| Issue |
145505
|
| Summary |
[clang] `friend` declaration does not apply during constraint validation
|
| Labels |
clang
|
| Assignees |
|
| Reporter |
yalavrinenko
|
I discovered that with the latest `clang-21` the following code stop compiling:
```c++
#include <concepts>
template <typename T>
concept FooType = requires (T *v){
{v->bar()} -> std::same_as<int>;
};
template <typename T>
struct Bar {
Bar(T *owner): owner_{owner}{}
bool func() {
return owner()->bar() == 10;
}
auto owner() requires FooType<T> {
return owner_;
}
T *owner_;
};
class Owner{
public:
auto& obj() { return obj_; }
private:
friend Bar<Owner>;
int bar() { return 10; }
Bar<Owner> obj_{this};
};
int main(){
Owner o;
return o.obj().func();
}
```
The compilation error is following:
```
<source>:14:16: error: invalid reference to function 'owner': constraints not satisfied
14 | return owner()->bar() == 10;
| ^
<source>:38:20: note: in instantiation of member function 'Bar<Owner>::func' requested here
38 | return o.obj().func();
| ^
<source>:17:27: note: because 'Owner' does not satisfy 'FooType'
17 | auto owner() requires FooType<T> {
| ^
<source>:6:9: note: because 'v->bar()' would be invalid: 'bar' is a private member of 'Owner'
6 | {v->bar()} -> std::same_as<int>;
```
Link to godbolt: https://godbolt.org/z/PasxrhaEa
Compiler info:
```
> clang --version
Ubuntu clang version 21.0.0 (++20250623082046+1c78d8d9d7bc-1~exp1~20250623082206.2496)
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/lib/llvm-21/bin
```
The code above compiles with `gcc` as well as with `clang-20` and early version of `clang-21`. Unfortunately I can not provide the last working revision of `clang-21`.
Please clarify whether this behavior is expected?
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