Removed annotations forced by union types

Removed annotations from the dotty codebase that were necessary because the inferred union types
caused inference errors later on.

Author: odersky

src/dotty/tools/dotc/ast/Desugar.scala

@@ -180,8 +180,9 @@ object desugar {
       constr1.mods, constr1.name, tparams, vparamss, constr1.tpt, constr1.rhs)
 
     // a reference to the class type, with all parameters given.
-    val classTypeRef: Tree = {
-        // Dotty deviation: Without type annotation infers Ident | AppliedTypeTree, which
+    val classTypeRef/*: Tree*/ = {
+        // -language:keepUnions difference: classTypeRef needs type annotation, otherwise
+        // infers Ident | AppliedTypeTree, which
         // renders the :\ in companions below untypable.
       val tycon = Ident(cdef.name) withPos cdef.pos.startPos
       val tparams = impl.constr.tparams

src/dotty/tools/dotc/core/Definitions.scala

@@ -286,8 +286,9 @@ class Definitions {
   object FunctionType {
     def apply(args: List[Type], resultType: Type) =
       FunctionClass(args.length).typeRef.appliedTo(args ::: resultType :: Nil)
-    def unapply(ft: Type): Option[(List[Type], Type)] = { // Dotty deviation: Type annotation needed because inferred type
-                                                          // is Some[(List[Type], Type)] | None, which is not a legal unapply type.
+    def unapply(ft: Type)/*: Option[(List[Type], Type)]*/ = {
+      // -language:keepUnions difference: unapply needs result type because inferred type
+      // is Some[(List[Type], Type)] | None, which is not a legal unapply type.
       val tsym = ft.typeSymbol
       lazy val targs = ft.argInfos
       if ((FunctionClasses contains tsym) &&