`PersistedAssemblyBuilder`: Fix encoding of custom modifiers.#123925

teo-tsirpanis · 2026-02-03T00:08:50Z

Added test that passes locally after the fix.

Copilot

Pull request overview

Fixes PersistedAssemblyBuilder emitting incorrect method reference signatures by ensuring required/optional custom modifiers (e.g., modreq(InAttribute) for in parameters) are preserved, preventing TypeLoadException when loading saved assemblies.

Changes:

Update signature blob generation to include custom modifiers from reflected parameter/return Types when explicit modifier arrays aren’t provided.
Add a regression test covering an interface method override involving a required custom modifier (modreq).
Update the test project to include TempDirectory test infrastructure and reference the System.Reflection.Emit project.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
src/libraries/System.Reflection.Emit/tests/System.Reflection.Emit.Tests.csproj	Adds `TempDirectory` support and a project reference needed for the new test scenario.
src/libraries/System.Reflection.Emit/tests/PersistedAssemblyBuilder/AssemblySaveTypeBuilderTests.cs	Adds regression test that saves/loads an assembly implementing an `in`-parameter interface method.
src/libraries/System.Reflection.Emit/src/System/Reflection/Emit/SignatureHelper.cs	Ensures method signature encoding includes required/optional custom modifiers from the `Type` when importing method references.

...raries/System.Reflection.Emit/tests/PersistedAssemblyBuilder/AssemblySaveTypeBuilderTests.cs

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Copilot reviewed 3 out of 3 changed files in this pull request and generated no new comments.

...raries/System.Reflection.Emit/tests/PersistedAssemblyBuilder/AssemblySaveTypeBuilderTests.cs

teo-tsirpanis · 2026-02-07T23:49:52Z

Hmm, Mono is failing. 🤔

The logic of `GetTypeParameter` follows the comment above more closely. Also make `TypeSignature` readonly.

Copilot

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Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

src/libraries/System.Reflection.Emit/src/System/Reflection/Emit/SignatureHelper.cs

teo-tsirpanis · 2026-02-09T03:23:48Z

I took a look at the new Mono failure. NestedType.TypeSignature.ParameterIndex contains the index of the method parameter, but here we treat it as the index of the generic parameter?

jkotas · 2026-02-09T03:26:46Z

Sounds like a bug to me.

The `ParameterInfo` object contains the index on its own; we shouldn't pass it to the `TypeSignature`'s `ParameterIndex`, because it gets used as index to generic parameter.

Copilot

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Copilot reviewed 6 out of 6 changed files in this pull request and generated no new comments.

src/libraries/System.Reflection.Emit/src/System/Reflection/Emit/SignatureHelper.cs

They are allowed per the amendments to ECMA-335.

src/libraries/System.Reflection.Emit/src/System/Reflection/Emit/SignatureHelper.cs

…t/SignatureHelper.cs

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Copilot reviewed 6 out of 6 changed files in this pull request and generated no new comments.

jkotas

Thank you!

stakx · 2026-02-17T22:57:51Z

Thanks for fixing this! Is there any chance that the fix could be backported to .NET 9 and 10?

(in parameters are so common these days that PersistedAssemblyBuilder isn't very useful IMHO if it doesn't support them.)

…#123925) Fixes dotnet#123857. --------- Co-authored-by: Jan Kotas <jkotas@microsoft.com>

…#123925) Fixes dotnet#123857.

jkotas · 2026-02-18T07:14:46Z

I can propose .NET 10 backport.

…#123925) Fixes dotnet#123857.

…#123925) Fixes dotnet#123857. --------- Co-authored-by: Jan Kotas <jkotas@microsoft.com>

jkotas · 2026-02-19T22:55:29Z

We would need to backport multiple fixes from main to make it work. It is not just the change in this PR.
#124537

teo-tsirpanis added 2 commits February 2, 2026 02:45

Include custom modifiers when importing method reference signatures.

911c101

Add test.

