[release/11.0-rc1] Fix Crossgen2 variance validation for type constraints by jtschuster · Pull Request #133117 · dotnet/runtime

jtschuster · 2026-09-02T17:56:39Z

Backport of #132809 to release/11.0-rc1

Customer Impact

Crossgen2 applied method generic-constraint variance rules to a generic type's own constraints. ECMA-335 II.9.7 explicitly leaves type-owned constraints unrestricted, so valid variant interfaces could fail automatic validation and omit READYTORUN_FLAG_SkipTypeValidation, disabling the perf optimization.

This change:

removes the invalid variance check for type-owned generic constraints
aligns interface method signature validation with the VM by checking all instance methods and - virtual methods, including static virtual and static abstract declarations
adds a ReadyToRun regression test based on the reported constraint pattern

Fixes#132724

Regression

Yes. #120459 introduced the regression.

Testing

A new test was added to ILCompiler.ReadyToRun.Tests that reproduced the issue. The test passes with the changes.

Risk

Low. The change makes the validation match the ECMA spec and matches the validation in the runtime.

Crossgen2 applied method generic-constraint variance rules to a generic type's own constraints. ECMA-335 II.9.7 explicitly leaves type-owned constraints unrestricted, so valid variant interfaces could fail automatic validation and omit `READYTORUN_FLAG_SkipTypeValidation`. This change: - removes the invalid variance check for type-owned generic constraints - aligns interface method signature validation with the VM by checking all instance methods and virtual methods, including static virtual and static abstract declarations - adds a ReadyToRun regression test based on the reported constraint pattern Fixesdotnet#132724 > [!NOTE] > This pull request was created with GitHub Copilot.

Retain the release/11.0-rc1 test condition while backporting the generic variance regression. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 142b5bce-0d17-49b6-95b8-3e4f236c1dd6

azure-pipelines · 2026-09-02T17:57:25Z

Azure Pipelines: Successfully started running 3 pipeline(s). 13 pipeline(s) were filtered out due to trigger conditions. There may be pipelines that require an authorized user to comment /azp run to run.

Copilot

🟢 Approval recommended

The behavioral change is narrowly scoped, matches the CoreCLR loader’s documented variance-check condition, and includes a targeted regression test for the reported scenario.

Pull request overview

Backport to release/11.0-rc1 that corrects Crossgen2 ReadyToRun type validation so generic variance rules are applied consistently with the CoreCLR type loader—specifically avoiding variance checks on a generic type’s own constraints while still validating interface method signatures appropriately.

Changes:

Adjust interface method-signature variance validation to match the runtime’s rule: validate all instance methods and virtual methods, while skipping non-virtual static methods.
Remove variance validation for a generic type’s own parameter constraints (per ECMA-335 II.9.7) to avoid false validation errors and preserve READYTORUN_FLAG_SkipTypeValidation.
Add a ReadyToRun regression test that asserts the generated image sets READYTORUN_FLAG_SkipTypeValidation for the reported constraint pattern.

File summaries

File	Description
src/coreclr/tools/aot/ILCompiler.ReadyToRun/Compiler/DependencyAnalysis/ReadyToRun/TypeValidationChecker.cs	Aligns Crossgen2 variance validation rules with the runtime (method-signature condition) and removes invalid variance checking on type-owned constraints.
src/coreclr/tools/aot/ILCompiler.ReadyToRun.Tests/TestCases/TypeValidation/GenericTypeConstraints.cs	New minimal source for the constraint/variance pattern used by the regression test.
src/coreclr/tools/aot/ILCompiler.ReadyToRun.Tests/TestCases/R2RTestSuites.cs	Adds a regression test asserting the R2R header retains `SkipTypeValidation` under automatic validation.

Review details

Files reviewed: 3/3 changed files
Comments generated: 0
Review effort level: Lite

jtschuster · 2026-09-02T17:56:39Z

Backport of #132809 to release/11.0-rc1

Customer Impact

Crossgen2 applied method generic-constraint variance rules to a generic type's own constraints. ECMA-335 II.9.7 explicitly leaves type-owned constraints unrestricted, so valid variant interfaces could fail automatic validation and omit READYTORUN_FLAG_SkipTypeValidation, disabling the perf optimization.

This change:

removes the invalid variance check for type-owned generic constraints
aligns interface method signature validation with the VM by checking all instance methods and - virtual methods, including static virtual and static abstract declarations
adds a ReadyToRun regression test based on the reported constraint pattern

Fixes#132724

Regression

Yes. #120459 introduced the regression.

Testing

A new test was added to ILCompiler.ReadyToRun.Tests that reproduced the issue. The test passes with the changes.

