[clang] [clang][Sema] Fix initialization of GRO when GRO-return type mismatches (CWG2563) (PR #179156)

[via cfe-commits]

github-actions[bot] wrote:

<!--PREMERGE ADVISOR COMMENT: Linux-->
# :penguin: Linux x64 Test Results

* 85991 tests passed
* 1227 tests skipped
* 1 test failed

## Failed Tests
(click on a test name to see its output)

### Clang
<details>
<summary>Clang.SemaCXX/coroutines.cpp</summary>

```
Exit Code: 1

Command Output (stdout):
--
# RUN: at line 4
/home/gha/actions-runner/_work/llvm-project/llvm-project/build/bin/clang -cc1 -internal-isystem /home/gha/actions-runner/_work/llvm-project/llvm-project/build/lib/clang/23/include -nostdsysteminc -std=c++23 -fsyntax-only -verify=expected,cxx20_23,cxx23    /home/gha/actions-runner/_work/llvm-project/llvm-project/clang/test/SemaCXX/coroutines.cpp -fcxx-exceptions -fexceptions -Wunused-result
# executed command: /home/gha/actions-runner/_work/llvm-project/llvm-project/build/bin/clang -cc1 -internal-isystem /home/gha/actions-runner/_work/llvm-project/llvm-project/build/lib/clang/23/include -nostdsysteminc -std=c++23 -fsyntax-only -verify=expected,cxx20_23,cxx23 /home/gha/actions-runner/_work/llvm-project/llvm-project/clang/test/SemaCXX/coroutines.cpp -fcxx-exceptions -fexceptions -Wunused-result
# .---command stderr------------
# | error: diagnostics with 'error' severity expected but not seen: 
# |   File /home/gha/actions-runner/_work/llvm-project/llvm-project/clang/test/SemaCXX/coroutines.cpp Line 1005 (directive at /home/gha/actions-runner/_work/llvm-project/llvm-project/clang/test/SemaCXX/coroutines.cpp:1006) 'cxx23-error': cannot initialize return object of type 'int' with an rvalue of type 'void *'
# | error: diagnostics with 'error' severity seen but not expected: 
# |   File /home/gha/actions-runner/_work/llvm-project/llvm-project/clang/test/SemaCXX/coroutines.cpp Line 1005: cannot initialize return object of type 'int' with an rvalue of type 'decltype(__promise.get_return_object())' (aka 'void *')
# | 2 errors generated.
# `-----------------------------
# error: command failed with exit status: 1

--

```
</details>

If these failures are unrelated to your changes (for example tests are broken or flaky at HEAD), please open an issue at https://github.com/llvm/llvm-project/issues and add the `infrastructure` label.

https://github.com/llvm/llvm-project/pull/179156