This patch reapplies #111173, fixing a bug when instantiating dependent
expressions that name a member template that is later explicitly
specialized for a class specialization that is implicitly instantiated.
The bug is addressed by adding the `hasMemberSpecialization` function,
which return `true` if _any_ redeclaration is a member specialization.
This is then used when determining the instantiation pattern for a
specialization of a template, and when collecting template arguments for
a specialization of a template.
TypedefNameDecl referenced by a synthesized CTAD guide for type aliases
was not transformed previously, resulting in a substitution failure in
BuildDeductionGuideForTypeAlias() when substituting into the
right-hand-side deduction guide.
This patch fixes it in the way we have been doing since
https://reviews.llvm.org/D80743. We transform all the function
parameters, parenting referenced TypedefNameDecls with the
CXXDeductionGuideDecl. Then we instantiate these declarations in
FindInstantiatedDecl() as we build up the eventual deduction guide,
using the mechanism introduced in D80743
Fixes#111508
Reapplies #106585, fixing an issue where non-dependent names of member
templates appearing prior to that member template being explicitly
specialized for an implicitly instantiated class template specialization
would incorrectly use the definition of the explicitly specialized
member template.
Currently, clang rejects the following explicit specialization of `f`
due to the constraints not being equivalent:
```
template<typename T>
struct A
{
template<bool B>
void f() requires B;
};
template<>
template<bool B>
void A<int>::f() requires B { }
```
This happens because, in most cases, we do not set the flag indicating
whether a `RedeclarableTemplate` is an explicit specialization of a
member of an implicitly instantiated class template specialization until
_after_ we compare constraints for equivalence. This patch addresses the
issue (and a number of other issues) by:
- storing the flag indicating whether a declaration is a member
specialization on a per declaration basis, and
- significantly refactoring `Sema::getTemplateInstantiationArgs` so we
collect the right set of template argument in all cases.
Many of our declaration matching & constraint evaluation woes can be
traced back to bugs in `Sema::getTemplateInstantiationArgs`. This
change/refactor should fix a lot of them. It also paves the way for
fixing #101330 and #105462 per my suggestion in #102267 (which I have
implemented on top of this patch but will merge in a subsequent PR).
We ended up having two transformTemplateParameter() after CTAD for type
aliases was landed. This patch cleans them up and allows them to share
one implementation.
As a bonus, this also uses getDepthAndIndex() in preference to
getTemplateParameter{Depth,Index}().
This seems to be low-hanging fruit: We could remove all calls to
`Context.getCanonicalTemplateArgument()` and gain a better
diagnostic/AST.
The non-canonical template arguments shouldn't make a difference when
synthesizing a CTAD guide, so this is intended to be an NFC.
Closes https://github.com/llvm/llvm-project/issues/79798
Split out the deduction guide related code from SemaTemplate.cpp to a
dedicated file.
These code has grown significantly, and moving it to a separate file
will improve code organization.
