| Issue |
127236
|
| Summary |
Clang 19.1.0 - Extremely poor error message when dealing with callback functions and std::format
|
| Labels |
|
| Assignees |
|
| Reporter |
9291Sam
|
Here's an MRE for this error.
[https://godbolt.org/z/b4sErhzqb](https://godbolt.org/z/b4sErhzqb)
```cpp
#include <iostream>
#include <vector>
#include <concepts>
struct CallBack
{
void callback(std::invocable<int, std::size_t> auto func)
{
for (std::size_t i = 0; i < foo.size(); ++i)
{
func(foo[i], i);
}
}
std::vector<int> foo;
};
void caller()
{
CallBack c {};
c.callback(
[&](int i, std::size_t s)
{
// the error is below, there are 4 {} which correspond with only 3 arguments
std::cout << std::format("{} {} {} {}", s, i, false);
});
}
```
->
```cpp
<source>:11:13: error: call to immediate function 'caller()::(anonymous class)::operator()' is not a constant _expression_
11 | func(foo[i], i);
| ^
<source>:22:7: note: in instantiation of function template specialization 'CallBack::callback<(lambda at <source>:23:9)>' requested here
22 | c.callback(
| ^
<source>:11:18: note: implicit use of 'this' pointer is only allowed within the evaluation of a call to a 'constexpr' member function
11 | func(foo[i], i);
| ^
1 error generated.
Compiler returned: 1
```
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