Handle nil with any number of parentheses

Author: HassanElDesouky

test/Constraints/optional.swift

@@ -439,6 +439,10 @@ func sr_12309() {
   _ = nil? // expected-error {{value of optional type 'Optional<_>' must be unwrapped to a value of type '_'}}
            // expected-note@-1 {{coalesce using '??' to provide a default when the optional value contains 'nil'}}
            // expected-note@-2 {{force-unwrap using '!' to abort execution if the optional value contains 'nil'}}
-  _ = (nil) // expected-error {{'nil' requires a contextual type}}
   _ = nil // expected-error {{'nil' requires a contextual type}}
+  _ = (nil) // expected-error {{'nil' requires a contextual type}}
+  _ = ((nil)) // expected-error {{'nil' requires a contextual type}}
+  _ = (((nil))) // expected-error {{'nil' requires a contextual type}}
+  _ = ((((((nil)))))) // expected-error {{'nil' requires a contextual type}}
+  _ = (((((((((nil))))))))) // expected-error {{'nil' requires a contextual type}}
 }