[release/10.0] PersistedAssemblyBuilder: Fix encoding of custom modifiers. (#123925)#124537
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JulieLeeMSFT merged 3 commits intodotnet:release/10.0from Feb 24, 2026
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Pull request overview
This PR fixes a critical bug in PersistedAssemblyBuilder where custom modifiers (like InAttribute on in parameters) were not being correctly encoded in method signatures when using types obtained via GetModifiedParameterType(). The issue manifested as a TypeLoadException when loading assemblies with interface implementations that have custom modifiers on parameters.
Changes:
- Refactored signature encoding to always extract custom modifiers from types when modifier arrays are null
- Added a test to verify interface overrides with custom modifiers work correctly
- Improved code clarity with better variable naming and simplified array encoding
Reviewed changes
Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.
| File | Description |
|---|---|
src/libraries/System.Reflection.Emit/src/System/Reflection/Emit/SignatureHelper.cs |
Core fix: Modified WriteSignatureForType to extract custom modifiers from types when modifier arrays are null; unified signature encoding logic across fields, methods, properties, and parameters; simplified array encoding |
src/libraries/System.Reflection.Emit/tests/PersistedAssemblyBuilder/AssemblySaveTypeBuilderTests.cs |
Added regression test SaveInterfaceOverrideWithCustomModifier that validates the fix by creating an interface override with in parameter modifiers and verifying the assembly loads without errors |
src/libraries/System.Reflection.Emit/tests/PersistedAssemblyBuilder/AssemblySaveILGeneratorTests.cs |
Renamed variable nestedParam to sectorParam for better code clarity |
src/libraries/System.Reflection.Emit/tests/System.Reflection.Emit.Tests.csproj |
Ensured project reference to System.Reflection.Emit source project |
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…119935) This fixes dotnet#111003. The current implementation is a **work in progress**, only **managed** function pointers with no modopts are supported. --------- Co-authored-by: Jan Kotas <[email protected]>
…#123925) Fixes dotnet#123857. --------- Co-authored-by: Jan Kotas <[email protected]>
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Backport of #119935, #121128, #123925 to release/10.0
Customer Impact
Unable to emit references to methods and fields with signatures that include modopts and modreqs using
PersistedAssemblyBuilder(e.g. method signatures that use C#readonly reforin).Regression
This is a bug in PersistedAssemblyBuilder that shipped in .NET 9. Adoption blocker with no workaround.
Testing
Dedicated tests.
Risk
Medium. The change is a combination of 3 different PRs that fixed different aspects of the bug. The size of the delta makes is a medium risk.