.html#grammar_generic-argument-clause)<sub>opt</sub> `.` [type-identifier](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type-identifier)  
-> type-name → [identifier](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_identifier)
-
-> GRAMMAR OF A TUPLE TYPE  
-> tuple-type → `(` `)` \| `(` [tuple-type-element](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_tuple-type-element) `,` [tuple-type-element-list](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_tuple-type-element-list) `)`  
-> tuple-type-element-list → [tuple-type-element](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_tuple-type-element) \| [tuple-type-element](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_tuple-type-element) `,` [tuple-type-element-list](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_tuple-type-element-list)  
-> tuple-type-element → [element-name](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_element-name) [type-annotation](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type-annotation) \| [type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type)  
-> element-name → [identifier](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_identifier)
-
-> GRAMMAR OF A FUNCTION TYPE  
-> function-type → [attributes](https://docs.swift.org/swift-book/ReferenceManual/Attributes.html#grammar_attributes)<sub>opt</sub> [function-type-argument-clause](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_function-type-argument-clause) `throws`<sub>opt</sub> `->` [type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type)  
-> function-type-argument-clause → `(` `)`  
-> function-type-argument-clause → `(` [function-type-argument-list](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_function-type-argument-list) `...`<sub>opt</sub> `)`  
-> function-type-argument-list → [function-type-argument](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_function-type-argument) \| [function-type-argument](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_function-type-argument) `,` [function-type-argument-list](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_function-type-argument-list)  
-> function-type-argument → [attributes](https://docs.swift.org/swift-book/ReferenceManual/Attributes.html#grammar_attributes)<sub>opt</sub> `inout`<sub>opt</sub> [type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type) \| [argument-label](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_argument-label) [type-annotation](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type-annotation)  
-> argument-label → [identifier](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_identifier)
-
-> GRAMMAR OF AN ARRAY TYPE  
-> array-type → `[` [type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type) `]`
-
-> GRAMMAR OF A DICTIONARY TYPE  
-> dictionary-type → `[` [type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type) `:` [type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type) `]`
-
-> GRAMMAR OF AN OPTIONAL TYPE  
-> optional-type → [type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type) `?`
-
-> GRAMMAR OF AN IMPLICITLY UNWRAPPED OPTIONAL TYPE  
-> implicitly-unwrapped-optional-type → [type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type) `!`
-
-> GRAMMAR OF A PROTOCOL COMPOSITION TYPE  
-> protocol-composition-type → [type-identifier](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type-identifier) `&` [protocol-composition-continuation](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_protocol-composition-continuation)  
-> protocol-composition-continuation → [type-identifier](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type-identifier) \| [protocol-composition-type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_protocol-composition-type)
-
-> GRAMMAR OF AN OPAQUE TYPE  
-> opaque-type → `some` [type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type)
-
-> GRAMMAR OF A METATYPE TYPE  
-> metatype-type → [type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type) `.` `Type` \| [type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type) `.` `Protocol`
-
-> GRAMMAR OF AN ANY TYPE  
-> any-type → `Any`
-
-> GRAMMAR OF A SELF TYPE  
-> self-type → `Self`
-
-> GRAMMAR OF A TYPE INHERITANCE CLAUSE  
-> type-inheritance-clause → `:` [type-inheritance-list](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type-inheritance-list)  
-> type-inheritance-list → [type-identifier](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type-identifier) \| [type-identifier](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type-identifier) `,` [type-inheritance-list](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type-inheritance-list)
+> Grammar of a variable declaration:
+>
+> *variable-declaration* → *variable-declaration-head* *pattern-initializer-list*
+>
+> *variable-declaration* → *variable-declaration-head* *variable-name* *type-annotation* *code-block*
+>
+> *variable-declaration* → *variable-declaration-head* *variable-name* *type-annotation* *getter-setter-block*
+>
+> *variable-declaration* → *variable-declaration-head* *variable-name* *type-annotation* *getter-setter-keyword-block*
+>
+> *variable-declaration* → *variable-declaration-head* *variable-name* *initializer* *willSet-didSet-block*
+>
+> *variable-declaration* → *variable-declaration-head* *variable-name* *type-annotation* *initializer*_?_ *willSet-didSet-block*
+>
+>
+>
+> *variable-declaration-head* → *attributes*_?_ *declaration-modifiers*_?_ **`var`**
+>
+> *variable-name* → *identifier*
+>
+>
+>
+> *getter-setter-block* → *code-block*
+>
+> *getter-setter-block* → **`{`** *getter-clause* *setter-clause*_?_ **`}`**
+>
+> *getter-setter-block* → **`{`** *setter-clause* *getter-clause* **`}`**
+>
+> *getter-clause* → *attributes*_?_ *mutation-modifier*_?_ **`get`** *code-block*
+>
+> *setter-clause* → *attributes*_?_ *mutation-modifier*_?_ **`set`** *setter-name*_?_ *code-block*
+>
+> *setter-name* → **`(`** *identifier* **`)`**
+>
+>
+>
+> *getter-setter-keyword-block* → **`{`** *getter-keyword-clause* *setter-keyword-clause*_?_ **`}`**
+>
+> *getter-setter-keyword-block* → **`{`** *setter-keyword-clause* *getter-keyword-clause* **`}`**
+>
+> *getter-keyword-clause* → *attributes*_?_ *mutation-modifier*_?_ **`get`**
+>
+> *setter-keyword-clause* → *attributes*_?_ *mutation-modifier*_?_ **`set`**
+>
+>
+>
+> *willSet-didSet-block* → **`{`** *willSet-clause* *didSet-clause*_?_ **`}`**
+>
+> *willSet-didSet-block* → **`{`** *didSet-clause* *willSet-clause*_?_ **`}`**
+>
+> *willSet-clause* → *attributes*_?_ **`willSet`** *setter-name*_?_ *code-block*
+>
+> *didSet-clause* → *attributes*_?_ **`didSet`** *setter-name*_?_ *code-block*
 
-## Expressions\(式\)
+> Grammar of a type alias declaration:
+>
+> *typealias-declaration* → *attributes*_?_ *access-level-modifier*_?_ **`typealias`** *typealias-name* *generic-parameter-clause*_?_ *typealias-assignment*
+>
+> *typealias-name* → *identifier*
+>
+> *typealias-assignment* → **`=`** *type*
 
-> GRAMMAR OF AN EXPRESSION  
-> expression → [try-operator](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_try-operator)<sub>opt</sub> [await-operator](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_await-operator)<sub>opt</sub> [prefix-expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_prefix-expression) [infix-expressions](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_infix-expressions)<sub>opt</sub>  
-> expression-list → [expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_expression) \| [expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_expression) `,` [expression-list](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_expression-list)
-
-> GRAMMAR OF A PREFIX EXPRESSION  
-> prefix-expression → [prefix-operator](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_prefix-operator)<sub>opt</sub> [postfix-expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_postfix-expression)  
-> prefix-expression → [in-out-expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_in-out-expression)
-
-> GRAMMAR OF AN IN-OUT EXPRESSION  
-> in-out-expression → `&` [identifier](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_identifier)
-
-> GRAMMAR OF A TRY EXPRESSION  
-> try-operator → `try` \| `try` `?` \| `try` `!`
-
-> GRAMMAR OF AN AWAIT EXPRESSION  
-> _await-operator_ → `await`
-
-> GRAMMAR OF A INFIX EXPRESSION  
-> infix-expression → [infix-operator](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_infix-operator) [prefix-expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_prefix-expression)  
-> infix-expression → [assignment-operator](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_assignment-operator)<sub>opt</sub> [prefix-expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_prefix-expression)  
-> infix-expression → [conditional-operator](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_conditional-operator)<sub>opt</sub> [prefix-expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_prefix-expression)  
-> infix-expression → [type-casting-operator](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_type-casting-operator)  
-> infix-expressions → [infix-expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_infix-expression) [infix-expressions](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_infix-expressions)<sub>opt</sub>
-
-> GRAMMAR OF AN ASSIGNMENT OPERATOR  
-> assignment-operator → `=`
-
-> GRAMMAR OF A CONDITIONAL OPERATOR  
-> conditional-operator → `?` [expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_expression) `:`
-
-> GRAMMAR OF A TYPE-CASTING OPERATOR  
-> type-casting-operator → `is` [type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type)  
-> type-casting-operator → `as` [type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type)  
-> type-casting-operator → `as` `?` [type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type)  
-> type-casting-operator → `as` `!` [type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type)
-
-> GRAMMAR OF A PRIMARY EXPRESSION  
-> primary-expression → [identifier](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_identifier) [generic-argument-clause](https://docs.swift.org/swift-book/ReferenceManual/GenericParametersAndArguments.html#grammar_generic-argument-clause)<sub>opt</sub>  
-> primary-expression → [literal-expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_literal-expression)  
-> primary-expression → [self-expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_self-expression)  
-> primary-expression → [superclass-expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_superclass-expression)  
-> *primary-expression* → *conditional-expression*  
-> primary-expression → [closure-expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_closure-expression)  
-> primary-expression → [parenthesized-expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_parenthesized-expression)  
-> primary-expression → [tuple-expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_tuple-expression)  
-> primary-expression → [implicit-member-expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_implicit-member-expression)  
-> primary-expression → [wildcard-expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_wildcard-expression)  
-> primary-expression → [key-path-expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_key-path-expression)  
-> primary-expression → [selector-expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_selector-expression)  
-> primary-expression → [key-path-string-expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_key-path-string-expression)
-
-> GRAMMAR OF A LITERAL EXPRESSION  
-> literal-expression → [literal](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_literal)  
-> literal-expression → [array-literal](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_array-literal) \| [dictionary-literal](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_dictionary-literal) \| [playground-literal](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_playground-literal)  
-> literal-expression → `#file` \| `#fileID` \| `#filePath`  
-> literal-expression → `#line` \| `#column` \| `#function` \| `#dsohandle`  
-> array-literal → `[` [array-literal-items](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_array-literal-items)<sub>opt</sub> `]`  
-> array-literal-items → [array-literal-item](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_array-literal-item) `,`<sub>opt</sub> \| [array-literal-item](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_array-literal-item) `,` [array-literal-items](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_array-literal-items)  
-> array-literal-item → [expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_expression)  
-> dictionary-literal → `[` [dictionary-literal-items](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_dictionary-literal-items) `]` \| `[` `:` `]`  
-> dictionary-literal-items → [dictionary-literal-item](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_dictionary-literal-item) `,`<sub>opt</sub> \| [dictionary-literal-item](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_dictionary-literal-item) `,` [dictionary-literal-items](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_dictionary-literal-items)  
-> dictionary-literal-item → [expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_expression) `:` [expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_expression)  
-> playground-literal → `#colorLiteral` `(` `red` `:` [expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_expression) `,` `green` `:` [expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_expression) `,` `blue` `:`[expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_expression) `,` `alpha` `:` [expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_expression) `)`  
-> playground-literal → `#fileLiteral` `(` `resourceName` `:` [expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_expression) `)`  
-> playground-literal → `#imageLiteral` `(` `resourceName` `:` [expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_expression) `)`
-
-> GRAMMAR OF A SELF EXPRESSION  
-> self-expression → `self` \| [self-method-expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_self-method-expression) \| [self-subscript-expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_self-subscript-expression) \| [self-initializer-expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_self-initializer-expression)  
-> self-method-expression → `self` `.` [identifier](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_identifier)  
-> self-subscript-expression → `self` `[` [function-call-argument-list](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_function-call-argument-list) `]`  
-> self-initializer-expression → `self` `.` `init`
-
-> GRAMMAR OF A SUPERCLASS EXPRESSION  
-> superclass-expression → [superclass-method-expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_superclass-method-expression) \| [superclass-subscript-expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_superclass-subscript-expression) \| [superclass-initializer-expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_superclass-initializer-expression)  
-> superclass-method-expression → `super` `.` [identifier](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_identifier)  
-> superclass-subscript-expression → `super` `[` [function-call-argument-list](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_function-call-argument-list) `]`  
-> superclass-initializer-expression → `super` `.` `init`
+> Grammar of a function declaration:
+>
+> *function-declaration* → *function-head* *function-name* *generic-parameter-clause*_?_ *function-signature* *generic-where-clause*_?_ *function-body*_?_
+>
+>
+>
+> *function-head* → *attributes*_?_ *declaration-modifiers*_?_ **`func`**
+>
+> *function-name* → *identifier* | *operator*
+>
+>
+>
+> *function-signature* → *parameter-clause* **`async`**_?_ **`throws`**_?_ *function-result*_?_
+>
+> *function-signature* → *parameter-clause* **`async`**_?_ **`rethrows`** *function-result*_?_
+>
+> *function-result* → **`->`** *attributes*_?_ *type*
+>
+> *function-body* → *code-block*
+>
+>
+>
+> *parameter-clause* → **`(`** **`)`** | **`(`** *parameter-list* **`)`**
+>
+> *parameter-list* → *parameter* | *parameter* **`,`** *parameter-list*
+>
+> *parameter* → *external-parameter-name*_?_ *local-parameter-name* *type-annotation* *default-argument-clause*_?_
+>
+> *parameter* → *external-parameter-name*_?_ *local-parameter-name* *type-annotation*
+>
+> *parameter* → *external-parameter-name*_?_ *local-parameter-name* *type-annotation* **`...`**
+>
+> *external-parameter-name* → *identifier*
+>
+> *local-parameter-name* → *identifier*
+>
+> *default-argument-clause* → **`=`** *expression*
 
