SI-7470 implements fundep materialization

This fix provides implicit macros with an ability to affect type inference
in a more or less sane manner. That's crucial for materialization of
multi-parametric type class instances (e.g. Iso's from shapeless).
Details of the technique can be found in comments.

2 files changed, 16 insertions, 0 deletions

diff --git a/test/files/run/t5923d/Macros_1.scala b/test/files/run/t5923d/Macros_1.scala
new file mode 100644
index 0000000000..f32d1af704
--- /dev/null
+++ b/test/files/run/t5923d/Macros_1.scala
@@ -0,0 +1,9 @@
+import scala.language.experimental.macros
+import scala.reflect.macros.Context
+
+trait MappedRow
+trait RowMapper[T <: MappedRow]
+object RowMapper {
+  implicit def mapper[T <: MappedRow]: RowMapper[T] = macro impl[T]
+  def impl[T <: MappedRow : c.WeakTypeTag](c: Context) = c.universe.reify(new RowMapper[T]{})
+}
\ No newline at end of file
diff --git a/test/files/run/t5923d/Test_2.scala b/test/files/run/t5923d/Test_2.scala
new file mode 100644
index 0000000000..6be10227c2
--- /dev/null
+++ b/test/files/run/t5923d/Test_2.scala
@@ -0,0 +1,7 @@
+class RowA extends MappedRow
+class RowB extends MappedRow
+
+object Test extends App {
+  implicitly[RowMapper[RowA]]
+  implicitly[RowMapper[RowB]]
+}
\ No newline at end of file