This reintroduces `Type.h`, having earlier been renamed to `TypeBase.h`,
as a redirection to `TypeBase.h`, and redirects most users to include
the former instead.
This is a preparatory patch for being able to provide inline definitions
for `Type` methods which would otherwise cause a circular dependency
with `Decl{,CXX}.h`.
Doing these operations into their own NFC patch helps the git rename
detection logic work, preserving the history.
This patch makes clang just a little slower to build (~0.17%), just
because it makes more code indirectly include `DeclCXX.h`.
This is a preparatory patch, to be able to provide inline definitions
for `Type` functions which depend on `Decl{,CXX}.h`. As the latter also
depends on `Type.h`, this would not be possible without some
reorganizing.
Splitting this rename into its own patch allows git to track this as a
rename, and preserve all git history, and not force any code
reformatting.
A later NFC patch will reintroduce `Type.h` as redirection to
`TypeBase.h`, rewriting most places back to directly including `Type.h`
instead of `TypeBase.h`, leaving only a handful of places where this is
necessary.
Then yet a later patch will exploit this by making more stuff inline.
This changes a bunch of places which use getAs<TagType>, including derived types, just to obtain the tag definition. This is preparation for #155028, offloading all the changes that PR used to introduce which don't depend on any new helpers.
The new builtin `__builtin_dedup_pack` removes duplicates from list of
types.
The added builtin is special in that they produce an unexpanded pack
in the spirit of P3115R0 proposal.
Produced packs can be used directly in template argument lists and get
immediately expanded as soon as results of the computation are
available.
It allows to easily combine them, e.g.:
```cpp
template <class ...T>
struct Normalize {
// Note: sort is not included in this PR, it illustrates the idea.
using result = std::tuple<
__builtin_sort_pack<
__builtin_dedup_pack<int, double, T...>...
>...>;
}
;
```
Limitations:
- only supported in template arguments and bases,
- can only be used inside the templates, even if non-dependent,
- the builtins cannot be assigned to template template parameters.
The actual implementation proceeds as follows:
- When the compiler encounters a `__builtin_dedup_pack` or other
type-producing
builtin with dependent arguments, it creates a dependent
`TemplateSpecializationType`.
- During substitution, if the template arguments are non-dependent, we
will produce: a new type `SubstBuiltinTemplatePackType`, which stores
an argument pack that needs to be substituted. This type is similar to
the existing `SubstTemplateParmPack` in that it carries the argument
pack that needs to be expanded further. The relevant code is shared.
- On top of that, Clang also wraps the resulting type into
`TemplateSpecializationType`, but this time only as a sugar.
- To actually expand those packs, we collect the produced
`SubstBuiltinTemplatePackType` inside `CollectUnexpandedPacks`.
Because we know the size of the produces packs only after the initial
substitution, places that do the actual expansion will need to have a
second run over the substituted type to finalize the expansions (in
this patch we only support this for template arguments, see
`ExpandTemplateArgument`).
If the expansion are requested in the places we do not currently
support, we will produce an error.
More follow-up work will be needed to fully shape this:
- adding the builtin that sorts types,
- remove the restrictions for expansions,
- implementing P3115R0 (scheduled for C++29, see
https://github.com/cplusplus/papers/issues/2300).
This fixes a regression reported here https://github.com/llvm/llvm-project/pull/147835#issuecomment-3181811371, where getTrivialTemplateArgumentLoc can't see through template name sugar when producing a trivial TemplateArgumentLoc for template template arguments. Since this regression was never released, there are no release notes.
This is a major change on how we represent nested name qualifications in the AST. * The nested name specifier itself and how it's stored is changed. The prefixes for types are handled within the type hierarchy, which makes canonicalization for them super cheap, no memory allocation required. Also translating a type into nested name specifier form becomes a no-op. An identifier is stored as a DependentNameType. The nested name specifier gains a lightweight handle class, to be used instead of passing around pointers, which is similar to what is implemented for TemplateName. There is still one free bit available, and this handle can be used within a PointerUnion and PointerIntPair, which should keep bit-packing aficionados happy. * The ElaboratedType node is removed, all type nodes in which it could previously apply to can now store the elaborated keyword and name qualifier, tail allocating when present. * TagTypes can now point to the exact declaration found when producing these, as opposed to the previous situation of there only existing one TagType per entity. This increases the amount of type sugar retained, and can have several applications, for example in tracking module ownership, and other tools which care about source file origins, such as IWYU. These TagTypes are lazily allocated, in order to limit the increase in AST size. This patch offers a great performance benefit. It greatly improves compilation time for [stdexec](https://github.com/NVIDIA/stdexec). For one datapoint, for `test_on2.cpp` in that project, which is the slowest compiling test, this patch improves `-c` compilation time by about 7.2%, with the `-fsyntax-only` improvement being at ~12%. This has great results on compile-time-tracker as well:  This patch also further enables other optimziations in the future, and will reduce the performance impact of template specialization resugaring when that lands. It has some other miscelaneous drive-by fixes. About the review: Yes the patch is huge, sorry about that. Part of the reason is that I started by the nested name specifier part, before the ElaboratedType part, but that had a huge performance downside, as ElaboratedType is a big performance hog. I didn't have the steam to go back and change the patch after the fact. There is also a lot of internal API changes, and it made sense to remove ElaboratedType in one go, versus removing it from one type at a time, as that would present much more churn to the users. Also, the nested name specifier having a different API avoids missing changes related to how prefixes work now, which could make existing code compile but not work. How to review: The important changes are all in `clang/include/clang/AST` and `clang/lib/AST`, with also important changes in `clang/lib/Sema/TreeTransform.h`. The rest and bulk of the changes are mostly consequences of the changes in API. PS: TagType::getDecl is renamed to `getOriginalDecl` in this patch, just for easier to rebasing. I plan to rename it back after this lands. Fixes #136624 Fixes https://github.com/llvm/llvm-project/issues/43179 Fixes https://github.com/llvm/llvm-project/issues/68670 Fixes https://github.com/llvm/llvm-project/issues/92757
This is a first pass at implementing [P2841R7](https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2025/p2841r7.pdf). The implementation is far from complete; however, I'm aiming to do that in chunks, to make our lives easier. In particular, this does not implement - Subsumption - Mangling - Satisfaction checking is minimal as we should focus on #141776 first (note that I'm currently very stuck) FTM, release notes, status page, etc, will be updated once the feature is more mature. Given the state of the feature, it is not yet allowed in older language modes. Of note: - Mismatches between template template arguments and template template parameters are a bit wonky. This is addressed by #130603 - We use `UnresolvedLookupExpr` to model template-id. While this is pre-existing, I have been wondering if we want to introduce a different OverloadExpr subclass for that. I did not make the change in this patch.
The synthesized deduction guides use injected template arguments for distinguishment of explicit and implicit deduction guides. In partial ordering, we may substitute into these injected types when checking consistency. Properly substituting them needs the instantiated class template specializations which isn't the case at that point. So instead, we check their template specialization types. No release note because I think we want a backport, after baking it for a couple of days. Fixes https://github.com/llvm/llvm-project/issues/134613
getParam already returns NamedDecl *.