-> Grammar of a conditional expression:
+> Grammar of an enumeration declaration:
 >
-> *conditional-expression* → *if-expression* | *switch-expression*
+> *enum-declaration* → *attributes*_?_ *access-level-modifier*_?_ *union-style-enum*
 >
+> *enum-declaration* → *attributes*_?_ *access-level-modifier*_?_ *raw-value-style-enum*
 >
 >
-> *if-expression* → **`if`** *condition-list* **`{`** *statement* **`}`** *if-expression-tail*
 >
-> *if-expression-tail* → **`else`** *if-expression*
+> *union-style-enum* → **`indirect`**_?_ **`enum`** *enum-name* *generic-parameter-clause*_?_ *type-inheritance-clause*_?_ *generic-where-clause*_?_ **`{`** *union-style-enum-members*_?_ **`}`**
 >
-> *if-expression-tail* → **`else`** **`{`** *statement* **`}`** *if-expression-tail*
+> *union-style-enum-members* → *union-style-enum-member* *union-style-enum-members*_?_
 >
+> *union-style-enum-member* → *declaration* | *union-style-enum-case-clause* | *compiler-control-statement*
 >
+> *union-style-enum-case-clause* → *attributes*_?_ **`indirect`**_?_ **`case`** *union-style-enum-case-list*
 >
-> *switch-expression* → **`switch`** *expression* **`{`** *switch-expression-cases* **`}`**
+> *union-style-enum-case-list* → *union-style-enum-case* | *union-style-enum-case* **`,`** *union-style-enum-case-list*
 >
-> *switch-expression-cases* → *switch-expression-case* *switch-expression-cases*_?_
+> *union-style-enum-case* → *enum-case-name* *tuple-type*_?_
 >
-> *switch-expression-case* → *case-label* *statement*
+> *enum-name* → *identifier*
 >
-> *switch-expression-case* → *default-label* *statement*
+> *enum-case-name* → *identifier*
+>
+>
+>
+> *raw-value-style-enum* → **`enum`** *enum-name* *generic-parameter-clause*_?_ *type-inheritance-clause* *generic-where-clause*_?_ **`{`** *raw-value-style-enum-members* **`}`**
+>
+> *raw-value-style-enum-members* → *raw-value-style-enum-member* *raw-value-style-enum-members*_?_
+>
+> *raw-value-style-enum-member* → *declaration* | *raw-value-style-enum-case-clause* | *compiler-control-statement*
+>
+> *raw-value-style-enum-case-clause* → *attributes*_?_ **`case`** *raw-value-style-enum-case-list*
+>
+> *raw-value-style-enum-case-list* → *raw-value-style-enum-case* | *raw-value-style-enum-case* **`,`** *raw-value-style-enum-case-list*
+>
+> *raw-value-style-enum-case* → *enum-case-name* *raw-value-assignment*_?_
+>
+> *raw-value-assignment* → **`=`** *raw-value-literal*
+>
+> *raw-value-literal* → *numeric-literal* | *static-string-literal* | *boolean-literal*
 
-> GRAMMAR OF A CLOSURE EXPRESSION  
-> closure-expression → `{` [closure-signature](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_closure-signature)<sub>opt</sub> [statements](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_statements)<sub>opt</sub> `}`  
-> closure-signature → [capture-list](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_capture-list)<sub>opt</sub> [closure-parameter-clause](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_closure-parameter-clause) `throws`<sub>opt</sub> [function-result](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_function-result)<sub>opt</sub> `in`  
-> closure-signature → [capture-list](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_capture-list) `in`  
-> closure-parameter-clause → `(` `)` \| `(` [closure-parameter-list](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_closure-parameter-list) `)` \| [identifier-list](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_identifier-list)  
-> closure-parameter-list → [closure-parameter](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_closure-parameter) \| [closure-parameter](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_closure-parameter) `,` [closure-parameter-list](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_closure-parameter-list)  
-> closure-parameter → [closure-parameter-name](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_closure-parameter-name) [type-annotation](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type-annotation)<sub>opt</sub>  
-> closure-parameter → [closure-parameter-name](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_closure-parameter-name) [type-annotation](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type-annotation) `...`  
-> closure-parameter-name → [identifier](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_identifier)  
-> capture-list → `[` [capture-list-items](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_capture-list-items) `]`  
-> capture-list-items → [capture-list-item](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_capture-list-item) \| [capture-list-item](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_capture-list-item) `,` [capture-list-items](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_capture-list-items)  
-> capture-list-item → [capture-specifier](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_capture-specifier)<sub>opt</sub> [identifier](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_identifier)  
-> capture-list-item → [capture-specifier](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_capture-specifier)<sub>opt</sub> [identifier](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_identifier) `=` [expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_expression)  
-> capture-list-item → [capture-specifier](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_capture-specifier)<sub>opt</sub> [self-expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_self-expression)  
-> capture-specifier → `weak` \| `unowned` \| `unowned(safe)` \| `unowned(unsafe)`
-
-> GRAMMAR OF A IMPLICIT MEMBER EXPRESSION  
-> implicit-member-expression → `.` [identifier](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_identifier)
-> implicit-member-expression → `.` [identifier](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_identifier) `.` [postfix-expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_postfix-expression)
-
-> GRAMMAR OF A PARENTHESIZED EXPRESSION  
-> parenthesized-expression → `(` [expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_expression) `)`
-
-> GRAMMAR OF A TUPLE EXPRESSION  
-> tuple-expression → `(` `)` \| `(` [tuple-element](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_tuple-element) `,` [tuple-element-list](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_tuple-element-list) `)`  
-> tuple-element-list → [tuple-element](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_tuple-element) \| [tuple-element](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_tuple-element) `,` [tuple-element-list](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_tuple-element-list)  
-> tuple-element → [expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_expression) \| [identifier](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_identifier) `:` [expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_expression)
-
-> GRAMMAR OF A WILDCARD EXPRESSION  
-> wildcard-expression → `_`
-
-> GRAMMAR OF A KEY-PATH EXPRESSION  
-> key-path-expression → `\` [type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type)<sub>opt</sub> `.` [key-path-components](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_key-path-components)  
-> key-path-components → [key-path-component](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_key-path-component) \| [key-path-component](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_key-path-component) `.` [key-path-components](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_key-path-components)  
-> key-path-component → [identifier](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_identifier) [key-path-postfixes](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_key-path-postfixes)<sub>opt</sub> \| [key-path-postfixes](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_key-path-postfixes)  
-> key-path-postfixes → [key-path-postfix](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_key-path-postfix) [key-path-postfixes](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_key-path-postfixes)<sub>opt</sub>  
-> key-path-postfix → `?` \| `!` \| `self` \| `[` [function-call-argument-list](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_function-call-argument-list) `]`
-
-> GRAMMAR OF A SELECTOR EXPRESSION  
-> selector-expression → `#selector` `(` [expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_expression) `)`  
-> selector-expression → `#selector` `(` `getter:` [expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_expression) `)`  
-> selector-expression → `#selector` `(` `setter:` [expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_expression) `)`
-
-> GRAMMAR OF A KEY-PATH STRING EXPRESSION  
-> key-path-string-expression → `#keyPath` `(` [expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_expression) `)`
-
-> GRAMMAR OF A POSTFIX EXPRESSION  
-> postfix-expression → [primary-expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_primary-expression)  
-> postfix-expression → [postfix-expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_postfix-expression) [postfix-operator](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_postfix-operator)  
-> postfix-expression → [function-call-expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_function-call-expression)  
-> postfix-expression → [initializer-expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_initializer-expression)  
-> postfix-expression → [explicit-member-expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_explicit-member-expression)  
-> postfix-expression → [postfix-self-expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_postfix-self-expression)  
-> postfix-expression → [subscript-expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_subscript-expression)  
-> postfix-expression → [forced-value-expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_forced-value-expression)  
-> postfix-expression → [optional-chaining-expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_optional-chaining-expression)
-
-> GRAMMAR OF A FUNCTION CALL EXPRESSION  
-> function-call-expression → [postfix-expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_postfix-expression) [function-call-argument-clause](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_function-call-argument-clause)  
-> function-call-expression → [postfix-expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_postfix-expression) [function-call-argument-clause](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_function-call-argument-clause)<sub>opt</sub> [trailing-closures](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_trailing-closures)  
-> function-call-argument-clause → `(` `)` \| `(` [function-call-argument-list](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_function-call-argument-list) `)`  
-> function-call-argument-list → [function-call-argument](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_function-call-argument) \| [function-call-argument](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_function-call-argument) `,` [function-call-argument-list](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_function-call-argument-list)  
-> function-call-argument → [expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_expression) \| [identifier](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_identifier) `:` [expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_expression)  
-> function-call-argument → [operator](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_operator) \| [identifier](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_identifier) `:` [operator](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_operator)  
-> trailing-closures → [closure-expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_closure-expression) [labeled-trailing-closures](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_labeled-trailing-closures)<sub>opt</sub>  
-> labeled-trailing-closures → [labeled-trailing-closure](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_labeled-trailing-closure) [labeled-trailing-closures](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_labeled-trailing-closures)<sub>opt</sub>  
-> labeled-trailing-closure → [identifier](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_identifier) `:` [closure-expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_closure-expression)
-
-> GRAMMAR OF AN INITIALIZER EXPRESSION  
-> initializer-expression → [postfix-expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_postfix-expression) `.` `init`  
-> initializer-expression → [postfix-expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_postfix-expression) `.` `init` `(` [argument-names](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_argument-names) `)`
-
-> GRAMMAR OF AN EXPLICIT MEMBER EXPRESSION  
-> explicit-member-expression → [postfix-expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_postfix-expression) `.` [decimal-digits](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_decimal-digits)  
-> explicit-member-expression → [postfix-expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_postfix-expression) `.` [identifier](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_identifier) [generic-argument-clause](https://docs.swift.org/swift-book/ReferenceManual/GenericParametersAndArguments.html#grammar_generic-argument-clause)<sub>opt</sub>  
-> explicit-member-expression → [postfix-expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_postfix-expression) `.` [identifier](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_identifier) `(` [argument-names](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_argument-names) `)`  
-> argument-names → [argument-name](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_argument-name) [argument-names](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_argument-names)<sub>opt</sub>  
-> argument-name → [identifier](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_identifier) `:`
-
-> GRAMMAR OF A POSTFIX SELF EXPRESSION  
-> postfix-self-expression → [postfix-expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_postfix-expression) `.` `self`
-
-> GRAMMAR OF A SUBSCRIPT EXPRESSION  
-> subscript-expression → [postfix-expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_postfix-expression) `[` [function-call-argument-list](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_function-call-argument-list) `]`
-
-> GRAMMAR OF A FORCED-VALUE EXPRESSION  
-> forced-value-expression → [postfix-expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_postfix-expression) `!`
-
-> GRAMMAR OF AN OPTIONAL-CHAINING EXPRESSION  
-> optional-chaining-expression → [postfix-expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_postfix-expression) `?`
+> Grammar of a structure declaration:
+>
+> *struct-declaration* → *attributes*_?_ *access-level-modifier*_?_ **`struct`** *struct-name* *generic-parameter-clause*_?_ *type-inheritance-clause*_?_ *generic-where-clause*_?_ *struct-body*
+>
+> *struct-name* → *identifier*
+>
+> *struct-body* → **`{`** *struct-members*_?_ **`}`**
+>
+>
+>
+> *struct-members* → *struct-member* *struct-members*_?_
+>
+> *struct-member* → *declaration* | *compiler-control-statement*
 
-## Statements\(文\)
+> Grammar of a class declaration:
+>
+> *class-declaration* → *attributes*_?_ *access-level-modifier*_?_ **`final`**_?_ **`class`** *class-name* *generic-parameter-clause*_?_ *type-inheritance-clause*_?_ *generic-where-clause*_?_ *class-body*
+>
+> *class-declaration* → *attributes*_?_ **`final`** *access-level-modifier*_?_ **`class`** *class-name* *generic-parameter-clause*_?_ *type-inheritance-clause*_?_ *generic-where-clause*_?_ *class-body*
+>
+> *class-name* → *identifier*
+>
+> *class-body* → **`{`** *class-members*_?_ **`}`**
+>
+>
+>
+> *class-members* → *class-member* *class-members*_?_
+>
+> *class-member* → *declaration* | *compiler-control-statement*
+
+> Grammar of an actor declaration:
+>
+> *actor-declaration* → *attributes*_?_ *access-level-modifier*_?_ **`actor`** *actor-name* *generic-parameter-clause*_?_ *type-inheritance-clause*_?_ *generic-where-clause*_?_ *actor-body*
+>
+> *actor-name* → *identifier*
+>
+> *actor-body* → **`{`** *actor-members*_?_ **`}`**
+>
+>
+>
+> *actor-members* → *actor-member* *actor-members*_?_
+>
+> *actor-member* → *declaration* | *compiler-control-statement*
+
+> Grammar of a protocol declaration:
+>
+> *protocol-declaration* → *attributes*_?_ *access-level-modifier*_?_ **`protocol`** *protocol-name* *type-inheritance-clause*_?_ *generic-where-clause*_?_ *protocol-body*
+>
+> *protocol-name* → *identifier*
+>
+> *protocol-body* → **`{`** *protocol-members*_?_ **`}`**
+>
+>
+>
+> *protocol-members* → *protocol-member* *protocol-members*_?_
+>
+> *protocol-member* → *protocol-member-declaration* | *compiler-control-statement*
+>
+>
+>
+> *protocol-member-declaration* → *protocol-property-declaration*
+>
+> *protocol-member-declaration* → *protocol-method-declaration*
+>
+> *protocol-member-declaration* → *protocol-initializer-declaration*
+>
+> *protocol-member-declaration* → *protocol-subscript-declaration*
+>
+> *protocol-member-declaration* → *protocol-associated-type-declaration*
+>
+> *protocol-member-declaration* → *typealias-declaration*
+
+> Grammar of a protocol property declaration:
+>
+> *protocol-property-declaration* → *variable-declaration-head* *variable-name* *type-annotation* *getter-setter-keyword-block*
+
+> Grammar of a protocol method declaration:
+>
+> *protocol-method-declaration* → *function-head* *function-name* *generic-parameter-clause*_?_ *function-signature* *generic-where-clause*_?_
+
+> Grammar of a protocol initializer declaration:
+>
+> *protocol-initializer-declaration* → *initializer-head* *generic-parameter-clause*_?_ *parameter-clause* **`throws`**_?_ *generic-where-clause*_?_
+>
+> *protocol-initializer-declaration* → *initializer-head* *generic-parameter-clause*_?_ *parameter-clause* **`rethrows`** *generic-where-clause*_?_
 
