Merge pull request #1878 from adriaanm/ticket-6925

SI-6925 use concrete type in applyOrElse's match's selecto

src/compiler/scala/tools/nsc/ast/TreeGen.scala

@@ -253,6 +253,11 @@ abstract class TreeGen extends scala.reflect.internal.TreeGen with TreeDSL {
     }
   }
 
+  // drop annotations generated by CPS plugin etc, since its annotationchecker rejects T @cps[U] <: Any
+  // let's assume for now annotations don't affect casts, drop them there, and bring them back using the outer Typed tree
+  def mkCastPreservingAnnotations(tree: Tree, pt: Type) =
+    Typed(mkCast(tree, pt.withoutAnnotations.dealias), TypeTree(pt))
+
   /** Generate a cast for tree Tree representing Array with
    *  elem type elemtp to expected type pt.
    */

src/compiler/scala/tools/nsc/typechecker/PatternMatching.scala

@@ -1478,14 +1478,9 @@ trait PatternMatching extends Transform with TypingTransformers with ast.TreeDSL
       def _equals(checker: Tree, binder: Symbol): Tree = checker MEMBER_== REF(binder)          // NOTE: checker must be the target of the ==, that's the patmat semantics for ya
       def and(a: Tree, b: Tree): Tree                  = a AND b
 
-      // drop annotations generated by CPS plugin etc, since its annotationchecker rejects T @cps[U] <: Any
-      // let's assume for now annotations don't affect casts, drop them there, and bring them back using the outer Typed tree
-      private def mkCast(t: Tree, tp: Type) =
-        Typed(gen.mkAsInstanceOf(t, tp.withoutAnnotations, true, false), TypeTree() setType tp)
-
       // the force is needed mainly to deal with the GADT typing hack (we can't detect it otherwise as tp nor pt need contain an abstract type, we're just casting wildly)
-      def _asInstanceOf(t: Tree, tp: Type): Tree = if (t.tpe != NoType && t.isTyped && typesConform(t.tpe, tp)) t else mkCast(t, tp)
-      def _asInstanceOf(b: Symbol, tp: Type): Tree = if (typesConform(b.info, tp)) REF(b) else mkCast(REF(b), tp)
+      def _asInstanceOf(t: Tree, tp: Type): Tree = if (t.tpe != NoType && t.isTyped && typesConform(t.tpe, tp)) t else gen.mkCastPreservingAnnotations(t, tp)
+      def _asInstanceOf(b: Symbol, tp: Type): Tree = if (typesConform(b.info, tp)) REF(b) else gen.mkCastPreservingAnnotations(REF(b), tp)
       def _isInstanceOf(b: Symbol, tp: Type): Tree = gen.mkIsInstanceOf(REF(b), tp.withoutAnnotations, true, false)
       //   if (typesConform(b.info, tpX)) { patmatDebug("warning: emitted spurious isInstanceOf: "+(b, tp)); TRUE }