[clang] [HLSL] Vector Usual Arithmetic Conversions (PR #108659)

[LLVM Continuous Integration via cfe-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `premerge-monolithic-linux` running on `premerge-linux-1` while building `clang` at step 7 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/153/builds/10210

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

```
Step 7 (test-build-unified-tree-check-all) failure: test (failure)
******************** TEST 'Clang :: SemaHLSL/Language/UsualArithmeticConversions.hlsl' FAILED ********************
Exit Code: 1

Command Output (stderr):
--
RUN: at line 1: /build/buildbot/premerge-monolithic-linux/build/bin/clang -cc1 -internal-isystem /build/buildbot/premerge-monolithic-linux/build/lib/clang/20/include -nostdsysteminc -triple dxil-pc-shadermodel6.3-library -finclude-default-header -fnative-half-type /build/buildbot/premerge-monolithic-linux/llvm-project/clang/test/SemaHLSL/Language/UsualArithmeticConversions.hlsl -DERRORS -Wconversion -Wdouble-promotion -verify
+ /build/buildbot/premerge-monolithic-linux/build/bin/clang -cc1 -internal-isystem /build/buildbot/premerge-monolithic-linux/build/lib/clang/20/include -nostdsysteminc -triple dxil-pc-shadermodel6.3-library -finclude-default-header -fnative-half-type /build/buildbot/premerge-monolithic-linux/llvm-project/clang/test/SemaHLSL/Language/UsualArithmeticConversions.hlsl -DERRORS -Wconversion -Wdouble-promotion -verify
RUN: at line 2: /build/buildbot/premerge-monolithic-linux/build/bin/clang -cc1 -internal-isystem /build/buildbot/premerge-monolithic-linux/build/lib/clang/20/include -nostdsysteminc -triple dxil-pc-shadermodel6.3-library -std=hlsl2018 -finclude-default-header -fnative-half-type /build/buildbot/premerge-monolithic-linux/llvm-project/clang/test/SemaHLSL/Language/UsualArithmeticConversions.hlsl -DERRORS -Wconversion -Wdouble-promotion -verify
+ /build/buildbot/premerge-monolithic-linux/build/bin/clang -cc1 -internal-isystem /build/buildbot/premerge-monolithic-linux/build/lib/clang/20/include -nostdsysteminc -triple dxil-pc-shadermodel6.3-library -std=hlsl2018 -finclude-default-header -fnative-half-type /build/buildbot/premerge-monolithic-linux/llvm-project/clang/test/SemaHLSL/Language/UsualArithmeticConversions.hlsl -DERRORS -Wconversion -Wdouble-promotion -verify
error: 'expected-warning' diagnostics seen but not expected: 
  (frontend): support for HLSL language version hlsl2018 is incomplete, recommend using hlsl202x instead
1 error generated.

--

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


```

</details>

https://github.com/llvm/llvm-project/pull/108659