-> GRAMMAR OF A STATEMENT  
-> statement → [expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_expression) `;`<sub>opt</sub>  
-> statement → [declaration](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_declaration) `;`<sub>opt</sub>  
-> statement → [loop-statement](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_loop-statement) `;`<sub>opt</sub>  
-> statement → [branch-statement](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_branch-statement) `;`<sub>opt</sub>  
-> statement → [labeled-statement](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_labeled-statement) `;`<sub>opt</sub>  
-> statement → [control-transfer-statement](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_control-transfer-statement) `;`<sub>opt</sub>  
-> statement → [defer-statement](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_defer-statement) `;`<sub>opt</sub>  
-> statement → [do-statement](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_do-statement) `;`<sub>opt</sub>  
-> statement → [compiler-control-statement](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_compiler-control-statement)  
-> statements → [statement](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_statement) [statements](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_statements)<sub>opt</sub>
-
-> GRAMMAR OF A LOOP STATEMENT  
-> loop-statement → [for-in-statement](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_for-in-statement)  
-> loop-statement → [while-statement](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_while-statement)  
-> loop-statement → [repeat-while-statement](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_repeat-while-statement)
-
-> GRAMMAR OF A FOR-IN STATEMENT  
-> for-in-statement → `for` `case`<sub>opt</sub> [pattern](https://docs.swift.org/swift-book/ReferenceManual/Patterns.html#grammar_pattern) `in` [expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_expression) [where-clause](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_where-clause)<sub>opt</sub> [code-block](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_code-block)
-
-> GRAMMAR OF A WHILE STATEMENT  
-> while-statement → `while` [condition-list](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_condition-list) [code-block](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_code-block)  
-> condition-list → [condition](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_condition) \| [condition](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_condition) `,` [condition-list](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_condition-list)  
-> condition → [expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_expression) \| [availability-condition](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_availability-condition) \| [case-condition](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_case-condition) \| [optional-binding-condition](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_optional-binding-condition)  
-> case-condition → `case` [pattern](https://docs.swift.org/swift-book/ReferenceManual/Patterns.html#grammar_pattern) [initializer](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_initializer)  
-> optional-binding-condition → `let` [pattern](https://docs.swift.org/swift-book/ReferenceManual/Patterns.html#grammar_pattern) [initializer](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_initializer) \| `var` [pattern](https://docs.swift.org/swift-book/ReferenceManual/Patterns.html#grammar_pattern) [initializer](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_initializer)
-
-> GRAMMAR OF A REPEAT-WHILE STATEMENT  
-> repeat-while-statement → `repeat` [code-block](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_code-block) `while` [expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_expression)
-
-> GRAMMAR OF A BRANCH STATEMENT  
-> branch-statement → [if-statement](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_if-statement)  
-> branch-statement → [guard-statement](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_guard-statement)  
-> branch-statement → [switch-statement](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_switch-statement)
-
-> GRAMMAR OF AN IF STATEMENT  
-> if-statement → `if` [condition-list](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_condition-list) [code-block](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_code-block) [else-clause](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_else-clause)<sub>opt</sub>  
-> else-clause → `else` [code-block](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_code-block) \| `else` [if-statement](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_if-statement)
-
-> GRAMMAR OF A GUARD STATEMENT  
-> guard-statement → `guard` [condition-list](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_condition-list) `else` [code-block](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_code-block)
-
-> GRAMMAR OF A SWITCH STATEMENT  
-> switch-statement → `switch` [expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_expression) `{` [switch-cases](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_switch-cases)<sub>opt</sub> `}`  
-> switch-cases → [switch-case](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_switch-case) [switch-cases](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_switch-cases)<sub>opt</sub>  
-> switch-case → [case-label](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_case-label) [statements](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_statements)  
-> switch-case → [default-label](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_default-label) [statements](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_statements)  
-> switch-case → [conditional-switch-case](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_conditional-switch-case)  
-> case-label → [attributes](https://docs.swift.org/swift-book/ReferenceManual/Attributes.html#grammar_attributes)<sub>opt</sub> `case` [case-item-list](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_case-item-list) `:`  
-> case-item-list → [pattern](https://docs.swift.org/swift-book/ReferenceManual/Patterns.html#grammar_pattern) [where-clause](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_where-clause)<sub>opt</sub> \| [pattern](https://docs.swift.org/swift-book/ReferenceManual/Patterns.html#grammar_pattern) [where-clause](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_where-clause)<sub>opt</sub> `,` [case-item-list](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_case-item-list)  
-> default-label → [attributes](https://docs.swift.org/swift-book/ReferenceManual/Attributes.html#grammar_attributes)<sub>opt</sub> `default` `:`  
-> where-clause → `where` [where-expression](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_where-expression)  
-> where-expression → [expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_expression)  
-> conditional-switch-case → [switch-if-directive-clause](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_switch-if-directive-clause) [switch-elseif-directive-clauses](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_switch-elseif-directive-clauses)<sub>opt</sub> [switch-else-directive-clause](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_switch-else-directive-clause)<sub>opt</sub> [endif-directive](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_endif-directive)  
-> switch-if-directive-clause → [if-directive](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_if-directive) [compilation-condition](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_compilation-condition) [switch-cases](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_switch-cases)<sub>opt</sub>  
-> switch-elseif-directive-clauses → [elseif-directive-clause](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_elseif-directive-clause) [switch-elseif-directive-clauses](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_switch-elseif-directive-clauses)<sub>opt</sub>  
-> switch-elseif-directive-clause → [elseif-directive](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_elseif-directive) [compilation-condition](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_compilation-condition) [switch-cases](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_switch-cases)<sub>opt</sub>  
-> switch-else-directive-clause → [else-directive](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_else-directive) [switch-cases](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_switch-cases)<sub>opt</sub>
-
-> GRAMMAR OF A LABELED STATEMENT  
-> labeled-statement → [statement-label](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_statement-label) [loop-statement](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_loop-statement)  
-> labeled-statement → [statement-label](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_statement-label) [if-statement](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_if-statement)  
-> labeled-statement → [statement-label](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_statement-label) [switch-statement](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_switch-statement)  
-> labeled-statement → [statement-label](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_statement-label) [do-statement](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_do-statement)  
-> statement-label → [label-name](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_label-name) `:`  
-> label-name → [identifier](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_identifier)
-
-> GRAMMAR OF A CONTROL TRANSFER STATEMENT  
-> control-transfer-statement → [break-statement](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_break-statement)  
-> control-transfer-statement → [continue-statement](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_continue-statement)  
-> control-transfer-statement → [fallthrough-statement](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_fallthrough-statement)  
-> control-transfer-statement → [return-statement](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_return-statement)  
-> control-transfer-statement → [throw-statement](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_throw-statement)
-
-> GRAMMAR OF A BREAK STATEMENT  
-> break-statement → `break` [label-name](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_label-name)<sub>opt</sub>
-
-> GRAMMAR OF A CONTINUE STATEMENT  
-> continue-statement → `continue` [label-name](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_label-name)<sub>opt</sub>
-
-> GRAMMAR OF A FALLTHROUGH STATEMENT  
-> fallthrough-statement → `fallthrough`
-
-> GRAMMAR OF A RETURN STATEMENT  
-> return-statement → `return` [expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_expression)<sub>opt</sub>
-
-> GRAMMAR OF A THROW STATEMENT  
-> throw-statement → `throw` [expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_expression)
-
-> GRAMMAR OF A DEFER STATEMENT  
-> defer-statement → `defer` [code-block](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_code-block)
-
-> GRAMMAR OF A DO STATEMENT  
-> do-statement → `do` [code-block](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_code-block) [catch-clauses](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_catch-clauses)<sub>opt</sub>  
-> catch-clauses → [catch-clause](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_catch-clause) [catch-clauses](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_catch-clauses)<sub>opt</sub>  
-> catch-clause → `catch` [catch-pattern-list](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_catch-pattern-list)<sub>opt</sub> [code-block](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_code-block)  
-> catch-pattern-list → [catch-pattern](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_catch-pattern) \| [catch-pattern](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_catch-pattern) `,` [catch-pattern-list](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_catch-pattern-list)  
-> catch-pattern → [pattern](https://docs.swift.org/swift-book/ReferenceManual/Patterns.html#grammar_pattern) [where-clause](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_where-clause)<sub>opt</sub>
-
-> GRAMMAR OF A COMPILER CONTROL STATEMENT  
-> compiler-control-statement → [conditional-compilation-block](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_conditional-compilation-block)  
-> compiler-control-statement → [line-control-statement](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_line-control-statement)  
-> compiler-control-statement → [diagnostic-statement](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_diagnostic-statement)
-
-> GRAMMAR OF A CONDITIONAL COMPILATION BLOCK  
-> conditional-compilation-block → [if-directive-clause](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_if-directive-clause) [elseif-directive-clauses](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_elseif-directive-clauses)<sub>opt</sub> [else-directive-clause](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_else-directive-clause)<sub>opt</sub> [endif-directive](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_endif-directive)  
-> if-directive-clause → [if-directive](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_if-directive) [compilation-condition](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_compilation-condition) [statements](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_statements)<sub>opt</sub>  
-> elseif-directive-clauses → [elseif-directive-clause](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_elseif-directive-clause) [elseif-directive-clauses](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_elseif-directive-clauses)<sub>opt</sub>  
-> elseif-directive-clause → [elseif-directive](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_elseif-directive) [compilation-condition](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_compilation-condition) [statements](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_statements)<sub>opt</sub>  
-> else-directive-clause → [else-directive](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_else-directive) [statements](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_statements)<sub>opt</sub>  
-> if-directive → `#if`  
-> elseif-directive → `#elseif`  
-> else-directive → `#else`  
-> endif-directive → `#endif`  
-> compilation-condition → [platform-condition](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_platform-condition)  
-> compilation-condition → [identifier](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_identifier)  
-> compilation-condition → [boolean-literal](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_boolean-literal)  
-> compilation-condition → `(` [compilation-condition](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_compilation-condition) `)`  
-> compilation-condition → `!` [compilation-condition](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_compilation-condition)  
-> compilation-condition → [compilation-condition](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_compilation-condition) `&&` [compilation-condition](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_compilation-condition)  
-> compilation-condition → [compilation-condition](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_compilation-condition) `||` [compilation-condition](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_compilation-condition)  
-> platform-condition → `os` `(` [operating-system](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_operating-system) `)`  
-> platform-condition → `arch` `(` [architecture](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_architecture) `)`  
-> platform-condition → `swift` `(` `>=` [swift-version](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_swift-version) `)` \| `swift` `(` `<` [swift-version](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_swift-version) `)`  
-> platform-condition → `compiler` `(` `>=` [swift-version](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_swift-version) `)` \| `compiler` `(` `<` [swift-version](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_swift-version) `)`  
-> platform-condition → `canImport` `(` [module-name](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_module-name) `)`  
-> platform-condition → `targetEnvironment` `(` [environment](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_environment) `)`  
-> operating-system → `macOS` \| `iOS` \| `watchOS` \| `tvOS` \| `Linux` \| `Windows`  
-> architecture → `i386` \| `x86_64` \| `arm` \| `arm64`  
-> swift-version → [decimal-digits](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_decimal-digits) [swift-version-continuation](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_swift-version-continuation)<sub>opt</sub>  
-> swift-version-continuation → `.` [decimal-digits](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_decimal-digits) [swift-version-continuation](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_swift-version-continuation)<sub>opt</sub>  
-> module-name → [identifier](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_identifier)  
-> environment → `simulator` \| `macCatalyst`
-
-> GRAMMAR OF A LINE CONTROL STATEMENT  
-> line-control-statement → `#sourceLocation` `(` `file:` [file-path](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_file-path) `,` `line:` [line-number](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_line-number) `)`  
-> line-control-statement → `#sourceLocation` `(` `)`  
-> line-number → 0 以上の 10進整数  
-> file-path → [static-string-literal](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_static-string-literal)
-
-> GRAMMAR OF A COMPILE-TIME DIAGNOSTIC STATEMENT  
-> diagnostic-statement → `#error` `(` [diagnostic-message](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_diagnostic-message) `)`  
-> diagnostic-statement → `#warning` `(` [diagnostic-message](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_diagnostic-message) `)`  
-> diagnostic-message → [static-string-literal](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_static-string-literal)
-
-> GRAMMAR OF AN AVAILABILITY CONDITION  
-> availability-condition → `#available` `(` [availability-arguments](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_availability-arguments) `)`  
-> availability-arguments → [availability-argument](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_availability-argument) \| [availability-argument](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_availability-argument) `,` [availability-arguments](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_availability-arguments)  
-> availability-argument → [platform-name](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_platform-name) [platform-version](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_platform-version)  
-> availability-argument → `*`  
-> platform-name → `iOS` \| `iOSApplicationExtension`  
-> platform-name → `macOS` \| `macOSApplicationExtension`  
-> platform-name → `macCatalyst` \| `macCatalystApplicationExtension`  
-> platform-name → `watchOS`  
-> platform-name → `tvOS`  
-> platform-version → [decimal-digits](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_decimal-digits)  
-> platform-version → [decimal-digits](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_decimal-digits) `.` [decimal-digits](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_decimal-digits)  
-> platform-version → [decimal-digits](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_decimal-digits) `.` [decimal-digits](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_decimal-digits) `.` [decimal-digits](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_decimal-digits)
-
-## Declarations\(宣言\)
-
-> GRAMMAR OF A DECLARATION  
-> declaration → [import-declaration](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_import-declaration)  
-> declaration → [constant-declaration](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_constant-declaration)  
-> declaration → [variable-declaration](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_variable-declaration)  
-> declaration → [typealias-declaration](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_typealias-declaration)  
-> declaration → [function-declaration](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_function-declaration)  
-> declaration → [enum-declaration](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_enum-declaration)  
-> declaration → [struct-declaration](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_struct-declaration)  
-> declaration → [class-declaration](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_class-declaration)  
-> declaration → [protocol-declaration](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_protocol-declaration)  
-> declaration → [initializer-declaration](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_initializer-declaration)  
-> declaration → [deinitializer-declaration](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_deinitializer-declaration)  
-> declaration → [extension-declaration](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_extension-declaration)  
-> declaration → [subscript-declaration](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_subscript-declaration)  
-> declaration → [operator-declaration](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_operator-declaration)  
-> declaration → [precedence-group-declaration](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_precedence-group-declaration)  
-> declarations → [declaration](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_declaration) [declarations](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_declarations)<sub>opt</sub>
-
-> GRAMMAR OF A TOP-LEVEL DECLARATION  
-> top-level-declaration → [statements](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_statements)<sub>opt</sub>
-
-> GRAMMAR OF A CODE BLOCK  
-> code-block → `{` [statements](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_statements)<sub>opt</sub> `}`
-
-> GRAMMAR OF AN IMPORT DECLARATION  
-> import-declaration → [attributes](https://docs.swift.org/swift-book/ReferenceManual/Attributes.html#grammar_attributes)<sub>opt</sub> `import` [import-kind](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_import-kind)<sub>opt</sub> [import-path](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_import-path)  
