[AArnott]

SA1121 could produce invalid native-integer replacements in XML documentation and in shared source compiled for multiple targets. This was reproduced with C# 14 and StyleCop.Analyzers 1.3.151-beta on microsoft/vs-threading commit c01683d2bf3a79e0de9c8cdce1476cb673357782.

Changes

• Exempt IntPtr and UIntPtr in XML documentation cref attributes, where nint and nuint are not recognized. Other built-in type aliases in documentation still report and fix normally.
• Before offering an individual fix or applying Fix All, check linked projects for native-integer support. Preserve framework type names if any linked target does not support C# 11 with .NET 7 or later.
• Cover member access, pointer constructors, compatible and incompatible linked projects, solution-wide fixing, older language/runtime combinations, and the reported SynchronizationContext.Wait(IntPtr[], bool, int) reference.
• Update the English, Czech, Russian, and Simplified Chinese rule documentation.

Multi-targeting behavior

The original member-access and constructor diagnostics come from the .NET 8 targets. Applying those replacements to the shared file breaks the netstandard2.0 target with CS0117 (nint.Size) and CS1729 (new nint(...)).

The analyzer still reports those locations in newer-target compilations because it cannot see other project compilations. The code fix now withholds unsafe replacements; users can suppress the remaining diagnostic where the framework type name is needed for compatibility.

Validation

• The cref regression failed on the unchanged analyzer with seven unwanted SA1121 diagnostics.
• The incompatible-linked-project regression failed before the code-fix change with the exact unwanted nint.Size, new nint(...), and new nuint(...) replacements.
• Built the supplied vs-threading commit with the suppression removed, then confirmed that the suggested edits produce CS0117 and CS1729 on netstandard2.0.
• Built the C# 15 test project and its dependencies with zero warnings.
• All SA1121 tests passed in the C# 6 baseline and C# 9 through C# 15 projects.
• Documentation source localization checks passed. Full documentation integration checks require generated DocFX assets absent from this worktree.

Performance

The analyzer adds an ancestor check only for supported IntPtr/UIntPtr identifiers, before semantic analysis; other identifier paths are unchanged. Linked-project compilation checks run only in code fixes for native-integer diagnostics in linked files. No benchmark was run.

[Copilot]

🟢 Approval recommended

No active review issues are reported for the SA1121 compatibility changes.

No open issues 🎉

What changed in this PR

This PR updates SA1121 to avoid native-integer replacements that break XML documentation references or shared source compiled for older targets.

Changes:

• Exempts IntPtr and UIntPtr in documentation cref attributes.
• Checks linked-project compatibility before offering individual fixes or applying Fix All.
• Adds compatibility regression tests and updates rule documentation in four languages.

File	Description
test/​StyleCop.Analyzers.Test.CSharp9/​ReadabilityRules/​SA1121CSharp9UnitTests.cs	Tests preservation of native-sized integer types in C# 9.
test/​StyleCop.Analyzers.Test.CSharp11/​ReadabilityRules/​SA1121CSharp11UnitTests.cs	Adds documentation-reference, linked-project, and language/runtime compatibility tests.
src/​StyleCop.Analyzers/​ReadabilityRules/​SA1121UseBuiltInTypeAlias.cs	Exempts native-sized integer references inside cref attributes.
src/​StyleCop.Analyzers.CodeFixes/​ReadabilityRules/​SA1121CodeFixProvider.cs	Guards individual fixes and Fix All against incompatible linked targets.
documentation/​zh-cn/​SA1121.md	Documents the exceptions and compatibility behavior in Simplified Chinese.
documentation/​SA1121.md	Documents the exceptions and compatibility behavior in English.
documentation/​ru-ru/​SA1121.md	Documents the exceptions and compatibility behavior in Russian.
documentation/​cs-cz/​SA1121.md	Documents the exceptions and compatibility behavior in Czech.

_{Review effort: Balanced}

[codecov]

Codecov Report

❌ Patch coverage is 99.76636% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 97.64%. Comparing base (9d24854) to head (25a7461).

Additional details and impacted files

@@           Coverage Diff            @@
##           master    #4395    +/-   ##
========================================
  Coverage   97.63%   97.64%            
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  Files        1349     1349            
  Lines      152904   153329   +425     
  Branches     5267     5272     +5     
========================================
+ Hits       149295   149719   +424     
  Misses       2280     2280            
- Partials     1329     1330     +1     

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