Scaladoc: improve refined function types rendering (#20333)

Fixes #19967
Improves rendering of refined function types - unneeded parameters names
are omitted when possible
[Cherry-picked 55025c2]

scaladoc-testcases/src/tests/refinedFunctionTypes.scala

@@ -0,0 +1,37 @@
+package tests
+package refinedFunctionTypes
+
+import annotation.experimental
+
+@experimental
+infix type $throws[R, +E <: Exception] = CanThrow[E] ?=> R
+
+@experimental
+infix type $throws2[+E <: Exception] = (c: CanThrow[E]) ?=> c.type
+
+@experimental
+infix type $throws3[+E <: Exception] = [T] => (c: CanThrow[E]) ?=> c.type
+
+@experimental
+infix type $throws4[+E <: Exception] = [T] => (c: CanThrow[E]) ?=> T //expected: infix type $throws4[+E <: Exception] = [T] => CanThrow[E] ?=> T
+
+type TA1 = (a: Int, b: (Boolean, String)) => List[(a.type, b.type)]
+
+type TA2 = (a: Int, b: (Boolean, String)) ?=> List[Boolean]
+
+@experimental
+type TB0 = [R, E <: Exception] =>> PolyFunction { def apply[T](c: CanThrow[E]): R; } //expected: type TB0[R, E <: Exception] = [T] => CanThrow[E] => R
+
+@experimental
+type TB1 = [R, E <: Exception] =>> PolyFunction { def apply[T](c: CanThrow[E], y: c.type): R; } //expected: type TB1[R, E <: Exception] = [T] => (c: CanThrow[E], y: c.type) => R
+
+@experimental
+type TB2 = [R, E <: Exception] =>> PolyFunction { def apply[T](using c: CanThrow[E]): c.type; } //expected: type TB2[R, E <: Exception] = [T] => (c: CanThrow[E]) ?=> c.type
+
+type TC1 = [T] => (a: T) => T //expected: type TC1 = [T] => T => T
+
+type TC2 = [T] => (a: T) ?=> T //expected: type TC2 = [T] => T ?=> T
+
+type TC3 = [T] => (a: T) => a.type
+
+type TC4 = [T] => (a: T) ?=> a.type

scaladoc-testcases/src/tests/thisType.scala

@@ -4,5 +4,5 @@ package thisType
 // issue 16024
 
 class X[Map[_, _[_]]]:
-  inline def map[F[_]](f: [t] => t => F[t]): Map[this.type, F] = //expected: inline def map[F[_]](f: [t] => (x$1: t) => F[t]): Map[this.type, F]
-    ???
+  inline def map[F[_]](f: [t] => t => F[t]): Map[this.type, F]
+    = ???

scaladoc-testcases/src/tests/typesSignatures.scala

@@ -28,7 +28,7 @@ class Base
   // Tests do not support multiline signatures
   type Elem[X] = X match { case String => Char case Array[t] => t case Iterable[t] => t }
 
-  type F = [X] => (x: X) => List[X]
+  type F = [X] => (x: X) => List[X] //expected: type F = [X] => X => List[X]
 
   type G = Int => Int
 

scaladoc/src/dotty/tools/scaladoc/tasty/TypesSupport.scala

@@ -4,6 +4,7 @@ package tasty
 import scala.jdk.CollectionConverters._
 
 import scala.quoted._
+import scala.util.control.NonFatal
 
 import NameNormalizer._
 import SyntheticsSupport._
@@ -124,6 +125,12 @@ trait TypesSupport:
         ++ keyword(" =>> ").l
         ++ inner(resType)
 