-> import-kind → `typealias` \| `struct` \| `class` \| `enum` \| `protocol` \| `let` \| `var` \| `func`  
-> import-path → [import-path-identifier](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_import-path-identifier) \| [import-path-identifier](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_import-path-identifier) `.` [import-path](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_import-path)  
-> import-path-identifier → [identifier](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_identifier) \| [operator](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_operator)
-
-> GRAMMAR OF A CONSTANT DECLARATION  
-> constant-declaration → [attributes](https://docs.swift.org/swift-book/ReferenceManual/Attributes.html#grammar_attributes)<sub>opt</sub> [declaration-modifiers](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_declaration-modifiers)<sub>opt</sub> `let` [pattern-initializer-list](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_pattern-initializer-list)  
-> pattern-initializer-list → [pattern-initializer](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_pattern-initializer) \| [pattern-initializer](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_pattern-initializer) `,` [pattern-initializer-list](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_pattern-initializer-list)  
-> pattern-initializer → [pattern](https://docs.swift.org/swift-book/ReferenceManual/Patterns.html#grammar_pattern) [initializer](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_initializer)<sub>opt</sub>  
-> initializer → `=` [expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_expression)
-
-> GRAMMAR OF A VARIABLE DECLARATION  
-> variable-declaration → [variable-declaration-head](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_variable-declaration-head) [pattern-initializer-list](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_pattern-initializer-list)  
-> variable-declaration → [variable-declaration-head](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_variable-declaration-head) [variable-name](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_variable-name) [type-annotation](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type-annotation) [code-block](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_code-block)  
-> variable-declaration → [variable-declaration-head](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_variable-declaration-head) [variable-name](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_variable-name) [type-annotation](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type-annotation) [getter-setter-block](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_getter-setter-block)  
-> variable-declaration → [variable-declaration-head](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_variable-declaration-head) [variable-name](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_variable-name) [type-annotation](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type-annotation) [getter-setter-keyword-block](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_getter-setter-keyword-block)  
-> variable-declaration → [variable-declaration-head](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_variable-declaration-head) [variable-name](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_variable-name) [initializer](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_initializer) [willSet-didSet-block](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_willSet-didSet-block)  
-> variable-declaration → [variable-declaration-head](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_variable-declaration-head) [variable-name](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_variable-name) [type-annotation](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type-annotation) [initializer](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_initializer)<sub>opt</sub> [willSet-didSet-block](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_willSet-didSet-block)  
-> variable-declaration-head → [attributes](https://docs.swift.org/swift-book/ReferenceManual/Attributes.html#grammar_attributes)<sub>opt</sub> [declaration-modifiers](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_declaration-modifiers)<sub>opt</sub> `var`  
-> variable-name → [identifier](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_identifier)  
-> getter-setter-block → [code-block](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_code-block)  
-> getter-setter-block → `{` [getter-clause](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_getter-clause) [setter-clause](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_setter-clause)<sub>opt</sub> `}`  
-> getter-setter-block → `{` [setter-clause](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_setter-clause) [getter-clause](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_getter-clause) `}`  
-> getter-clause → [attributes](https://docs.swift.org/swift-book/ReferenceManual/Attributes.html#grammar_attributes)<sub>opt</sub> [mutation-modifier](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_mutation-modifier)<sub>opt</sub> `get` [code-block](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_code-block)  
-> setter-clause → [attributes](https://docs.swift.org/swift-book/ReferenceManual/Attributes.html#grammar_attributes)<sub>opt</sub> [mutation-modifier](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_mutation-modifier)<sub>opt</sub> `set` [setter-name](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_setter-name)<sub>opt</sub> [code-block](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_code-block)  
-> setter-name → `(` [identifier](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_identifier) `)`  
-> getter-setter-keyword-block → `{` [getter-keyword-clause](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_getter-keyword-clause) [setter-keyword-clause](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_setter-keyword-clause)<sub>opt</sub> `}`  
-> getter-setter-keyword-block → `{` [setter-keyword-clause](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_setter-keyword-clause) [getter-keyword-clause](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_getter-keyword-clause) `}`  
-> getter-keyword-clause → [attributes](https://docs.swift.org/swift-book/ReferenceManual/Attributes.html#grammar_attributes)<sub>opt</sub> [mutation-modifier](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_mutation-modifier)<sub>opt</sub> `get`  
-> setter-keyword-clause → [attributes](https://docs.swift.org/swift-book/ReferenceManual/Attributes.html#grammar_attributes)<sub>opt</sub> [mutation-modifier](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_mutation-modifier)<sub>opt</sub> `set`  
-> willSet-didSet-block → `{` [willSet-clause](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_willSet-clause) [didSet-clause](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_didSet-clause)<sub>opt</sub> `}`  
-> willSet-didSet-block → `{` [didSet-clause](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_didSet-clause) [willSet-clause](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_willSet-clause)<sub>opt</sub> `}`  
-> willSet-clause → [attributes](https://docs.swift.org/swift-book/ReferenceManual/Attributes.html#grammar_attributes)<sub>opt</sub> `willSet` [setter-name](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_setter-name)<sub>opt</sub> [code-block](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_code-block)  
-> didSet-clause → [attributes](https://docs.swift.org/swift-book/ReferenceManual/Attributes.html#grammar_attributes)<sub>opt</sub> `didSet` [setter-name](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_setter-name)<sub>opt</sub> [code-block](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_code-block)
-
-> GRAMMAR OF A TYPE ALIAS DECLARATION  
-> typealias-declaration → [attributes](https://docs.swift.org/swift-book/ReferenceManual/Attributes.html#grammar_attributes)<sub>opt</sub> [access-level-modifier](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_access-level-modifier)<sub>opt</sub> `typealias` [typealias-name](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_typealias-name) [generic-parameter-clause](https://docs.swift.org/swift-book/ReferenceManual/GenericParametersAndArguments.html#grammar_generic-parameter-clause)<sub>opt</sub> [typealias-assignment](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_typealias-assignment)  
-> typealias-name → [identifier](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_identifier)  
-> typealias-assignment → `=` [type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type)
-
-> GRAMMAR OF A FUNCTION DECLARATION  
-> function-declaration → [function-head](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_function-head) [function-name](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_function-name) [generic-parameter-clause](https://docs.swift.org/swift-book/ReferenceManual/GenericParametersAndArguments.html#grammar_generic-parameter-clause)<sub>opt</sub> [function-signature](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_function-signature)[generic-where-clause](https://docs.swift.org/swift-book/ReferenceManual/GenericParametersAndArguments.html#grammar_generic-where-clause)<sub>opt</sub> [function-body](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_function-body)<sub>opt</sub>  
-> function-head → [attributes](https://docs.swift.org/swift-book/ReferenceManual/Attributes.html#grammar_attributes)<sub>opt</sub> [declaration-modifiers](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_declaration-modifiers)<sub>opt</sub> `func`  
-> function-name → [identifier](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_identifier) \| [operator](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_operator)  
-> function-signature → [parameter-clause](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_parameter-clause) `async`<sub>opt</sub> `throws`<sub>opt</sub> [function-result](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_function-result)<sub>opt</sub>  
-> function-signature → [parameter-clause](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_parameter-clause) `async`<sub>opt</sub> `rethrows` [function-result](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_function-result)<sub>opt</sub>  
-> function-result → `->` [attributes](https://docs.swift.org/swift-book/ReferenceManual/Attributes.html#grammar_attributes)<sub>opt</sub> [type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type)  
-> function-body → [code-block](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_code-block)  
-> parameter-clause → `(` `)` \| `(` [parameter-list](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_parameter-list) `)`  
-> parameter-list → [parameter](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_parameter) \| [parameter](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_parameter) `,` [parameter-list](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_parameter-list)  
-> parameter → [external-parameter-name](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_external-parameter-name)<sub>opt</sub> [local-parameter-name](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_local-parameter-name) [type-annotation](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type-annotation) [default-argument-clause](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_default-argument-clause)<sub>opt</sub>  
-> parameter → [external-parameter-name](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_external-parameter-name)<sub>opt</sub> [local-parameter-name](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_local-parameter-name) [type-annotation](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type-annotation)  
-> parameter → [external-parameter-name](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_external-parameter-name)<sub>opt</sub> [local-parameter-name](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_local-parameter-name) [type-annotation](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type-annotation) `...`  
-> external-parameter-name → [identifier](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_identifier)  
-> local-parameter-name → [identifier](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_identifier)  
-> default-argument-clause → `=` [expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_expression)
-
-> GRAMMAR OF AN ENUMERATION DECLARATION  
-> enum-declaration → [attributes](https://docs.swift.org/swift-book/ReferenceManual/Attributes.html#grammar_attributes)<sub>opt</sub> [access-level-modifier](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_access-level-modifier)<sub>opt</sub> [union-style-enum](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_union-style-enum)  
-> enum-declaration → [attributes](https://docs.swift.org/swift-book/ReferenceManual/Attributes.html#grammar_attributes)<sub>opt</sub> [access-level-modifier](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_access-level-modifier)<sub>opt</sub> [raw-value-style-enum](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_raw-value-style-enum)  
-> union-style-enum → `indirect`<sub>opt</sub> `enum` [enum-name](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_enum-name) [generic-parameter-clause](https://docs.swift.org/swift-book/ReferenceManual/GenericParametersAndArguments.html#grammar_generic-parameter-clause)<sub>opt</sub> [type-inheritance-clause](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type-inheritance-clause)<sub>opt</sub> [generic-where-clause](https://docs.swift.org/swift-book/ReferenceManual/GenericParametersAndArguments.html#grammar_generic-where-clause)<sub>opt</sub> `{` [union-style-enum-members](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_union-style-enum-members)<sub>opt</sub> `}`  
-> union-style-enum-members → [union-style-enum-member](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_union-style-enum-member) [union-style-enum-members](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_union-style-enum-members)<sub>opt</sub>  
-> union-style-enum-member → [declaration](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_declaration) \| [union-style-enum-case-clause](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_union-style-enum-case-clause) \| [compiler-control-statement](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_compiler-control-statement)  
-> union-style-enum-case-clause → [attributes](https://docs.swift.org/swift-book/ReferenceManual/Attributes.html#grammar_attributes)<sub>opt</sub> `indirect`<sub>opt</sub> `case` [union-style-enum-case-list](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_union-style-enum-case-list)  
-> union-style-enum-case-list → [union-style-enum-case](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_union-style-enum-case) \| [union-style-enum-case](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_union-style-enum-case) `,` [union-style-enum-case-list](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_union-style-enum-case-list)  
-> union-style-enum-case → [enum-case-name](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_enum-case-name) [tuple-type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_tuple-type)<sub>opt</sub>  
-> enum-name → [identifier](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_identifier)  
-> enum-case-name → [identifier](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_identifier)  
-> raw-value-style-enum → `enum` [enum-name](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_enum-name) [generic-parameter-clause](https://docs.swift.org/swift-book/ReferenceManual/GenericParametersAndArguments.html#grammar_generic-parameter-clause)<sub>opt</sub> [type-inheritance-clause](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type-inheritance-clause)[generic-where-clause](https://docs.swift.org/swift-book/ReferenceManual/GenericParametersAndArguments.html#grammar_generic-where-clause)<sub>opt</sub> `{` [raw-value-style-enum-members](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_raw-value-style-enum-members) `}`  
-> raw-value-style-enum-members → [raw-value-style-enum-member](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_raw-value-style-enum-member) [raw-value-style-enum-members](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_raw-value-style-enum-members)<sub>opt</sub>  
-> raw-value-style-enum-member → [declaration](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_declaration) \| [raw-value-style-enum-case-clause](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_raw-value-style-enum-case-clause) \| [compiler-control-statement](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_compiler-control-statement)  
-> raw-value-style-enum-case-clause → [attributes](https://docs.swift.org/swift-book/ReferenceManual/Attributes.html#grammar_attributes)<sub>opt</sub> `case` [raw-value-style-enum-case-list](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_raw-value-style-enum-case-list)  
-> raw-value-style-enum-case-list → [raw-value-style-enum-case](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_raw-value-style-enum-case) \| [raw-value-style-enum-case](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_raw-value-style-enum-case) `,` [raw-value-style-enum-case-list](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_raw-value-style-enum-case-list)  
-> raw-value-style-enum-case → [enum-case-name](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_enum-case-name) [raw-value-assignment](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_raw-value-assignment)<sub>opt</sub>  
-> raw-value-assignment → `=` [raw-value-literal](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_raw-value-literal)  
-> raw-value-literal → [numeric-literal](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_numeric-literal) \| [static-string-literal](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_static-string-literal) \| [boolean-literal](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_boolean-literal)
-
-> GRAMMAR OF A STRUCTURE DECLARATION  
-> struct-declaration → [attributes](https://docs.swift.org/swift-book/ReferenceManual/Attributes.html#grammar_attributes)<sub>opt</sub> [access-level-modifier](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_access-level-modifier)<sub>opt</sub> `struct` [struct-name](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_struct-name) [generic-parameter-clause](https://docs.swift.org/swift-book/ReferenceManual/GenericParametersAndArguments.html#grammar_generic-parameter-clause)<sub>opt</sub> [type-inheritance-clause](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type-inheritance-clause)<sub>opt</sub> [generic-where-clause](https://docs.swift.org/swift-book/ReferenceManual/GenericParametersAndArguments.html#grammar_generic-where-clause)<sub>opt</sub> [struct-body](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_struct-body)  
-> struct-name → [identifier](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_identifier)  
-> struct-body → `{` [struct-members](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_struct-members)<sub>opt</sub> `}`  
-> struct-members → [struct-member](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_struct-member) [struct-members](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_struct-members)<sub>opt</sub>  
-> struct-member → [declaration](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_declaration) \| [compiler-control-statement](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_compiler-control-statement)
-
-> GRAMMAR OF A CLASS DECLARATION  
-> class-declaration → [attributes](https://docs.swift.org/swift-book/ReferenceManual/Attributes.html#grammar_attributes)<sub>opt</sub> [access-level-modifier](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_access-level-modifier)<sub>opt</sub> `final`<sub>opt</sub> `class` [class-name](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_class-name) [generic-parameter-clause](https://docs.swift.org/swift-book/ReferenceManual/GenericParametersAndArguments.html#grammar_generic-parameter-clause)<sub>opt</sub> [type-inheritance-clause](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type-inheritance-clause)<sub>opt</sub> [generic-where-clause](https://docs.swift.org/swift-book/ReferenceManual/GenericParametersAndArguments.html#grammar_generic-where-clause)<sub>opt</sub> [class-body](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_class-body)  
-> class-declaration → [attributes](https://docs.swift.org/swift-book/ReferenceManual/Attributes.html#grammar_attributes)<sub>opt</sub> `final` [access-level-modifier](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_access-level-modifier)<sub>opt</sub> `class` [class-name](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_class-name) [generic-parameter-clause](https://docs.swift.org/swift-book/ReferenceManual/GenericParametersAndArguments.html#grammar_generic-parameter-clause)<sub>opt</sub> [type-inheritance-clause](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type-inheritance-clause)<sub>opt</sub> [generic-where-clause](https://docs.swift.org/swift-book/ReferenceManual/GenericParametersAndArguments.html#grammar_generic-where-clause)<sub>opt</sub> [class-body](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_class-body)  
-> class-name → [identifier](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_identifier)  
-> class-body → `{` [class-members](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_class-members)<sub>opt</sub> `}`  
-> class-members → [class-member](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_class-member) [class-members](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_class-members)<sub>opt</sub>  
-> class-member → [declaration](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_declaration) \| [compiler-control-statement](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_compiler-control-statement)
-
-> GRAMMAR OF A ACTOR DECLARATION  
