https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99518
Bug ID: 99518
Summary: trailing requires clause adds nonexistent reference
declarator to function parameter
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: nickgray0 at brown dot edu
Target Milestone: ---
the following code fails to compile
#include <concepts>
auto f(std::integral auto x) {}
auto g(auto x) requires requires { { x }->std::integral; } {}
auto main()->int {
f(42); // OK
g(42); // error
}
error message: In function 'int main()':
<source>:8:9: error: no matching function for call to 'g(int)'
8 | g(42); // error
| ^
<source>:4:6: note: candidate: 'template<class auto:2> auto g(auto:2) requires
requires{{g::x} -> decltype(auto) [requires std::integral<<placeholder>, >];}'
4 | auto g(auto x) requires requires { { x }->std::integral; } {}
| ^
<source>:4:6: note: template argument deduction/substitution failed:
<source>:4:6: note: constraints not satisfied
<source>: In substitution of 'template<class auto:2> auto g(auto:2) requires
requires{{x} -> decltype(auto) [requires std::integral<<placeholder>, >];}
[with auto:2 = int]':
<source>:8:9: required from here
<source>:4:6: required by the constraints of 'template<class auto:2> auto
g(auto:2) requires requires{{x} -> decltype(auto) [requires
std::integral<<placeholder>, >];}'
<source>:4:25: in requirements [with auto:2 = int]
<source>:4:38: note: 'x' does not satisfy return-type-requirement, because
4 | auto g(auto x) requires requires { { x }->std::integral; } {}
| ^
<source>:4:38: error: deduced expression type does not satisfy placeholder
constraints
4 | auto g(auto x) requires requires { { x }->std::integral; } {}
| ~~^~~~~~~~~~~~~~~~~~
<source>:4:38: note: constraints not satisfied
In file included from <source>:1:
/opt/compiler-explorer/gcc-trunk-20210310/include/c++/11.0.1/concepts:102:13:
required for the satisfaction of 'integral<decltype(auto) [requires
std::integral<<placeholder>, >]>' [with decltype(auto) [requires
std::integral<<placeholder>, >] = int&]
/opt/compiler-explorer/gcc-trunk-20210310/include/c++/11.0.1/concepts:102:24:
note: the expression 'is_integral_v<_Tp> [with _Tp = int&]' evaluated to
'false'
102 | concept integral = is_integral_v<_Tp>;
