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.

1 files changed, 1 insertions, 0 deletions

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