-> actor-declaration → [attributes](https://docs.swift.org/swift-book/ReferenceManual/Attributes.html#grammar_attributes)<sub>opt</sub> [access-level-modifier](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_access-level-modifier)<sub>opt</sub> `actor` [struct-name](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_actor-name) [generic-parameter-clause](https://docs.swift.org/swift-book/ReferenceManual/GenericParametersAndArguments.html#grammar_generic-parameter-clause)<sub>opt</sub> [type-inheritance-clause](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type-inheritance-clause)<sub>opt</sub> [generic-where-clause](https://docs.swift.org/swift-book/ReferenceManual/GenericParametersAndArguments.html#grammar_generic-where-clause)<sub>opt</sub> [actor-body](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_actor-body)  
-> actor-name → [identifier](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_identifier)  
-> actor-body → `{` [actor-members](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_actor-members)<sub>opt</sub> `}`  
-> actor-members → [actor-member](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_actor-member) [actor-members](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_actor-members)<sub>opt</sub>  
-> actor-member → [declaration](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_declaration) \| [compiler-control-statement](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_compiler-control-statement)
-
-> GRAMMAR OF A PROTOCOL DECLARATION  
-> protocol-declaration → [attributes](https://docs.swift.org/swift-book/ReferenceManual/Attributes.html#grammar_attributes)<sub>opt</sub> [access-level-modifier](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_access-level-modifier)<sub>opt</sub> `protocol` [protocol-name](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_protocol-name) [type-inheritance-clause](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type-inheritance-clause)<sub>opt</sub> [generic-where-clause](https://docs.swift.org/swift-book/ReferenceManual/GenericParametersAndArguments.html#grammar_generic-where-clause)<sub>opt</sub> [protocol-body](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_protocol-body)  
-> protocol-name → [identifier](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_identifier)  
-> protocol-body → `{` [protocol-members](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_protocol-members)<sub>opt</sub> `}`  
-> protocol-members → [protocol-member](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_protocol-member) [protocol-members](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_protocol-members)<sub>opt</sub>  
-> protocol-member → [protocol-member-declaration](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_protocol-member-declaration) \| [compiler-control-statement](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_compiler-control-statement)  
-> protocol-member-declaration → [protocol-property-declaration](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_protocol-property-declaration)  
-> protocol-member-declaration → [protocol-method-declaration](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_protocol-method-declaration)  
-> protocol-member-declaration → [protocol-initializer-declaration](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_protocol-initializer-declaration)  
-> protocol-member-declaration → [protocol-subscript-declaration](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_protocol-subscript-declaration)  
-> protocol-member-declaration → [protocol-associated-type-declaration](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_protocol-associated-type-declaration)  
-> protocol-member-declaration → [typealias-declaration](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_typealias-declaration)
-
-> GRAMMAR OF A PROTOCOL PROPERTY DECLARATION  
-> protocol-property-declaration → [variable-declaration-head](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_variable-declaration-head) [variable-name](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_variable-name) [type-annotation](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type-annotation) [getter-setter-keyword-block](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_getter-setter-keyword-block)
-
-> GRAMMAR OF A PROTOCOL METHOD DECLARATION  
-> protocol-method-declaration → [function-head](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_function-head) [function-name](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_function-name) [generic-parameter-clause](https://docs.swift.org/swift-book/ReferenceManual/GenericParametersAndArguments.html#grammar_generic-parameter-clause)<sub>opt</sub> [function-signature](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_function-signature) [generic-where-clause](https://docs.swift.org/swift-book/ReferenceManual/GenericParametersAndArguments.html#grammar_generic-where-clause)<sub>opt</sub>
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-> GRAMMAR OF A PROTOCOL INITIALIZER DECLARATION  
-> protocol-initializer-declaration → [initializer-head](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_initializer-head) [generic-parameter-clause](https://docs.swift.org/swift-book/ReferenceManual/GenericParametersAndArguments.html#grammar_generic-parameter-clause)<sub>opt</sub> [parameter-clause](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_parameter-clause) `throws`<sub>opt</sub> [generic-where-clause](https://docs.swift.org/swift-book/ReferenceManual/GenericParametersAndArguments.html#grammar_generic-where-clause)<sub>opt</sub>  
-> protocol-initializer-declaration → [initializer-head](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_initializer-head) [generic-parameter-clause](https://docs.swift.org/swift-book/ReferenceManual/GenericParametersAndArguments.html#grammar_generic-parameter-clause)<sub>opt</sub> [parameter-clause](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_parameter-clause) `rethrows` [generic-where-clause](https://docs.swift.org/swift-book/ReferenceManual/GenericParametersAndArguments.html#grammar_generic-where-clause)<sub>opt</sub>
-
-> GRAMMAR OF A PROTOCOL SUBSCRIPT DECLARATION  
-> protocol-subscript-declaration → [subscript-head](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_subscript-head) [subscript-result](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_subscript-result) [generic-where-clause](https://docs.swift.org/swift-book/ReferenceManual/GenericParametersAndArguments.html#grammar_generic-where-clause)<sub>opt</sub> [getter-setter-keyword-block](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_getter-setter-keyword-block)
-
-> GRAMMAR OF A PROTOCOL ASSOCIATED TYPE DECLARATION  
-> protocol-associated-type-declaration → [attributes](https://docs.swift.org/swift-book/ReferenceManual/Attributes.html#grammar_attributes)<sub>opt</sub> [access-level-modifier](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_access-level-modifier)<sub>opt</sub> `associatedtype`[typealias-name](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_typealias-name) [type-inheritance-clause](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type-inheritance-clause)<sub>opt</sub> [typealias-assignment](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_typealias-assignment)<sub>opt</sub> [generic-where-clause](https://docs.swift.org/swift-book/ReferenceManual/GenericParametersAndArguments.html#grammar_generic-where-clause)<sub>opt</sub>
-
-> GRAMMAR OF AN INITIALIZER DECLARATION  
-> initializer-declaration → [initializer-head](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_initializer-head) [generic-parameter-clause](https://docs.swift.org/swift-book/ReferenceManual/GenericParametersAndArguments.html#grammar_generic-parameter-clause)<sub>opt</sub> [parameter-clause](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_parameter-clause) `throws`<sub>opt</sub> [generic-where-clause](https://docs.swift.org/swift-book/ReferenceManual/GenericParametersAndArguments.html#grammar_generic-where-clause)<sub>opt</sub> [initializer-body](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_initializer-body)  
-> initializer-declaration → [initializer-head](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_initializer-head) [generic-parameter-clause](https://docs.swift.org/swift-book/ReferenceManual/GenericParametersAndArguments.html#grammar_generic-parameter-clause)<sub>opt</sub> [parameter-clause](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_parameter-clause) `rethrows` [generic-where-clause](https://docs.swift.org/swift-book/ReferenceManual/GenericParametersAndArguments.html#grammar_generic-where-clause)<sub>opt</sub> [initializer-body](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_initializer-body)  
-> initializer-head → [attributes](https://docs.swift.org/swift-book/ReferenceManual/Attributes.html#grammar_attributes)<sub>opt</sub> [declaration-modifiers](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_declaration-modifiers)<sub>opt</sub> `init`  
-> initializer-head → [attributes](https://docs.swift.org/swift-book/ReferenceManual/Attributes.html#grammar_attributes)<sub>opt</sub> [declaration-modifiers](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_declaration-modifiers)<sub>opt</sub> `init` `?`  
-> initializer-head → [attributes](https://docs.swift.org/swift-book/ReferenceManual/Attributes.html#grammar_attributes)<sub>opt</sub> [declaration-modifiers](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_declaration-modifiers)<sub>opt</sub> `init` `!`  
-> initializer-body → [code-block](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_code-block)
-
-> GRAMMAR OF A DEINITIALIZER DECLARATION  
-> deinitializer-declaration → [attributes](https://docs.swift.org/swift-book/ReferenceManual/Attributes.html#grammar_attributes)<sub>opt</sub> `deinit` [code-block](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_code-block)
-
-> GRAMMAR OF AN EXTENSION DECLARATION  
-> extension-declaration → [attributes](https://docs.swift.org/swift-book/ReferenceManual/Attributes.html#grammar_attributes)<sub>opt</sub> [access-level-modifier](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_access-level-modifier)<sub>opt</sub> `extension` [type-identifier](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type-identifier) [type-inheritance-clause](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type-inheritance-clause)<sub>opt</sub> [generic-where-clause](https://docs.swift.org/swift-book/ReferenceManual/GenericParametersAndArguments.html#grammar_generic-where-clause)<sub>opt</sub> [extension-body](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_extension-body)  
-> extension-body → `{` [extension-members](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_extension-members)<sub>opt</sub> `}`  
-> extension-members → [extension-member](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_extension-member) [extension-members](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_extension-members)<sub>opt</sub>  
-> extension-member → [declaration](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_declaration) \| [compiler-control-statement](https://docs.swift.org/swift-book/ReferenceManual/Statements.html#grammar_compiler-control-statement)
-
-> GRAMMAR OF A SUBSCRIPT DECLARATION  
-> subscript-declaration → [subscript-head](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_subscript-head) [subscript-result](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_subscript-result) [generic-where-clause](https://docs.swift.org/swift-book/ReferenceManual/GenericParametersAndArguments.html#grammar_generic-where-clause)<sub>opt</sub> [code-block](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_code-block)  
-> subscript-declaration → [subscript-head](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_subscript-head) [subscript-result](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_subscript-result) [generic-where-clause](https://docs.swift.org/swift-book/ReferenceManual/GenericParametersAndArguments.html#grammar_generic-where-clause)<sub>opt</sub> [getter-setter-block](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_getter-setter-block)  
-> subscript-declaration → [subscript-head](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_subscript-head) [subscript-result](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_subscript-result) [generic-where-clause](https://docs.swift.org/swift-book/ReferenceManual/GenericParametersAndArguments.html#grammar_generic-where-clause)<sub>opt</sub> [getter-setter-keyword-block](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_getter-setter-keyword-block)  
-> subscript-head → [attributes](https://docs.swift.org/swift-book/ReferenceManual/Attributes.html#grammar_attributes)<sub>opt</sub> [declaration-modifiers](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_declaration-modifiers)<sub>opt</sub> `subscript` [generic-parameter-clause](https://docs.swift.org/swift-book/ReferenceManual/GenericParametersAndArguments.html#grammar_generic-parameter-clause)<sub>opt</sub> [parameter-clause](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_parameter-clause)  
-> subscript-result → `->` [attributes](https://docs.swift.org/swift-book/ReferenceManual/Attributes.html#grammar_attributes)<sub>opt</sub> [type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type)
-
-> GRAMMAR OF AN OPERATOR DECLARATION  
-> operator-declaration → [prefix-operator-declaration](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_prefix-operator-declaration) \| [postfix-operator-declaration](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_postfix-operator-declaration) \| [infix-operator-declaration](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_infix-operator-declaration)  
-> prefix-operator-declaration → `prefix` `operator` [operator](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_operator)  
-> postfix-operator-declaration → `postfix` `operator` [operator](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_operator)  
-> infix-operator-declaration → `infix` `operator` [operator](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_operator) [infix-operator-group](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_infix-operator-group)<sub>opt</sub>  
-> infix-operator-group → `:` [precedence-group-name](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_precedence-group-name)
-
-> GRAMMAR OF A PRECEDENCE GROUP DECLARATION
-> precedence-group-declaration → `precedencegroup` [precedence-group-name](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_precedence-group-name) `{` [precedence-group-attributes](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_precedence-group-attributes)<sub>opt</sub> `}`  
-> precedence-group-attributes → [precedence-group-attribute](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_precedence-group-attribute) [precedence-group-attributes](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_precedence-group-attributes)<sub>opt</sub>  
-> precedence-group-attribute → [precedence-group-relation](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_precedence-group-relation)  
-> precedence-group-attribute → [precedence-group-assignment](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_precedence-group-assignment)  
-> precedence-group-attribute → [precedence-group-associativity](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_precedence-group-associativity)  
-> precedence-group-relation → `higherThan` `:` [precedence-group-names](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_precedence-group-names)  
-> precedence-group-relation → `lowerThan` `:` [precedence-group-names](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_precedence-group-names)  
-> precedence-group-assignment → `assignment` `:` [boolean-literal](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_boolean-literal)  
-> precedence-group-associativity → `associativity` `:` `left`  
-> precedence-group-associativity → `associativity` `:` `right`  
-> precedence-group-associativity → `associativity` `:` `none`  
-> precedence-group-names → [precedence-group-name](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_precedence-group-name) \| [precedence-group-name](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_precedence-group-name) `,` [precedence-group-names](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_precedence-group-names)  
-> precedence-group-name → [identifier](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_identifier)
-
-> GRAMMAR OF A DECLARATION MODIFIER  
-> declaration-modifier → `class` \| `convenience` \| `dynamic` \| `final` \| `infix` \| `lazy` \| `optional` \| `override` \| `postfix` \| `prefix` \| `required` \| `static` \| `unowned` \| `unowned` `(` `safe` `)` \| `unowned(` `unsafe` `)` \| `weak`  
-> declaration-modifier → [access-level-modifier](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_access-level-modifier)  
-> declaration-modifier → [mutation-modifier](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_mutation-modifier)  
-> declaration-modifiers → [declaration-modifier](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_declaration-modifier) [declaration-modifiers](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_declaration-modifiers)<sub>opt</sub>  
-> access-level-modifier → `private` \| `private` `(` `set` `)`  
-> access-level-modifier → `fileprivate` \| `fileprivate` `(` `set` `)`  
-> access-level-modifier → `internal` \| `internal` `(` `set` `)`  
-> access-level-modifier → `public` \| `public` `(` `set` `)`  
-> access-level-modifier → `open` \| `open` `(` `set` `)`  
-> mutation-modifier → `mutating` \| `nonmutating`  
-> actor-isolation-modifier → `nonisolated`
+> Grammar of a protocol subscript declaration:
+>
+> *protocol-subscript-declaration* → *subscript-head* *subscript-result* *generic-where-clause*_?_ *getter-setter-keyword-block*
+
+> Grammar of a protocol associated type declaration:
+>
+> *protocol-associated-type-declaration* → *attributes*_?_ *access-level-modifier*_?_ **`associatedtype`** *typealias-name* *type-inheritance-clause*_?_ *typealias-assignment*_?_ *generic-where-clause*_?_
+
+> Grammar of an initializer declaration:
+>
+> *initializer-declaration* → *initializer-head* *generic-parameter-clause*_?_ *parameter-clause* **`async`**_?_ **`throws`**_?_ *generic-where-clause*_?_ *initializer-body*
+>
+> *initializer-declaration* → *initializer-head* *generic-parameter-clause*_?_ *parameter-clause* **`async`**_?_ **`rethrows`** *generic-where-clause*_?_ *initializer-body*
+>
+> *initializer-head* → *attributes*_?_ *declaration-modifiers*_?_ **`init`**
+>
+> *initializer-head* → *attributes*_?_ *declaration-modifiers*_?_ **`init`** **`?`**
+>
+> *initializer-head* → *attributes*_?_ *declaration-modifiers*_?_ **`init`** **`!`**
+>
+> *initializer-body* → *code-block*
+
+> Grammar of a deinitializer declaration:
+>
+> *deinitializer-declaration* → *attributes*_?_ **`deinit`** *code-block*
+
+> Grammar of an extension declaration:
+>
+> *extension-declaration* → *attributes*_?_ *access-level-modifier*_?_ **`extension`** *type-identifier* *type-inheritance-clause*_?_ *generic-where-clause*_?_ *extension-body*
+>
+> *extension-body* → **`{`** *extension-members*_?_ **`}`**
+>
+>
+>
+> *extension-members* → *extension-member* *extension-members*_?_
+>
+> *extension-member* → *declaration* | *compiler-control-statement*
+
+> Grammar of a subscript declaration:
+>
+> *subscript-declaration* → *subscript-head* *subscript-result* *generic-where-clause*_?_ *code-block*
+>
+> *subscript-declaration* → *subscript-head* *subscript-result* *generic-where-clause*_?_ *getter-setter-block*
+>
+> *subscript-declaration* → *subscript-head* *subscript-result* *generic-where-clause*_?_ *getter-setter-keyword-block*
+>
+> *subscript-head* → *attributes*_?_ *declaration-modifiers*_?_ **`subscript`** *generic-parameter-clause*_?_ *parameter-clause*
+>
+> *subscript-result* → **`->`** *attributes*_?_ *type*
+
+> Grammar of an operator declaration:
+>
+> *operator-declaration* → *prefix-operator-declaration* | *postfix-operator-declaration* | *infix-operator-declaration*
+>
+>
+>
+> *prefix-operator-declaration* → **`prefix`** **`operator`** *operator*
+>
+> *postfix-operator-declaration* → **`postfix`** **`operator`** *operator*
+>
+> *infix-operator-declaration* → **`infix`** **`operator`** *operator* *infix-operator-group*_?_
+>
+>
+>
+> *infix-operator-group* → **`:`** *precedence-group-name*
+
+> Grammar of a precedence group declaration:
+>
+> *precedence-group-declaration* → **`precedencegroup`** *precedence-group-name* **`{`** *precedence-group-attributes*_?_ **`}`**
+>
+>
+>
+> *precedence-group-attributes* → *precedence-group-attribute* *precedence-group-attributes*_?_
+>
+> *precedence-group-attribute* → *precedence-group-relation*
+>
+> *precedence-group-attribute* → *precedence-group-assignment*
+>
+> *precedence-group-attribute* → *precedence-group-associativity*
+>
+>
+>
+> *precedence-group-relation* → **`higherThan`** **`:`** *precedence-group-names*
+>
+> *precedence-group-relation* → **`lowerThan`** **`:`** *precedence-group-names*
+>
+>
+>
+> *precedence-group-assignment* → **`assignment`** **`:`** *boolean-literal*
+>
+>
+>
+> *precedence-group-associativity* → **`associativity`** **`:`** **`left`**
+>
+> *precedence-group-associativity* → **`associativity`** **`:`** **`right`**
+>
+> *precedence-group-associativity* → **`associativity`** **`:`** **`none`**
+>
+>
+>
+> *precedence-group-names* → *precedence-group-name* | *precedence-group-name* **`,`** *precedence-group-names*
+>
+> *precedence-group-name* → *identifier*
+
+> Grammar of a declaration modifier:
+>
+> *declaration-modifier* → **`class`** | **`convenience`** | **`dynamic`** | **`final`** | **`infix`** | **`lazy`** | **`optional`** | **`override`** | **`postfix`** | **`prefix`** | **`required`** | **`static`** | **`unowned`** | **`unowned`** **`(`** **`safe`** **`)`** | **`unowned`** **`(`** **`unsafe`** **`)`** | **`weak`**
+>
+> *declaration-modifier* → *access-level-modifier*
+>
+> *declaration-modifier* → *mutation-modifier*
+>
+> *declaration-modifier* → *actor-isolation-modifier*
+>
+> *declaration-modifiers* → *declaration-modifier* *declaration-modifiers*_?_
+>
+>
+>
+> *access-level-modifier* → **`private`** | **`private`** **`(`** **`set`** **`)`**
+>
+> *access-level-modifier* → **`fileprivate`** | **`fileprivate`** **`(`** **`set`** **`)`**
+>
+> *access-level-modifier* → **`internal`** | **`internal`** **`(`** **`set`** **`)`**
+>
+> *access-level-modifier* → **`public`** | **`public`** **`(`** **`set`** **`)`**
+>
+> *access-level-modifier* → **`open`** | **`open`** **`(`** **`set`** **`)`**
+>
+>
+>
+> *mutation-modifier* → **`mutating`** | **`nonmutating`**
+>
+>
+>
+> *actor-isolation-modifier* → **`nonisolated`**
 
