Description
Godbolt: https://godbolt.org/z/817Kve9zc
It seems that clang can't compile code if I decide to separate the declaration and implementation of a function with pack indexing in some cases. However, if you comment out the declaration, it will compile.
#include <concepts>
#include <iostream>
// in requires expression
template <class... Types>
requires std::same_as<Types...[0], int>
void print(double d);
template <class... Types>
requires std::same_as<Types...[0], int>
void print(double d) {
std::cout << "it doesn't work " << static_cast<Types...[0]>(d) << "\n";
}
// in return type
template <class... Types>
Types...[0] convert(double d);
template <class... Types>
Types...[0] convert(double d) {
return static_cast<Types...[0]>(d);
}
int main() {
print<int, int>(12.34);
std::cout << "convert: " << convert<int, int>(12.34) << "\n";
return 0;
}Output
<source>:30:5: error: call to 'print' is ambiguous
30 | print<int, int>(12.34);
| ^~~~~~~~~~~~~~~
<source>:9:6: note: candidate function [with Types = <int, int>]
9 | void print(double d);
| ^
<source>:13:6: note: candidate function [with Types = <int, int>]
13 | void print(double d) {
| ^
<source>:31:33: error: call to 'convert' is ambiguous
31 | std::cout << "convert: " << convert<int, int>(12.34) << "\n";
| ^~~~~~~~~~~~~~~~~
<source>:21:13: note: candidate function [with Types = <int, int>]
21 | Types...[0] convert(double d);
| ^
<source>:24:13: note: candidate function [with Types = <int, int>]
24 | Types...[0] convert(double d) {
| ^
2 errors generated.
Compiler returned: 1