[PATCH] D145639: [Coroutines] Fix premature conversion of return object

[Bruno Cardoso Lopes via Phabricator via cfe-commits]

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Fix https://github.com/llvm/llvm-project/issues/56532

Effectively, this reverts behavior introduced in https://reviews.llvm.org/D117087,
which did two things:

1. Change delayed to early conversion of return object.
2. Introduced RVO possibilities because of early conversion.

This patches fixes (1) and removes (2). I already worked on a follow up for (2)
in a separated patch. I believe it's important to split these two because if the RVO
causes any problems we can explore reverting (2) while maintaining (1).

Notes on some testcase changes:

- `pr59221.cpp` changed to `-O1` so we can check that the front-end honors the value checked for. Sounds like `-O3` without RVO is more likely to work with LLVM optimizations...
- Comment out delete members `coroutine-no-move-ctor.cpp` since behavior now requires copies again.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D145639

Files:
  clang/include/clang/AST/StmtCXX.h
  clang/lib/AST/StmtCXX.cpp
  clang/lib/CodeGen/CGCoroutine.cpp
  clang/lib/Sema/SemaCoroutine.cpp
  clang/lib/Sema/TreeTransform.h
  clang/test/CodeGenCoroutines/coro-gro.cpp
  clang/test/CodeGenCoroutines/pr59221.cpp
  clang/test/SemaCXX/coroutine-no-move-ctor.cpp
  clang/test/SemaCXX/coroutines.cpp
  clang/test/SemaCXX/warn-throw-out-noexcept-coro.cpp

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