Risk

Low. The change makes the validation match the ECMA spec and matches the validation in the runtime.

Crossgen2 applied method generic-constraint variance rules to a generic type's own constraints. ECMA-335 II.9.7 explicitly leaves type-owned constraints unrestricted, so valid variant interfaces could fail automatic validation and omit `READYTORUN_FLAG_SkipTypeValidation`. This change: - removes the invalid variance check for type-owned generic constraints - aligns interface method signature validation with the VM by checking all instance methods and virtual methods, including static virtual and static abstract declarations - adds a ReadyToRun regression test based on the reported constraint pattern Fixesdotnet#132724 > [!NOTE] > This pull request was created with GitHub Copilot.

Retain the release/11.0-rc1 test condition while backporting the generic variance regression. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 142b5bce-0d17-49b6-95b8-3e4f236c1dd6

azure-pipelines · 2026-09-02T17:57:25Z

Azure Pipelines: Successfully started running 3 pipeline(s). 13 pipeline(s) were filtered out due to trigger conditions. There may be pipelines that require an authorized user to comment /azp run to run.

Copilot

🟢 Approval recommended

The behavioral change is narrowly scoped, matches the CoreCLR loader’s documented variance-check condition, and includes a targeted regression test for the reported scenario.

Pull request overview

Backport to release/11.0-rc1 that corrects Crossgen2 ReadyToRun type validation so generic variance rules are applied consistently with the CoreCLR type loader—specifically avoiding variance checks on a generic type’s own constraints while still validating interface method signatures appropriately.

Changes:

Adjust interface method-signature variance validation to match the runtime’s rule: validate all instance methods and virtual methods, while skipping non-virtual static methods.
Remove variance validation for a generic type’s own parameter constraints (per ECMA-335 II.9.7) to avoid false validation errors and preserve READYTORUN_FLAG_SkipTypeValidation.
Add a ReadyToRun regression test that asserts the generated image sets READYTORUN_FLAG_SkipTypeValidation for the reported constraint pattern.

File summaries

File	Description
src/coreclr/tools/aot/ILCompiler.ReadyToRun/Compiler/DependencyAnalysis/ReadyToRun/TypeValidationChecker.cs	Aligns Crossgen2 variance validation rules with the runtime (method-signature condition) and removes invalid variance checking on type-owned constraints.
src/coreclr/tools/aot/ILCompiler.ReadyToRun.Tests/TestCases/TypeValidation/GenericTypeConstraints.cs	New minimal source for the constraint/variance pattern used by the regression test.
src/coreclr/tools/aot/ILCompiler.ReadyToRun.Tests/TestCases/R2RTestSuites.cs	Adds a regression test asserting the R2R header retains `SkipTypeValidation` under automatic validation.

Review details

Files reviewed: 3/3 changed files
Comments generated: 0
Review effort level: Lite

jtschuster · 2026-09-02T17:56:39Z

Backport of #132809 to release/11.0-rc1

Customer Impact

Crossgen2 applied method generic-constraint variance rules to a generic type's own constraints. ECMA-335 II.9.7 explicitly leaves type-owned constraints unrestricted, so valid variant interfaces could fail automatic validation and omit READYTORUN_FLAG_SkipTypeValidation, disabling the perf optimization.

This change:

removes the invalid variance check for type-owned generic constraints
aligns interface method signature validation with the VM by checking all instance methods and - virtual methods, including static virtual and static abstract declarations
adds a ReadyToRun regression test based on the reported constraint pattern

Fixes#132724

Regression

Yes. #120459 introduced the regression.

Testing

A new test was added to ILCompiler.ReadyToRun.Tests that reproduced the issue. The test passes with the changes.

Risk

Low. The change makes the validation match the ECMA spec and matches the validation in the runtime.

Crossgen2 applied method generic-constraint variance rules to a generic type's own constraints. ECMA-335 II.9.7 explicitly leaves type-owned constraints unrestricted, so valid variant interfaces could fail automatic validation and omit `READYTORUN_FLAG_SkipTypeValidation`. This change: - removes the invalid variance check for type-owned generic constraints - aligns interface method signature validation with the VM by checking all instance methods and virtual methods, including static virtual and static abstract declarations - adds a ReadyToRun regression test based on the reported constraint pattern Fixesdotnet#132724 > [!NOTE] > This pull request was created with GitHub Copilot.

Retain the release/11.0-rc1 test condition while backporting the generic variance regression. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 142b5bce-0d17-49b6-95b8-3e4f236c1dd6

azure-pipelines · 2026-09-02T17:57:25Z

Azure Pipelines: Successfully started running 3 pipeline(s). 13 pipeline(s) were filtered out due to trigger conditions. There may be pipelines that require an authorized user to comment /azp run to run.

