Handle canonical types in casting logic - #127146

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MichalStrehovsky merged 5 commits into
dotnet:mainfrom
MichalStrehovsky:fix126604
Apr 21, 2026
Merged

Handle canonical types in casting logic#127146
MichalStrehovsky merged 5 commits into
dotnet:mainfrom
MichalStrehovsky:fix126604

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Fixes#126604.

When we're doing dataflow analysis of MakeGenericXXX calls, we run constraint validation to ensure we don't precompile something invalid. However, because most reflection analysis within the compiler happens with canonical types, we can end up in a situation where a constraint check is necessary but all we have are canonical types. Constraint checking and CanCastTo logic was treating this a class __Canon : object { } case, but this is not that.

Cc @dotnet/ilc-contrib

MichalStrehovskyand others added 4 commits April 20, 2026 16:04
@MichalStrehovsky
Make constraint checking canon-aware for type constraints
c74f22b
The AOT compiler's CheckConstraints was rejecting valid canonical
instantiations because CanCastTo has no awareness of canonical types.
When MakeGenericType produces canonical forms like GenericType<TestRequest,
__Canon>, type constraints (interface/base-type) would fail because e.g.
IRequest<TestRequest, string> doesn't match IRequest<TestRequest, __Canon>.
Add CanCastToConstraintWithCanon to TypeSystemConstraintsHelpers that
handles canonical types in constraint checking:
- __Canon/__UniversalCanon as the instantiation param: wildcard, accepts
any type constraint (runtime validates with concrete types).
- __Canon/__UniversalCanon as the constraint type itself: __Canon accepts
reference types, __UniversalCanon accepts anything.
- Canonical subtypes in constraint type args: uses ConvertToCanonForm to
compare canonicalized forms, with variance support for variant positions.
- Universal canon fallback for nested __UniversalCanon under Specific
canonicalization.
Split into Canon/NonCanon partial files following the existing pattern
for IsSpecialTypeMeetingConstraint. Add NormalizeInstantiation call in
HandleCallAction's MakeGenericTypeSite.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@MichalStrehovsky
Move canon awareness from constraint helpers into CastingHelper
bb84090
Move IsCanonicalTypeArgMatch and IsCanonEquivalent from
TypeSystemConstraintsHelpers.Canon.cs into CastingHelper.Canon.cs so
that CanCastTo naturally handles canonical types. This eliminates the
duplicated interface-walking, base-chain-walking, and variance logic
that was in CanCastToConstraintWithCanon.
Key changes to CastingHelper:
- IsCanonicalCastTarget in CanCastToInternal: __Canon accepts any
reference type as a cast source, __UniversalCanon accepts any type.
This makes array covariance (string[] -> __Canon[]) work naturally.
- IsCanonicalTypeArgMatch in CanCastByVarianceToInterfaceOrDelegate:
handles invariant positions where type args differ by canonicalization.
- IsCanonEquivalent in CanCastToNonVariantInterface and CanCastToClass:
handles non-variant interfaces and base types with canon type args.
CanCastToConstraintWithCanon is simplified to only handle wildcard cases
where the param or constraint IS __Canon/__UniversalCanon directly.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@MichalStrehovsky
Handle parameterized types in canonical type arg matching
3fe978a
IsCanonicalTypeArgMatch did not handle parameterized types like arrays:
string[] vs __Canon[] failed because IsCanonEquivalent checks
Instantiation which is empty for arrays. Add ParameterizedType
structural matching that recursively compares element types.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@MichalStrehovsky
Add regression test for MakeGenericType with constrained canonicals
6f5cf18
Exercises MakeGenericType where the canonical instantiation
(Gen<Atom, __Canon, object>) must pass constraint checking with
__Canon satisfying interface and new() constraints.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
CopilotAI review requested due to automatic review settings April 20, 2026 11:27
CopilotAI reviewed Apr 20, 2026
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Pull request overview

This PR fixes NativeAOT reflection/dataflow constraint validation when generic instantiations are analyzed in canonical form (__Canon / __UniversalCanon), ensuring MakeGenericType sites aren’t incorrectly treated as invalid and therefore skipped for rooting/compilation.

Changes:

  • Normalize instantiated reflected generic types before constraint checking in MakeGenericType dataflow handling.
  • Extend casting and constraint-validation helpers to correctly treat canonical definition types as wildcards/compatible where appropriate (with canon vs non-canon partial implementations).
  • Add unit and smoke tests covering canonical-type constraint scenarios and constrained MakeGenericType dataflow.

Reviewed changes

Copilot reviewed 13 out of 13 changed files in this pull request and generated 4 comments.

Show a summary per file
FileDescription
src/tests/nativeaot/SmokeTests/TrimmingBehaviors/Dataflow.csAdds a new smoke test exercising constrained MakeGenericType rooting during dataflow analysis.
src/coreclr/tools/aot/ILCompiler.TypeSystem/ILCompiler.TypeSystem.csprojIncludes new Canon-specific helper implementations in the TypeSystem build.
src/coreclr/tools/aot/ILCompiler.TypeSystem.Tests/CoreTestAssembly/GenericConstraints.csAdds new generic constraint shapes for canonical constraint tests.
src/coreclr/tools/aot/ILCompiler.TypeSystem.Tests/ConstraintsValidationTest.csAdds a comprehensive canonical-constraint validation test suite.
src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/Dataflow/HandleCallAction.csNormalizes instantiated generic types before constraint validation/rooting.
src/coreclr/tools/ILVerification/ILVerification.projitemsAdds non-canon stub helper files required by the verifier’s non-canon TypeSystem build.
src/coreclr/tools/Common/TypeSystem/Common/TypeSystemConstraintsHelpers.csMakes helpers partial and adds canon-aware special-constraint and type-constraint checks.
src/coreclr/tools/Common/TypeSystem/Common/TypeSystemConstraintsHelpers.NonCanon.csProvides non-canon stub implementations for new partial helpers.
src/coreclr/tools/Common/TypeSystem/Common/CastingHelper.csAdds canon-aware matching hooks into cast logic (interfaces, variance, base chain).
src/coreclr/tools/Common/TypeSystem/Common/CastingHelper.NonCanon.csProvides non-canon stubs for new canon-aware cast helpers.
src/coreclr/tools/Common/TypeSystem/Canon/TypeSystemConstraintsHelpers.Canon.csCanon-specific implementations for wildcard-like canonical constraint handling.
src/coreclr/tools/Common/TypeSystem/Canon/CastingHelper.Canon.csCanon-specific canonical matching logic for casts and type-arg comparisons.
src/coreclr/nativeaot/System.Private.TypeLoader/src/System.Private.TypeLoader.csprojEnsures TypeLoader picks up canon-aware casting helper.

Comment threadsrc/tests/nativeaot/SmokeTests/TrimmingBehaviors/Dataflow.cs
Comment threadsrc/coreclr/tools/aot/ILCompiler.TypeSystem.Tests/ConstraintsValidationTest.cs Outdated
Comment threadsrc/coreclr/tools/Common/TypeSystem/Common/TypeSystemConstraintsHelpers.NonCanon.cs Outdated
Comment threadsrc/coreclr/tools/Common/TypeSystem/Canon/TypeSystemConstraintsHelpers.Canon.cs Outdated
This was referenced Apr 20, 2026
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Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
CopilotAI review requested due to automatic review settings April 21, 2026 00:48
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Pull request overview

Copilot reviewed 13 out of 13 changed files in this pull request and generated 1 comment.

