Merge pull request #661 from retronym/ticket/5683

SI-5683 Fail gracefully when transposing a ragged type arg matrix.

2 files changed, 39 insertions, 0 deletions

diff --git a/test/files/neg/t5683.check b/test/files/neg/t5683.check
new file mode 100644
index 0000000000..7c0e50113c
--- /dev/null
+++ b/test/files/neg/t5683.check
@@ -0,0 +1,16 @@
+t5683.scala:12: error: inferred kinds of the type arguments (Object,Int) do not conform to the expected kinds of the type parameters (type M,type B).
+Object's type parameters do not match type M's expected parameters:
+class Object has no type parameters, but type M has one
+  val crash: K[StringW,Int,Int] = k{ (y: Int) => null: W[String, Int] }
+                                  ^
+t5683.scala:12: error: type mismatch;
+ found   : Int => Test.W[String,Int]
+ required: Int => M[B]
+  val crash: K[StringW,Int,Int] = k{ (y: Int) => null: W[String, Int] }
+                                              ^
+t5683.scala:12: error: type mismatch;
+ found   : Test.K[M,Int,B]
+ required: Test.K[Test.StringW,Int,Int]
+  val crash: K[StringW,Int,Int] = k{ (y: Int) => null: W[String, Int] }
+                                   ^
+three errors found
diff --git a/test/files/neg/t5683.scala b/test/files/neg/t5683.scala
new file mode 100644
index 0000000000..05ab035792
--- /dev/null
+++ b/test/files/neg/t5683.scala
@@ -0,0 +1,23 @@
+object Test {
+  trait NT[X]
+  trait W[W, A] extends NT[Int]
+  type StringW[T] = W[String, T]
+  trait K[M[_], A, B]
+
+  def k[M[_], B](f: Int => M[B]): K[M, Int, B] = null
+
+  val okay1: K[StringW,Int,Int] = k{ (y: Int) => null: StringW[Int] }
+  val okay2 = k[StringW,Int]{ (y: Int) => null: W[String, Int] }
+
+  val crash: K[StringW,Int,Int] = k{ (y: Int) => null: W[String, Int] }
+
+  // remove `extends NT[Int]`, and the last line gives an inference error
+  // rather than a crash.
+  //   test/files/pos/t5683.scala:12: error: no type parameters for method k: (f: Int => M[B])Test.K[M,Int,B] exist so that it can be applied to arguments (Int => Test.W[String,Int])
+  //  --- because ---
+  // argument expression's type is not compatible with formal parameter type;
+  //  found   : Int => Test.W[String,Int]
+  //  required: Int => ?M[?B]
+  //   val crash: K[StringW,Int,Int] = k{ (y: Int) => null: W[String, Int] }
+  //                                   ^
+}