https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79668
Bug ID: 79668
Summary: [c++1z] inconsistent handling of parameter matching in
template template arguments
Product: gcc
Version: 7.0.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: richard-gccbugzilla at metafoo dot co.uk
Target Milestone: ---
Consider the following:
template<template<short x> typename> struct A;
template<typename T, template<T x> typename> struct B;
template<int x> struct C;
A<C> *ac;
B<short, C> *bc;
It should hopefully be clear that the type 'A<C>' is valid if and only if the
type 'B<short, C>' is valid. However, under -std=c++1z, GCC accepts 'A<C>' but
rejects 'B<short, C>':
<source>:5:11: error: type/value mismatch at argument 2 in template parameter
list for 'template<class T, template<T x> class<template-parameter-1-2> >
struct B'
B<short, C> *bc;
^
<source>:5:11: note: expected a template of type 'template<T x>
class<template-parameter-1-2>', got 'template<int x> struct C'
Compiler exited with result code 1
Note that the above error is also the one produced outside C++1z mode, so
perhaps whatever special handling is engaged for P0522R0 is missed in the case
where the template template parameter is dependent?
FWIW, Clang's implementation of P0522R0 accepts both cases.