 ## Attributes\(属性\)
 
-> GRAMMAR OF AN ATTRIBUTE  
-> attribute → `@` [attribute-name](https://docs.swift.org/swift-book/ReferenceManual/Attributes.html#grammar_attribute-name) [attribute-argument-clause](https://docs.swift.org/swift-book/ReferenceManual/Attributes.html#grammar_attribute-argument-clause)<sub>opt</sub>  
-> attribute-name → [identifier](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_identifier)  
-> attribute-argument-clause → `(` [balanced-tokens](https://docs.swift.org/swift-book/ReferenceManual/Attributes.html#grammar_balanced-tokens)<sub>opt</sub> `)`  
-> attributes → [attribute](https://docs.swift.org/swift-book/ReferenceManual/Attributes.html#grammar_attribute) [attributes](https://docs.swift.org/swift-book/ReferenceManual/Attributes.html#grammar_attributes)<sub>opt</sub>  
-> balanced-tokens → [balanced-token](https://docs.swift.org/swift-book/ReferenceManual/Attributes.html#grammar_balanced-token) [balanced-tokens](https://docs.swift.org/swift-book/ReferenceManual/Attributes.html#grammar_balanced-tokens)<sub>opt</sub>  
-> balanced-token → `(` [balanced-tokens](https://docs.swift.org/swift-book/ReferenceManual/Attributes.html#grammar_balanced-tokens)<sub>opt</sub> `)`  
-> balanced-token → `[` [balanced-tokens](https://docs.swift.org/swift-book/ReferenceManual/Attributes.html#grammar_balanced-tokens)<sub>opt</sub> `]`  
-> balanced-token → `{` [balanced-tokens](https://docs.swift.org/swift-book/ReferenceManual/Attributes.html#grammar_balanced-tokens)<sub>opt</sub> `}`  
-> balanced-token → 任意の識別子、キーワード、リテラル、または演算子  
-> balanced-token → `(`, `)`, `[`, `]`, `{`, または `}` を除く任意の句読点
+> Grammar of an attribute:
+>
+> *attribute* → **`@`** *attribute-name* *attribute-argument-clause*_?_
+>
+> *attribute-name* → *identifier*
+>
+> *attribute-argument-clause* → **`(`** *balanced-tokens*_?_ **`)`**
+>
+> *attributes* → *attribute* *attributes*_?_
+>
+>
+>
+> *balanced-tokens* → *balanced-token* *balanced-tokens*_?_
+>
+> *balanced-token* → **`(`** *balanced-tokens*_?_ **`)`**
+>
+> *balanced-token* → **`[`** *balanced-tokens*_?_ **`]`**
+>
+> *balanced-token* → **`{`** *balanced-tokens*_?_ **`}`**
+>
+> *balanced-token* → Any identifier, keyword, literal, または operator
+>
+> *balanced-token* → Any punctuation except  **`(`**,  **`)`**,  **`[`**,  **`]`**,  **`{`**, または  **`}`**
 
 ## Patterns\(パターン\)
 
-> GRAMMAR OF A PATTERN  
-> pattern → [wildcard-pattern](https://docs.swift.org/swift-book/ReferenceManual/Patterns.html#grammar_wildcard-pattern) [type-annotation](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type-annotation)<sub>opt</sub>  
-> pattern → [identifier-pattern](https://docs.swift.org/swift-book/ReferenceManual/Patterns.html#grammar_identifier-pattern) [type-annotation](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type-annotation)<sub>opt</sub>  
-> pattern → [value-binding-pattern](https://docs.swift.org/swift-book/ReferenceManual/Patterns.html#grammar_value-binding-pattern)  
-> pattern → [tuple-pattern](https://docs.swift.org/swift-book/ReferenceManual/Patterns.html#grammar_tuple-pattern) [type-annotation](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type-annotation)<sub>opt</sub>  
-> pattern → [enum-case-pattern](https://docs.swift.org/swift-book/ReferenceManual/Patterns.html#grammar_enum-case-pattern)  
-> pattern → [optional-pattern](https://docs.swift.org/swift-book/ReferenceManual/Patterns.html#grammar_optional-pattern)  
-> pattern → [type-casting-pattern](https://docs.swift.org/swift-book/ReferenceManual/Patterns.html#grammar_type-casting-pattern)  
-> pattern → [expression-pattern](https://docs.swift.org/swift-book/ReferenceManual/Patterns.html#grammar_expression-pattern)
+> Grammar of a pattern:
+>
+> *pattern* → *wildcard-pattern* *type-annotation*_?_
+>
+> *pattern* → *identifier-pattern* *type-annotation*_?_
+>
+> *pattern* → *value-binding-pattern*
+>
+> *pattern* → *tuple-pattern* *type-annotation*_?_
+>
+> *pattern* → *enum-case-pattern*
+>
+> *pattern* → *optional-pattern*
+>
+> *pattern* → *type-casting-pattern*
+>
+> *pattern* → *expression-pattern*
 
-> GRAMMAR OF A WILDCARD PATTERN  
-> wildcard-pattern → `_`
+> Grammar of a wildcard pattern:
+>
+> *wildcard-pattern* → **`_`**
 
-> GRAMMAR OF AN IDENTIFIER PATTERN  
-> identifier-pattern → [identifier](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_identifier)
+> Grammar of an identifier pattern:
+>
+> *identifier-pattern* → *identifier*
 
-> GRAMMAR OF A VALUE-BINDING PATTERN  
-> value-binding-pattern → `var` [pattern](https://docs.swift.org/swift-book/ReferenceManual/Patterns.html#grammar_pattern) \| `let` [pattern](https://docs.swift.org/swift-book/ReferenceManual/Patterns.html#grammar_pattern)
+> Grammar of a value-binding pattern:
+>
+> *value-binding-pattern* → **`var`** *pattern* | **`let`** *pattern*
 