Copilot

🟢 Approval recommended

The behavioral change is narrowly scoped, matches the CoreCLR loader’s documented variance-check condition, and includes a targeted regression test for the reported scenario.

Pull request overview

Backport to release/11.0-rc1 that corrects Crossgen2 ReadyToRun type validation so generic variance rules are applied consistently with the CoreCLR type loader—specifically avoiding variance checks on a generic type’s own constraints while still validating interface method signatures appropriately.

Changes:

Adjust interface method-signature variance validation to match the runtime’s rule: validate all instance methods and virtual methods, while skipping non-virtual static methods.
Remove variance validation for a generic type’s own parameter constraints (per ECMA-335 II.9.7) to avoid false validation errors and preserve READYTORUN_FLAG_SkipTypeValidation.
Add a ReadyToRun regression test that asserts the generated image sets READYTORUN_FLAG_SkipTypeValidation for the reported constraint pattern.

File summaries

File	Description
src/coreclr/tools/aot/ILCompiler.ReadyToRun/Compiler/DependencyAnalysis/ReadyToRun/TypeValidationChecker.cs	Aligns Crossgen2 variance validation rules with the runtime (method-signature condition) and removes invalid variance checking on type-owned constraints.
src/coreclr/tools/aot/ILCompiler.ReadyToRun.Tests/TestCases/TypeValidation/GenericTypeConstraints.cs	New minimal source for the constraint/variance pattern used by the regression test.
src/coreclr/tools/aot/ILCompiler.ReadyToRun.Tests/TestCases/R2RTestSuites.cs	Adds a regression test asserting the R2R header retains `SkipTypeValidation` under automatic validation.

Review details

Files reviewed: 3/3 changed files
Comments generated: 0
Review effort level: Lite

jtschuster · 2026-09-02T17:56:39Z

Backport of #132809 to release/11.0-rc1

Customer Impact

Crossgen2 applied method generic-constraint variance rules to a generic type's own constraints. ECMA-335 II.9.7 explicitly leaves type-owned constraints unrestricted, so valid variant interfaces could fail automatic validation and omit READYTORUN_FLAG_SkipTypeValidation, disabling the perf optimization.

This change:

removes the invalid variance check for type-owned generic constraints
aligns interface method signature validation with the VM by checking all instance methods and - virtual methods, including static virtual and static abstract declarations
adds a ReadyToRun regression test based on the reported constraint pattern

Fixes#132724

Regression

Yes. #120459 introduced the regression.

Testing

A new test was added to ILCompiler.ReadyToRun.Tests that reproduced the issue. The test passes with the changes.

Risk

Low. The change makes the validation match the ECMA spec and matches the validation in the runtime.

Crossgen2 applied method generic-constraint variance rules to a generic type's own constraints. ECMA-335 II.9.7 explicitly leaves type-owned constraints unrestricted, so valid variant interfaces could fail automatic validation and omit `READYTORUN_FLAG_SkipTypeValidation`. This change: - removes the invalid variance check for type-owned generic constraints - aligns interface method signature validation with the VM by checking all instance methods and virtual methods, including static virtual and static abstract declarations - adds a ReadyToRun regression test based on the reported constraint pattern Fixesdotnet#132724 > [!NOTE] > This pull request was created with GitHub Copilot.

Retain the release/11.0-rc1 test condition while backporting the generic variance regression. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 142b5bce-0d17-49b6-95b8-3e4f236c1dd6

azure-pipelines · 2026-09-02T17:57:25Z

Azure Pipelines: Successfully started running 3 pipeline(s). 13 pipeline(s) were filtered out due to trigger conditions. There may be pipelines that require an authorized user to comment /azp run to run.

Copilot

🟢 Approval recommended

The behavioral change is narrowly scoped, matches the CoreCLR loader’s documented variance-check condition, and includes a targeted regression test for the reported scenario.

Pull request overview

Backport to release/11.0-rc1 that corrects Crossgen2 ReadyToRun type validation so generic variance rules are applied consistently with the CoreCLR type loader—specifically avoiding variance checks on a generic type’s own constraints while still validating interface method signatures appropriately.

Changes:

Adjust interface method-signature variance validation to match the runtime’s rule: validate all instance methods and virtual methods, while skipping non-virtual static methods.
Remove variance validation for a generic type’s own parameter constraints (per ECMA-335 II.9.7) to avoid false validation errors and preserve READYTORUN_FLAG_SkipTypeValidation.
Add a ReadyToRun regression test that asserts the generated image sets READYTORUN_FLAG_SkipTypeValidation for the reported constraint pattern.

