Keep rhs of TypeDef in typed tree

This is important for IDEs who want to see the full tree.
The tree now gets replaced by a TypeTree in PostTyper.

Author: odersky

src/dotty/tools/dotc/transform/PostTyper.scala

@@ -180,6 +180,15 @@ class PostTyper extends MacroTransform with IdentityDenotTransformer  { thisTran
         case tree: DefDef =>
           transformAnnots(tree)
           superAcc.wrapDefDef(tree)(super.transform(tree).asInstanceOf[DefDef])
+        case tree: TypeDef =>
+          transformAnnots(tree)
+          val sym = tree.symbol
+          val tree1 =
+            if (sym.isClass) tree
+            else {
+              cpy.TypeDef(tree)(rhs = TypeTree(tree.symbol.info))
+            }
+          super.transform(tree1)
         case tree: MemberDef =>
           transformAnnots(tree)
           super.transform(tree)

src/dotty/tools/dotc/typer/Typer.scala

@@ -961,8 +961,7 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
     val TypeDef(name, rhs) = tdef
     checkLowerNotHK(sym, tdef.tparams.map(symbolOfTree), tdef.pos)
     completeAnnotations(tdef, sym)
-    val _ = typedType(rhs) // unused, typecheck only to remove from typedTree
-    assignType(cpy.TypeDef(tdef)(name, TypeTree(sym.info), Nil), sym)
+    assignType(cpy.TypeDef(tdef)(name, typedType(rhs), Nil), sym)
   }
 
   def typedClassDef(cdef: untpd.TypeDef, cls: ClassSymbol)(implicit ctx: Context) = track("typedClassDef") {