+      case Refinement(parent, "apply", mt : MethodType) if isPolyOrEreased(parent) =>
+        val isCtx = isContextualMethod(mt)
+        val sym = defn.FunctionClass(mt.paramTypes.length, isCtx)
+        val at = sym.typeRef.appliedTo(mt.paramTypes :+ mt.resType)
+        inner(Refinement(at, "apply", mt))
+
       case r: Refinement => { //(parent, name, info)
         def getRefinementInformation(t: TypeRepr): List[TypeRepr] = t match {
           case r: Refinement => getRefinementInformation(r.parent) :+ r
@@ -164,16 +171,22 @@ trait TypesSupport:
           case t: PolyType =>
             val paramBounds = getParamBounds(t)
             val method = t.resType.asInstanceOf[MethodType]
-            val paramList = getParamList(method)
-            val resType = inner(method.resType)
-            plain("[").l ++ paramBounds ++ plain("]").l ++ keyword(" => ").l ++ paramList ++ keyword(" => ").l ++ resType
+            val rest = parseDependentFunctionType(method)
+            plain("[").l ++ paramBounds ++ plain("]").l ++ keyword(" => ").l ++ rest
           case other => noSupported(s"Not supported type in refinement $info")
         }
 
         def parseDependentFunctionType(info: TypeRepr): SSignature = info match {
           case m: MethodType =>
-            val paramList = getParamList(m)
-            paramList ++ keyword(" => ").l ++ inner(m.resType)
+            val isCtx = isContextualMethod(m)
+            if isDependentMethod(m) then
+              val paramList = getParamList(m)
+              val arrow = keyword(if isCtx then " ?=> " else " => ").l
+              val resType = inner(m.resType)
+              paramList ++ arrow ++ resType
+            else
+              val sym = defn.FunctionClass(m.paramTypes.length, isCtx)
+              inner(sym.typeRef.appliedTo(m.paramTypes :+ m.resType))
           case other => noSupported("Dependent function type without MethodType refinement")
         }
 
@@ -213,8 +226,9 @@ trait TypesSupport:
             case Seq(rtpe) =>
               plain("()").l ++ keyword(arrow).l ++ inner(rtpe)
             case Seq(arg, rtpe) =>
-              val partOfSignature = arg match
+              val partOfSignature = stripAnnotated(arg) match
                 case _: TermRef | _: TypeRef | _: ConstantType | _: ParamRef => inner(arg)
+                case at: AppliedType if !isInfix(at) && !at.isFunctionType && !at.isTupleN => inner(arg)
                 case _ => inParens(inner(arg))
               partOfSignature ++ keyword(arrow).l ++ inner(rtpe)
             case args =>
@@ -385,3 +399,21 @@ trait TypesSupport:
         case _ => false
 
     at.args.size == 2 && (!at.typeSymbol.name.forall(isIdentifierPart) || infixAnnot)
+
+  private def isPolyOrEreased(using Quotes)(tr: reflect.TypeRepr) =
+    Set("scala.PolyFunction", "scala.runtime.ErasedFunction")
+      .contains(tr.typeSymbol.fullName)
+
+  private def isContextualMethod(using Quotes)(mt: reflect.MethodType) =
+    mt.asInstanceOf[dotty.tools.dotc.core.Types.MethodType].isContextualMethod
+
+  private def isDependentMethod(using Quotes)(mt: reflect.MethodType) =
+    val method = mt.asInstanceOf[dotty.tools.dotc.core.Types.MethodType]
+    try method.isParamDependent || method.isResultDependent
+    catch case NonFatal(_) => true
+
+  private def stripAnnotated(using Quotes)(tr: reflect.TypeRepr): reflect.TypeRepr =
+    import reflect.*
+    tr match
+      case AnnotatedType(tr, _) => stripAnnotated(tr)
+      case other => other

scaladoc/test/dotty/tools/scaladoc/signatures/TranslatableSignaturesTestCases.scala

@@ -120,3 +120,5 @@ class MatchTypeTuple extends SignatureTest("matchTypeTuple", SignatureTest.all)
 class InfixTypes extends SignatureTest("infixTypes", SignatureTest.all)
 
 class ExtendsCall extends SignatureTest("extendsCall", SignatureTest.all)
+
+class RefinedFunctionTypes extends SignatureTest("refinedFunctionTypes", SignatureTest.all)