File summaries

File	Description
src/coreclr/tools/aot/ILCompiler.ReadyToRun/Compiler/DependencyAnalysis/ReadyToRun/TypeValidationChecker.cs	Aligns Crossgen2 variance validation rules with the runtime (method-signature condition) and removes invalid variance checking on type-owned constraints.
src/coreclr/tools/aot/ILCompiler.ReadyToRun.Tests/TestCases/TypeValidation/GenericTypeConstraints.cs	New minimal source for the constraint/variance pattern used by the regression test.
src/coreclr/tools/aot/ILCompiler.ReadyToRun.Tests/TestCases/R2RTestSuites.cs	Adds a regression test asserting the R2R header retains `SkipTypeValidation` under automatic validation.

Review details

Files reviewed: 3/3 changed files
Comments generated: 0
Review effort level: Lite

jtschuster · 2026-09-02T17:56:39Z

Backport of #132809 to release/11.0-rc1

Customer Impact

Crossgen2 applied method generic-constraint variance rules to a generic type's own constraints. ECMA-335 II.9.7 explicitly leaves type-owned constraints unrestricted, so valid variant interfaces could fail automatic validation and omit READYTORUN_FLAG_SkipTypeValidation, disabling the perf optimization.

This change:

removes the invalid variance check for type-owned generic constraints
aligns interface method signature validation with the VM by checking all instance methods and - virtual methods, including static virtual and static abstract declarations
adds a ReadyToRun regression test based on the reported constraint pattern

Fixes#132724

Regression

Yes. #120459 introduced the regression.

Testing

A new test was added to ILCompiler.ReadyToRun.Tests that reproduced the issue. The test passes with the changes.

Risk

Low. The change makes the validation match the ECMA spec and matches the validation in the runtime.

Crossgen2 applied method generic-constraint variance rules to a generic type's own constraints. ECMA-335 II.9.7 explicitly leaves type-owned constraints unrestricted, so valid variant interfaces could fail automatic validation and omit `READYTORUN_FLAG_SkipTypeValidation`. This change: - removes the invalid variance check for type-owned generic constraints - aligns interface method signature validation with the VM by checking all instance methods and virtual methods, including static virtual and static abstract declarations - adds a ReadyToRun regression test based on the reported constraint pattern Fixesdotnet#132724 > [!NOTE] > This pull request was created with GitHub Copilot.

Retain the release/11.0-rc1 test condition while backporting the generic variance regression. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 142b5bce-0d17-49b6-95b8-3e4f236c1dd6

azure-pipelines · 2026-09-02T17:57:25Z

Azure Pipelines: Successfully started running 3 pipeline(s). 13 pipeline(s) were filtered out due to trigger conditions. There may be pipelines that require an authorized user to comment /azp run to run.

Copilot

🟢 Approval recommended

The behavioral change is narrowly scoped, matches the CoreCLR loader’s documented variance-check condition, and includes a targeted regression test for the reported scenario.

Pull request overview

Backport to release/11.0-rc1 that corrects Crossgen2 ReadyToRun type validation so generic variance rules are applied consistently with the CoreCLR type loader—specifically avoiding variance checks on a generic type’s own constraints while still validating interface method signatures appropriately.

Changes:

Adjust interface method-signature variance validation to match the runtime’s rule: validate all instance methods and virtual methods, while skipping non-virtual static methods.
Remove variance validation for a generic type’s own parameter constraints (per ECMA-335 II.9.7) to avoid false validation errors and preserve READYTORUN_FLAG_SkipTypeValidation.
Add a ReadyToRun regression test that asserts the generated image sets READYTORUN_FLAG_SkipTypeValidation for the reported constraint pattern.

File summaries

File	Description
src/coreclr/tools/aot/ILCompiler.ReadyToRun/Compiler/DependencyAnalysis/ReadyToRun/TypeValidationChecker.cs	Aligns Crossgen2 variance validation rules with the runtime (method-signature condition) and removes invalid variance checking on type-owned constraints.
src/coreclr/tools/aot/ILCompiler.ReadyToRun.Tests/TestCases/TypeValidation/GenericTypeConstraints.cs	New minimal source for the constraint/variance pattern used by the regression test.
src/coreclr/tools/aot/ILCompiler.ReadyToRun.Tests/TestCases/R2RTestSuites.cs	Adds a regression test asserting the R2R header retains `SkipTypeValidation` under automatic validation.

