SI-6221 inference with Function1 subtypes.

There appears to be no upper bound on the number of places
we have to remove calls to typeSymbol and introduce calls to
baseType. This one was type inference for function parameter
types: worked when expected type was A => B, but not if there
was an implicit conversion from A => B to the expected type.

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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