[clang] [libcxxabi] [clang][ItaniumMangle] Mangle friend function templates with a constr… (PR #110247)

[LLVM Continuous Integration via cfe-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `clang-aarch64-quick` running on `linaro-clang-aarch64-quick` while building `clang,libcxxabi` at step 5 "ninja check 1".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/65/builds/5396

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 5 (ninja check 1) failure: stage 1 checked (failure)
******************** TEST 'Clang :: CodeGenCXX/mangle-concept.cpp' FAILED ********************
Exit Code: 2

Command Output (stderr):
--
RUN: at line 1: /home/tcwg-buildbot/worker/clang-aarch64-quick/stage1/bin/clang -cc1 -internal-isystem /home/tcwg-buildbot/worker/clang-aarch64-quick/stage1/lib/clang/20/include -nostdsysteminc -verify -std=c++20 -emit-llvm -triple aarch64-unknown-linux-gnu -o - /home/tcwg-buildbot/worker/clang-aarch64-quick/llvm/clang/test/CodeGenCXX/mangle-concept.cpp -fclang-abi-compat=latest | /home/tcwg-buildbot/worker/clang-aarch64-quick/stage1/bin/FileCheck /home/tcwg-buildbot/worker/clang-aarch64-quick/llvm/clang/test/CodeGenCXX/mangle-concept.cpp
+ /home/tcwg-buildbot/worker/clang-aarch64-quick/stage1/bin/clang -cc1 -internal-isystem /home/tcwg-buildbot/worker/clang-aarch64-quick/stage1/lib/clang/20/include -nostdsysteminc -verify -std=c++20 -emit-llvm -triple aarch64-unknown-linux-gnu -o - /home/tcwg-buildbot/worker/clang-aarch64-quick/llvm/clang/test/CodeGenCXX/mangle-concept.cpp -fclang-abi-compat=latest
+ /home/tcwg-buildbot/worker/clang-aarch64-quick/stage1/bin/FileCheck /home/tcwg-buildbot/worker/clang-aarch64-quick/llvm/clang/test/CodeGenCXX/mangle-concept.cpp
error: 'expected-error' diagnostics seen but not expected: 
  File /home/tcwg-buildbot/worker/clang-aarch64-quick/llvm/clang/test/CodeGenCXX/mangle-concept.cpp Line 39: redefinition of 'h'
  File /home/tcwg-buildbot/worker/clang-aarch64-quick/llvm/clang/test/CodeGenCXX/mangle-concept.cpp Line 38: default template argument not permitted on a friend template
  File /home/tcwg-buildbot/worker/clang-aarch64-quick/llvm/clang/test/CodeGenCXX/mangle-concept.cpp Line 45: redefinition of 'j'
  File /home/tcwg-buildbot/worker/clang-aarch64-quick/llvm/clang/test/CodeGenCXX/mangle-concept.cpp Line 44: default template argument not permitted on a friend template
  File /home/tcwg-buildbot/worker/clang-aarch64-quick/llvm/clang/test/CodeGenCXX/mangle-concept.cpp Line 51: redefinition of 'l'
  File /home/tcwg-buildbot/worker/clang-aarch64-quick/llvm/clang/test/CodeGenCXX/mangle-concept.cpp Line 50: default template argument not permitted on a friend template
error: 'expected-note' diagnostics seen but not expected: 
  File /home/tcwg-buildbot/worker/clang-aarch64-quick/llvm/clang/test/CodeGenCXX/mangle-concept.cpp Line 55: in instantiation of template class 'test2::A<bool>' requested here
  File /home/tcwg-buildbot/worker/clang-aarch64-quick/llvm/clang/test/CodeGenCXX/mangle-concept.cpp Line 39: previous definition is here
  File /home/tcwg-buildbot/worker/clang-aarch64-quick/llvm/clang/test/CodeGenCXX/mangle-concept.cpp Line 45: previous definition is here
  File /home/tcwg-buildbot/worker/clang-aarch64-quick/llvm/clang/test/CodeGenCXX/mangle-concept.cpp Line 51: previous definition is here
10 errors generated.
FileCheck error: '<stdin>' is empty.
FileCheck command line:  /home/tcwg-buildbot/worker/clang-aarch64-quick/stage1/bin/FileCheck /home/tcwg-buildbot/worker/clang-aarch64-quick/llvm/clang/test/CodeGenCXX/mangle-concept.cpp

--

********************


```

</details>

https://github.com/llvm/llvm-project/pull/110247