Comment threadsrc/coreclr/tools/Common/TypeSystem/Common/TypeSystemConstraintsHelpers.NonCanon.cs
@build-analysisbuild-analysisBot mentioned this pull request Apr 21, 2026
Open
@MichalStrehovsky
MichalStrehovsky merged commit 7bba220 into dotnet:mainApr 21, 2026
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@MichalStrehovsky
MichalStrehovsky deleted the fix126604 branch April 21, 2026 09:50
@build-analysisbuild-analysisBot mentioned this pull request Apr 21, 2026
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@MichalStrehovskyMichalStrehovsky mentioned this pull request Apr 22, 2026
Merged
MichalStrehovsky added a commit that referenced this pull request Apr 23, 2026
@MichalStrehovsky
Revert "Handle canonical types in casting logic" (#127301)
9619cf5
Resolves#127259
Reverts #127146
@github-actionsgithub-actionsBot locked and limited conversation to collaborators May 21, 2026
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NativeAOT MakeGenericType fails to activate reflected generic type when generic parameter has self-referential interface constraint

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, 'i'); if (__m === '*' || __re.test(location.href)) { injectUserscript("// Add copy buttons to all 
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}
} catch(__e) { console.warn('[Userscript:Add Copy Buttons to Code Blocks]', __e); }
})();
(function(){
try {
var __m = "github.com";
var __re = new RegExp('^' + "github\\.com" + '

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Handle canonical types in casting logic - #127146
Merged
MichalStrehovsky merged 5 commits into
dotnet:mainfrom 
MichalStrehovsky:fix126604
Apr 21, 2026
Merged
Handle canonical types in casting logic#127146
MichalStrehovsky merged 5 commits into
dotnet:mainfrom 
MichalStrehovsky:fix126604
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@MichalStrehovskyMichalStrehovsky
commented
Apr 20, 2026

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Fixes#126604.
When we're doing dataflow analysis of MakeGenericXXX calls, we run constraint validation to ensure we don't precompile something invalid. However, because most reflection analysis within the compiler happens with canonical types, we can end up in a situation where a constraint check is necessary but all we have are canonical types. Constraint checking and CanCastTo logic was treating this a class __Canon : object { } case, but this is not that.
Cc @dotnet/ilc-contrib
MichalStrehovskyand others
added 4 commits
April 20, 2026 16:04
@MichalStrehovsky
Make constraint checking canon-aware for type constraints
c74f22b
The AOT compiler's CheckConstraints was rejecting valid canonical
instantiations because CanCastTo has no awareness of canonical types.
When MakeGenericType produces canonical forms like GenericType<TestRequest,
__Canon>, type constraints (interface/base-type) would fail because e.g.
IRequest<TestRequest, string> doesn't match IRequest<TestRequest, __Canon>.
Add CanCastToConstraintWithCanon to TypeSystemConstraintsHelpers that
handles canonical types in constraint checking:
- __Canon/__UniversalCanon as the instantiation param: wildcard, accepts
any type constraint (runtime validates with concrete types).
- __Canon/__UniversalCanon as the constraint type itself: __Canon accepts
reference types, __UniversalCanon accepts anything.
- Canonical subtypes in constraint type args: uses ConvertToCanonForm to
compare canonicalized forms, with variance support for variant positions.
- Universal canon fallback for nested __UniversalCanon under Specific
canonicalization.
Split into Canon/NonCanon partial files following the existing pattern
for IsSpecialTypeMeetingConstraint. Add NormalizeInstantiation call in
HandleCallAction's MakeGenericTypeSite.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@MichalStrehovsky
Move canon awareness from constraint helpers into CastingHelper
bb84090
Move IsCanonicalTypeArgMatch and IsCanonEquivalent from
TypeSystemConstraintsHelpers.Canon.cs into CastingHelper.Canon.cs so
that CanCastTo naturally handles canonical types. This eliminates the
duplicated interface-walking, base-chain-walking, and variance logic
that was in CanCastToConstraintWithCanon.
Key changes to CastingHelper:
- IsCanonicalCastTarget in CanCastToInternal: __Canon accepts any
reference type as a cast source, __UniversalCanon accepts any type.
This makes array covariance (string[] -> __Canon[]) work naturally.
- IsCanonicalTypeArgMatch in CanCastByVarianceToInterfaceOrDelegate:
handles invariant positions where type args differ by canonicalization.
- IsCanonEquivalent in CanCastToNonVariantInterface and CanCastToClass:
handles non-variant interfaces and base types with canon type args.
CanCastToConstraintWithCanon is simplified to only handle wildcard cases
where the param or constraint IS __Canon/__UniversalCanon directly.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@MichalStrehovsky
Handle parameterized types in canonical type arg matching
3fe978a
IsCanonicalTypeArgMatch did not handle parameterized types like arrays:
string[] vs __Canon[] failed because IsCanonEquivalent checks
Instantiation which is empty for arrays. Add ParameterizedType
structural matching that recursively compares element types.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@MichalStrehovsky
Add regression test for MakeGenericType with constrained canonicals
6f5cf18
Exercises MakeGenericType where the canonical instantiation
(Gen<Atom, __Canon, object>) must pass constraint checking with
__Canon satisfying interface and new() constraints.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
CopilotAI
review requested due to automatic review settings
April 20, 2026 11:27
CopilotAI
reviewed
Apr 20, 2026
View reviewed changes
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left a comment


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Pull request overview
This PR fixes NativeAOT reflection/dataflow constraint validation when generic instantiations are analyzed in canonical form (__Canon / __UniversalCanon), ensuring MakeGenericType sites aren’t incorrectly treated as invalid and therefore skipped for rooting/compilation.
Changes:
  • Normalize instantiated reflected generic types before constraint checking in MakeGenericType dataflow handling.
  • Extend casting and constraint-validation helpers to correctly treat canonical definition types as wildcards/compatible where appropriate (with canon vs non-canon partial implementations).
  • Add unit and smoke tests covering canonical-type constraint scenarios and constrained MakeGenericType dataflow.
Reviewed changes
Copilot reviewed 13 out of 13 changed files in this pull request and generated 4 comments.
Show a summary per file
FileDescription
src/tests/nativeaot/SmokeTests/TrimmingBehaviors/Dataflow.csAdds a new smoke test exercising constrained MakeGenericType rooting during dataflow analysis.
src/coreclr/tools/aot/ILCompiler.TypeSystem/ILCompiler.TypeSystem.csprojIncludes new Canon-specific helper implementations in the TypeSystem build.
src/coreclr/tools/aot/ILCompiler.TypeSystem.Tests/CoreTestAssembly/GenericConstraints.csAdds new generic constraint shapes for canonical constraint tests.
src/coreclr/tools/aot/ILCompiler.TypeSystem.Tests/ConstraintsValidationTest.csAdds a comprehensive canonical-constraint validation test suite.
src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/Dataflow/HandleCallAction.csNormalizes instantiated generic types before constraint validation/rooting.
src/coreclr/tools/ILVerification/ILVerification.projitemsAdds non-canon stub helper files required by the verifier’s non-canon TypeSystem build.
src/coreclr/tools/Common/TypeSystem/Common/TypeSystemConstraintsHelpers.csMakes helpers partial and adds canon-aware special-constraint and type-constraint checks.
src/coreclr/tools/Common/TypeSystem/Common/TypeSystemConstraintsHelpers.NonCanon.csProvides non-canon stub implementations for new partial helpers.
src/coreclr/tools/Common/TypeSystem/Common/CastingHelper.csAdds canon-aware matching hooks into cast logic (interfaces, variance, base chain).
src/coreclr/tools/Common/TypeSystem/Common/CastingHelper.NonCanon.csProvides non-canon stubs for new canon-aware cast helpers.
src/coreclr/tools/Common/TypeSystem/Canon/TypeSystemConstraintsHelpers.Canon.csCanon-specific implementations for wildcard-like canonical constraint handling.
src/coreclr/tools/Common/TypeSystem/Canon/CastingHelper.Canon.csCanon-specific canonical matching logic for casts and type-arg comparisons.
src/coreclr/nativeaot/System.Private.TypeLoader/src/System.Private.TypeLoader.csprojEnsures TypeLoader picks up canon-aware casting helper.
Comment threadsrc/tests/nativeaot/SmokeTests/TrimmingBehaviors/Dataflow.cs
Comment threadsrc/coreclr/tools/aot/ILCompiler.TypeSystem.Tests/ConstraintsValidationTest.cs
Outdated

