[ci-scan] Test failure: GB18030.Tests.RegexTests fails with FileNotFoundException 'Microsoft.CodeAnalysis.CSharp' on NativeAOT

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Build Information

Build: https://dev.azure.com/dnceng-public/public/_build/results?buildId=1545024
Build error leg or test failing: NativeAOT Compliance.Tests — GB18030.Tests.RegexTests.UnicodeCategory_ExclusionAsync

Pipeline: runtime-nativeaot-outerloop (definition 265), branch main. The GB18030.Tests.RegexTests cases fail across the NativeAOT Compliance.Tests work item in source build 1545024 and persist into follow-up build 1545347.

Under NativeAOT the Regex tests attempt to load Microsoft.CodeAnalysis.CSharp (used by the Regex source-generator compilation path in the test) and fail with System.IO.FileNotFoundException, thrown from the NativeAOT type loader. The failure affects every Regex engine variant (Interpreter, Compiled, NonBacktracking).

Error Details

[FAIL] GB18030.Tests.RegexTests.UnicodeCategory_ExclusionAsync(engine: Interpreter, culture: CultureInfo { })
System.IO.FileNotFoundException : Could not find file 'Microsoft.CodeAnalysis.CSharp'.
   at Internal.Runtime.TypeLoaderExceptionHelper.CreateFileNotFoundException(ExceptionStringID, String) in /_/src/coreclr/nativeaot/System.Private.CoreLib/src/Internal/Runtime/TypeLoaderExceptionHelper.cs:line 49

Error Message

{
  "ErrorMessage": [
    "[FAIL] GB18030.Tests.RegexTests.UnicodeCategory_ExclusionAsync",
    "System.IO.FileNotFoundException : Could not find file 'Microsoft.CodeAnalysis.CSharp'."
  ],
  "ErrorPattern": "",
  "BuildRetry": false,
  "ExcludeConsoleLog": false
}

First build it occurred

Observed in source build 1545024 (2026-08-08) and again in follow-up build 1545347 (2026-08-08) — at least two distinct builds.

Duplicate search

Searched open and closed issues/KBEs for GB18030.Tests.RegexTests and Could not find file 'Microsoft.CodeAnalysis.CSharp': no existing KBE matches. No open or merged PR references this NativeAOT signature.

---

Filed by ci-failure-scan (detection only). ci-failure-fix walks open [ci-scan] KBEs and either opens a small fix PR or comments here to loop in owners — it never disables the test.

Note

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Generated by CI Outer-Loop Failure Scanner · 719.9 AIC · ⌖ 16.6 AIC · ⊞ 18.3K · ◷

Report

Build	Repository	Test	Pull Request
1546065	dotnet/runtime	Compliance.Tests.WorkItemExecution
1545949	dotnet/runtime	GB18030.Tests.RegexTests.NamedBlock_InclusionAsync
1545856	dotnet/runtime	GB18030.Tests.RegexTests.UnicodeCategory_ExclusionAsync	#131907
1545740	dotnet/runtime	GB18030.Tests.RegexTests.NamedBlock_InclusionAsync
1545668	dotnet/runtime	Compliance.Tests.WorkItemExecution
1545587	dotnet/runtime	GB18030.Tests.RegexTests.NamedBlock_ExclusionAsync	#131907
1545564	dotnet/runtime	GB18030.Tests.RegexTests.UnicodeCategory_InclusionAsync

Summary

24-Hour Hit Count	7-Day Hit Count	1-Month Count
4	7	7

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