Fix type-shifting problem in vcInlineMethods

vcInlineMethods could produce a different type on rewire which led to a -Ycheck failure. We now insert
a cast when that happens.

Test case: pos/flowops1.scala with -Ycheck:vcInline.

Author: odersky

src/dotty/tools/dotc/transform/VCInlineMethods.scala

@@ -90,7 +90,7 @@ class VCInlineMethods extends MiniPhaseTransform with IdentityDenotTransformer {
       tree // The rewiring will be handled by a fully-applied parent node
     case _ =>
       if (isMethodWithExtension(tree.symbol))
-        rewire(tree)
+        rewire(tree).ensureConforms(tree.tpe)
       else
         tree
   }