Do ignore expected prototypes of New

It turns out an sjsJUnitTest fails otherwise, since that one _does_ insert an implicit conversion after a `new`.

This is all goes to show that what we do to deal with implicit conversions
is completely crazy. It's a black art when to propagate exected types. There's
often no better or worse. Almost any change we do can heal some code and break
some other code. I believe the only way to get our of this swamp is to get
rid of unrestricted implicit conversions.

Author: odersky

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

@@ -893,8 +893,8 @@ trait Applications extends Compatibility {
 
     def realApply(using Context): Tree = {
       val resultProto = tree.fun match
-        case Select(New(_), _) => pt
-          // Don't ignore expected types of `new` expressions. If we have a `new C()`
+        case Select(New(_), _) if pt.isInstanceOf[ValueType] => pt
+          // Don't ignore expected value types of `new` expressions. If we have a `new C()`
           // with expected type `C[T]` we want to use the type to instantiate `C`
           // immediately. This is necessary since `C` might _also_ have using clauses
           // that we want to instantiate with the best available type. See i15664.scala.