Reuse type nodes from optional parameters even when not written as a union with undefined (#48605)

* Reuse type nodes from optional parameters and properties even when not written as a union with `undefined`

* Remove newly unneeded NodeBuilderFlag

* Update public API

* Update baselines from main

Author: andrewbranch

src/compiler/checker.ts

@@ -5915,9 +5915,6 @@ namespace ts {
                 if (parameterDeclaration && isRequiredInitializedParameter(parameterDeclaration)) {
                     parameterType = getOptionalType(parameterType);
                 }
-                if ((context.flags & NodeBuilderFlags.NoUndefinedOptionalParameterType) && parameterDeclaration && !isJSDocParameterTag(parameterDeclaration) && isOptionalUninitializedParameter(parameterDeclaration)) {
-                    parameterType = getTypeWithFacts(parameterType, TypeFacts.NEUndefined);
-                }
                 const parameterTypeNode = serializeTypeForDeclaration(context, parameterType, parameterSymbol, context.enclosingDeclaration, privateSymbolVisitor, bundledImports);
 
                 const modifiers = !(context.flags & NodeBuilderFlags.OmitParameterModifiers) && preserveModifierFlags && parameterDeclaration && parameterDeclaration.modifiers ? parameterDeclaration.modifiers.map(factory.cloneNode) : undefined;
@@ -6544,7 +6541,7 @@ namespace ts {
                     if (declWithExistingAnnotation && !isFunctionLikeDeclaration(declWithExistingAnnotation) && !isGetAccessorDeclaration(declWithExistingAnnotation)) {
                         // try to reuse the existing annotation
                         const existing = getEffectiveTypeAnnotationNode(declWithExistingAnnotation)!;
-                        if (getTypeFromTypeNode(existing) === type && existingTypeNodeIsNotReferenceOrIsReferenceWithCompatibleTypeArgumentCount(existing, type)) {
+                        if (typeNodeIsEquivalentToType(existing, declWithExistingAnnotation, type) && existingTypeNodeIsNotReferenceOrIsReferenceWithCompatibleTypeArgumentCount(existing, type)) {
                             const result = serializeExistingTypeNode(context, existing, includePrivateSymbol, bundled);
                             if (result) {
                                 return result;
@@ -6562,6 +6559,17 @@ namespace ts {
                 return result;
             }
 
+            function typeNodeIsEquivalentToType(typeNode: TypeNode, annotatedDeclaration: Declaration, type: Type) {
+                const typeFromTypeNode = getTypeFromTypeNode(typeNode);
+                if (typeFromTypeNode === type) {
+                    return true;
+                }
+                if (isParameter(annotatedDeclaration) && annotatedDeclaration.questionToken) {
+                    return getTypeWithFacts(type, TypeFacts.NEUndefined) === typeFromTypeNode;
+                }
+                return false;
+            }
+
             function serializeReturnTypeForSignature(context: NodeBuilderContext, type: Type, signature: Signature, includePrivateSymbol?: (s: Symbol) => void, bundled?: boolean) {
                 if (!isErrorType(type) && context.enclosingDeclaration) {
                     const annotation = signature.declaration && getEffectiveReturnTypeNode(signature.declaration);
@@ -42579,12 +42587,6 @@ namespace ts {
                 hasSyntacticModifier(parameter, ModifierFlags.ParameterPropertyModifier);
         }
 
-        function isOptionalUninitializedParameter(parameter: ParameterDeclaration) {
-            return !!strictNullChecks &&
-                isOptionalParameter(parameter) &&
-                !parameter.initializer;
-        }
-
         function isExpandoFunctionDeclaration(node: Declaration): boolean {
             const declaration = getParseTreeNode(node, isFunctionDeclaration);
             if (!declaration) {

src/compiler/types.ts

@@ -4490,7 +4490,6 @@ namespace ts {
         UseAliasDefinedOutsideCurrentScope      = 1 << 14,  // Allow non-visible aliases
         UseSingleQuotesForStringLiteralType     = 1 << 28,  // Use single quotes for string literal type
         NoTypeReduction                         = 1 << 29,  // Don't call getReducedType
-        NoUndefinedOptionalParameterType        = 1 << 30,  // Do not add undefined to optional parameter type
 