-> GRAMMAR OF A TUPLE PATTERN  
-> tuple-pattern → `(` [tuple-pattern-element-list](https://docs.swift.org/swift-book/ReferenceManual/Patterns.html#grammar_tuple-pattern-element-list)<sub>opt</sub> `)`  
-> tuple-pattern-element-list → [tuple-pattern-element](https://docs.swift.org/swift-book/ReferenceManual/Patterns.html#grammar_tuple-pattern-element) \| [tuple-pattern-element](https://docs.swift.org/swift-book/ReferenceManual/Patterns.html#grammar_tuple-pattern-element) `,` [tuple-pattern-element-list](https://docs.swift.org/swift-book/ReferenceManual/Patterns.html#grammar_tuple-pattern-element-list)  
-> tuple-pattern-element → [pattern](https://docs.swift.org/swift-book/ReferenceManual/Patterns.html#grammar_pattern) \| [identifier](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_identifier) `:` [pattern](https://docs.swift.org/swift-book/ReferenceManual/Patterns.html#grammar_pattern)
+> Grammar of a tuple pattern:
+>
+> *tuple-pattern* → **`(`** *tuple-pattern-element-list*_?_ **`)`**
+>
+> *tuple-pattern-element-list* → *tuple-pattern-element* | *tuple-pattern-element* **`,`** *tuple-pattern-element-list*
+>
+> *tuple-pattern-element* → *pattern* | *identifier* **`:`** *pattern*
 
-> GRAMMAR OF AN ENUMERATION CASE PATTERN  
-> enum-case-pattern → [type-identifier](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type-identifier)<sub>opt</sub> `.` [enum-case-name](https://docs.swift.org/swift-book/ReferenceManual/Declarations.html#grammar_enum-case-name) [tuple-pattern](https://docs.swift.org/swift-book/ReferenceManual/Patterns.html#grammar_tuple-pattern)<sub>opt</sub>
+> Grammar of an enumeration case pattern:
+>
+> *enum-case-pattern* → *type-identifier*_?_ **`.`** *enum-case-name* *tuple-pattern*_?_
 
-> GRAMMAR OF AN OPTIONAL PATTERN  
-> optional-pattern → [identifier-pattern](https://docs.swift.org/swift-book/ReferenceManual/Patterns.html#grammar_identifier-pattern) `?`
+> Grammar of an optional pattern:
+>
+> *optional-pattern* → *identifier-pattern* **`?`**
 
-> GRAMMAR OF A TYPE CASTING PATTERN  
-> type-casting-pattern → [is-pattern](https://docs.swift.org/swift-book/ReferenceManual/Patterns.html#grammar_is-pattern) \| [as-pattern](https://docs.swift.org/swift-book/ReferenceManual/Patterns.html#grammar_as-pattern)  
-> is-pattern → `is` [type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type)  
-> as-pattern → [pattern](https://docs.swift.org/swift-book/ReferenceManual/Patterns.html#grammar_pattern) `as` [type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type)
+> Grammar of a type casting pattern:
+>
+> *type-casting-pattern* → *is-pattern* | *as-pattern*
+>
+> *is-pattern* → **`is`** *type*
+>
+> *as-pattern* → *pattern* **`as`** *type*
 
-> GRAMMAR OF AN EXPRESSION PATTERN  
-> expression-pattern → [expression](https://docs.swift.org/swift-book/ReferenceManual/Expressions.html#grammar_expression)
+> Grammar of an expression pattern:
+>
+> *expression-pattern* → *expression*
 
 ## Generic Parameters and Arguments\(ジェネリックパラメータと引数\)
 
-> GRAMMAR OF A GENERIC PARAMETER CLAUSE  
-> generic-parameter-clause → `<` [generic-parameter-list](https://docs.swift.org/swift-book/ReferenceManual/GenericParametersAndArguments.html#grammar_generic-parameter-list) `>`  
-> generic-parameter-list → [generic-parameter](https://docs.swift.org/swift-book/ReferenceManual/GenericParametersAndArguments.html#grammar_generic-parameter) \| [generic-parameter](https://docs.swift.org/swift-book/ReferenceManual/GenericParametersAndArguments.html#grammar_generic-parameter) `,` [generic-parameter-list](https://docs.swift.org/swift-book/ReferenceManual/GenericParametersAndArguments.html#grammar_generic-parameter-list)  
-> generic-parameter → [type-name](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type-name)  
-> generic-parameter → [type-name](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type-name) `:` [type-identifier](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type-identifier)  
-> generic-parameter → [type-name](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type-name) `:` [protocol-composition-type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_protocol-composition-type)  
-> generic-where-clause → `where` [requirement-list](https://docs.swift.org/swift-book/ReferenceManual/GenericParametersAndArguments.html#grammar_requirement-list)  
-> requirement-list → [requirement](https://docs.swift.org/swift-book/ReferenceManual/GenericParametersAndArguments.html#grammar_requirement) \| [requirement](https://docs.swift.org/swift-book/ReferenceManual/GenericParametersAndArguments.html#grammar_requirement) `,` [requirement-list](https://docs.swift.org/swift-book/ReferenceManual/GenericParametersAndArguments.html#grammar_requirement-list)  
-> requirement → [conformance-requirement](https://docs.swift.org/swift-book/ReferenceManual/GenericParametersAndArguments.html#grammar_conformance-requirement) \| [same-type-requirement](https://docs.swift.org/swift-book/ReferenceManual/GenericParametersAndArguments.html#grammar_same-type-requirement)  
-> conformance-requirement → [type-identifier](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type-identifier) `:` [type-identifier](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type-identifier)  
-> conformance-requirement → [type-identifier](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type-identifier) `:` [protocol-composition-type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_protocol-composition-type)  
-> same-type-requirement → [type-identifier](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type-identifier) `==` [type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type)
-
-> GRAMMAR OF A GENERIC ARGUMENT CLAUSE  
-> generic-argument-clause → `<` [generic-argument-list](https://docs.swift.org/swift-book/ReferenceManual/GenericParametersAndArguments.html#grammar_generic-argument-list) `>`  
-> generic-argument-list → [generic-argument](https://docs.swift.org/swift-book/ReferenceManual/GenericParametersAndArguments.html#grammar_generic-argument) \| [generic-argument](https://docs.swift.org/swift-book/ReferenceManual/GenericParametersAndArguments.html#grammar_generic-argument) `,` [generic-argument-list](https://docs.swift.org/swift-book/ReferenceManual/GenericParametersAndArguments.html#grammar_generic-argument-list)  
-> generic-argument → [type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type)
+> Grammar of a generic parameter clause:
+>
+> *generic-parameter-clause* → **`<`** *generic-parameter-list* **`>`**
+>
+> *generic-parameter-list* → *generic-parameter* | *generic-parameter* **`,`** *generic-parameter-list*
+>
+> *generic-parameter* → *type-name*
+>
+> *generic-parameter* → *type-name* **`:`** *type-identifier*
+>
+> *generic-parameter* → *type-name* **`:`** *protocol-composition-type*
+>
+>
+>
+> *generic-where-clause* → **`where`** *requirement-list*
+>
+> *requirement-list* → *requirement* | *requirement* **`,`** *requirement-list*
+>
+> *requirement* → *conformance-requirement* | *same-type-requirement*
+>
+>
+>
+> *conformance-requirement* → *type-identifier* **`:`** *type-identifier*
+>
+> *conformance-requirement* → *type-identifier* **`:`** *protocol-composition-type*
+>
+> *same-type-requirement* → *type-identifier* **`==`** *type*
 
+> Grammar of a generic argument clause:
+>
+> *generic-argument-clause* → **`<`** *generic-argument-list* **`>`**
+>
+> *generic-argument-list* → *generic-argument* | *generic-argument* **`,`** *generic-argument-list*
+>
+> *generic-argument* → *type*
\ No newline at end of file
diff --git a/language-reference/types.md b/language-reference/types.md
index d102f3ec..6cc82da5 100644
--- a/language-reference/types.md
+++ b/language-reference/types.md
@@ -1,6 +1,6 @@
 # 型\(Types\)
 
-最終更新日: 2023/1/15  
+最終更新日: 2023/5/28  
 原文: https://docs.swift.org/swift-book/ReferenceManual/Types.html
 
 組み込みの名前付き型と複合型を使用します。
@@ -15,20 +15,35 @@ Swift では、_名前付き型_\(_named type_\)と_複合型_\(_compound type_\
 
 この章では、Swift 言語自体で定義されている型について説明し、Swift の型推論の動作について説明します。
 
-> GRAMMAR OF A TYPE  
-> type → [function-type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_function-type)  
-> type → [array-type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_array-type)  
-> type → [dictionary-type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_dictionary-type)  
-> type → [type-identifier](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type-identifier)  
-> type → [tuple-type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_tuple-type)  
-> type → [optional-type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_optional-type)  
-> type → [implicitly-unwrapped-optional-type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_implicitly-unwrapped-optional-type)  
-> type → [protocol-composition-type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_protocol-composition-type)  
-> type → [opaque-type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_opaque-type)  
-> type → [metatype-type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_metatype-type)  
-> type → [any-type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_any-type)  
-> type → [self-type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_self-type)  
-> type → `(` [type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type) `)`
+> Grammar of a type:
+>
+> *type* → *function-type*
+>
+> *type* → *array-type*
+>
+> *type* → *dictionary-type*
+>
+> *type* → *type-identifier*
+>
+> *type* → *tuple-type*
+>
+> *type* → *optional-type*
+>
+> *type* → *implicitly-unwrapped-optional-type*
+>
+> *type* → *protocol-composition-type*
+>
+> *type* → *boxed-protocol-type*
+>
+> *type* → *opaque-type*
+>
+> *type* → *metatype-type*
+>
+> *type* → *any-type*
+>
+> *type* → *self-type*
+>
+> *type* → **`(`** *type* **`)`**
 
 ## 型注釈\(Type Annotation\)
 
@@ -43,8 +58,9 @@ func someFunction(a: Int) { /* ... */ }
 
 型注釈は、型の前に型属性の任意のリストを含めることができます。
 
-> GRAMMAR OF A TYPE ANNOTATION  
-> type-annotation → `:` [attributes](https://docs.swift.org/swift-book/ReferenceManual/Attributes.html#grammar_attributes)<sub>opt</sub> **inout**<sub>opt</sub> [type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type)
+> Grammar of a type annotation:
+>
+> *type-annotation* → **`:`** *attributes*_?_ **`inout`**_?_ *type*
 
