[vpm] avoid verifyerror: leave jump to tail-pos label

the following commit deals with the fall-out in basicblocks
(double closing of blocks in ignore mode)

4 files changed, 22 insertions, 2 deletions

diff --git a/src/compiler/scala/tools/nsc/transform/TailCalls.scala b/src/compiler/scala/tools/nsc/transform/TailCalls.scala
index ef76fe1b1c..9915f7e9fc 100644
--- a/src/compiler/scala/tools/nsc/transform/TailCalls.scala
+++ b/src/compiler/scala/tools/nsc/transform/TailCalls.scala
@@ -341,13 +341,18 @@ abstract class TailCalls extends Transform {
           else if (fun.symbol.isLabel && args.nonEmpty && args.tail.isEmpty && ctx.tailLabels(fun.symbol)) {
             // this is to detect tailcalls in translated matches
             // it's a one-argument call to a label that is in a tailposition and that looks like label(x) {x}
-            // thus, the argument to the call is in tailposition and we don't need to jump to the label, tail jump instead
+            // thus, the argument to the call is in tailposition
             val saved = ctx.tailPos
             ctx.tailPos = true
             debuglog("in tailpos label: "+ args.head)
             val res = transform(args.head)
             ctx.tailPos = saved
-            if (res ne args.head) res // we tail-called -- TODO: shield from false-positives where we rewrite but don't tail-call
+            if (res ne args.head) {
+              // we tail-called -- TODO: shield from false-positives where we rewrite but don't tail-call
+              // must leave the jump to the original tailpos-label (fun)!
+              // there might be *a* tailcall *in* res, but it doesn't mean res *always* tailcalls
+              treeCopy.Apply(tree, fun, List(res))
+            }
             else rewriteApply(fun, fun, Nil, args)
           } else rewriteApply(fun, fun, Nil, args)
 
diff --git a/test/files/run/virtpatmat_tailcalls_verifyerror.check b/test/files/run/virtpatmat_tailcalls_verifyerror.check
new file mode 100644
index 0000000000..c508d5366f
--- /dev/null
+++ b/test/files/run/virtpatmat_tailcalls_verifyerror.check
@@ -0,0 +1 @@
+false
diff --git a/test/files/run/virtpatmat_tailcalls_verifyerror.flags b/test/files/run/virtpatmat_tailcalls_verifyerror.flags
new file mode 100644
index 0000000000..9769db9257
--- /dev/null
+++ b/test/files/run/virtpatmat_tailcalls_verifyerror.flags
@@ -0,0 +1 @@
+ -Yvirtpatmat -Xexperimental
diff --git a/test/files/run/virtpatmat_tailcalls_verifyerror.scala b/test/files/run/virtpatmat_tailcalls_verifyerror.scala
new file mode 100644
index 0000000000..1ee613f09e
--- /dev/null
+++ b/test/files/run/virtpatmat_tailcalls_verifyerror.scala
@@ -0,0 +1,13 @@
+// shouldn't result in a verify error when run...
+object Test extends App {
+  @annotation.tailrec
+  final def test(meh: Boolean): Boolean = {
+    Some("a") match {
+      case x =>
+        x match {
+          case _ => if(meh) test(false) else false
+        }
+    }
+  }
+  println(test(true))
+}
\ No newline at end of file