Use supercall context when calling inserted super traits

This is analgous to inserting a call for a superclass. In either case we
should not be able to see local class definitions.

Author: odersky

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

@@ -2290,7 +2290,7 @@ class Typer extends Namer
             var added: Tree = TypeTree(parent).withSpan(cdef.nameSpan.focus)
             if psym.is(Trait) && psym.primaryConstructor.info.takesImplicitParams then
               // classes get a constructor separately using a different context
-              added = ensureConstrCall(cls, added)
+              added = ensureConstrCall(cls, added)(using superCtx)
             added :: parentTrees(parents1, ptrees)
       case _ =>
         ptrees

tests/run/i11966.check

@@ -0,0 +1 @@
+1

tests/run/i11966.scala

@@ -0,0 +1,17 @@
+trait A[T]:
+  def f: T
+
+trait B[T: A]:
+  println(summon[A[T]].f)
+
+trait C[T: A] extends B[T]
+
+given a1: A[Int] with
+  def f = 1
+
+class D extends C[Int]:
+  given a2: A[Int] with
+    def f = 2
+
+@main def Test = D()
+