Merge pull request #2650 from paulp/issue/6221

SI-6221 inference with Function1 subtypes.

1 files changed, 29 insertions, 0 deletions

diff --git a/test/files/pos/t6221.scala b/test/files/pos/t6221.scala
new file mode 100644
index 0000000000..dd7776f596
--- /dev/null
+++ b/test/files/pos/t6221.scala
@@ -0,0 +1,29 @@
+class MyFunc[-A, +B] extends (A => B) { def apply(x: A): B = ??? }
+
+class MyCollection[A] {
+  def map[B](f: MyFunc[A, B]): MyCollection[B] = new MyCollection[B]
+}
+
+class OtherFunc[-A, +B] {}
+
+object Test {
+  implicit def functionToMyFunc[A, B](f: A => B): MyFunc[A, B] = new MyFunc
+
+  implicit def otherFuncToMyFunc[A, B](f: OtherFunc[A, B]): MyFunc[A, B] = new MyFunc
+
+  def main(args: Array[String]) {
+    val col = new MyCollection[Int]
+
+    // Doesn't compile: error: missing parameter type for expanded function ((x$1) => x$1.toString)
+    println(col.map(_.toString))
+
+    // Doesn't compile: error: missing parameter type
+    println(col.map(x => x.toString))
+
+    // Does compile
+    println(col.map((x: Int) => x.toString))
+
+    // Does compile (even though type params of OtherFunc not given)
+    println(col.map(new OtherFunc))
+  }
+}
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