Comment threadsrc/coreclr/tools/Common/TypeSystem/Common/TypeSystemConstraintsHelpers.NonCanon.cs
Outdated

Comment threadsrc/coreclr/tools/Common/TypeSystem/Canon/TypeSystemConstraintsHelpers.Canon.cs
Outdated


This was referenced Apr 20, 2026

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@MichalStrehovsky
Apply suggestions from code review
8289ab1
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
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review requested due to automatic review settings
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Pull request overview
Copilot reviewed 13 out of 13 changed files in this pull request and generated 1 comment.
Comment threadsrc/coreclr/tools/Common/TypeSystem/Common/TypeSystemConstraintsHelpers.NonCanon.cs
@build-analysisbuild-analysisBot
mentioned this pull request
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fix126604

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@MichalStrehovsky
Revert "Handle canonical types in casting logic" (#127301)
9619cf5
Resolves#127259
Reverts #127146
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Successfully merging this pull request may close these issues.

NativeAOT MakeGenericType fails to activate reflected generic type when generic parameter has self-referential interface constraint


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@MichalStrehovsky@jkoritzinsky@jkotas

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Force GitHub README to respect dark mode\n(function() {\n var style = document.createElement('style');\n style.textContent = '\n .markdown-body {\n color-scheme: dark light;\n }\n .markdown-body pre { background: #161b22 !important; }\n .markdown-body code { background: rgba(110, 118, 129, 0.4) !important; }\n .markdown-body table th, .markdown-body table td { border-color: #30363d !important; }\n .markdown-body img { background: #0d1117; }\n .markdown-body blockquote { border-left-color: #8b949e; }\n .markdown-body hr { border-color: #30363d; }\n ';\n document.head.appendChild(style);\n})();", "GitHub Dark Mode README Fix");
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})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
Handle canonical types in casting logic - #127146
Merged
MichalStrehovsky merged 5 commits into
dotnet:mainfrom 
MichalStrehovsky:fix126604
Apr 21, 2026
Merged
Handle canonical types in casting logic#127146
MichalStrehovsky merged 5 commits into
dotnet:mainfrom 
MichalStrehovsky:fix126604
Conversation
@MichalStrehovsky
@MichalStrehovskyMichalStrehovsky
commented
Apr 20, 2026

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Fixes#126604.
When we're doing dataflow analysis of MakeGenericXXX calls, we run constraint validation to ensure we don't precompile something invalid. However, because most reflection analysis within the compiler happens with canonical types, we can end up in a situation where a constraint check is necessary but all we have are canonical types. Constraint checking and CanCastTo logic was treating this a class __Canon : object { } case, but this is not that.
Cc @dotnet/ilc-contrib
MichalStrehovskyand others
added 4 commits
April 20, 2026 16:04
@MichalStrehovsky
Make constraint checking canon-aware for type constraints
c74f22b
The AOT compiler's CheckConstraints was rejecting valid canonical
instantiations because CanCastTo has no awareness of canonical types.
When MakeGenericType produces canonical forms like GenericType<TestRequest,
__Canon>, type constraints (interface/base-type) would fail because e.g.
IRequest<TestRequest, string> doesn't match IRequest<TestRequest, __Canon>.
Add CanCastToConstraintWithCanon to TypeSystemConstraintsHelpers that
handles canonical types in constraint checking:
- __Canon/__UniversalCanon as the instantiation param: wildcard, accepts
any type constraint (runtime validates with concrete types).
- __Canon/__UniversalCanon as the constraint type itself: __Canon accepts
reference types, __UniversalCanon accepts anything.
- Canonical subtypes in constraint type args: uses ConvertToCanonForm to
compare canonicalized forms, with variance support for variant positions.
- Universal canon fallback for nested __UniversalCanon under Specific
canonicalization.
Split into Canon/NonCanon partial files following the existing pattern
for IsSpecialTypeMeetingConstraint. Add NormalizeInstantiation call in
HandleCallAction's MakeGenericTypeSite.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@MichalStrehovsky
Move canon awareness from constraint helpers into CastingHelper
bb84090
Move IsCanonicalTypeArgMatch and IsCanonEquivalent from
TypeSystemConstraintsHelpers.Canon.cs into CastingHelper.Canon.cs so
that CanCastTo naturally handles canonical types. This eliminates the
duplicated interface-walking, base-chain-walking, and variance logic
that was in CanCastToConstraintWithCanon.
Key changes to CastingHelper:
- IsCanonicalCastTarget in CanCastToInternal: __Canon accepts any
reference type as a cast source, __UniversalCanon accepts any type.
This makes array covariance (string[] -> __Canon[]) work naturally.
- IsCanonicalTypeArgMatch in CanCastByVarianceToInterfaceOrDelegate:
handles invariant positions where type args differ by canonicalization.
- IsCanonEquivalent in CanCastToNonVariantInterface and CanCastToClass:
handles non-variant interfaces and base types with canon type args.
CanCastToConstraintWithCanon is simplified to only handle wildcard cases
where the param or constraint IS __Canon/__UniversalCanon directly.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@MichalStrehovsky
Handle parameterized types in canonical type arg matching
3fe978a
IsCanonicalTypeArgMatch did not handle parameterized types like arrays:
string[] vs __Canon[] failed because IsCanonEquivalent checks
Instantiation which is empty for arrays. Add ParameterizedType
structural matching that recursively compares element types.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@MichalStrehovsky
Add regression test for MakeGenericType with constrained canonicals
6f5cf18
Exercises MakeGenericType where the canonical instantiation
(Gen<Atom, __Canon, object>) must pass constraint checking with
__Canon satisfying interface and new() constraints.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
CopilotAI
review requested due to automatic review settings
April 20, 2026 11:27
CopilotAI
reviewed
Apr 20, 2026
View reviewed changes
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left a comment


