blackbox restriction #2: can't guide type inference

When an application of a blackbox macro still has undetermined type
parameters after Scala’s type inference algorithm has finished working,
these type parameters are inferred forcedly, in exactly the same manner
as type inference happens for normal methods.

This makes it impossible for blackbox macros to influence type inference,
prohibiting fundep materialization.

2 files changed, 21 insertions, 0 deletions

diff --git a/test/files/run/macro-blackbox-materialization/Macros_1.scala b/test/files/run/macro-blackbox-materialization/Macros_1.scala
new file mode 100644
index 0000000000..7c31dd7dc2
--- /dev/null
+++ b/test/files/run/macro-blackbox-materialization/Macros_1.scala
@@ -0,0 +1,16 @@
+// For the full version of the test, take a look at run/t5923a
+
+import scala.reflect.macros.BlackboxContext
+import language.experimental.macros
+
+case class C[T](t: String)
+object C {
+  implicit def foo[T]: C[T] = macro Macros.impl[T]
+}
+
+object Macros {
+  def impl[T: c.WeakTypeTag](c: BlackboxContext) = {
+    import c.universe._
+    reify(C[T](c.literal(weakTypeOf[T].toString).splice))
+  }
+}
\ No newline at end of file
diff --git a/test/files/run/macro-blackbox-materialization/Test_2.scala b/test/files/run/macro-blackbox-materialization/Test_2.scala
new file mode 100644
index 0000000000..001ff9aea8
--- /dev/null
+++ b/test/files/run/macro-blackbox-materialization/Test_2.scala
@@ -0,0 +1,5 @@
+object Test extends App {
+  println(implicitly[C[Int]])
+  println(implicitly[C[String]])
+  println(implicitly[C[Nothing]])
+}
\ No newline at end of file