 ## 型識別子\(Type Identifier\)
 
@@ -65,9 +81,11 @@ let origin: PoInt = (0, 0)
 var someValue: ExampleModule.MyType
 ```
 
-> GRAMMAR OF A TYPE IDENTIFIER  
-> type-identifier → [type-name](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type-name) [generic-argument-clause](https://docs.swift.org/swift-book/ReferenceManual/GenericParametersAndArguments.html#grammar_generic-argument-clause)<sub>opt</sub> \| [type-name](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type-name) [generic-argument-clause](https://docs.swift.org/swift-book/ReferenceManual/GenericParametersAndArguments.html#grammar_generic-argument-clause)<sub>opt</sub> `.`[type-identifier](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type-identifier)  
-> type-name → [identifier](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_identifier)
+> Grammar of a type identifier:
+>
+> *type-identifier* → *type-name* *generic-argument-clause*_?_ | *type-name* *generic-argument-clause*_?_ **`.`** *type-identifier*
+>
+> *type-name* → *identifier*
 
 ## タプル型\(Tuple Type\)
 
@@ -86,17 +104,23 @@ someTuple = (left: 5, right: 5)  // Error: 名前が一致していません
 
 全てのタプル型には、空のタプル型 `()` のタイプエイリアスの `Void` を除いて、2 つ以上の型が含まれています。
 
-> GRAMMAR OF A TUPLE TYPE  
-> tuple-type → `(` `)` \| `(` [tuple-type-element](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_tuple-type-element) `,` [tuple-type-element-list](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_tuple-type-element-list) `)`  
-> tuple-type-element-list → [tuple-type-element](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_tuple-type-element) \| [tuple-type-element](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_tuple-type-element) `,` [tuple-type-element-list](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_tuple-type-element-list)  
-> tuple-type-element → [element-name](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_element-name) [type-annotation](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type-annotation) \| [type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type)  
-> element-name → [identifier](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_identifier)
+> Grammar of a tuple type:
+>
+> *tuple-type* → **`(`** **`)`** | **`(`** *tuple-type-element* **`,`** *tuple-type-element-list* **`)`**
+>
+> *tuple-type-element-list* → *tuple-type-element* | *tuple-type-element* **`,`** *tuple-type-element-list*
+>
+> *tuple-type-element* → *element-name* *type-annotation* | *type*
+>
+> *element-name* → *identifier*
 
 ## <a id="types-function-type">関数型\(Function Type\)</a>
 
 _関数型_は関数、メソッド、またはクロージャの型を表し、パラメータと矢印で区切られた戻り値の型で構成されています\(`->`\)。
 
-![Function Type\(&#x95A2;&#x6570;&#x578B;\)](../assets/function_type.png)
+```swift
+(<#parameter type#>) -> <#return type#>
+```
 
 _パラメータ型_は、型のカンマ\(`,`\)区切りのリストです。関数型は、_戻り値の型_がタプル型の可能性があるため、複数の値を返す関数とメソッドをサポートします。
 
@@ -164,19 +188,31 @@ func takesTwoFunctions(first: (() -> Void) -> Void, second: (() -> Void) -> Void
 
 この制限を回避する必要がある場合は、いずれかのパラメータを `@esescaping` とマークしたり、パラメータの非エスケープ関数の 1 つを `withoutActuallyEscaping(_:do:)` を使ってエスケープ関数に一時的に変換します。メモリへのアクセス競合を回避する方法については、[Memory Safety\(メモリ安全性\)](../language-guide/memory-safety.md)を参照ください。
 
-> GRAMMAR OF A FUNCTION TYPE  
-> function-type → [attributes](https://docs.swift.org/swift-book/ReferenceManual/Attributes.html#grammar_attributes)<sub>opt</sub> [function-type-argument-clause](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_function-type-argument-clause) `throws`<sub>opt</sub> `->` [type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type)  
-> function-type-argument-clause → `(` `)`  
-> function-type-argument-clause → `(` [function-type-argument-list](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_function-type-argument-list) `...`<sub>opt</sub> `)`  
-> function-type-argument-list → [function-type-argument](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_function-type-argument) \| [function-type-argument](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_function-type-argument) `,` [function-type-argument-list](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_function-type-argument-list)  
-> function-type-argument → [attributes](https://docs.swift.org/swift-book/ReferenceManual/Attributes.html#grammar_attributes)<sub>opt</sub> `inout`<sub>opt</sub> [type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type) \| [argument-label](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_argument-label) [type-annotation](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type-annotation)  
-> argument-label → [identifier](https://docs.swift.org/swift-book/ReferenceManual/LexicalStructure.html#grammar_identifier)
+> Grammar of a function type:
+>
+> *function-type* → *attributes*_?_ *function-type-argument-clause* **`async`**_?_ **`throws`**_?_ **`->`** *type*
+>
+>
+>
+> *function-type-argument-clause* → **`(`** **`)`**
+>
+> *function-type-argument-clause* → **`(`** *function-type-argument-list* **`...`**_?_ **`)`**
+>
+>
+>
+> *function-type-argument-list* → *function-type-argument* | *function-type-argument* **`,`** *function-type-argument-list*
+>
+> *function-type-argument* → *attributes*_?_ **`inout`**_?_ *type* | *argument-label* *type-annotation*
+>
+> *argument-label* → *identifier*
 
 ## 配列型\(Array Type\)
 
 Swift は、標準ライブラリで定義されている `Array<Element>` の次の糖衣構文\(シンタックスシュガー\)を提供しています。
 
-![&#x914D;&#x5217;&#x578B;&#x306E;&#x7CD6;&#x8863;&#x69CB;&#x6587;](../assets/array_type.png)
+```swift
+[<#type#>]
+```
 
 つまり、次の 2 つの宣言は同等です:
 
@@ -197,14 +233,17 @@ var array3D: [[[Int]]] = [[[1, 2], [3, 4]], [[5, 6], [7, 8]]]
 
 Swift 標準ライブラリの配列型の詳細については、[Arrays\(配列\)](../language-guide/collection-types.md#arrays)を参照ください。
 
-> GRAMMAR OF AN ARRAY TYPE  
-> array-type → `[` [type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type) `]`
+> Grammar of an array type:
+>
+> *array-type* → **`[`** *type* **`]`**
 
 ## 辞書型\(Dictionary Type\)
 
 Swift は、標準ライブラリで定義されている `Dictionary<Key, Value>` 型に次の糖衣構文\(シンタックスシュガー\)を提供しています。
 
-![&#x8F9E;&#x66F8;](../assets/dictionary_type.png)
+```swift
+[<#key type#>: <#value type#>]
+```
 
 つまり、次の 2 つの宣言は同等です:
 
@@ -221,8 +260,9 @@ let someDictionary: Dictionary<String, Int> = ["Alex": 31, "Paul": 39]
 
 標準ライブラリ `Dictionary` 型の詳細については、[Dictionaries\(辞書\)](../language-guide/collection-types.md#dictionaries)を参照ください。
 
-> GRAMMAR OF A DICTIONARY TYPE  
-> dictionary-type → `[` [type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type) `:` [type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type) `]`
+> Grammar of a dictionary type:
+>
+> *dictionary-type* → **`[`** *type* **`:`** *type* **`]`**
 
 ## オプショナル型\(Optional Type\)
 
@@ -250,8 +290,9 @@ optionalInteger! // 42
 
 オプショナル型の使用方法を示す例を示した詳細については、[Optionals\(オプショナル\)](../language-guide/the-basics.md#optionals)を参照ください。
 
-> GRAMMAR OF AN OPTIONAL TYPE  
-> optional-type → [type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type) `?`
+> Grammar of an optional type:
+>
+> *optional-type* → *type* **`?`**
 
 ## 暗黙アンラップオプショナル型\(Implicitly Unwrapped Optional Type\)
 
@@ -282,8 +323,9 @@ let implicitlyUnwrappedArray: [Int]!                  // OK
 
 暗黙アンラップオプショナル型の詳細については、[Implicitly Unwrapped Optionals\(暗黙アンラップオプショナル\)](../language-guide/the-basics.md#implicitly-unwrapped-optionals)を参照ください。
 
-> GRAMMAR OF AN IMPLICITLY UNWRAPPED OPTIONAL TYPE  
-> implicitly-unwrapped-optional-type → [type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type) `!`
+> Grammar of an implicitly unwrapped optional type:
+>
+> *implicitly-unwrapped-optional-type* → *type* **`!`**
 
 ## <a id="protocol-composition-type">プロトコル合成型\(Protocol Composition Type\)</a>
 
@@ -291,7 +333,9 @@ let implicitlyUnwrappedArray: [Int]!                  // OK
 
 プロトコル合成型の形式は次のとおりです:
 
-![&#x30D7;&#x30ED;&#x30C8;&#x30B3;&#x30EB;&#x5408;&#x6210;&#x578B;](../assets/protocol_compose_type.png)
+```swift
+<#Protocol 1#> & <#Protocol 2#>
+```
 
 プロトコル合成型を使用すると、型に準拠した各プロトコルを継承した新しい名前のプロトコルを明示的に定義することなく、型が複数のプロトコルの要件に準拠することを指定できます。例えば、`ProtocolA` と `ProtocolB` と `ProtocolC` を継承する新しいプロトコルを宣言する代わりに、プロトコル合成型の `ProtocolA & ProtocolB & ProtocolC` を使用できます。同様に、`SuperClass` のサブクラスと `ProtocolA` に準拠した新しいプロトコルを宣言する代わりに `SuperClass & ProtocolA` を使用することができ、`ProtocolA` に準拠できます。
 
@@ -308,9 +352,11 @@ typealias PQ = P & Q
 typealias PQR = PQ & Q & R
 ```
 
-> GRAMMAR OF A PROTOCOL COMPOSITION TYPE  
-> protocol-composition-type → [type-identifier](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type-identifier) `&` [protocol-composition-continuation](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_protocol-composition-continuation)  
-> protocol-composition-continuation → [type-identifier](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type-identifier) \| [protocol-composition-type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_protocol-composition-type)
+> Grammar of a protocol composition type:
+>
+> *protocol-composition-type* → *type-identifier* **`&`** *protocol-composition-continuation*
+>
+> *protocol-composition-continuation* → *type-identifier* | *protocol-composition-type*
 
 ## Opaque 型\(Opaque Type\)
 
@@ -320,16 +366,40 @@ Opaque 型は、関数または `subscript` の戻り値の型、またはプロ
 
 Opaque 型の形式は次のとおりです:
 
-![Opaque &#x578B;](../assets/opaque_type.png)
+```swift
+some <#constraint#>
+```
 
 _constraint_ に入るのは、クラス型、プロトコル型、プロトコル合成型、または `Any` 型です。値としては、リスト内のプロトコルまたはプロトコル合成に準拠した型、またはリスト内のクラスを継承した型のインスタンスのみ使用できます。Opaque 型の値とやり取りするコードは、_constraint_ に定義された型のインターフェイスを通してのみ使用できます。
 
+コンパイル時に、Opaque 型の値は特定の具象型を持っています。そして、Swift は、最適化のためにその基礎となる型を使用することができます。しかし、利用時には、Opaque 型は、その基礎となる型に関する情報との間に超えることができない境界を形成します。
+
 プロトコルの宣言には Opaque 型を含めることはできません。また、クラスは、`final` ではないメソッドの戻り値の型として Opaque 型を使用することはできません。
 
 戻り値の型として Opaque 型を使用する関数は、単一の型の値を返す必要があります。戻り値の型には、関数のジェネリックな型パラメータの一部を含めることができます。例えば、`someFunction<T>()` は `T` 型または `Dictionary<String, T>` 型の値を返すことができます。
 
-> GRAMMAR OF AN OPAQUE TYPE  
-> opaque-type → `some` [type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type)
+> Grammar of an opaque type:
+>
+> *opaque-type* → **`some`** *type*
+
+## Box プロトコル型\(Boxed Protocol Type\)
+
+*Box プロトコル型*は、プロトコルまたはプロトコル合成に準拠する型を定義し、その準拠する型がプログラムの実行中に動的に変わる能力を持ちます。
+
+Box プロトコル型の形式は次のとおりです:
+
+```swift
+any <#constraint#>
+```
+
+*制約*は、プロトコル型、プロトコル合成型、プロトコル型のメタタイプ、またはプロトコル合成型のメタタイプです。
+
+実行時に、Box プロトコル型のインスタンスは、制約を満たす任意の型の値を含むことができます。この動作は、コンパイル時に既知の特定の準拠型が存在する Opaque 型の動作とは対照的です。Box プロトコル型を扱う際に使用される追加の間接層は、`boxing` と呼ばれます。`boxing` は通常、ストレージのための別のメモリ割り当てと、アクセスのための追加の間接層を必要とし、実行時にパフォーマンスコストを発生させます。
+`Any` 型や `AnyObject` 型に `any` を適用しても、これらの型はすでに Box プロトコル型であるため、何の効果もありません。
+
+> Grammar of a boxed protocol type:
+>
+> *boxed-protocol-type* → **`any`** *type*
 
 ## <a id="metatype-type">Metatype 型\(Metatype Type\)</a>
 
@@ -375,8 +445,9 @@ let metatype: AnotherSubClass.Type = AnotherSubClass.self
 let anotherInstance = metatype.init(string: "some string")
 ```
 
-> GRAMMAR OF A METATYPE TYPE  
-> metatype-type → [type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type) `.` `Type` \| [type](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type) `.` `Protocol`
+> Grammar of a metatype type:
+>
+> *metatype-type* → *type* **`.`** **`Type`** | *type* **`.`** **`Protocol`**
 
 ## <a id="any-type">Any 型\(Any Type\)</a>
 
@@ -404,8 +475,9 @@ if let first = mixed.first as? String {
 
 `AnyObject` プロトコルは `Any` 型と似ています。全てのクラスは暗黙的に `AnyObject` に準拠しています。言語によって定義されているものとは異なり、`AnyObject` は標準ライブラリで定義されています。詳細については、[Class-Only Protocols\(クラス専用プロトコル\)](../language-guide/protocols.md#class-only-protocols)と [AnyObject](https://developer.apple.com/documentation/swift/anyobject)を参照ください。
 
-> GRAMMAR OF AN ANY TYPE  
-> any-type → `Any`
+> Grammar of an Any type:
+>
+> *any-type* → **`Any`**
 
 ## <a id="self-type">Self 型\(Self Type\)</a>
 
@@ -446,8 +518,9 @@ prInt(type(of: z.f()))
 
 `Self` 型は、標準ライブラリ[type\(of:\)](https://developer.apple.com/documentation/swift/2885064-type)関数と同じ型を指します。現在の型のメンバにアクセスするめに `Self.SomeStaticMember` を書くことは、`type(of: self).someStaticMember` を書くのと同じです。
 
-> GRAMMAR OF A SELF TYPE  
-> self-type → `Self`
+> Grammar of a Self type:
+>
+> *self-type* → **`Self`**
 
 ## 型継承句\(Type Inheritance Clause\)
 
@@ -459,9 +532,11 @@ _型継承句_は、名前付き型がどのクラスを継承しているか、
 
 列挙型の型継承句は、プロトコルのリスト、または列挙ケースに Raw Value を割り当てる場合は、それらの Raw Value の型を特定する単一の名前付き型を継承することができます。型継承句を使用して Raw Value 型を指定する列挙型の定義の例については、[Raw Values](../language-guide/enumerations.md#raw-values)を参照ください。
 
-> GRAMMAR OF A TYPE INHERITANCE CLAUSE  
-> type-inheritance-clause → `:` [type-inheritance-list](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type-inheritance-list)  
-> type-inheritance-list → [type-identifier](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type-identifier) \| [type-identifier](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type-identifier) `,` [type-inheritance-list](https://docs.swift.org/swift-book/ReferenceManual/Types.html#grammar_type-inheritance-list)
+> Grammar of a type inheritance clause:
+>
+> *type-inheritance-clause* → **`:`** *type-inheritance-list*
+>
+> *type-inheritance-list* → *attributes*_?_ *type-identifier* | *attributes*_?_ *type-identifier* **`,`** *type-inheritance-list*
 
 ## <a id="type-inference">型推論\(Type Inference\)</a>
 
diff --git a/welcome-to-swift/a-swift-tour.md b/welcome-to-swift/a-swift-tour.md
index 24225c54..63a5bdd2 100644
--- a/welcome-to-swift/a-swift-tour.md
+++ b/welcome-to-swift/a-swift-tour.md
@@ -738,10 +738,10 @@ print(7.simpleDescription)
 > Experiment  
 > `absoluteValue` プロパティを `Double` に追加する `extension` を書いてみましょう。
 
-プロトコルの名前は、他の名前が付いた型と同じように使用することができます。例えば、同じ 1 つのプロトコルに準拠した異なる型のオブジェクトのコレクションを作成することができます。プロトコル型の値をそのまま扱っている場合、プロトコルの外側で定義されたメソッドを使用することはできません。
+プロトコルの名前は、他の名前が付いた型と同じように使用することができます。例えば、同じ 1 つのプロトコルに準拠した異なる型のオブジェクトのコレクションを作成することができます。Box プロトコル型の値をそのまま扱っている場合、プロトコルの外側で定義されたメソッドを使用することはできません。
 
 ```swift
-let protocolValue: ExampleProtocol = a
+let protocolValue: any ExampleProtocol = a
 print(protocolValue.simpleDescription)
 // A very simple class.  Now 100% adjusted. が出力されます。
 // print(protocolValue.anotherProperty)  // エラーを確認したい場合はコメントアウトを外しましょう