[PATCH?] 'this' in typedefs, possibly overly complicated code in other 'this' checks?

[Alp Toker]

On 16/01/2014 06:38, Harald van Dijk wrote:
> Ah, thanks, you're right. If the in-class declaration doesn't use
> 'this', but the definition does, then 'this' would not be diagnosed with
> my approach.

Hi Harald,

If you have the time could you throw together a couple of tests for 
those cases as well?

checkThisInStaticMemberFunctionAttributes() looks like it can be dropped 
now that RecursiveASTVisitor visits attributes (r198224) so I'm hopeful 
we can still apply the bulk of the cleanup from your original patch 
without regressing.

Alp.



> Normally, if the definition does, so would the in-class
> declaration, where it would be diagnosed, but an example of where it
> doesn't is
>
> struct Foo {
>    static bool f();
> };
>
> auto Foo::f() -> decltype(this != 0) {
>    return true;
> }
>
> Cheers,
> Harald van Dijk
>
> On 16/01/14 01:25, Richard Smith wrote:
>> How does this deal with the case where 'this' appears in a declarator
>> for an out-of-line definition of a static member function? In that case,
>> we don't know we're parsing a static member function declaration until
>> *after* we've already parsed the 'this' expression. I believe the
>> existing complexity was aimed at correctly handling that case; it seems
>> surprising that we don't have any tests for it.
>>
>> On Wed Jan 15 2014 at 3:33:07 PM, Harald van Dijk <harald at gigawatt.nl
>> <mailto:harald at gigawatt.nl>> wrote:
>>
>>      Hi all,
>>
>>      This came up on StackOverflow recently:
>>
>>      'this' is rejected by clang in static member functions:
>>
>>      error: 'this' cannot be used in a static member function declaration
>>        static auto f() -> decltype(this);
>>                                    ^
>>
>>      However, what the standard actually says is that 'this' is not allowed
>>      except in non-static member functions (and some more bits not relevant
>>      here). Declarations that look like member functions but aren't, not even
>>      static ones, shouldn't allow 'this' either.
>>
>>        typedef auto f() -> decltype(this);
>>
>>      Looking to see what clang implements, I was very surprised. There is
>>      already perfectly functional code that rejects 'this' in 'friend'
>>      functions, and that code is not reused for 'static' functions (and
>>      'typedef's): instead, the checks have effectively been rewritten for
>>      'static'.
>>
>>      I'm wondering, why is that? If I do attempt to re-use the existing code,
>>      as in the attached patch, then the only changes in the test results are
>>      actually correct, as references to non-static data members are permitted
>>      even in 'static' functions, so long as they appear in unevaluated
>>      expressions. There is even a FIXME comment about this in the test. But
>>      I'm sure the current checks have been added for a good reason. Am I
>>      overlooking some important details that are not covered by the
>>      testsuite?
>>
>>      Cheers,
>>      Harald van Dijk
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