Open Radar

 
Summary: in the SDK, the declaration -[NSString isEqualToString:(NSString *)s] falls within an NS_ASSUME_NONNULL_BEGIN/NS_ASSUME_NONNULL_END block, and thus causes the parameter to be nil.




Steps to Reproduce:
(a)
NSString *x = @"test"; // line 1
if ([x isEqualToString:nil]) { // line 2
    NSLog(@"error: x is not equal to nil"); // line 3
} // line 4

(b)
NSString *x = @"test"; // line 1
if ([x isEqualToString:(NSString * _Nonnull)nil]) { // line 2
    NSLog(@"error: x is not equal to nil"); // line 3
} // line 4

(c)
NSString *RandomNullableString()
{
    return (arc4random_uniform(2) < 1) ? @"test" : nil;
}

NSString *x = @"test"; // line 1
NSString *y = RandomNullableString(); // line 2
if ([x isEqualToString:y]) { // line 3
    NSLog(@"error: x is not equal to nil"); // line 4
} // line 5

Expected Results (based on preference for nullable parameter):
(a) no compiler/analyzer issues; conditional line 2 is NO, line 3 is not executed
(b) no compiler/analyzer issues; conditional line 2 is NO, line 3 is not executed
(c) no compiler/analyzer issues; conditional line 3 is YES half the time and NO half the time, line 4 is not executed

Actual Results:
(a) compiler error (parameter requires non-nil value)
(b) works as expected
(c) some instances (haven't figured out why) result in an analyzer issue about a potential nil being passed

Version/Build: Xcode 9.3


Configuration: macOS High Sierra (10.13.4), MacBook Pro (Retina, 15-inch, Mid 2015)