This improves and unifies our approach to printing all template
arguments.
The same approach to printing types is extended to all
TemplateArguments: A sugared version is printed in quotes, followed by
printing the canonical form, unless they would print the same.
Special improvements are done to add more detail to template template
arguments.
It's planned in a future patch to use this improved TemplateName printer
for other places besides TemplateArguments.
Note: The sugared/desugared printing does not show up for TemplateNames
in tests yet, because we do a poor job of preserving their type sugar.
This will be improved in a future patch.
The standard requires[0] member function constraints to be checked when
explicitly instantiating classes. This patch adds this constraints
check.
This issue is tracked as #46029 [1].
Note that there's an related open CWG issue (2421[2]) about what to do when
multiple candidates have satisfied constraints. This is particularly an
issue because mangling doesn't contain function constraints, and so the
following code still ICEs with definition with same mangled name
'_ZN1BIiE1fEv' as another definition:
template<class T>
struct B {
int f() requires std::same_as<T, int> {
return 0;
}
int f() requires (std::same_as<T, int> &&
!std::same_as<T, char>) {
return 1;
}
};
template struct B<int>;
Also note that the constraints checking while instantiating *functions*
is still not implemented. I started looking at it but It's a bit more
complicated. I believe in such a case we have to consider the partial
constraints order and potentially choose the best candidate out of the
set of multiple valid ones.
[0]: https://eel.is/c++draft/temp.explicit#10
[1]: https://github.com/llvm/llvm-project/issues/46029
[2]: https://cplusplus.github.io/CWG/issues/2421.html
Differential Revision: https://reviews.llvm.org/D120255