9981ae2

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Address Copilot feedback.

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This was referenced Feb 3, 2026

iOS.Device test WorkItemExecutions #122874

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XHarness package install failure on iOS due to devicectl NSPOSIXErrorDomain error 49 #123796

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Make the interface method's signature more complex.

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Cannot find 'arm64-v8a' device dotnet/dnceng#2284

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...raries/System.Reflection.Emit/tests/PersistedAssemblyBuilder/AssemblySaveTypeBuilderTests.cs Outdated Show resolved Hide resolved

Simplify test.

df3ae75

Fix test failures in Mono.

85c837a

The logic of `GetTypeParameter` follows the comment above more closely. Also make `TypeSignature` readonly.

teo-tsirpanis requested a review from steveisok as a code owner February 9, 2026 01:26

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src/libraries/System.Reflection.Emit/src/System/Reflection/Emit/SignatureHelper.cs Outdated Show resolved Hide resolved

Fix another test failure.

47f8113

The `ParameterInfo` object contains the index on its own; we shouldn't pass it to the `TypeSignature`'s `ParameterIndex`, because it gets used as index to generic parameter.

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[mono] The type initializer for System.Drawing.DrawingCom threw an exception: Operation is not supported on this platform #110150

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teo-tsirpanis added 2 commits February 17, 2026 09:28

Generalize encoding of custom modifiers.

d2259c7

Allow custom modifiers in the types of complex array signatures.

f30fd17

They are allowed per the amendments to ECMA-335.

teo-tsirpanis changed the title ~~PersistedAssemblyBuilder: Include custom modifiers when importing method reference signatures.~~ PersistedAssemblyBuilder: Fix encoding of custom modifiers. Feb 17, 2026

build-analysis bot mentioned this pull request Feb 17, 2026

LibraryImportGenerator.Unit.Tests crashing on linux-x64 mono interpreter #100800

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Update src/libraries/System.Reflection.Emit/src/System/Reflection/Emi…

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…t/SignatureHelper.cs

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Mono interpreter Segmentation fault crashes #124525

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jkotas merged commit 2ff39b5 into dotnet:main Feb 17, 2026
103 of 107 checks passed

teo-tsirpanis deleted the sre-import-custom-mods branch February 17, 2026 21:36

dotnet-maestro bot mentioned this pull request Feb 18, 2026

[main] Source code updates from dotnet/runtime dotnet/dotnet#4923

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jkotas added a commit to jkotas/runtime that referenced this pull request Feb 18, 2026

PersistedAssemblyBuilder: Fix encoding of custom modifiers. (dotnet…

61f807d

…#123925) Fixes dotnet#123857. --------- Co-authored-by: Jan Kotas <jkotas@microsoft.com>

jkotas pushed a commit to jkotas/runtime that referenced this pull request Feb 18, 2026

PersistedAssemblyBuilder: Fix encoding of custom modifiers. (dotnet…

1176aa9

…#123925) Fixes dotnet#123857.

jkotas pushed a commit to jkotas/runtime that referenced this pull request Feb 18, 2026

PersistedAssemblyBuilder: Fix encoding of custom modifiers. (dotnet…

4c94d43

…#123925) Fixes dotnet#123857.

jkotas pushed a commit to jkotas/runtime that referenced this pull request Feb 18, 2026

PersistedAssemblyBuilder: Fix encoding of custom modifiers. (dotnet…

349b9f7

…#123925) Fixes dotnet#123857.

jkotas added a commit to jkotas/runtime that referenced this pull request Feb 19, 2026

PersistedAssemblyBuilder: Fix encoding of custom modifiers. (dotnet…

eefcb22

…#123925) Fixes dotnet#123857. --------- Co-authored-by: Jan Kotas <jkotas@microsoft.com>

jkotas mentioned this pull request Feb 20, 2026

[release/10.0] PersistedAssemblyBuilder: Fix encoding of custom modifiers. (#123925) #124537

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