Add a test that verifyies comparing to a .none case that isn't Optional.none still works

Author: calda

test/expr/cast/nil_value_to_optional.swift

@@ -34,4 +34,14 @@ _ = d! // expected-error {{cannot force unwrap value of non-optional type 'D'}}
 _ = dopt == nil
 _ = diuopt == nil
 _ = diuopt is ExpressibleByNilLiteral // expected-warning {{'is' test is always true}}
-_ = produceD() is ExpressibleByNilLiteral // expected-warning {{'is' test is always true}}
+_ = produceD() is ExpressibleByNilLiteral // expected-warning {{'is' test is always true}}
+
+enum E {
+  case none
+}
+func test(_ e: E) {
+  _ = e == .none
+  _ = e == E.none
+  _ = e == Optional.none // expected-warning {{comparing non-optional value of type 'E' to 'nil' or 'Optional.none' always returns false}}
+  _ = e == E?.none // expected-warning {{comparing non-optional value of type 'E' to 'nil' or 'Optional.none' always returns false}}
+}