Check that qual of Super is always This

Author: liufengyun

compiler/src/dotty/tools/dotc/transform/TreeChecker.scala

@@ -413,6 +413,10 @@ class TreeChecker extends Phase with SymTransformer {
       res
     }
 
+    override def typedSuper(tree: untpd.Super, pt: Type)(using Context): Tree =
+      assert(tree.qual.isInstanceOf[untpd.This], i"expect prefix of Super to be This, actual = ${tree.qual}")
+      super.typedSuper(tree, pt)
+
     private def checkOwner(tree: untpd.Tree)(using Context): Unit = {
       def ownerMatches(symOwner: Symbol, ctxOwner: Symbol): Boolean =
         symOwner == ctxOwner ||