Merge pull request #3312 from xeno-by/topic/fine-points-of-whiteboxity-210x

(2.10.x) codifies the state of the art wrt SI-8104

6 files changed, 98 insertions, 0 deletions

diff --git a/test/files/neg/t8104a.check b/test/files/neg/t8104a.check
new file mode 100644
index 0000000000..ef92c2e1ef
--- /dev/null
+++ b/test/files/neg/t8104a.check
@@ -0,0 +1,4 @@
+Test_2.scala:19: error: could not find implicit value for parameter e: Generic.Aux[Test.C,(Int, Int)]
+  implicitly[Generic.Aux[C, (Int, Int)]]
+            ^
+one error found
diff --git a/test/files/neg/t8104a/Macros_1.scala b/test/files/neg/t8104a/Macros_1.scala
new file mode 100644
index 0000000000..688d0694c0
--- /dev/null
+++ b/test/files/neg/t8104a/Macros_1.scala
@@ -0,0 +1,23 @@
+import scala.reflect.macros.Context
+
+object Macros {
+  def impl[T](c: Context)(implicit T: c.WeakTypeTag[T]) = {
+    import c.universe._
+    import Flag._
+    import definitions._
+    val fields = T.tpe.declarations.toList.collect{ case x: TermSymbol if x.isVal && x.isCaseAccessor => x }
+    val Repr = appliedType(TupleClass(fields.length).asType.toType, fields.map(_.typeSignature))
+    c.Expr(Block(
+      List(ClassDef(
+        Modifiers(FINAL),
+        newTypeName("$anon"),
+        List(),
+        Template(
+          List(AppliedTypeTree(Ident(newTypeName("Generic")), List(TypeTree(T.tpe)))),
+          emptyValDef,
+          List(
+            DefDef(Modifiers(), nme.CONSTRUCTOR, List(), List(List()), TypeTree(), Block(List(Apply(Select(Super(This(tpnme.EMPTY), tpnme.EMPTY), nme.CONSTRUCTOR), List())), Literal(Constant(())))),
+            TypeDef(Modifiers(), newTypeName("Repr"), List(), TypeTree(Repr)))))),
+      Apply(Select(New(Ident(newTypeName("$anon"))), nme.CONSTRUCTOR), List())))
+  }
+}
\ No newline at end of file
diff --git a/test/files/neg/t8104a/Test_2.scala b/test/files/neg/t8104a/Test_2.scala
new file mode 100644
index 0000000000..f601fc3570
--- /dev/null
+++ b/test/files/neg/t8104a/Test_2.scala
@@ -0,0 +1,20 @@
+trait Generic[T] { type Repr }
+object Generic {
+  type Aux[T, Repr0] = Generic[T] { type Repr = Repr0 }
+  import scala.language.experimental.macros
+  implicit def materializeGeneric[T]: Generic[T] = macro Macros.impl[T]
+}
+
+object Test extends App {
+  case class C(x: Int, y: Int)
+
+  def reprify[T, Repr](x: T)(implicit generic: Generic.Aux[T, Repr]) = ???
+  reprify(C(40, 2))
+
+  // this is a compilation error at the moment as explained in SI-8104
+  // because matchesPt in implicit search says that depoly(<type of materializeGeneric>) isn't a subtype of Generic.Aux[C, (Int, Int)]
+  // which is rightfully so, because depoly only replaces type parameters, not type members with wildcard types
+  // however in the future we might want to relax the matchesPt check, so this might start compiling
+  // therefore, if you've broken this test, then you should be happy, because most likely you've just enabled an interesting use case!
+  implicitly[Generic.Aux[C, (Int, Int)]]
+}
diff --git a/test/files/neg/t8104b.check b/test/files/neg/t8104b.check
new file mode 100644
index 0000000000..3214a132c2
--- /dev/null
+++ b/test/files/neg/t8104b.check
@@ -0,0 +1,4 @@
+Test_2.scala:16: error: could not find implicit value for parameter generic: Generic.Aux[Test.C,Repr]
+  reprify(C(40, 2))
+         ^
+one error found
diff --git a/test/files/neg/t8104b/Macros_1.scala b/test/files/neg/t8104b/Macros_1.scala
new file mode 100644
index 0000000000..688d0694c0
--- /dev/null
+++ b/test/files/neg/t8104b/Macros_1.scala
@@ -0,0 +1,23 @@
+import scala.reflect.macros.Context
+
+object Macros {
+  def impl[T](c: Context)(implicit T: c.WeakTypeTag[T]) = {
+    import c.universe._
+    import Flag._
+    import definitions._
+    val fields = T.tpe.declarations.toList.collect{ case x: TermSymbol if x.isVal && x.isCaseAccessor => x }
+    val Repr = appliedType(TupleClass(fields.length).asType.toType, fields.map(_.typeSignature))
+    c.Expr(Block(
+      List(ClassDef(
+        Modifiers(FINAL),
+        newTypeName("$anon"),
+        List(),
+        Template(
+          List(AppliedTypeTree(Ident(newTypeName("Generic")), List(TypeTree(T.tpe)))),
+          emptyValDef,
+          List(
+            DefDef(Modifiers(), nme.CONSTRUCTOR, List(), List(List()), TypeTree(), Block(List(Apply(Select(Super(This(tpnme.EMPTY), tpnme.EMPTY), nme.CONSTRUCTOR), List())), Literal(Constant(())))),
+            TypeDef(Modifiers(), newTypeName("Repr"), List(), TypeTree(Repr)))))),
+      Apply(Select(New(Ident(newTypeName("$anon"))), nme.CONSTRUCTOR), List())))
+  }
+}
\ No newline at end of file
diff --git a/test/files/neg/t8104b/Test_2.scala b/test/files/neg/t8104b/Test_2.scala
new file mode 100644
index 0000000000..a0d35942ba
--- /dev/null
+++ b/test/files/neg/t8104b/Test_2.scala
@@ -0,0 +1,24 @@
+trait Generic[T] { type Repr }
+object Generic {
+  type Aux[T, Repr0] = Generic[T] { type Repr = Repr0 }
+  import scala.language.experimental.macros
+  implicit def materializeGeneric[T, Repr]: Generic.Aux[T, Repr] = macro Macros.impl[T]
+}
+
+object Test extends App {
+  case class C(x: Int, y: Int)
+
+  // this doesn't work because of SI-7470
+  // well, in fact SI-7470 has been fixed: https://github.com/scala/scala/pull/2499
+  // it's just that the fix hasn't been backported to 2.10.x
+  // if you've made this compile, consider taking a look at the aforementioned pull request
+  def reprify[T, Repr](x: T)(implicit generic: Generic.Aux[T, Repr]) = ???
+  reprify(C(40, 2))
+
+  // this is a compilation error at the moment as explained in SI-8104
+  // because matchesPt in implicit search says that depoly(<type of materializeGeneric>) isn't a subtype of Generic.Aux[C, (Int, Int)]
+  // which is rightfully so, because depoly only replaces type parameters, not type members with wildcard types
+  // however in the future we might want to relax the matchesPt check, so this might start compiling
+  // therefore, if you've broken this test, then you should be happy, because most likely you've just enabled an interesting use case!
+  implicitly[Generic.Aux[C, (Int, Int)]]
+}