[C++ Patch] PR 39970

[Jason Merrill]

On 04/24/2012 05:24 PM, Paolo Carlini wrote:
>> Perhaps we aren't checking default arguments unless they're actually
>> used; a could change that if they aren't dependent.
>>
> Your reply reached the mailing list a bit mangled, could you please
> clarify?

If the default argument isn't dependent on other template parameters, we 
can check immediately whether it is a suitable template argument for its 
parameter, including being a constant expression.  That ought to give an 
appropriate diagnostic for this testcase.

Jason