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Pull request overview
This PR fixes NativeAOT reflection/dataflow constraint validation when generic instantiations are analyzed in canonical form (__Canon / __UniversalCanon), ensuring MakeGenericType sites aren’t incorrectly treated as invalid and therefore skipped for rooting/compilation.
Changes:
  • Normalize instantiated reflected generic types before constraint checking in MakeGenericType dataflow handling.
  • Extend casting and constraint-validation helpers to correctly treat canonical definition types as wildcards/compatible where appropriate (with canon vs non-canon partial implementations).
  • Add unit and smoke tests covering canonical-type constraint scenarios and constrained MakeGenericType dataflow.
Reviewed changes
Copilot reviewed 13 out of 13 changed files in this pull request and generated 4 comments.
Show a summary per file
FileDescription
src/tests/nativeaot/SmokeTests/TrimmingBehaviors/Dataflow.csAdds a new smoke test exercising constrained MakeGenericType rooting during dataflow analysis.
src/coreclr/tools/aot/ILCompiler.TypeSystem/ILCompiler.TypeSystem.csprojIncludes new Canon-specific helper implementations in the TypeSystem build.
src/coreclr/tools/aot/ILCompiler.TypeSystem.Tests/CoreTestAssembly/GenericConstraints.csAdds new generic constraint shapes for canonical constraint tests.
src/coreclr/tools/aot/ILCompiler.TypeSystem.Tests/ConstraintsValidationTest.csAdds a comprehensive canonical-constraint validation test suite.
src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/Dataflow/HandleCallAction.csNormalizes instantiated generic types before constraint validation/rooting.
src/coreclr/tools/ILVerification/ILVerification.projitemsAdds non-canon stub helper files required by the verifier’s non-canon TypeSystem build.
src/coreclr/tools/Common/TypeSystem/Common/TypeSystemConstraintsHelpers.csMakes helpers partial and adds canon-aware special-constraint and type-constraint checks.
src/coreclr/tools/Common/TypeSystem/Common/TypeSystemConstraintsHelpers.NonCanon.csProvides non-canon stub implementations for new partial helpers.
src/coreclr/tools/Common/TypeSystem/Common/CastingHelper.csAdds canon-aware matching hooks into cast logic (interfaces, variance, base chain).
src/coreclr/tools/Common/TypeSystem/Common/CastingHelper.NonCanon.csProvides non-canon stubs for new canon-aware cast helpers.
src/coreclr/tools/Common/TypeSystem/Canon/TypeSystemConstraintsHelpers.Canon.csCanon-specific implementations for wildcard-like canonical constraint handling.
src/coreclr/tools/Common/TypeSystem/Canon/CastingHelper.Canon.csCanon-specific canonical matching logic for casts and type-arg comparisons.
src/coreclr/nativeaot/System.Private.TypeLoader/src/System.Private.TypeLoader.csprojEnsures TypeLoader picks up canon-aware casting helper.
Comment threadsrc/tests/nativeaot/SmokeTests/TrimmingBehaviors/Dataflow.cs
Comment threadsrc/coreclr/tools/aot/ILCompiler.TypeSystem.Tests/ConstraintsValidationTest.cs
Outdated

Comment threadsrc/coreclr/tools/Common/TypeSystem/Common/TypeSystemConstraintsHelpers.NonCanon.cs
Outdated

Comment threadsrc/coreclr/tools/Common/TypeSystem/Canon/TypeSystemConstraintsHelpers.Canon.cs
Outdated


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Pull request overview
Copilot reviewed 13 out of 13 changed files in this pull request and generated 1 comment.
Comment threadsrc/coreclr/tools/Common/TypeSystem/Common/TypeSystemConstraintsHelpers.NonCanon.cs
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@MichalStrehovsky
Revert "Handle canonical types in casting logic" (#127301)
9619cf5
Resolves#127259
Reverts #127146
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NativeAOT MakeGenericType fails to activate reflected generic type when generic parameter has self-referential interface constraint


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@MichalStrehovsky@jkoritzinsky@jkotas

