Fix type aliases in beta-reduction of polyfunctions (#17054)

Fixes #17052

Author: nicolasstucki

compiler/src/dotty/tools/dotc/transform/BetaReduce.scala

@@ -117,7 +117,7 @@ object BetaReduce:
           case ref @ TypeRef(NoPrefix, _) =>
             ref.symbol
           case _ =>
-            val binding = TypeDef(newSymbol(ctx.owner, tparam.name, EmptyFlags, targ.tpe, coord = targ.span)).withSpan(targ.span)
+            val binding = TypeDef(newSymbol(ctx.owner, tparam.name, EmptyFlags, TypeAlias(targ.tpe), coord = targ.span)).withSpan(targ.span)
             bindings += binding
             binding.symbol
 

compiler/src/dotty/tools/dotc/transform/TreeChecker.scala

@@ -533,6 +533,11 @@ object TreeChecker {
         i"owner chain = ${tree.symbol.ownersIterator.toList}%, %, ctxOwners = ${ctx.outersIterator.map(_.owner).toList}%, %")
     }
 
+    override def typedTypeDef(tdef: untpd.TypeDef, sym: Symbol)(using Context): Tree = {
+      assert(sym.info.isInstanceOf[ClassInfo | TypeBounds], i"wrong type, expect a template or type bounds for ${sym.fullName}, but found: ${sym.info}")
+      super.typedTypeDef(tdef, sym)
+    }
+
     override def typedClassDef(cdef: untpd.TypeDef, cls: ClassSymbol)(using Context): Tree = {
       val TypeDef(_, impl @ Template(constr, _, _, _)) = cdef: @unchecked
       assert(cdef.symbol == cls)

compiler/src/scala/quoted/runtime/impl/printers/SourceCode.scala

@@ -1345,18 +1345,22 @@ object SourceCode {
     }
 
     private def printBoundsTree(bounds: TypeBoundsTree)(using elideThis: Option[Symbol]): this.type = {
-      bounds.low match {
-        case Inferred() =>
-        case low =>
-          this += " >: "
-          printTypeTree(low)
-      }
-      bounds.hi match {
-        case Inferred() => this
-        case hi =>
-          this += " <: "
-          printTypeTree(hi)
-      }
+      if bounds.low.tpe == bounds.hi.tpe then
+        this += " = "
+        printTypeTree(bounds.low)
+      else
+        bounds.low match {
+          case Inferred() =>
+          case low =>
+            this += " >: "
+            printTypeTree(low)
+        }
+        bounds.hi match {
+          case Inferred() => this
+          case hi =>
+            this += " <: "
+            printTypeTree(hi)
+        }
     }
 
     private def printBounds(bounds: TypeBounds)(using elideThis: Option[Symbol]): this.type = {

scaladoc/src/dotty/tools/scaladoc/tasty/Scaladoc2AnchorCreator.scala

@@ -7,10 +7,66 @@ import scala.util.matching.Regex
 
 object Scaladoc2AnchorCreator:
 
-  def getScaladoc2Type(using Quotes)(t: reflect.Tree) =
-    import reflect.*
-    val regex = t match
-      case d: DefDef =>  "def"
-      case t: TypeDef => "type"
-      case v: ValDef =>  "val|var"
-    t.show(using Printer.TreeShortCode).split(regex, 2)(1).replace(" ","")
+  def getScaladoc2Type(using Quotes)(sym: quotes.reflect.Symbol) = signatureAnchor(sym)
+
+  /** Creates the signature anchor
+   *
+   *  - `X` for a `type X ...`
+   *  - `x:X` for a `val x: X`
+   *  - `f[U1,...](x1:T1,...)(impliciti1:U1,impliciti2:U2,...)...:R` for a `def f[U1, ...](x1: T1, ...)(implicit i1: U1, i2: U2...)...: R`
+   *
+   *  Types are printed without their paths. No spaces are printed in the output.
+   */
+  private def signatureAnchor(using Quotes)(sym: quotes.reflect.Symbol): String =
+    import quotes.reflect.*
+    def signatureType(tp: quotes.reflect.TypeRepr): String =
+      tp match
+        case mt @ MethodType(paramNames, paramTypes, res) =>
+          val implicitPrefix = if mt.isImplicit then "implicit" else ""
+          val closeClause = res match
+            case _: MethodOrPoly => ")"
+            case _ => "):"
+          paramNames.zip(paramTypes.map(signatureType))
+            .map((name, tpe) => s"$implicitPrefix$name:$tpe")
+            .mkString("(", ",", closeClause) + signatureType(res)
+        case PolyType(paramNames, paramBounds, res) =>
+          val closeClause = res match
+            case _: MethodOrPoly => "]"
+            case _ => "]:"
+          paramNames.zip(paramBounds.map(signatureType))
+            .map((name, tpe) => s"$name$tpe")
+            .mkString("[", ",", closeClause) + signatureType(res)
+        case TypeLambda(paramNames, paramBounds, res) =>
+          paramNames.zip(paramBounds.map(signatureType))
+            .map((name, tpe) => s"$name$tpe")
+            .mkString("[", ",", "]") + "=>" + signatureType(res)
+        case ByNameType(tp) =>
+          ":" + signatureType(tp)
+        case TypeBounds(low, hi) =>
+          val lowBound = if low =:= defn.NothingClass.typeRef then "" else ">:" + signatureType(low)
+          val hiBound = if low =:= defn.AnyClass.typeRef then "" else "<:" + signatureType(hi)
+          lowBound + hiBound
+        case tp: ParamRef =>
+          tp.binder match
+            case binder: MethodType => binder.paramNames(tp.paramNum) + ".type"
+            case binder: PolyType => binder.paramNames(tp.paramNum)
+            case binder: LambdaType => binder.paramNames(tp.paramNum)
+        case AppliedType(tycon, args) =>
+          args.map {
+            case tp: TypeBounds => "_" + signatureType(tp)
+            case tp => signatureType(tp)
+          }.mkString(signatureType(tycon) + "[", ",", "]")
+        case tp: AnnotatedType =>
+          signatureType(tp.underlying) + "@" + tp.annotation.symbol.owner.name
+        case tp: ThisType =>
+          signatureType(tp.tref) + ".this"
+        case tp: TypeRef =>
+          tp.name
+        case tp =>
+          // TODO handle other cases without using show (show does not have a stable representation)
+          tp.show(using Printer.TypeReprShortCode).replace(" ","")
+
+    sym match
+      case sym if sym.isType => sym.name
+      case sym if sym.flags.is(Flags.Method) => sym.name + signatureType(sym.info)
+      case sym => sym.name + ":" + signatureType(sym.info)

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

@@ -235,7 +235,7 @@ class SymOpsWithLinkCache:
       def constructPathForScaladoc2: String =
         val l = escapeUrl(location.mkString("/"))
         val scaladoc2Anchor = if anchor.isDefined then {
-          "#" + getScaladoc2Type(sym.tree)
+          "#" + getScaladoc2Type(sym)
         } else ""
         docURL + l + extension + scaladoc2Anchor
 

tests/pos/i17052.scala

@@ -0,0 +1,2 @@
+def test[F[_]](fAny: F[Any]) =
+  { [X] => (fx: F[X]) => { val fx2: F[X] = fx; () } }.apply[Any](fAny)