Review details

Files reviewed: 3/3 changed files
Comments generated: 0
Review effort level: Lite

jtschuster · 2026-09-02T17:56:39Z

Backport of #132809 to release/11.0-rc1

Customer Impact

Crossgen2 applied method generic-constraint variance rules to a generic type's own constraints. ECMA-335 II.9.7 explicitly leaves type-owned constraints unrestricted, so valid variant interfaces could fail automatic validation and omit READYTORUN_FLAG_SkipTypeValidation, disabling the perf optimization.

This change:

removes the invalid variance check for type-owned generic constraints
aligns interface method signature validation with the VM by checking all instance methods and - virtual methods, including static virtual and static abstract declarations
adds a ReadyToRun regression test based on the reported constraint pattern

Fixes#132724

Regression

Yes. #120459 introduced the regression.

Testing

A new test was added to ILCompiler.ReadyToRun.Tests that reproduced the issue. The test passes with the changes.

Risk

Low. The change makes the validation match the ECMA spec and matches the validation in the runtime.

Crossgen2 applied method generic-constraint variance rules to a generic type's own constraints. ECMA-335 II.9.7 explicitly leaves type-owned constraints unrestricted, so valid variant interfaces could fail automatic validation and omit `READYTORUN_FLAG_SkipTypeValidation`. This change: - removes the invalid variance check for type-owned generic constraints - aligns interface method signature validation with the VM by checking all instance methods and virtual methods, including static virtual and static abstract declarations - adds a ReadyToRun regression test based on the reported constraint pattern Fixesdotnet#132724 > [!NOTE] > This pull request was created with GitHub Copilot.

Retain the release/11.0-rc1 test condition while backporting the generic variance regression. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 142b5bce-0d17-49b6-95b8-3e4f236c1dd6

azure-pipelines · 2026-09-02T17:57:25Z

Azure Pipelines: Successfully started running 3 pipeline(s). 13 pipeline(s) were filtered out due to trigger conditions. There may be pipelines that require an authorized user to comment /azp run to run.

Copilot

🟢 Approval recommended

The behavioral change is narrowly scoped, matches the CoreCLR loader’s documented variance-check condition, and includes a targeted regression test for the reported scenario.

Pull request overview

Backport to release/11.0-rc1 that corrects Crossgen2 ReadyToRun type validation so generic variance rules are applied consistently with the CoreCLR type loader—specifically avoiding variance checks on a generic type’s own constraints while still validating interface method signatures appropriately.

Changes:

Adjust interface method-signature variance validation to match the runtime’s rule: validate all instance methods and virtual methods, while skipping non-virtual static methods.
Remove variance validation for a generic type’s own parameter constraints (per ECMA-335 II.9.7) to avoid false validation errors and preserve READYTORUN_FLAG_SkipTypeValidation.
Add a ReadyToRun regression test that asserts the generated image sets READYTORUN_FLAG_SkipTypeValidation for the reported constraint pattern.

File summaries

File	Description
src/coreclr/tools/aot/ILCompiler.ReadyToRun/Compiler/DependencyAnalysis/ReadyToRun/TypeValidationChecker.cs	Aligns Crossgen2 variance validation rules with the runtime (method-signature condition) and removes invalid variance checking on type-owned constraints.
src/coreclr/tools/aot/ILCompiler.ReadyToRun.Tests/TestCases/TypeValidation/GenericTypeConstraints.cs	New minimal source for the constraint/variance pattern used by the regression test.
src/coreclr/tools/aot/ILCompiler.ReadyToRun.Tests/TestCases/R2RTestSuites.cs	Adds a regression test asserting the R2R header retains `SkipTypeValidation` under automatic validation.

Review details

Files reviewed: 3/3 changed files
Comments generated: 0
Review effort level: Lite

jtschuster · 2026-09-02T17:56:39Z

Backport of #132809 to release/11.0-rc1

Customer Impact

Crossgen2 applied method generic-constraint variance rules to a generic type's own constraints. ECMA-335 II.9.7 explicitly leaves type-owned constraints unrestricted, so valid variant interfaces could fail automatic validation and omit READYTORUN_FLAG_SkipTypeValidation, disabling the perf optimization.

This change:

removes the invalid variance check for type-owned generic constraints
aligns interface method signature validation with the VM by checking all instance methods and - virtual methods, including static virtual and static abstract declarations
adds a ReadyToRun regression test based on the reported constraint pattern

Fixes#132724

Regression

Yes. #120459 introduced the regression.

Testing

A new test was added to ILCompiler.ReadyToRun.Tests that reproduced the issue. The test passes with the changes.

Risk

Low. The change makes the validation match the ECMA spec and matches the validation in the runtime.