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Highlight search terms from Google/DuckDuckGo/Bing referrer\n(function() {\n var ref = document.referrer;\n var terms = [];\n \n if (ref.includes('google.com') || ref.includes('duckduckgo.com') || ref.includes('bing.com')) {\n var url = new URL(ref);\n var q = url.searchParams.get('q') || url.searchParams.get('p');\n if (q) {\n terms = q.split(/\\s+/).filter(function(t) { return t.length > 2; });\n }\n }\n \n if (terms.length === 0) return;\n \n var style = document.createElement('style');\n style.textContent = '.userscript-highlight { background: #fbbf24; color: #1a1a2e; padding: 1px 3px; border-radius: 2px; }';\n document.head.appendChild(style);\n \n function highlight(node) {\n if (node.nodeType === 3) { // text node\n var text = node.textContent;\n var found = false;\n terms.forEach(function(term) {\n var regex = new RegExp('(' + term.replace(/[.*+?^${}()|[\\]\\\\]/g, '\\\\') + ')', 'gi');\n if (regex.test(text)) {\n found = true;\n var frag = document.createDocumentFragment();\n var parts = text.split(regex);\n parts.forEach(function(part, i) {\n if (i % 2 === 0) {\n frag.appendChild(document.createTextNode(part));\n } else {\n var span = document.createElement('span');\n span.className = 'userscript-highlight';\n span.textContent = part;\n frag.appendChild(span);\n }\n });\n node.parentNode.replaceChild(frag, node);\n }\n });\n } else if (node.nodeType === 1 && node.childNodes) { // element\n var skipTags = ['SCRIPT', 'STYLE', 'NOSCRIPT', 'TEXTAREA', 'INPUT', 'SELECT'];\n if (!skipTags.includes(node.tagName)) {\n Array.from(node.childNodes).forEach(highlight);\n }\n }\n }\n \n highlight(document.body);\n \n // Re-highlight on dynamic content\n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1 || node.nodeType === 3) highlight(node);\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Highlight Search Terms");
}
} catch(__e) { console.warn('[Userscript:Highlight Search Terms]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
Handle canonical types in casting logic - #127146
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MichalStrehovsky:fix126604
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Merged
Handle canonical types in casting logic#127146
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MichalStrehovsky:fix126604
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Fixes#126604.
When we're doing dataflow analysis of MakeGenericXXX calls, we run constraint validation to ensure we don't precompile something invalid. However, because most reflection analysis within the compiler happens with canonical types, we can end up in a situation where a constraint check is necessary but all we have are canonical types. Constraint checking and CanCastTo logic was treating this a class __Canon : object { } case, but this is not that.
Cc @dotnet/ilc-contrib
MichalStrehovskyand others
added 4 commits
April 20, 2026 16:04
@MichalStrehovsky
Make constraint checking canon-aware for type constraints
c74f22b
The AOT compiler's CheckConstraints was rejecting valid canonical
instantiations because CanCastTo has no awareness of canonical types.
When MakeGenericType produces canonical forms like GenericType<TestRequest,
__Canon>, type constraints (interface/base-type) would fail because e.g.
IRequest<TestRequest, string> doesn't match IRequest<TestRequest, __Canon>.
Add CanCastToConstraintWithCanon to TypeSystemConstraintsHelpers that
handles canonical types in constraint checking:
- __Canon/__UniversalCanon as the instantiation param: wildcard, accepts
any type constraint (runtime validates with concrete types).
- __Canon/__UniversalCanon as the constraint type itself: __Canon accepts
reference types, __UniversalCanon accepts anything.
- Canonical subtypes in constraint type args: uses ConvertToCanonForm to
compare canonicalized forms, with variance support for variant positions.
- Universal canon fallback for nested __UniversalCanon under Specific
canonicalization.
Split into Canon/NonCanon partial files following the existing pattern
for IsSpecialTypeMeetingConstraint. Add NormalizeInstantiation call in
HandleCallAction's MakeGenericTypeSite.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@MichalStrehovsky
Move canon awareness from constraint helpers into CastingHelper
bb84090
Move IsCanonicalTypeArgMatch and IsCanonEquivalent from
TypeSystemConstraintsHelpers.Canon.cs into CastingHelper.Canon.cs so
that CanCastTo naturally handles canonical types. This eliminates the
duplicated interface-walking, base-chain-walking, and variance logic
that was in CanCastToConstraintWithCanon.
Key changes to CastingHelper:
- IsCanonicalCastTarget in CanCastToInternal: __Canon accepts any
reference type as a cast source, __UniversalCanon accepts any type.
This makes array covariance (string[] -> __Canon[]) work naturally.
- IsCanonicalTypeArgMatch in CanCastByVarianceToInterfaceOrDelegate:
handles invariant positions where type args differ by canonicalization.
- IsCanonEquivalent in CanCastToNonVariantInterface and CanCastToClass:
handles non-variant interfaces and base types with canon type args.
CanCastToConstraintWithCanon is simplified to only handle wildcard cases
where the param or constraint IS __Canon/__UniversalCanon directly.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@MichalStrehovsky
Handle parameterized types in canonical type arg matching
3fe978a
IsCanonicalTypeArgMatch did not handle parameterized types like arrays:
string[] vs __Canon[] failed because IsCanonEquivalent checks
Instantiation which is empty for arrays. Add ParameterizedType
structural matching that recursively compares element types.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@MichalStrehovsky
Add regression test for MakeGenericType with constrained canonicals
6f5cf18
Exercises MakeGenericType where the canonical instantiation
(Gen<Atom, __Canon, object>) must pass constraint checking with
__Canon satisfying interface and new() constraints.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
CopilotAI
review requested due to automatic review settings
April 20, 2026 11:27
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reviewed
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Pull request overview
This PR fixes NativeAOT reflection/dataflow constraint validation when generic instantiations are analyzed in canonical form (__Canon / __UniversalCanon), ensuring MakeGenericType sites aren’t incorrectly treated as invalid and therefore skipped for rooting/compilation.
Changes:
  • Normalize instantiated reflected generic types before constraint checking in MakeGenericType dataflow handling.
  • Extend casting and constraint-validation helpers to correctly treat canonical definition types as wildcards/compatible where appropriate (with canon vs non-canon partial implementations).
  • Add unit and smoke tests covering canonical-type constraint scenarios and constrained MakeGenericType dataflow.
Reviewed changes
Copilot reviewed 13 out of 13 changed files in this pull request and generated 4 comments.
Show a summary per file
FileDescription
src/tests/nativeaot/SmokeTests/TrimmingBehaviors/Dataflow.csAdds a new smoke test exercising constrained MakeGenericType rooting during dataflow analysis.
src/coreclr/tools/aot/ILCompiler.TypeSystem/ILCompiler.TypeSystem.csprojIncludes new Canon-specific helper implementations in the TypeSystem build.
src/coreclr/tools/aot/ILCompiler.TypeSystem.Tests/CoreTestAssembly/GenericConstraints.csAdds new generic constraint shapes for canonical constraint tests.
src/coreclr/tools/aot/ILCompiler.TypeSystem.Tests/ConstraintsValidationTest.csAdds a comprehensive canonical-constraint validation test suite.
src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/Dataflow/HandleCallAction.csNormalizes instantiated generic types before constraint validation/rooting.
src/coreclr/tools/ILVerification/ILVerification.projitemsAdds non-canon stub helper files required by the verifier’s non-canon TypeSystem build.
src/coreclr/tools/Common/TypeSystem/Common/TypeSystemConstraintsHelpers.csMakes helpers partial and adds canon-aware special-constraint and type-constraint checks.
src/coreclr/tools/Common/TypeSystem/Common/TypeSystemConstraintsHelpers.NonCanon.csProvides non-canon stub implementations for new partial helpers.
src/coreclr/tools/Common/TypeSystem/Common/CastingHelper.csAdds canon-aware matching hooks into cast logic (interfaces, variance, base chain).
src/coreclr/tools/Common/TypeSystem/Common/CastingHelper.NonCanon.csProvides non-canon stubs for new canon-aware cast helpers.
src/coreclr/tools/Common/TypeSystem/Canon/TypeSystemConstraintsHelpers.Canon.csCanon-specific implementations for wildcard-like canonical constraint handling.
src/coreclr/tools/Common/TypeSystem/Canon/CastingHelper.Canon.csCanon-specific canonical matching logic for casts and type-arg comparisons.
src/coreclr/nativeaot/System.Private.TypeLoader/src/System.Private.TypeLoader.csprojEnsures TypeLoader picks up canon-aware casting helper.
Comment threadsrc/tests/nativeaot/SmokeTests/TrimmingBehaviors/Dataflow.cs
Comment threadsrc/coreclr/tools/aot/ILCompiler.TypeSystem.Tests/ConstraintsValidationTest.cs
Outdated

Comment threadsrc/coreclr/tools/Common/TypeSystem/Common/TypeSystemConstraintsHelpers.NonCanon.cs
Outdated

Comment threadsrc/coreclr/tools/Common/TypeSystem/Canon/TypeSystemConstraintsHelpers.Canon.cs
Outdated


This was referenced Apr 20, 2026

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@MichalStrehovsky
Apply suggestions from code review
8289ab1
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
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review requested due to automatic review settings
April 21, 2026 00:48
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Pull request overview
Copilot reviewed 13 out of 13 changed files in this pull request and generated 1 comment.
Comment threadsrc/coreclr/tools/Common/TypeSystem/Common/TypeSystemConstraintsHelpers.NonCanon.cs
@build-analysisbuild-analysisBot
mentioned this pull request
Apr 21, 2026

Open

@MichalStrehovsky
MichalStrehovsky
merged commit 7bba220
into
dotnet:mainApr 21, 2026

139 of 144 checks passed

@MichalStrehovsky
MichalStrehovsky
deleted the

fix126604

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April 21, 2026 09:50
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mentioned this pull request
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@MichalStrehovsky
Revert "Handle canonical types in casting logic" (#127301)
9619cf5
Resolves#127259
Reverts #127146
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Successfully merging this pull request may close these issues.