         // Error handling
         AllowThisInObjectLiteral                = 1 << 15,

src/compiler/utilities.ts

@@ -7654,4 +7654,8 @@ namespace ts {
 
         return state > States.NodeModules ? { topLevelNodeModulesIndex, topLevelPackageNameIndex, packageRootIndex, fileNameIndex } : undefined;
     }
+
+    export function getParameterTypeNode(parameter: ParameterDeclaration | JSDocParameterTag) {
+        return parameter.kind === SyntaxKind.JSDocParameterTag ? parameter.typeExpression?.type : parameter.type;
+    }
 }

src/services/codefixes/helpers.ts

@@ -194,7 +194,6 @@ namespace ts.codefix {
         const scriptTarget = getEmitScriptTarget(program.getCompilerOptions());
         const flags =
             NodeBuilderFlags.NoTruncation
-            | NodeBuilderFlags.NoUndefinedOptionalParameterType
             | NodeBuilderFlags.SuppressAnyReturnType
             | NodeBuilderFlags.AllowEmptyTuple
             | (quotePreference === QuotePreference.Single ? NodeBuilderFlags.UseSingleQuotesForStringLiteralType : NodeBuilderFlags.None);

tests/baselines/reference/api/tsserverlibrary.d.ts

@@ -2394,7 +2394,6 @@ declare namespace ts {
         UseAliasDefinedOutsideCurrentScope = 16384,
         UseSingleQuotesForStringLiteralType = 268435456,
         NoTypeReduction = 536870912,
-        NoUndefinedOptionalParameterType = 1073741824,
         AllowThisInObjectLiteral = 32768,
         AllowQualifiedNameInPlaceOfIdentifier = 65536,
         /** @deprecated AllowQualifedNameInPlaceOfIdentifier. Use AllowQualifiedNameInPlaceOfIdentifier instead. */

tests/baselines/reference/api/typescript.d.ts

@@ -2394,7 +2394,6 @@ declare namespace ts {
         UseAliasDefinedOutsideCurrentScope = 16384,
         UseSingleQuotesForStringLiteralType = 268435456,
         NoTypeReduction = 536870912,
-        NoUndefinedOptionalParameterType = 1073741824,
         AllowThisInObjectLiteral = 32768,
         AllowQualifiedNameInPlaceOfIdentifier = 65536,
         /** @deprecated AllowQualifedNameInPlaceOfIdentifier. Use AllowQualifiedNameInPlaceOfIdentifier instead. */

tests/baselines/reference/arrayFakeFlatNoCrashInferenceDeclarations.types

@@ -19,7 +19,7 @@ type BadFlatArray<Arr, Depth extends number> = {obj: {
 >1 : 1
 
 declare function flat<A, D extends number = 1>(
->flat : <A, D extends number = 1>(arr: A, depth?: D | undefined) => BadFlatArray<A, D>[]
+>flat : <A, D extends number = 1>(arr: A, depth?: D) => BadFlatArray<A, D>[]
 
     arr: A,
 >arr : A

tests/baselines/reference/assertionTypePredicates1.types

@@ -270,7 +270,7 @@ namespace Debug {
 >Debug : typeof Debug
 
     export declare function assert(value: unknown, message?: string): asserts value;
->assert : (value: unknown, message?: string | undefined) => asserts value
+>assert : (value: unknown, message?: string) => asserts value
 >value : unknown
 >message : string | undefined
 

tests/baselines/reference/asyncFunctionsAndStrictNullChecks.types

@@ -75,7 +75,7 @@ declare function resolve2<T>(value: T): Windows.Foundation.IPromise<T>;
 >Foundation : any
 
 async function sample2(x?: number) {
->sample2 : (x?: number | undefined) => Promise<void>
+>sample2 : (x?: number) => Promise<void>
 >x : number | undefined
 
