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Subject: [Bug c++/45873] Parameter packs not expanding consistently in function return types
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45873

--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> 2011-05-16 17:04:12 UTC ---
(In reply to comment #3)
> This seems like a dup of 35722.

Ah yes, it definitely is for the call to foo<p1> in my second example in
comment 2: modifying pt.c to always complain at the FIXME in
coerce_template_parms produces the "sorry" for the call to foo<p1>

45873.c2.cc: In function 'int main()':
45873.c2.cc:14:18: sorry, unimplemented: cannot expand 'Args ...' into a
fixed-length argument list
45873.c2.cc:14:18: error: no matching function for call to 'foo(int, double)'
45873.c2.cc:14:18: note: candidate is:
45873.c2.cc:8:6: note: template<template<class ...> class T, class ... Args>
T<Args ...> foo(Args ...)
45873.c2.cc:15:18: error: no matching function for call to 'foo(int, double)'
45873.c2.cc:15:18: note: candidate is:
45873.c2.cc:8:6: note: template<template<class ...> class T, class ... Args>
T<Args ...> foo(Args ...)

But that "sorry" isn't reached for foo<p2> or for any foo<pair> in the other
testcases.

I don't know if that means something else is going on there, or if it's just an
undiagnosed case of the same situation.