NativeAOT MakeGenericType fails to activate reflected generic type when generic parameter has self-referential interface constraint


4 participants

@MichalStrehovsky@jkoritzinsky@jkotas

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Strip utm_, fbclid, gclid, etc. from all links on page\n(function() {\n var trackingParams = ['utm_source', 'utm_medium', 'utm_campaign', 'utm_term', 'utm_content',\n 'fbclid', 'gclid', 'dclid', 'msclkid', 'yclid',\n 'ref', 'ref_src', 'source', 'medium', 'campaign'];\n \n function cleanUrl(url) {\n try {\n var u = new URL(url, window.location.origin);\n var changed = false;\n trackingParams.forEach(function(p) {\n if (u.searchParams.has(p)) {\n u.searchParams.delete(p);\n changed = true;\n }\n });\n return changed ? u.toString() : url;\n } catch (e) {\n return url;\n }\n }\n \n function cleanLinks() {\n document.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n \n cleanLinks();\n \n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1) {\n if (node.tagName === 'A') cleanLinks();\n node.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Remove Tracking Parameters from Links");
}
} catch(__e) { console.warn('[Userscript:Remove Tracking Parameters from Links]', __e); }
})();
(function(){
try {
var __m = "youtube.com";
var __re = new RegExp('^' + "youtube\\.com" + '

Skip to content
Handle canonical types in casting logic - #127146
Merged
MichalStrehovsky merged 5 commits into
dotnet:mainfrom 
MichalStrehovsky:fix126604
Apr 21, 2026
Merged
Handle canonical types in casting logic#127146
MichalStrehovsky merged 5 commits into
dotnet:mainfrom 
MichalStrehovsky:fix126604
Conversation
@MichalStrehovsky
@MichalStrehovskyMichalStrehovsky
commented
Apr 20, 2026

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Fixes#126604.
When we're doing dataflow analysis of MakeGenericXXX calls, we run constraint validation to ensure we don't precompile something invalid. However, because most reflection analysis within the compiler happens with canonical types, we can end up in a situation where a constraint check is necessary but all we have are canonical types. Constraint checking and CanCastTo logic was treating this a class __Canon : object { } case, but this is not that.
Cc @dotnet/ilc-contrib
MichalStrehovskyand others
added 4 commits
April 20, 2026 16:04
@MichalStrehovsky
Make constraint checking canon-aware for type constraints
c74f22b
The AOT compiler's CheckConstraints was rejecting valid canonical
instantiations because CanCastTo has no awareness of canonical types.
When MakeGenericType produces canonical forms like GenericType<TestRequest,
__Canon>, type constraints (interface/base-type) would fail because e.g.
IRequest<TestRequest, string> doesn't match IRequest<TestRequest, __Canon>.
Add CanCastToConstraintWithCanon to TypeSystemConstraintsHelpers that
handles canonical types in constraint checking:
- __Canon/__UniversalCanon as the instantiation param: wildcard, accepts
any type constraint (runtime validates with concrete types).
- __Canon/__UniversalCanon as the constraint type itself: __Canon accepts
reference types, __UniversalCanon accepts anything.
- Canonical subtypes in constraint type args: uses ConvertToCanonForm to
compare canonicalized forms, with variance support for variant positions.
- Universal canon fallback for nested __UniversalCanon under Specific
canonicalization.
Split into Canon/NonCanon partial files following the existing pattern
for IsSpecialTypeMeetingConstraint. Add NormalizeInstantiation call in
HandleCallAction's MakeGenericTypeSite.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@MichalStrehovsky
Move canon awareness from constraint helpers into CastingHelper
bb84090
Move IsCanonicalTypeArgMatch and IsCanonEquivalent from
TypeSystemConstraintsHelpers.Canon.cs into CastingHelper.Canon.cs so
that CanCastTo naturally handles canonical types. This eliminates the
duplicated interface-walking, base-chain-walking, and variance logic
that was in CanCastToConstraintWithCanon.
Key changes to CastingHelper:
- IsCanonicalCastTarget in CanCastToInternal: __Canon accepts any
reference type as a cast source, __UniversalCanon accepts any type.
This makes array covariance (string[] -> __Canon[]) work naturally.
- IsCanonicalTypeArgMatch in CanCastByVarianceToInterfaceOrDelegate:
handles invariant positions where type args differ by canonicalization.
- IsCanonEquivalent in CanCastToNonVariantInterface and CanCastToClass:
handles non-variant interfaces and base types with canon type args.
CanCastToConstraintWithCanon is simplified to only handle wildcard cases
where the param or constraint IS __Canon/__UniversalCanon directly.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@MichalStrehovsky
Handle parameterized types in canonical type arg matching
3fe978a
IsCanonicalTypeArgMatch did not handle parameterized types like arrays:
string[] vs __Canon[] failed because IsCanonEquivalent checks
Instantiation which is empty for arrays. Add ParameterizedType
structural matching that recursively compares element types.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@MichalStrehovsky
Add regression test for MakeGenericType with constrained canonicals
6f5cf18
Exercises MakeGenericType where the canonical instantiation
(Gen<Atom, __Canon, object>) must pass constraint checking with
__Canon satisfying interface and new() constraints.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
CopilotAI
review requested due to automatic review settings
April 20, 2026 11:27
CopilotAI
reviewed
Apr 20, 2026
View reviewed changes
CopilotAI
left a comment


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Pull request overview
This PR fixes NativeAOT reflection/dataflow constraint validation when generic instantiations are analyzed in canonical form (__Canon / __UniversalCanon), ensuring MakeGenericType sites aren’t incorrectly treated as invalid and therefore skipped for rooting/compilation.
Changes:
  • Normalize instantiated reflected generic types before constraint checking in MakeGenericType dataflow handling.
  • Extend casting and constraint-validation helpers to correctly treat canonical definition types as wildcards/compatible where appropriate (with canon vs non-canon partial implementations).
  • Add unit and smoke tests covering canonical-type constraint scenarios and constrained MakeGenericType dataflow.
Reviewed changes
Copilot reviewed 13 out of 13 changed files in this pull request and generated 4 comments.
Show a summary per file
FileDescription
src/tests/nativeaot/SmokeTests/TrimmingBehaviors/Dataflow.csAdds a new smoke test exercising constrained MakeGenericType rooting during dataflow analysis.
src/coreclr/tools/aot/ILCompiler.TypeSystem/ILCompiler.TypeSystem.csprojIncludes new Canon-specific helper implementations in the TypeSystem build.
src/coreclr/tools/aot/ILCompiler.TypeSystem.Tests/CoreTestAssembly/GenericConstraints.csAdds new generic constraint shapes for canonical constraint tests.
src/coreclr/tools/aot/ILCompiler.TypeSystem.Tests/ConstraintsValidationTest.csAdds a comprehensive canonical-constraint validation test suite.
src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/Dataflow/HandleCallAction.csNormalizes instantiated generic types before constraint validation/rooting.
src/coreclr/tools/ILVerification/ILVerification.projitemsAdds non-canon stub helper files required by the verifier’s non-canon TypeSystem build.
src/coreclr/tools/Common/TypeSystem/Common/TypeSystemConstraintsHelpers.csMakes helpers partial and adds canon-aware special-constraint and type-constraint checks.
src/coreclr/tools/Common/TypeSystem/Common/TypeSystemConstraintsHelpers.NonCanon.csProvides non-canon stub implementations for new partial helpers.
src/coreclr/tools/Common/TypeSystem/Common/CastingHelper.csAdds canon-aware matching hooks into cast logic (interfaces, variance, base chain).
src/coreclr/tools/Common/TypeSystem/Common/CastingHelper.NonCanon.csProvides non-canon stubs for new canon-aware cast helpers.
src/coreclr/tools/Common/TypeSystem/Canon/TypeSystemConstraintsHelpers.Canon.csCanon-specific implementations for wildcard-like canonical constraint handling.
src/coreclr/tools/Common/TypeSystem/Canon/CastingHelper.Canon.csCanon-specific canonical matching logic for casts and type-arg comparisons.
src/coreclr/nativeaot/System.Private.TypeLoader/src/System.Private.TypeLoader.csprojEnsures TypeLoader picks up canon-aware casting helper.
Comment threadsrc/tests/nativeaot/SmokeTests/TrimmingBehaviors/Dataflow.cs
Comment threadsrc/coreclr/tools/aot/ILCompiler.TypeSystem.Tests/ConstraintsValidationTest.cs
Outdated

