erichkeane added a comment.
Herald added a reviewer: dang.
@rsmith pointed out https://eel.is/c++draft/temp#friend-9 which I think is
supposed to fix the friend function issues:
> A non-template friend declaration with a requires-clause shall be a
> definition.
> A friend function template with a constraint that depends on a template
> parameter from an enclosing template shall be a definition.
> Such a constrained friend function or function template declaration does not
> declare the same function or function template as a declaration in any other
> scope.
To me, this says that
template<typename T>
struct S {
friend void foo() requires true {}
};
void bar() {
S<int> s;
S<float> s2;
}
Should be perfectly fine, and NOT a redefinition? At least this:
https://godbolt.org/z/PaK1Yhn1E seems to show that all 3 compilers get this
wrong currently? Or I'm misreading this.
It ALSO means that:
template<typename T>
struct S {
template<typename U>
friend void foo() requires constriant<T> {}
};
void bar() {
S<int> s;
S<float> s2;
}
is perfectly fine, and not a redefinition. (CURRENT Clang and GCC get this
right, but MSVC seems to get it wrong: https://godbolt.org/z/a7dYezoPW)
HOWEVER, By reading the rule, a slightly DIFFERENT version of that
template<typename T>
struct S {
template<typename U>
friend void foo() requires constriant<U> {} // No longer relies on the
enclosing template
};
void bar() {
S<int> s;
S<float> s2;
}
Is a redefinition. All 3 compilers diagnose this.
https://godbolt.org/z/7qbYsb635
Do I have this right? I'm having trouble figuring out the implementation
strategy here. It seems my SemaOverload.cpp changes would need to do special
work to get example #1 to work, and I got close on #2 (with the exception of
some assert in libc++). And #3 I probably had right?
Can someone else read the standard bit there and make sure I got a good spread
of the issues and interpreted the prose correctly?
Thanks!
-Erich
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D119544/new/
https://reviews.llvm.org/D119544
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