fixed bug1234

1 files changed, 17 insertions, 8 deletions

diff --git a/src/compiler/scala/tools/nsc/typechecker/Typers.scala b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
index bed72e52a9..701b2fe245 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Typers.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
@@ -1302,14 +1302,23 @@ trait Typers { self: Analyzer =>
       var body1: Tree = typed(cdef.body, pt)
       if (!context.savedTypeBounds.isEmpty) {
         body1.tpe = context.restoreTypeBounds(body1.tpe)
-        if (isFullyDefined(pt) && !(body1.tpe <:< pt))
-        // the following is a hack to make the pattern matcher work !!! (still needed?)
-          body1 =
-            typed {
-              atPos(body1.pos) {
-                TypeApply(Select(body1, Any_asInstanceOf), List(TypeTree(pt))) // @M no need for pt.normalize here, is done in erasure
-              }
-            }
+        if (isFullyDefined(pt)) {
+          // the following is a hack to make the pattern matcher work:
+          // add an .asInstanceOf[pt] unless there is already one.
+          // (the ...unless... part is necessary to make type checking idempotent).
+          body1 match {
+            case TypeApply(qual, List(targ))
+            if (qual.symbol == Any_asInstanceOf && targ.tpe <:< pt) =>
+              ;
+            case _ =>
+              body1 =
+                typed {
+                  atPos(body1.pos) {
+                    TypeApply(Select(body1, Any_asInstanceOf), List(TypeTree(pt))) // @M no need for pt.normalize here, is done in erasure
+                  }
+                }
+          }
+        }
       }
 //    body1 = checkNoEscaping.locals(context.scope, pt, body1)
       copy.CaseDef(cdef, pat1, guard1, body1) setType body1.tpe