Fix a problem due to different type inference

Author: odersky

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

@@ -433,8 +433,12 @@ trait Applications extends Compatibility { self: Typer =>
 
   /** Subclass of Application for type checking an Apply node with typed arguments. */
   class ApplyToTyped(app: untpd.Apply, fun: Tree, methRef: TermRef, args: List[Tree], resultType: Type)(implicit ctx: Context)
-  extends TypedApply(app, fun, methRef, args, resultType) {
-    def typedArg(arg: Tree, formal: Type): TypedArg = arg
+  extends TypedApply[Type](app, fun, methRef, args, resultType) {
+      // Dotty deviation: Dotc infers Untyped for the supercall. This seems to be according to the rules
+      // (of both Scala and Dotty). Untyped is legal, and a subtype of Typed, whereas TypeApply
+      // is invariant in the type parameter, so the minimal type should be inferred. But then typedArg does
+      // not match the abstract method in Application and an abstract class error results.
+    def typedArg(arg: tpd.Tree, formal: Type): TypedArg = arg
     def treeToArg(arg: Tree): Tree = arg
   }