Open Radar

 
Summary:
In Objective–C++ code, using the `auto` keyword correctly preserves type annotations for e.g. NSArray return values, such as the following:

    // given that view is some UIView *:
    auto const interestingViews = view.subviews;
    // interestingViews is of type NSArray<__kindof UIView *> *const -- as expected

If, however, those values are indirected through other generic class methods, the type annotations are lost:

    // again we have some UIView *view:
    auto const viewsToFilter = [NSMutableArray arrayWithArray:view.subviews];
    // type information is lost: viewsToFilter is of type NSMutableArray *const
    // even though arrayWithArray: is annotated with ObjectType
    // i.e. it _should_ produce NSMutableArray<ObjectType> *

Steps to Reproduce:
1. Create a new iOS single view app project in Xcode 7
2. Change the view controller’s implementation file extension to .mm
3. In the viewDidLoad method, after the super call add the line `auto view = self.view;`
4. Copy and paste the code snippets from the description in there.
5. Observe the types in the auto completion list when you type `viewsT` and `intere`

Expected Results:
`intere` yields `interestingViews` with a type of `NSArray<__kindof UIView *> *const` in the auto complete list, `viewsT` yields `viewsToFilter` with a type of `NSMutableArray<__kindof UIView *> *const` in the auto complete list

Actual Results:
`intere` yields `interestingViews` with a type of `NSArray<__kindof UIView *> *const` in the auto complete list — that’s good.

`viewsT` yields `viewsToFilter` with a type of `NSMutableArray *const` in the auto complete list — that’s bad: the type annotation has been swallowed.

Version:
Happens in all Xcode 7 seeds, last checked with Version 7.0 beta 3 (7A152u)

Notes:
This is a duplicate of rdar://21765641

Configuration:


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