Fix for rangepos crasher.

wrapClassTagUnapply was generating an unpositioned tree
which would crash under -Yrangepos.  See SI-6338.

4 files changed, 10 insertions, 6 deletions

diff --git a/src/compiler/scala/tools/nsc/typechecker/Typers.scala b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
index 12e26a812d..cf9a07a7e4 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Typers.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
@@ -3298,12 +3298,13 @@ trait Typers extends Modes with Adaptations with Tags {
       // println(util.Position.formatMessage(uncheckedPattern.pos, "made unchecked type test into a checked one", true))
 
       val args = List(uncheckedPattern)
+      val app  = atPos(uncheckedPattern.pos)(Apply(classTagExtractor, args))
       // must call doTypedUnapply directly, as otherwise we get undesirable rewrites
       // and re-typechecks of the target of the unapply call in PATTERNmode,
       // this breaks down when the classTagExtractor (which defineds the unapply member) is not a simple reference to an object,
       // but an arbitrary tree as is the case here
-      doTypedUnapply(Apply(classTagExtractor, args), classTagExtractor, classTagExtractor, args, PATTERNmode, pt)
-      }
+      doTypedUnapply(app, classTagExtractor, classTagExtractor, args, PATTERNmode, pt)
+    }
 
     // if there's a ClassTag that allows us to turn the unchecked type test for `pt` into a checked type test
     // return the corresponding extractor (an instance of ClassTag[`pt`])
diff --git a/test/files/neg/t3015.check b/test/files/neg/t3015.check
index 4a03c940f4..6948392bb0 100644
--- a/test/files/neg/t3015.check
+++ b/test/files/neg/t3015.check
@@ -3,7 +3,4 @@ t3015.scala:7: error: scrutinee is incompatible with pattern type;
  required: String
   val b(foo) = "foo" 
        ^
-error: type mismatch;
- found   : _$1
- required: String
-two errors found
+one error found
diff --git a/test/files/pos/classtag-pos.flags b/test/files/pos/classtag-pos.flags
new file mode 100644
index 0000000000..281f0a10cd
--- /dev/null
+++ b/test/files/pos/classtag-pos.flags
@@ -0,0 +1 @@
+-Yrangepos
diff --git a/test/files/pos/classtag-pos.scala b/test/files/pos/classtag-pos.scala
new file mode 100644
index 0000000000..768d2e27f4
--- /dev/null
+++ b/test/files/pos/classtag-pos.scala
@@ -0,0 +1,5 @@
+import scala.reflect.runtime.universe._
+
+class A {
+  def f[T: TypeTag] = typeOf[T] match { case TypeRef(_, _, args) => args }
+}