[NFC] [Coroutines] Refactor implementation in checkFinalSuspendNoThrow

Now when we are checking if the expression `co_await
promise.final_suspend()` is not throw, we would check unconditionally
for

[NFC] [Coroutines] Refactor implementation in checkFinalSuspendNoThrow

Now when we are checking if the expression `co_await
promise.final_suspend()` is not throw, we would check unconditionally
for its child expressions recursively. It takes unnecessary time. And
the compiler would complains if the implementation in final_suspend()
may throw even if the higher level function signature marked noexcept
already.

This fixes bug48453 too.

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[Coroutines] [Frontend] Lookup in std namespace first

Now in libcxx and clang, all the coroutine components are defined in
std::experimental namespace.
And now the coroutine TS is merged into C++20.

[Coroutines] [Frontend] Lookup in std namespace first

Now in libcxx and clang, all the coroutine components are defined in
std::experimental namespace.
And now the coroutine TS is merged into C++20. So in the working draft
like N4892, we could find the coroutine components is defined in std
namespace instead of std::experimental namespace.
And the coroutine support in clang seems to be relatively stable. So I
think it may be suitable to move the coroutine component into the
experiment namespace now.

This patch would make clang lookup coroutine_traits in std namespace
first. For the compatibility consideration, clang would lookup in
std::experimental namespace if it can't find definitions in std
namespace. So the existing codes wouldn't be break after update
compiler.

And in case the compiler found std::coroutine_traits and
std::experimental::coroutine_traits at the same time, it would emit an
error for it.

The support for looking up std::experimental::coroutine_traits would be
removed in Clang16.

Reviewed By: lxfind, Quuxplusone

Differential Revision: https://reviews.llvm.org/D108696

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Revert "[Coroutines] [Clang] Look up coroutine component in std namespace first"

This reverts commit 2fbd254aa46b, which broke the libc++ CI. I'm reverting
to get things stable again until we've fig

Revert "[Coroutines] [Clang] Look up coroutine component in std namespace first"

This reverts commit 2fbd254aa46b, which broke the libc++ CI. I'm reverting
to get things stable again until we've figured out a way forward.

Differential Revision: https://reviews.llvm.org/D108696

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[Coroutines] [Clang] Look up coroutine component in std namespace first

Summary: Now in libcxx and clang, all the coroutine components are
defined in std::experimental namespace.
And now the corouti

[Coroutines] [Clang] Look up coroutine component in std namespace first

Summary: Now in libcxx and clang, all the coroutine components are
defined in std::experimental namespace.
And now the coroutine TS is merged into C++20. So in the working draft
like N4892, we could find the coroutine components is defined in std
namespace instead of std::experimental namespace.
And the coroutine support in clang seems to be relatively stable. So I
think it may be suitable to move the coroutine component into the
experiment namespace now.

But move the coroutine component into the std namespace may be an break
change. So I planned to split this change into two patch. One in clang
and other in libcxx.

This patch would make clang lookup coroutine_traits in std namespace
first. For the compatibility consideration, clang would lookup in
std::experimental namespace if it can't find definitions in std
namespace and emit a warning in this case. So the existing codes
wouldn't be break after update compiler.

Test Plan: check-clang, check-libcxx

Reviewed By: lxfind

Differential Revision: https://reviews.llvm.org/D108696

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[Coroutines] Handle dependent promise types for final_suspend non-throw check

Summary:
Check that the co_await promise.final_suspend() does not potentially throw again after we have resolved depende

[Coroutines] Handle dependent promise types for final_suspend non-throw check

Summary:
Check that the co_await promise.final_suspend() does not potentially throw again after we have resolved dependent types.
This takes care of the cases where promises types are templated.
Added test cases for this scenario and confirmed that the checks happen now.
Also run libcxx tests locally to make sure all tests pass.

Reviewers: Benabik, lewissbaker, junparser, modocache

Reviewed By: modocache

Subscribers: modocache, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D82332

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[Coroutines] Ensure co_await promise.final_suspend() does not throw

Summary:
This patch addresses https://bugs.llvm.org/show_bug.cgi?id=46256
The spec of coroutine requires that the expression co_­a

[Coroutines] Ensure co_await promise.final_suspend() does not throw

Summary:
This patch addresses https://bugs.llvm.org/show_bug.cgi?id=46256
The spec of coroutine requires that the expression co_­await promise.final_­suspend() shall not be potentially-throwing.
To check this, we recursively look at every call (including Call, MemberCall, OperatorCall and Constructor) in all code
generated by the final suspend, and ensure that the callees are declared with noexcept. We also look at any returned data
type that requires explicit destruction, and check their destructors for noexcept.

This patch does not check declarations with dependent types yet, which will be done in future patches.

Updated all tests to add noexcept to the required functions, and added a dedicated test for this patch.

This patch might start to cause existing codebase fail to compile because most people may not have been strict in tagging
all the related functions noexcept.

Reviewers: lewissbaker, modocache, junparser

Reviewed By: modocache

Subscribers: arphaman, junparser, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D82029

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