Make This and Super take idents as qualifier/mixin

The qualifier of a This and the mixin of a Super were names, which meant
that their positions were lost. Now they are untyped idents.

4 files changed, 19 insertions, 12 deletions

diff --git a/src/dotty/tools/dotc/ast/Desugar.scala b/src/dotty/tools/dotc/ast/Desugar.scala
index 3c510c7b9..8f9c42e21 100644
--- a/src/dotty/tools/dotc/ast/Desugar.scala
+++ b/src/dotty/tools/dotc/ast/Desugar.scala
@@ -340,7 +340,7 @@ object desugar {
         val isDefinedMeth = syntheticProperty(nme.isDefined, Literal(Constant(true)))
         val caseParams = constrVparamss.head.toArray
         val productElemMeths = for (i <- 0 until arity) yield
-          syntheticProperty(nme.selectorName(i), Select(This(EmptyTypeName), caseParams(i).name))
+          syntheticProperty(nme.selectorName(i), Select(This(EmptyTypeIdent), caseParams(i).name))
         def isRepeated(tree: Tree): Boolean = tree match {
           case PostfixOp(_, nme.raw.STAR) => true
           case ByNameTypeTree(tree1) => isRepeated(tree1)
diff --git a/src/dotty/tools/dotc/ast/Trees.scala b/src/dotty/tools/dotc/ast/Trees.scala
index 78ac66812..2801bcae2 100644
--- a/src/dotty/tools/dotc/ast/Trees.scala
+++ b/src/dotty/tools/dotc/ast/Trees.scala
@@ -159,7 +159,7 @@ object Trees {
     /** Does this tree define a new symbol that is not defined elsewhere? */
     def isDef: Boolean = false
 
-    /** Is this tree either the empty tree or the empty ValDef? */
+    /** Is this tree either the empty tree or the empty ValDef or an empty type ident? */
     def isEmpty: Boolean = false
 
     /** Convert tree to a list. Gives a singleton list, except
@@ -353,7 +353,7 @@ object Trees {
   }
 
   /** qual.this */
-  case class This[-T >: Untyped] private[ast] (qual: TypeName)
+  case class This[-T >: Untyped] private[ast] (qual: untpd.Ident)
     extends DenotingTree[T] with TermTree[T] {
     type ThisTree[-T >: Untyped] = This[T]
     // Denotation of a This tree is always the underlying class; needs correction for modules.
@@ -368,7 +368,7 @@ object Trees {
   }
 
   /** C.super[mix], where qual = C.this */
-  case class Super[-T >: Untyped] private[ast] (qual: Tree[T], mix: TypeName)
+  case class Super[-T >: Untyped] private[ast] (qual: Tree[T], mix: untpd.Ident)
     extends ProxyTree[T] with TermTree[T] {
     type ThisTree[-T >: Untyped] = Super[T]
     def forwardTo = qual
@@ -890,12 +890,12 @@ object Trees {
         case tree: Select if (qualifier eq tree.qualifier) && (name == tree.name) => tree
         case _ => finalize(tree, untpd.Select(qualifier, name))
       }
-      def This(tree: Tree)(qual: TypeName): This = tree match {
-        case tree: This if qual == tree.qual => tree
+      def This(tree: Tree)(qual: untpd.Ident): This = tree match {
+        case tree: This if qual eq tree.qual => tree
         case _ => finalize(tree, untpd.This(qual))
       }
-      def Super(tree: Tree)(qual: Tree, mix: TypeName): Super = tree match {
-        case tree: Super if (qual eq tree.qual) && (mix == tree.mix) => tree
+      def Super(tree: Tree)(qual: Tree, mix: untpd.Ident): Super = tree match {
+        case tree: Super if (qual eq tree.qual) && (mix eq tree.mix) => tree
         case _ => finalize(tree, untpd.Super(qual, mix))
       }
       def Apply(tree: Tree)(fun: Tree, args: List[Tree])(implicit ctx: Context): Apply = tree match {
diff --git a/src/dotty/tools/dotc/ast/tpd.scala b/src/dotty/tools/dotc/ast/tpd.scala
index 09f2099d2..219d6d4ec 100644
--- a/src/dotty/tools/dotc/ast/tpd.scala
+++ b/src/dotty/tools/dotc/ast/tpd.scala
@@ -31,11 +31,14 @@ object tpd extends Trees.Instance[Type] with TypedTreeInfo {
     untpd.Select(qualifier, tp.name).withType(tp)
 
   def This(cls: ClassSymbol)(implicit ctx: Context): This =
-    untpd.This(cls.name).withType(cls.thisType)
+    untpd.This(untpd.Ident(cls.name)).withType(cls.thisType)
 
-  def Super(qual: Tree, mix: TypeName, inConstrCall: Boolean, mixinClass: Symbol = NoSymbol)(implicit ctx: Context): Super =
+  def Super(qual: Tree, mix: untpd.Ident, inConstrCall: Boolean, mixinClass: Symbol)(implicit ctx: Context): Super =
     ta.assignType(untpd.Super(qual, mix), qual, inConstrCall, mixinClass)
 
+  def Super(qual: Tree, mixName: TypeName, inConstrCall: Boolean, mixinClass: Symbol = NoSymbol)(implicit ctx: Context): Super =
+    Super(qual, if (mixName.isEmpty) untpd.EmptyTypeIdent else untpd.Ident(mixName), inConstrCall, mixinClass)
+
   def Apply(fn: Tree, args: List[Tree])(implicit ctx: Context): Apply =
     ta.assignType(untpd.Apply(fn, args), fn, args)
 
diff --git a/src/dotty/tools/dotc/ast/untpd.scala b/src/dotty/tools/dotc/ast/untpd.scala
index ac35ad09c..6c5210287 100644
--- a/src/dotty/tools/dotc/ast/untpd.scala
+++ b/src/dotty/tools/dotc/ast/untpd.scala
@@ -80,6 +80,10 @@ object untpd extends Trees.Instance[Untyped] with UntypedTreeInfo {
   case class ContextBounds(bounds: TypeBoundsTree, cxBounds: List[Tree]) extends TypTree
   case class PatDef(mods: Modifiers, pats: List[Tree], tpt: Tree, rhs: Tree) extends DefTree
 
+  @sharable object EmptyTypeIdent extends Ident(tpnme.EMPTY) with WithoutTypeOrPos[Untyped] {
+    override def isEmpty = true
+  }
+
   /** A block arising from a right-associative infix operation, where, e.g.
    *
    *     a +: b
@@ -225,8 +229,8 @@ object untpd extends Trees.Instance[Untyped] with UntypedTreeInfo {
   def BackquotedIdent(name: Name): BackquotedIdent = new BackquotedIdent(name)
   def Select(qualifier: Tree, name: Name): Select = new Select(qualifier, name)
   def SelectWithSig(qualifier: Tree, name: Name, sig: Signature): Select = new SelectWithSig(qualifier, name, sig)
-  def This(qual: TypeName): This = new This(qual)
-  def Super(qual: Tree, mix: TypeName): Super = new Super(qual, mix)
+  def This(qual: Ident): This = new This(qual)
+  def Super(qual: Tree, mix: Ident): Super = new Super(qual, mix)
   def Apply(fun: Tree, args: List[Tree]): Apply = new Apply(fun, args)
   def TypeApply(fun: Tree, args: List[Tree]): TypeApply = new TypeApply(fun, args)
   def Literal(const: Constant): Literal = new Literal(const)