https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90098
Bug ID: 90098
Summary: [P0732] Partial specialization of a class template
with variadic parameter pack fails
Product: gcc
Version: 9.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: mateusz.pusz at gmail dot com
Target Milestone: ---
Hi,
Compiling the code provided below with the following options produces an error:
"-std=c++2a -Wall -Wextra"
```
// works
template<typename... Ts>
struct X {};
template<typename T, typename... Rest>
struct X<T, Rest...> {};
// works
template<int... Is>
struct Y {};
template<int I, int... Rest>
struct Y<I, Rest...> {};
// error
struct A {
int value;
// auto operator<=>(const A&) = default;
};
template<A... Us>
struct Z {};
template<A V, A... Rest>
struct Z<V, Rest...> {};
```
Error:
<source>:25:8: error: partial specialization 'struct
Z<((A*)(void)0)->A::__ct_comp (((const A)V)), (const A)Rest ...>' is not more
specialized than [-fpermissive]
25 | struct Z<V, Rest...> {};
| ^~~~~~~~~~~~~
<source>:22:8: note: primary template 'template<A ...Us> struct Z'
22 | struct Z {};
| ^
<source>:25:8: error: template argument '((A*)(void)0)->A::__ct_comp (((const
A)V))' involves template parameter(s)
25 | struct Z<V, Rest...> {};
| ^~~~~~~~~~~~~
<source>:25:8: error: template argument '(const A)Rest' involves template
parameter(s)
See also: https://godbolt.org/z/G96q1_.
Best
Mat
