[cdt-dev] use of hasMultipleArgs() in TemplateIdStrategy

[Nathan Ridge <zeratul976@xxxxxxxxxxx>]

Hi,

I'm investigating bug 445177, where CDT fails to parse the following declaration:

a<b<c,b<c>::*member;

The only valid parse here is 

a<(b<c),(b<c)>::*member, 

i.e. the first '<' starts a template-parameter-list while other two '<' are less-than operators.

However, CDT does not consider this parse. The reason is that in TemplateIdStrategy, we skip over the alternative that would interpret the first '<' as opening a template-parameter-list but the second '<' as less-than.

This is because in setNextAlternative(), the code that would consider the second '<' as less-than is conditioned on '!hasMultipleArgs(names[--nameLen])', where 'names[--nameLen]' in this case is the first 'b', and 'hasMultipleArgs()' checks whether the name is part of a template-id with multiple template arguments.

As it happens, the check fails, because while considering the previous alternative, the first 'b' was parsed as part of the template-id 'b<c,(b<c)>', which has two arguments.

I see that the use of hasMultipleArgs() was added in bug 363609 for performance reasons. However, is there a correctness argument for conditioning on hasMultipleArgs() here? The above example would lead me to believe 'no', but perhaps I'm missing something.

cc'ing Markus, who originally wrote this code.

Thanks,
Nate