Don't pursue SAM translation after an arity mismatch.

Before this change:

    scala> trait T { def apply(a: Int): Int }
    defined trait T

    scala> ((x: Int, y: Int) => 0): T
    <console>:9: error: object creation impossible, since method apply in trait T of type (a: Int)Int is not defined
                  ((x: Int, y: Int) => 0): T
                                    ^
After the change, these cases report the same errors as they do
*without* -Xexperimental.

3 files changed, 75 insertions, 0 deletions

diff --git a/test/files/neg/sammy_wrong_arity.check b/test/files/neg/sammy_wrong_arity.check
new file mode 100644
index 0000000000..af547a201d
--- /dev/null
+++ b/test/files/neg/sammy_wrong_arity.check
@@ -0,0 +1,52 @@
+sammy_wrong_arity.scala:6: error: type mismatch;
+ found   : () => Int
+ required: T1
+  (() => 0): T1
+      ^
+sammy_wrong_arity.scala:7: error: type mismatch;
+ found   : Any => Int
+ required: T2
+  ((x: Any) => 0): T2
+            ^
+sammy_wrong_arity.scala:9: error: type mismatch;
+ found   : Any => Int
+ required: T0
+  ((x: Any) => 0): T0
+            ^
+sammy_wrong_arity.scala:10: error: type mismatch;
+ found   : Any => Int
+ required: T2
+  ((x: Any) => 0): T2
+            ^
+sammy_wrong_arity.scala:12: error: type mismatch;
+ found   : (Any, Any) => Int
+ required: T0
+  ((x: Any, y: Any) => 0): T0
+                    ^
+sammy_wrong_arity.scala:13: error: type mismatch;
+ found   : (Any, Any) => Int
+ required: T1
+  ((x: Any, y: Any) => 0): T1
+                    ^
+sammy_wrong_arity.scala:15: error: missing parameter type
+  ((x) => 0): T2
+    ^
+sammy_wrong_arity.scala:17: error: missing parameter type
+  ((x) => 0): T0
+    ^
+sammy_wrong_arity.scala:18: error: missing parameter type
+  ((x) => 0): T2
+    ^
+sammy_wrong_arity.scala:20: error: missing parameter type
+  ((x, y) => 0): T0
+    ^
+sammy_wrong_arity.scala:20: error: missing parameter type
+  ((x, y) => 0): T0
+       ^
+sammy_wrong_arity.scala:21: error: missing parameter type
+  ((x, y) => 0): T1
+    ^
+sammy_wrong_arity.scala:21: error: missing parameter type
+  ((x, y) => 0): T1
+       ^
+13 errors found
diff --git a/test/files/neg/sammy_wrong_arity.flags b/test/files/neg/sammy_wrong_arity.flags
new file mode 100644
index 0000000000..48fd867160
--- /dev/null
+++ b/test/files/neg/sammy_wrong_arity.flags
@@ -0,0 +1 @@
+-Xexperimental
diff --git a/test/files/neg/sammy_wrong_arity.scala b/test/files/neg/sammy_wrong_arity.scala
new file mode 100644
index 0000000000..d03d266a0b
--- /dev/null
+++ b/test/files/neg/sammy_wrong_arity.scala
@@ -0,0 +1,22 @@
+trait T0 { def ap(): Int }
+trait T1 { def ap(a: Any): Int }
+trait T2 { def ap(a: Any, b: Any): Int }
+
+class Test {
+  (() => 0): T1
+  ((x: Any) => 0): T2
+
+  ((x: Any) => 0): T0
+  ((x: Any) => 0): T2
+
+  ((x: Any, y: Any) => 0): T0
+  ((x: Any, y: Any) => 0): T1
+
+  ((x) => 0): T2
+
+  ((x) => 0): T0
+  ((x) => 0): T2
+
+  ((x, y) => 0): T0
+  ((x, y) => 0): T1
+}