Crossgen2 applied method generic-constraint variance rules to a generic type's own constraints. ECMA-335 II.9.7 explicitly leaves type-owned constraints unrestricted, so valid variant interfaces could fail automatic validation and omit `READYTORUN_FLAG_SkipTypeValidation`. This change: - removes the invalid variance check for type-owned generic constraints - aligns interface method signature validation with the VM by checking all instance methods and virtual methods, including static virtual and static abstract declarations - adds a ReadyToRun regression test based on the reported constraint pattern Fixesdotnet#132724 > [!NOTE] > This pull request was created with GitHub Copilot.

Retain the release/11.0-rc1 test condition while backporting the generic variance regression. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 142b5bce-0d17-49b6-95b8-3e4f236c1dd6

azure-pipelines · 2026-09-02T17:57:25Z

Azure Pipelines: Successfully started running 3 pipeline(s). 13 pipeline(s) were filtered out due to trigger conditions. There may be pipelines that require an authorized user to comment /azp run to run.

Copilot

🟢 Approval recommended

The behavioral change is narrowly scoped, matches the CoreCLR loader’s documented variance-check condition, and includes a targeted regression test for the reported scenario.

Pull request overview

Backport to release/11.0-rc1 that corrects Crossgen2 ReadyToRun type validation so generic variance rules are applied consistently with the CoreCLR type loader—specifically avoiding variance checks on a generic type’s own constraints while still validating interface method signatures appropriately.

Changes:

Adjust interface method-signature variance validation to match the runtime’s rule: validate all instance methods and virtual methods, while skipping non-virtual static methods.
Remove variance validation for a generic type’s own parameter constraints (per ECMA-335 II.9.7) to avoid false validation errors and preserve READYTORUN_FLAG_SkipTypeValidation.
Add a ReadyToRun regression test that asserts the generated image sets READYTORUN_FLAG_SkipTypeValidation for the reported constraint pattern.

File summaries

File	Description
src/coreclr/tools/aot/ILCompiler.ReadyToRun/Compiler/DependencyAnalysis/ReadyToRun/TypeValidationChecker.cs	Aligns Crossgen2 variance validation rules with the runtime (method-signature condition) and removes invalid variance checking on type-owned constraints.
src/coreclr/tools/aot/ILCompiler.ReadyToRun.Tests/TestCases/TypeValidation/GenericTypeConstraints.cs	New minimal source for the constraint/variance pattern used by the regression test.
src/coreclr/tools/aot/ILCompiler.ReadyToRun.Tests/TestCases/R2RTestSuites.cs	Adds a regression test asserting the R2R header retains `SkipTypeValidation` under automatic validation.

Review details

Files reviewed: 3/3 changed files
Comments generated: 0
Review effort level: Lite

jtschuster · 2026-09-02T17:56:39Z

Backport of #132809 to release/11.0-rc1

Customer Impact

Crossgen2 applied method generic-constraint variance rules to a generic type's own constraints. ECMA-335 II.9.7 explicitly leaves type-owned constraints unrestricted, so valid variant interfaces could fail automatic validation and omit READYTORUN_FLAG_SkipTypeValidation, disabling the perf optimization.

This change:

removes the invalid variance check for type-owned generic constraints
aligns interface method signature validation with the VM by checking all instance methods and - virtual methods, including static virtual and static abstract declarations
adds a ReadyToRun regression test based on the reported constraint pattern

Fixes#132724

Regression

Yes. #120459 introduced the regression.

Testing

A new test was added to ILCompiler.ReadyToRun.Tests that reproduced the issue. The test passes with the changes.

Risk

Low. The change makes the validation match the ECMA spec and matches the validation in the runtime.

Crossgen2 applied method generic-constraint variance rules to a generic type's own constraints. ECMA-335 II.9.7 explicitly leaves type-owned constraints unrestricted, so valid variant interfaces could fail automatic validation and omit `READYTORUN_FLAG_SkipTypeValidation`. This change: - removes the invalid variance check for type-owned generic constraints - aligns interface method signature validation with the VM by checking all instance methods and virtual methods, including static virtual and static abstract declarations - adds a ReadyToRun regression test based on the reported constraint pattern Fixesdotnet#132724 > [!NOTE] > This pull request was created with GitHub Copilot.

Retain the release/11.0-rc1 test condition while backporting the generic variance regression. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 142b5bce-0d17-49b6-95b8-3e4f236c1dd6

azure-pipelines · 2026-09-02T17:57:25Z

Azure Pipelines: Successfully started running 3 pipeline(s). 13 pipeline(s) were filtered out due to trigger conditions. There may be pipelines that require an authorized user to comment /azp run to run.