Comment threadsrc/coreclr/tools/Common/TypeSystem/Common/TypeSystemConstraintsHelpers.NonCanon.cs
Outdated

Comment threadsrc/coreclr/tools/Common/TypeSystem/Canon/TypeSystemConstraintsHelpers.Canon.cs
Outdated


This was referenced Apr 20, 2026

Open


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Closed


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@MichalStrehovsky
Apply suggestions from code review
8289ab1
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
CopilotAI
review requested due to automatic review settings
April 21, 2026 00:48
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Pull request overview
Copilot reviewed 13 out of 13 changed files in this pull request and generated 1 comment.
Comment threadsrc/coreclr/tools/Common/TypeSystem/Common/TypeSystemConstraintsHelpers.NonCanon.cs
@build-analysisbuild-analysisBot
mentioned this pull request
Apr 21, 2026

Open

@MichalStrehovsky
MichalStrehovsky
merged commit 7bba220
into
dotnet:mainApr 21, 2026

139 of 144 checks passed

@MichalStrehovsky
MichalStrehovsky
deleted the

fix126604

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April 21, 2026 09:50
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Apr 21, 2026

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This was referenced Apr 21, 2026
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mentioned this pull request
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mentioned this pull request
Apr 22, 2026
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MichalStrehovsky added a commit
that referenced
this pull request
Apr 23, 2026
@MichalStrehovsky
Revert "Handle canonical types in casting logic" (#127301)
9619cf5
Resolves#127259
Reverts #127146
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Copilot left review comments
@jkoritzinskyjkoritzinskyjkoritzinsky approved these changes

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Successfully merging this pull request may close these issues.

NativeAOT MakeGenericType fails to activate reflected generic type when generic parameter has self-referential interface constraint


4 participants

@MichalStrehovsky@jkoritzinsky@jkotas

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Auto-enable theater mode on YouTube\n(function() {\n function tryTheater() {\n var btn = document.querySelector('button[aria-label=\"Theater mode\"], ytd-player #player button[title=\"Theater mode\"]');\n if (btn && !btn.classList.contains('activated')) {\n btn.click();\n }\n }\n \n // Try immediately\n tryTheater();\n \n // Try after navigation (SPA)\n var lastUrl = location.href;\n setInterval(function() {\n if (location.href !== lastUrl) {\n lastUrl = location.href;\n setTimeout(tryTheater, 500);\n }\n }, 1000);\n \n // Also try on player load\n var observer = new MutationObserver(tryTheater);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "YouTube Theater Mode Default");
}
} catch(__e) { console.warn('[Userscript:YouTube Theater Mode Default]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
Handle canonical types in casting logic - #127146
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MichalStrehovsky:fix126604
Apr 21, 2026
Merged
Handle canonical types in casting logic#127146
MichalStrehovsky merged 5 commits into
dotnet:mainfrom 
MichalStrehovsky:fix126604
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Fixes#126604.
When we're doing dataflow analysis of MakeGenericXXX calls, we run constraint validation to ensure we don't precompile something invalid. However, because most reflection analysis within the compiler happens with canonical types, we can end up in a situation where a constraint check is necessary but all we have are canonical types. Constraint checking and CanCastTo logic was treating this a class __Canon : object { } case, but this is not that.
Cc @dotnet/ilc-contrib
MichalStrehovskyand others
added 4 commits
April 20, 2026 16:04
@MichalStrehovsky
Make constraint checking canon-aware for type constraints
c74f22b
The AOT compiler's CheckConstraints was rejecting valid canonical
instantiations because CanCastTo has no awareness of canonical types.
When MakeGenericType produces canonical forms like GenericType<TestRequest,
__Canon>, type constraints (interface/base-type) would fail because e.g.
IRequest<TestRequest, string> doesn't match IRequest<TestRequest, __Canon>.
Add CanCastToConstraintWithCanon to TypeSystemConstraintsHelpers that
handles canonical types in constraint checking:
- __Canon/__UniversalCanon as the instantiation param: wildcard, accepts
any type constraint (runtime validates with concrete types).
- __Canon/__UniversalCanon as the constraint type itself: __Canon accepts
reference types, __UniversalCanon accepts anything.
- Canonical subtypes in constraint type args: uses ConvertToCanonForm to
compare canonicalized forms, with variance support for variant positions.
- Universal canon fallback for nested __UniversalCanon under Specific
canonicalization.
Split into Canon/NonCanon partial files following the existing pattern
for IsSpecialTypeMeetingConstraint. Add NormalizeInstantiation call in
HandleCallAction's MakeGenericTypeSite.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@MichalStrehovsky
Move canon awareness from constraint helpers into CastingHelper
bb84090
Move IsCanonicalTypeArgMatch and IsCanonEquivalent from
TypeSystemConstraintsHelpers.Canon.cs into CastingHelper.Canon.cs so
that CanCastTo naturally handles canonical types. This eliminates the
duplicated interface-walking, base-chain-walking, and variance logic
that was in CanCastToConstraintWithCanon.
Key changes to CastingHelper:
- IsCanonicalCastTarget in CanCastToInternal: __Canon accepts any
reference type as a cast source, __UniversalCanon accepts any type.
This makes array covariance (string[] -> __Canon[]) work naturally.
- IsCanonicalTypeArgMatch in CanCastByVarianceToInterfaceOrDelegate:
handles invariant positions where type args differ by canonicalization.
- IsCanonEquivalent in CanCastToNonVariantInterface and CanCastToClass:
handles non-variant interfaces and base types with canon type args.
CanCastToConstraintWithCanon is simplified to only handle wildcard cases
where the param or constraint IS __Canon/__UniversalCanon directly.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@MichalStrehovsky
Handle parameterized types in canonical type arg matching
3fe978a
IsCanonicalTypeArgMatch did not handle parameterized types like arrays:
string[] vs __Canon[] failed because IsCanonEquivalent checks
Instantiation which is empty for arrays. Add ParameterizedType
structural matching that recursively compares element types.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@MichalStrehovsky
Add regression test for MakeGenericType with constrained canonicals
6f5cf18
Exercises MakeGenericType where the canonical instantiation
(Gen<Atom, __Canon, object>) must pass constraint checking with
__Canon satisfying interface and new() constraints.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
CopilotAI
review requested due to automatic review settings
April 20, 2026 11:27
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reviewed
Apr 20, 2026
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Pull request overview
This PR fixes NativeAOT reflection/dataflow constraint validation when generic instantiations are analyzed in canonical form (__Canon / __UniversalCanon), ensuring MakeGenericType sites aren’t incorrectly treated as invalid and therefore skipped for rooting/compilation.
Changes:
  • Normalize instantiated reflected generic types before constraint checking in MakeGenericType dataflow handling.
  • Extend casting and constraint-validation helpers to correctly treat canonical definition types as wildcards/compatible where appropriate (with canon vs non-canon partial implementations).
  • Add unit and smoke tests covering canonical-type constraint scenarios and constrained MakeGenericType dataflow.
Reviewed changes
Copilot reviewed 13 out of 13 changed files in this pull request and generated 4 comments.
Show a summary per file
FileDescription
src/tests/nativeaot/SmokeTests/TrimmingBehaviors/Dataflow.csAdds a new smoke test exercising constrained MakeGenericType rooting during dataflow analysis.
src/coreclr/tools/aot/ILCompiler.TypeSystem/ILCompiler.TypeSystem.csprojIncludes new Canon-specific helper implementations in the TypeSystem build.
src/coreclr/tools/aot/ILCompiler.TypeSystem.Tests/CoreTestAssembly/GenericConstraints.csAdds new generic constraint shapes for canonical constraint tests.
src/coreclr/tools/aot/ILCompiler.TypeSystem.Tests/ConstraintsValidationTest.csAdds a comprehensive canonical-constraint validation test suite.
src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/Dataflow/HandleCallAction.csNormalizes instantiated generic types before constraint validation/rooting.
src/coreclr/tools/ILVerification/ILVerification.projitemsAdds non-canon stub helper files required by the verifier’s non-canon TypeSystem build.
src/coreclr/tools/Common/TypeSystem/Common/TypeSystemConstraintsHelpers.csMakes helpers partial and adds canon-aware special-constraint and type-constraint checks.
src/coreclr/tools/Common/TypeSystem/Common/TypeSystemConstraintsHelpers.NonCanon.csProvides non-canon stub implementations for new partial helpers.
src/coreclr/tools/Common/TypeSystem/Common/CastingHelper.csAdds canon-aware matching hooks into cast logic (interfaces, variance, base chain).
src/coreclr/tools/Common/TypeSystem/Common/CastingHelper.NonCanon.csProvides non-canon stubs for new canon-aware cast helpers.
src/coreclr/tools/Common/TypeSystem/Canon/TypeSystemConstraintsHelpers.Canon.csCanon-specific implementations for wildcard-like canonical constraint handling.
src/coreclr/tools/Common/TypeSystem/Canon/CastingHelper.Canon.csCanon-specific canonical matching logic for casts and type-arg comparisons.
src/coreclr/nativeaot/System.Private.TypeLoader/src/System.Private.TypeLoader.csprojEnsures TypeLoader picks up canon-aware casting helper.
Comment threadsrc/tests/nativeaot/SmokeTests/TrimmingBehaviors/Dataflow.cs
Comment threadsrc/coreclr/tools/aot/ILCompiler.TypeSystem.Tests/ConstraintsValidationTest.cs
Outdated

