Scaladoc: fixes and improvements to context bounds and extension methods (#22156)

Closes #21662 

More specifically:
- Fixed issue with ambiguity of type params in right-associative
extension methods (see `\:` and `\\:` in
`extensionMethodSignatures.scala`, also see #22170)
- Fixed issue with context bounds in type parameters in extensions (`><`
in `extensionMethodSignatures.scala`)

Additionally fixed and improved simplifying of type lambdas
(`TypesSupport.scala`)

Removed `MemberInfo` and `unwrapMemberInfo`, which were quite
complicated, doing several things at the same time and caused
`parseMember` to have two sources of truth.

---------

Co-authored-by: Jan Chyb <[email protected]>

Author: Florian3k

scaladoc-testcases/src/tests/classSignatureTestSource.scala

@@ -17,14 +17,18 @@ abstract class Documentation[T, A <: Int, B >: String, -X, +Y](c1: String, val c
     def this(x: T)
     = this()
 
+    //expected: def toArray[B >: T : ClassTag]: Array[B]
+
     class innerDocumentationClass
     {
 
     }
 
     sealed trait CaseImplementThis(id: Int)
 
-    case class IAmACaseClass(x: T, id: Int) extends CaseImplementThis/*<-*/(id)/*->*/
+    case class IAmACaseClass(x: T, id: Int) extends CaseImplementThis(id) //expected: case class IAmACaseClass(x: Documentation.this.T, id: Int) extends CaseImplementThis
+
+    case class IAmACaseClassWithParam[T](x: Documentation.this.T, id: T)
 
     case object IAmACaseObject extends CaseImplementThis/*<-*/(0)/*->*/
 

scaladoc-testcases/src/tests/contextBounds.scala

@@ -4,6 +4,16 @@ package contextBounds
 import scala.reflect.ClassTag
 
 class A:
+  type :+:[X, Y] = [Z] =>> Map[Z, (X, Y)]
+
+  extension [T : ([X] =>> String) : ([X] =>> Int)](x: Int)
+    def foo[U : ([X] =>> String)](y: Int): Nothing
+      = ???
+    def bar[W : T match { case String => List case Int => Option } : Set]: Nothing
+      = ???
+    def baz[V : Int :+: String : Option]: Nothing
+      = ???
+
   def basic[A : ClassTag]: A
     = ???
 
@@ -35,5 +45,5 @@ class A:
   //   = 1
 
   class Outer[A]:
-    def falsePositiveInner[T](implicit evidence$3: ClassTag[A]): Int
-      = 1
+    def falsePositiveInner[T](implicit evidence$3: ClassTag[A]): Int //expected: def falsePositiveInner[T]: Int
+      = 1

scaladoc-testcases/src/tests/exports1.scala

@@ -14,15 +14,15 @@ class A: //unexpected
    = 1
   var aVar1: 1
    = 1
-  type HKT[T[_], X] //expected: final type HKT = [T[_], X] =>> a.HKT[T, X]
+  type HKT[T[_], X] //expected: final type HKT = a.HKT
    = T[X]
   type SomeRandomType = (List[?] | Seq[?]) & String //expected: final type SomeRandomType = a.SomeRandomType
-  def x[T[_], X](x: X): HKT[T, X] //expected: def x[T[_], X](x: X): A.this.HKT[T, X]
+  def x[T[_], X](x: X): HKT[T, X]
    = ???
   def fn[T, U]: T => U
    = ???
   object Object //expected: val Obj: Object.type
-  val x: HKT[List, Int] //expected: val x: A.this.HKT[List, Int]
+  val x: HKT[List, Int]
    = ???
   class Class(val a: Int, val b: Int) extends Serializable //expected: final type Class = a.Class
   enum Enum: //expected: final type Enum = a.Enum

scaladoc-testcases/src/tests/extensionMethodSignatures.scala

@@ -44,4 +44,23 @@ case class ClassTwo(a: String, b: String)
 
 }
 
-class ClassOneTwo extends ClassOne
+class ClassOneTwo extends ClassOne
+
+trait C[T]
+trait Equiv[T]:
+  extension [U : C](x: U)
+    def ><[V](y: V): Nothing
+      = ???
+
+trait Monoid[T]:
+  extension (a: T)
+    def \:[U](b: U): Nothing
+      = ???
+  extension [U](a: T)
+    def \\:(b: U): Nothing
+      = ???
+
+class Clazz[U]:
+  extension [T : ([X] =>> String) : ([X] =>> String)](x: Int)
+    def bar[U : ([X] =>> String) : List](y: Int): Nothing
+      = ???

scaladoc-testcases/src/tests/innerClasses.scala

@@ -0,0 +1,25 @@
+package tests
+package innerClasses
+
+trait A:
+  def baz: B
+    = baz2
+  def baz2: A.this.B //expected: def baz2: B
+    = baz
+  type B
+  class C extends A:
+    def foo: A.this.B
+      = ???
+    def foo2: B
+      = ???
+    def bar: B
+      = ???
+
+class T1:
+  trait T
+  class T2:
+    trait T
+    class Impl extends T1.this.T //expected: class Impl extends T
+    // we get rid of the this-type above,
+    // as ambiguity created by removing this-types is alleviated by links
+    // (but this can be changed if needed)

scaladoc-testcases/src/tests/thisType.scala

@@ -1,8 +1,35 @@
 package tests
 package thisType
 
-// issue 16024
 
 class X[Map[_, _[_]]]:
+  // issue 16024
   inline def map[F[_]](f: [t] => t => F[t]): Map[this.type, F]
     = ???
+
+sealed trait Tuple[Y[_]]:
+  def ++[This >: this.type <: Tuple[Y]](that: Y[Tuple[Y]]): Any
+    = ???
+
+sealed trait NonEmptyTuple extends Tuple[Option]
+//expected: def ++[This >: this.type <: Tuple[Option]](that: Option[Tuple[Option]]): Any
+
+trait Foo[X]:
+  def foo0[T <: Foo.this.type](x: X): Foo.this.type //expected: def foo0[T <: this.type](x: X): this.type
+    = bar0[T](x)
+  def bar0[T <: this.type](x: X): this.type
+    = foo0[T](x)
+
+  sealed abstract class Nested[+H, +T <: (Tuple), A <: Tuple[List]] extends NonEmptyTuple, Foo[Int]:
+  //                                     ^^^^^^^ TODO fix
+    //expected: def ++[This >: this.type <: Tuple[Option]](that: Option[Tuple[Option]]): Any
+
+    //expected: def foo0[T <: this.type](x: Int): this.type
+
+    //expected: def bar0[T <: this.type](x: Int): this.type
+
+    def foo1[T <: Foo.this.type]: Nothing
+      = ???
+
+    def foo2[T <: this.type]: Nothing
+      = ???