Hi,

finally sending a patch for this issue. As noticed by submitter himself, 
it appears to boil down to a rather straightforward case of not 
rejecting unexpanded parameter packs in default arguments. In order to 
handle all the combinations (in/out of class, template 
parameter/function parameter) I added calls of 
check_for_bare_parameter_packs both to cp_parser_default_argument and 
cp_parser_late_parsing_default_args (to have a meaningful location for 
the latter, the patchlet which I sent earlier today is a must). Tested 
x86_64-linux.

Thanks,
Paolo.

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