[cfe-dev] class template methods

[Peter Stirling]

Anyone?

On 16/04/15 06:25, Peter Stirling wrote:
> This does sound promising, but I'm not sure how to make use of it.
>
> At the moment my walker (which is based on clang::ASTConsumer) has a 
> handler for class templates that looks like:
>
> void Walker::TraverseClassTemplate(clang::ClassTemplateDecl const* d) {
>   TRACE(1, "walk template " + getDeclMetadataString(d));
>
>   bool was = inInstantiation;
>   inInstantiation = true;
>
>   for(auto decl : d->specializations()) {
>     visitor->RequestCompleteType(decl);
>     TraverseCXXRecord(decl);
>   }
>
>   inInstantiation = was;
> }
>
> Visitor::RequestCompleteType() calls Sema::RequireCompleteType() 
> (which IMO has the wrong name, it returns false on what I would 
> consider, from the name, success).
>
> So, I don't construct the specializations for methods directly in my 
> code, I assume that some of the instantiation is performed by 
> RequireCompleteType(), but surely if I checked for SFINAE at that 
> level then I would lose EVERY methods for std::pair<int const, int 
> const> and not just the ones that involve mutation?
>
> On 14/04/15 18:26, Richard Smith wrote:
>> On Tue, Apr 14, 2015 at 8:38 AM, Reid Kleckner <rnk at google.com 
>> <mailto:rnk at google.com>> wrote:
>>
>>     Sounds a lot like a SFINAE test. Assuming you already have an AST
>>     with the class template instantiation, then you'd attempt to
>>     instantiate the assignment operator inside a SFINAETrap.
>>     Instantiation will either pass or fail and you'll get your
>>     answer, and you should be able to continue compilation or further
>>     queries normally.
>>
>>
>> I think the above is about the best that you can do.
>>
>> One note: if an error occurs outside of the immediate context of the 
>> substitution, a SFINAETrap will not suppress it (which is actually a 
>> good thing in this case, because you cannot continue compilation 
>> normally after such an error -- any part of the AST that failed may 
>> be marked invalid, suppressing further errors in other contexts).
>>
>>     On Mon, Apr 13, 2015 at 9:57 PM, Peter Stirling
>>     <peter at pjstirling.plus.com <mailto:peter at pjstirling.plus.com>> wrote:
>>
>>         Hi,
>>
>>         Is there a way to ask clang whether a method for an
>>         instantiation of a class template would be an error to call?
>>         (I only need yes/no)
>>
>>         For example:
>>
>>         std::pair has assignment operators defined, but for the
>>         instantiation std::pair<int const, int const> calling the
>>         assignment operators is an error, because you can't assign to
>>         int const.
>>
>>         If clang can't tell me this, I'm looking at generating a
>>         translation unit with a call to the method, and then checking
>>         whether there was an error compiling it. Given that I will
>>         need to do this once per method, per instantiation, per
>>         template, (which looks to be in the thousands based on a test
>>         I just did) what is the best way to do this?
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>>
>>
>>
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>>
>
>
>
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