Copilot

🟢 Approval recommended

The behavioral change is narrowly scoped, matches the CoreCLR loader’s documented variance-check condition, and includes a targeted regression test for the reported scenario.

Pull request overview

Backport to release/11.0-rc1 that corrects Crossgen2 ReadyToRun type validation so generic variance rules are applied consistently with the CoreCLR type loader—specifically avoiding variance checks on a generic type’s own constraints while still validating interface method signatures appropriately.

Changes:

Adjust interface method-signature variance validation to match the runtime’s rule: validate all instance methods and virtual methods, while skipping non-virtual static methods.
Remove variance validation for a generic type’s own parameter constraints (per ECMA-335 II.9.7) to avoid false validation errors and preserve READYTORUN_FLAG_SkipTypeValidation.
Add a ReadyToRun regression test that asserts the generated image sets READYTORUN_FLAG_SkipTypeValidation for the reported constraint pattern.

File summaries

File	Description
src/coreclr/tools/aot/ILCompiler.ReadyToRun/Compiler/DependencyAnalysis/ReadyToRun/TypeValidationChecker.cs	Aligns Crossgen2 variance validation rules with the runtime (method-signature condition) and removes invalid variance checking on type-owned constraints.
src/coreclr/tools/aot/ILCompiler.ReadyToRun.Tests/TestCases/TypeValidation/GenericTypeConstraints.cs	New minimal source for the constraint/variance pattern used by the regression test.
src/coreclr/tools/aot/ILCompiler.ReadyToRun.Tests/TestCases/R2RTestSuites.cs	Adds a regression test asserting the R2R header retains `SkipTypeValidation` under automatic validation.

Review details

Files reviewed: 3/3 changed files
Comments generated: 0
Review effort level: Lite

jtschuster added 2 commits September 2, 2026 10:15

Restore release WASM test attribute
6b39dc6
Retain the release/11.0-rc1 test condition while backporting the generic variance regression. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 142b5bce-0d17-49b6-95b8-3e4f236c1dd6

jtschuster added this to the 11.0.0 milestone Sep 2, 2026

jtschuster requested review from davidwrighton and jkoritzinsky September 2, 2026 17:56

jtschuster self-assigned this Sep 2, 2026

CopilotAI lite review requested due to automatic review settings September 2, 2026 17:56

jtschuster added this to AppModel Sep 2, 2026

github-actionsBot added the area-ReadyToRun label Sep 2, 2026

jtschuster requested a review from agocke September 2, 2026 17:57

Copilotstarted reviewing on behalf of jtschuster September 2, 2026 17:57 View session

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jtschuster added 2 commits September 2, 2026 10:15

Restore release WASM test attribute
6b39dc6
Retain the release/11.0-rc1 test condition while backporting the generic variance regression. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 142b5bce-0d17-49b6-95b8-3e4f236c1dd6

jtschuster added this to the 11.0.0 milestone Sep 2, 2026

jtschuster requested review from davidwrighton and jkoritzinsky September 2, 2026 17:56

jtschuster self-assigned this Sep 2, 2026

CopilotAI lite review requested due to automatic review settings September 2, 2026 17:56

jtschuster added this to AppModel Sep 2, 2026

github-actionsBot added the area-ReadyToRun label Sep 2, 2026

jtschuster requested a review from agocke September 2, 2026 17:57

Copilotstarted reviewing on behalf of jtschuster September 2, 2026 17:57 View session

CopilotAI reviewed Sep 2, 2026
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jtschuster added 2 commits September 2, 2026 10:15

Restore release WASM test attribute
6b39dc6
Retain the release/11.0-rc1 test condition while backporting the generic variance regression. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 142b5bce-0d17-49b6-95b8-3e4f236c1dd6

jtschuster added this to the 11.0.0 milestone Sep 2, 2026

jtschuster requested review from davidwrighton and jkoritzinsky September 2, 2026 17:56

jtschuster self-assigned this Sep 2, 2026

CopilotAI lite review requested due to automatic review settings September 2, 2026 17:56

jtschuster added this to AppModel Sep 2, 2026

github-actionsBot added the area-ReadyToRun label Sep 2, 2026

jtschuster requested a review from agocke September 2, 2026 17:57

Copilotstarted reviewing on behalf of jtschuster September 2, 2026 17:57 View session