     let x1 = await resolve1(x);

tests/baselines/reference/callsOnComplexSignatures.types

@@ -110,7 +110,7 @@ function test3(items: string[] | number[]) {
 }
 
 function test4(
->test4 : (arg1: ((...objs: {    x: number;}[]) => number) | ((...objs: {    y: number;}[]) => number), arg2: ((a: {    x: number;}, b: object) => number) | ((a: object, b: {    x: number;}) => number), arg3: ((a: {    x: number;}, ...objs: {    y: number;}[]) => number) | ((...objs: {    x: number;}[]) => number), arg4: ((a?: { x: number; } | undefined, b?: { x: number; } | undefined) => number) | ((a?: { y: number; } | undefined) => number), arg5: ((a?: { x: number; } | undefined, ...b: {    x: number;}[]) => number) | ((a?: { y: number; } | undefined) => number), arg6: ((a?: { x: number; } | undefined, b?: { x: number; } | undefined) => number) | ((...a: {    y: number;}[]) => number)) => void
+>test4 : (arg1: ((...objs: {    x: number;}[]) => number) | ((...objs: {    y: number;}[]) => number), arg2: ((a: {    x: number;}, b: object) => number) | ((a: object, b: {    x: number;}) => number), arg3: ((a: {    x: number;}, ...objs: {    y: number;}[]) => number) | ((...objs: {    x: number;}[]) => number), arg4: ((a?: {    x: number;}, b?: {    x: number;}) => number) | ((a?: {    y: number;}) => number), arg5: ((a?: {    x: number;}, ...b: {    x: number;}[]) => number) | ((a?: {    y: number;}) => number), arg6: ((a?: {    x: number;}, b?: {    x: number;}) => number) | ((...a: {    y: number;}[]) => number)) => void
 
     arg1: ((...objs: {x: number}[]) => number) | ((...objs: {y: number}[]) => number),
 >arg1 : ((...objs: {    x: number;}[]) => number) | ((...objs: {    y: number;}[]) => number)
@@ -138,7 +138,7 @@ function test4(
 >x : number
 
     arg4: ((a?: {x: number}, b?: {x: number}) => number) | ((a?: {y: number}) => number),
->arg4 : ((a?: { x: number; } | undefined, b?: { x: number; } | undefined) => number) | ((a?: { y: number; } | undefined) => number)
+>arg4 : ((a?: {    x: number;}, b?: {    x: number;}) => number) | ((a?: {    y: number;}) => number)
 >a : { x: number; } | undefined
 >x : number
 >b : { x: number; } | undefined
@@ -147,7 +147,7 @@ function test4(
 >y : number
 
     arg5: ((a?: {x: number}, ...b: {x: number}[]) => number) | ((a?: {y: number}) => number),
->arg5 : ((a?: { x: number; } | undefined, ...b: {    x: number;}[]) => number) | ((a?: { y: number; } | undefined) => number)
+>arg5 : ((a?: {    x: number;}, ...b: {    x: number;}[]) => number) | ((a?: {    y: number;}) => number)
 >a : { x: number; } | undefined
 >x : number
 >b : { x: number; }[]
@@ -156,7 +156,7 @@ function test4(
 >y : number
 
     arg6: ((a?: {x: number}, b?: {x: number}) => number) | ((...a: {y: number}[]) => number),
->arg6 : ((a?: { x: number; } | undefined, b?: { x: number; } | undefined) => number) | ((...a: {    y: number;}[]) => number)
+>arg6 : ((a?: {    x: number;}, b?: {    x: number;}) => number) | ((...a: {    y: number;}[]) => number)
 >a : { x: number; } | undefined
 >x : number
 >b : { x: number; } | undefined
@@ -339,7 +339,7 @@ function test5() {
 
     // Pair of non-like intrinsics
     function render(url?: string): React.ReactNode {
->render : (url?: string | undefined) => React.ReactNode
+>render : (url?: string) => React.ReactNode
 >url : string | undefined
 >React : any