Fix for SI-6447, macro dependent type propagation.

It really pays not to write new TypeMaps unless it is
absolutely necessary, because there are about 1000 ways
to get them wrong. I'm 98% sure this one can be dropped.
Review by @xeno-by.

2 files changed, 19 insertions, 1 deletions

diff --git a/src/compiler/scala/tools/nsc/typechecker/Macros.scala b/src/compiler/scala/tools/nsc/typechecker/Macros.scala
index bcc37e8b37..db3c133ee1 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Macros.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Macros.scala
@@ -315,7 +315,7 @@ trait Macros extends scala.tools.reflect.FastTrack with Traces {
                 case _ =>
                   pre
               }
-              TypeRef(pre1, sym, args map mapOver)
+              typeRef(apply(pre1), sym, mapOverArgs(args, sym.typeParams))
             case _ =>
               mapOver(tp)
           }
diff --git a/test/files/pos/t6447.scala b/test/files/pos/t6447.scala
new file mode 100644
index 0000000000..1c0c0f2a31
--- /dev/null
+++ b/test/files/pos/t6447.scala
@@ -0,0 +1,18 @@
+import scala.language.experimental.macros
+import scala.reflect.macros.Context
+
+class X { type T }
+
+object X {
+  // this works
+  def foo(x: X): x.T = macro fooImpl
+  def fooImpl(c: Context)(x: c.Expr[X]): c.Expr[x.value.T] = ???
+
+  // this doesn't
+  def bar(x: X, y: X): (x.T, y.T) = macro barImpl
+  def barImpl(c: Context)(x: c.Expr[X], y: c.Expr[X]): c.Expr[(x.value.T, y.value.T)] = ???
+
+  // neither does this
+  def baz(x: X)(xs: List[x.T]): Unit = macro bazImpl
+  def bazImpl(c: Context)(x: c.Expr[X])(xs: c.Expr[List[x.value.T]]): c.Expr[Unit] = ???
+}