[PATCH] Add AttrDocs for objc_boxable attribute

[John McCall]

> On Jul 23, 2015, at 2:24 PM, AlexDenisov <1101.debian at gmail.com> wrote:
> Thank you for the corrections.
> Natural language is not my cup of tea.
> 
> <objc_boxable_attr_docs.patch>

+with the Objective-C boxed expression syntax, ``@(…)``.

This turned into a Unicode character, probably on my end, but in the .td file it needs to be spelled with three periods.

With that, LGTM, please commit.

John.

> 
> 
>> On 23 Jul 2015, at 22:57, John McCall <rjmccall at apple.com> wrote:
>> 
>>> On Jul 23, 2015, at 1:20 PM, AlexDenisov <1101.debian at gmail.com> wrote:
>>> Patch adds rough documentation for objc_boxable attribute
>> 
>> +def ObjCBoxableDocs : Documentation {
>> +    let Category = DocCatType;
>> +    let Content = [{
>> +Structs and unions marked with ``objc_boxable`` attribute can be used inside of boxed expressions.
>> 
>> “Structs and unions marked with the ``objc_boxable`` attribute can be used with the Objective-C boxed expression syntax, ``@(…)``.”
>> 
>> +**Usage**: ``__attribute__((objc_boxable))``.  This attribute
>> +can only be placed at record declaration or record definition:
>> 
>> This should be a separate paragraph; just add an empty line before **Usage**.
>> 
>> “This attribute can only be placed on a declaration of a trivially-copyable struct or union:”
>> 
>> +
>> +.. code-block:: objc
>> +
>> +  struct __attribute__((objc_boxable)) some_struct {
>> +    int i;
>> +  };
>> +  union __attribute__((objc_boxable)) some_union {
>> +    int i;
>> +    float f;
>> +  };
>> +  typedef struct __attribute__((objc_boxable)) _some_struct some_struct;
>> +
>> +  // ...
>> +
>> +  some_struct ss;
>> +  NSValue *boxed = @(ss);
>> 
>> John.
>