r240155 - Implement the 'null_resettable' attribute for Objective-C properties.

[Douglas Gregor]

> On Jun 20, 2015, at 12:10 PM, Aaron Ballman <aaron at aaronballman.com> wrote:
> 
> On Fri, Jun 19, 2015 at 2:14 PM, Douglas Gregor <dgregor at apple.com <mailto:dgregor at apple.com>> wrote:
> 
>> +  for (const auto *propertyImpl : impDecl->property_impls()) {
>> +    const auto *property = propertyImpl->getPropertyDecl();
>> +
>> +    // Warn about null_resettable properties with synthesized setters,
>> +    // because the setter won't properly handle nil.
>> +    if (propertyImpl->getPropertyImplementation()
>> +          == ObjCPropertyImplDecl::Synthesize &&
>> +        (property->getPropertyAttributes() &
>> +         ObjCPropertyDecl::OBJC_PR_null_resettable) &&
> 
> The more I see the bitwise tests, the more I wonder if having a
> propertyAttributeIsSet() function might make sense?

Probably, yes.

> 
>> +        property->getGetterMethodDecl() &&
>> +        property->getSetterMethodDecl()) {
>> +      auto *getterMethod = property->getGetterMethodDecl();
>> +      auto *setterMethod = property->getSetterMethodDecl();
>> +      if (!impDecl->getInstanceMethod(setterMethod->getSelector()) &&
>> +          !impDecl->getInstanceMethod(getterMethod->getSelector())) {
>> +        SourceLocation loc = propertyImpl->getLocation();
>> +        if (loc.isInvalid())
>> +          loc = impDecl->getLocStart();
> 
> Under what circumstances would loc be invalid here? (I may simply be
> unfamiliar with ObjC and that's not a problem.)

Getters and setters can be synthesized by the @implementation, which means they won’t have useful source locations.

(Comments appreciated and cleanup commits coming, thanks!)

	- Doug

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