[clang] Fix ICE on invalid when defining a friend function in a template (PR #181890)

[via cfe-commits]

github-actions[bot] wrote:

<!--PREMERGE ADVISOR COMMENT: Windows-->
# :window: Windows x64 Test Results

* 52620 tests passed
* 966 tests skipped
* 1 test failed

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

### Clang
<details>
<summary>Clang.SemaTemplate/GH55509.cpp</summary>

```
Exit Code: 3221225501

Command Output (stdout):
--
# RUN: at line 1
c:\_work\llvm-project\llvm-project\build\bin\clang.exe -cc1 -internal-isystem C:\_work\llvm-project\llvm-project\build\lib\clang\23\include -nostdsysteminc -fsyntax-only -verify -std=c++26 C:\_work\llvm-project\llvm-project\clang\test\SemaTemplate\GH55509.cpp
# executed command: 'c:\_work\llvm-project\llvm-project\build\bin\clang.exe' -cc1 -internal-isystem 'C:\_work\llvm-project\llvm-project\build\lib\clang\23\include' -nostdsysteminc -fsyntax-only -verify -std=c++26 'C:\_work\llvm-project\llvm-project\clang\test\SemaTemplate\GH55509.cpp'
# .---command stderr------------
# | Assertion failed: D && "missing definition for pattern of instantiated definition", file C:\_work\llvm-project\llvm-project\clang\lib\Sema\SemaType.cpp, line 9351
# | PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace, preprocessed source, and associated run script.
# | Stack dump:
# | 0.	Program arguments: c:\\_work\\llvm-project\\llvm-project\\build\\bin\\clang.exe -cc1 -internal-isystem C:\\_work\\llvm-project\\llvm-project\\build\\lib\\clang\\23\\include -nostdsysteminc -fsyntax-only -verify -std=c++26 C:\\_work\\llvm-project\\llvm-project\\clang\\test\\SemaTemplate\\GH55509.cpp
# | 1.	<eof> parser at end of file
# | Exception Code: 0xC000001D
# |  #0 0x00007ff72f07f416 (c:\_work\llvm-project\llvm-project\build\bin\clang.exe+0x7ff416)
# |  #1 0x00007ffd3528bb04 (C:\Windows\System32\ucrtbase.dll+0x7bb04)
# |  #2 0x00007ffd3528cad1 (C:\Windows\System32\ucrtbase.dll+0x7cad1)
# |  #3 0x00007ffd3528e4a1 (C:\Windows\System32\ucrtbase.dll+0x7e4a1)
# |  #4 0x00007ffd3528e6e1 (C:\Windows\System32\ucrtbase.dll+0x7e6e1)
# |  #5 0x00007ff733ddfd5e (c:\_work\llvm-project\llvm-project\build\bin\clang.exe+0x555fd5e)
# |  #6 0x00007ff733ddff44 (c:\_work\llvm-project\llvm-project\build\bin\clang.exe+0x555ff44)
# |  #7 0x00007ff734ecf395 (c:\_work\llvm-project\llvm-project\build\bin\clang.exe+0x664f395)
# |  #8 0x00007ff733d291c5 (c:\_work\llvm-project\llvm-project\build\bin\clang.exe+0x54a91c5)
# |  #9 0x00007ff733d2e078 (c:\_work\llvm-project\llvm-project\build\bin\clang.exe+0x54ae078)
# | #10 0x00007ff73146f6f1 (c:\_work\llvm-project\llvm-project\build\bin\clang.exe+0x2bef6f1)
# | #11 0x00007ff7314700b6 (c:\_work\llvm-project\llvm-project\build\bin\clang.exe+0x2bf00b6)
# | #12 0x00007ff7352d825d (c:\_work\llvm-project\llvm-project\build\bin\clang.exe+0x6a5825d)
# | #13 0x00007ff73425410e (c:\_work\llvm-project\llvm-project\build\bin\clang.exe+0x59d410e)
# | #14 0x00007ff7315a9f6f (c:\_work\llvm-project\llvm-project\build\bin\clang.exe+0x2d29f6f)
# | #15 0x00007ff72f1badc4 (c:\_work\llvm-project\llvm-project\build\bin\clang.exe+0x93adc4)
# | #16 0x00007ff72f261713 (c:\_work\llvm-project\llvm-project\build\bin\clang.exe+0x9e1713)
# | #17 0x00007ff72e8891e7 (c:\_work\llvm-project\llvm-project\build\bin\clang.exe+0x91e7)
# | #18 0x00007ff72e884774 (c:\_work\llvm-project\llvm-project\build\bin\clang.exe+0x4774)
# | #19 0x00007ff72e8829ca (c:\_work\llvm-project\llvm-project\build\bin\clang.exe+0x29ca)
# | #20 0x00007ff72e898e0c (c:\_work\llvm-project\llvm-project\build\bin\clang.exe+0x18e0c)
# | #21 0x00007ff735a4d510 (c:\_work\llvm-project\llvm-project\build\bin\clang.exe+0x71cd510)
# | #22 0x00007ffd38614cb0 (C:\Windows\System32\KERNEL32.DLL+0x14cb0)
# | #23 0x00007ffd4b09edcb (C:\Windows\SYSTEM32\ntdll.dll+0x7edcb)
# `-----------------------------
# error: command failed with exit status: 0xc000001d

--

```
</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/181890