CopilotAI reviewed Sep 2, 2026
View reviewed changes

jtschuster added 2 commits September 2, 2026 10:15

Restore release WASM test attribute
6b39dc6
Retain the release/11.0-rc1 test condition while backporting the generic variance regression. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 142b5bce-0d17-49b6-95b8-3e4f236c1dd6

jtschuster added this to the 11.0.0 milestone Sep 2, 2026

jtschuster requested review from davidwrighton and jkoritzinsky September 2, 2026 17:56

jtschuster self-assigned this Sep 2, 2026

CopilotAI lite review requested due to automatic review settings September 2, 2026 17:56

jtschuster added this to AppModel Sep 2, 2026

github-actionsBot added the area-ReadyToRun label Sep 2, 2026

jtschuster requested a review from agocke September 2, 2026 17:57

Copilotstarted reviewing on behalf of jtschuster September 2, 2026 17:57 View session

CopilotAI reviewed Sep 2, 2026
View reviewed changes

jtschuster added 2 commits September 2, 2026 10:15

Restore release WASM test attribute
6b39dc6
Retain the release/11.0-rc1 test condition while backporting the generic variance regression. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 142b5bce-0d17-49b6-95b8-3e4f236c1dd6

jtschuster added this to the 11.0.0 milestone Sep 2, 2026

jtschuster requested review from davidwrighton and jkoritzinsky September 2, 2026 17:56

jtschuster self-assigned this Sep 2, 2026

CopilotAI lite review requested due to automatic review settings September 2, 2026 17:56

jtschuster added this to AppModel Sep 2, 2026

github-actionsBot added the area-ReadyToRun label Sep 2, 2026

jtschuster requested a review from agocke September 2, 2026 17:57

Copilotstarted reviewing on behalf of jtschuster September 2, 2026 17:57 View session

CopilotAI reviewed Sep 2, 2026
View reviewed changes

jtschuster added 2 commits September 2, 2026 10:15

Restore release WASM test attribute
6b39dc6
Retain the release/11.0-rc1 test condition while backporting the generic variance regression. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 142b5bce-0d17-49b6-95b8-3e4f236c1dd6

jtschuster added this to the 11.0.0 milestone Sep 2, 2026

jtschuster requested review from davidwrighton and jkoritzinsky September 2, 2026 17:56

jtschuster self-assigned this Sep 2, 2026

CopilotAI lite review requested due to automatic review settings September 2, 2026 17:56

jtschuster added this to AppModel Sep 2, 2026

github-actionsBot added the area-ReadyToRun label Sep 2, 2026

jtschuster requested a review from agocke September 2, 2026 17:57

Copilotstarted reviewing on behalf of jtschuster September 2, 2026 17:57 View session

CopilotAI reviewed Sep 2, 2026
View reviewed changes

jtschuster added 2 commits September 2, 2026 10:15

Restore release WASM test attribute
6b39dc6
Retain the release/11.0-rc1 test condition while backporting the generic variance regression. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 142b5bce-0d17-49b6-95b8-3e4f236c1dd6

jtschuster added this to the 11.0.0 milestone Sep 2, 2026

jtschuster requested review from davidwrighton and jkoritzinsky September 2, 2026 17:56

jtschuster self-assigned this Sep 2, 2026

CopilotAI lite review requested due to automatic review settings September 2, 2026 17:56

jtschuster added this to AppModel Sep 2, 2026

github-actionsBot added the area-ReadyToRun label Sep 2, 2026

jtschuster requested a review from agocke September 2, 2026 17:57

Copilotstarted reviewing on behalf of jtschuster September 2, 2026 17:57 View session

CopilotAI reviewed Sep 2, 2026
View reviewed changes

jtschuster added 2 commits September 2, 2026 10:15

Restore release WASM test attribute
6b39dc6
Retain the release/11.0-rc1 test condition while backporting the generic variance regression. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 142b5bce-0d17-49b6-95b8-3e4f236c1dd6

jtschuster added this to the 11.0.0 milestone Sep 2, 2026

jtschuster requested review from davidwrighton and jkoritzinsky September 2, 2026 17:56

jtschuster self-assigned this Sep 2, 2026

CopilotAI lite review requested due to automatic review settings September 2, 2026 17:56

jtschuster added this to AppModel Sep 2, 2026

github-actionsBot added the area-ReadyToRun label Sep 2, 2026

jtschuster requested a review from agocke September 2, 2026 17:57

Copilotstarted reviewing on behalf of jtschuster September 2, 2026 17:57 View session

CopilotAI reviewed Sep 2, 2026
View reviewed changes

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jtschuster commented Sep 2, 2026

Customer Impact

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Risk

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jtschuster commented Sep 2, 2026

Customer Impact

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Risk

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jtschuster commented Sep 2, 2026

Customer Impact

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Risk

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jtschuster commented Sep 2, 2026

Customer Impact

Regression

Testing

Risk

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azure-pipelinesBot commented Sep 2, 2026

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