Comment threadsrc/coreclr/tools/Common/TypeSystem/Common/TypeSystemConstraintsHelpers.NonCanon.cs
Outdated

Comment threadsrc/coreclr/tools/Common/TypeSystem/Canon/TypeSystemConstraintsHelpers.Canon.cs
Outdated


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Pull request overview
Copilot reviewed 13 out of 13 changed files in this pull request and generated 1 comment.
Comment threadsrc/coreclr/tools/Common/TypeSystem/Common/TypeSystemConstraintsHelpers.NonCanon.cs
@build-analysisbuild-analysisBot
mentioned this pull request
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MichalStrehovsky
merged commit 7bba220
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fix126604

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@MichalStrehovsky
Revert "Handle canonical types in casting logic" (#127301)
9619cf5
Resolves#127259
Reverts #127146
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NativeAOT MakeGenericType fails to activate reflected generic type when generic parameter has self-referential interface constraint


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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Remove or un-stick sticky/fixed headers that block content\n(function() {\n function unstick() {\n document.querySelectorAll('header, nav, [role=\"banner\"], .header, .navbar, .sticky, .fixed-top, [style*=\"position: fixed\"], [style*=\"position:sticky\"]').forEach(function(el) {\n if (el.style.position === 'fixed' || el.style.position === 'sticky' || \n getComputedStyle(el).position === 'fixed' || getComputedStyle(el).position === 'sticky') {\n el.style.position = 'static';\n el.style.top = 'auto';\n el.style.zIndex = 'auto';\n }\n });\n }\n \n unstick();\n \n var observer = new MutationObserver(unstick);\n observer.observe(document.body, { childList: true, subtree: true, attributes: true, attributeFilter: ['style', 'class'] });\n})();", "Kill Sticky Headers");
}
} catch(__e) { console.warn('[Userscript:Kill Sticky Headers]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
Handle canonical types in casting logic - #127146
Merged
MichalStrehovsky merged 5 commits into
dotnet:mainfrom 
MichalStrehovsky:fix126604
Apr 21, 2026
Merged
Handle canonical types in casting logic#127146
MichalStrehovsky merged 5 commits into
dotnet:mainfrom 
MichalStrehovsky:fix126604
Conversation
@MichalStrehovsky
@MichalStrehovskyMichalStrehovsky
commented
Apr 20, 2026

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Fixes#126604.
When we're doing dataflow analysis of MakeGenericXXX calls, we run constraint validation to ensure we don't precompile something invalid. However, because most reflection analysis within the compiler happens with canonical types, we can end up in a situation where a constraint check is necessary but all we have are canonical types. Constraint checking and CanCastTo logic was treating this a class __Canon : object { } case, but this is not that.
Cc @dotnet/ilc-contrib
MichalStrehovskyand others
added 4 commits
April 20, 2026 16:04
@MichalStrehovsky
Make constraint checking canon-aware for type constraints
c74f22b
The AOT compiler's CheckConstraints was rejecting valid canonical
instantiations because CanCastTo has no awareness of canonical types.
When MakeGenericType produces canonical forms like GenericType<TestRequest,
__Canon>, type constraints (interface/base-type) would fail because e.g.
IRequest<TestRequest, string> doesn't match IRequest<TestRequest, __Canon>.
Add CanCastToConstraintWithCanon to TypeSystemConstraintsHelpers that
handles canonical types in constraint checking:
- __Canon/__UniversalCanon as the instantiation param: wildcard, accepts
any type constraint (runtime validates with concrete types).
- __Canon/__UniversalCanon as the constraint type itself: __Canon accepts
reference types, __UniversalCanon accepts anything.
- Canonical subtypes in constraint type args: uses ConvertToCanonForm to
compare canonicalized forms, with variance support for variant positions.
- Universal canon fallback for nested __UniversalCanon under Specific
canonicalization.
Split into Canon/NonCanon partial files following the existing pattern
for IsSpecialTypeMeetingConstraint. Add NormalizeInstantiation call in
HandleCallAction's MakeGenericTypeSite.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@MichalStrehovsky
Move canon awareness from constraint helpers into CastingHelper
bb84090
Move IsCanonicalTypeArgMatch and IsCanonEquivalent from
TypeSystemConstraintsHelpers.Canon.cs into CastingHelper.Canon.cs so
that CanCastTo naturally handles canonical types. This eliminates the
duplicated interface-walking, base-chain-walking, and variance logic
that was in CanCastToConstraintWithCanon.
Key changes to CastingHelper:
- IsCanonicalCastTarget in CanCastToInternal: __Canon accepts any
reference type as a cast source, __UniversalCanon accepts any type.
This makes array covariance (string[] -> __Canon[]) work naturally.
- IsCanonicalTypeArgMatch in CanCastByVarianceToInterfaceOrDelegate:
handles invariant positions where type args differ by canonicalization.
- IsCanonEquivalent in CanCastToNonVariantInterface and CanCastToClass:
handles non-variant interfaces and base types with canon type args.
CanCastToConstraintWithCanon is simplified to only handle wildcard cases
where the param or constraint IS __Canon/__UniversalCanon directly.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@MichalStrehovsky
Handle parameterized types in canonical type arg matching
3fe978a
IsCanonicalTypeArgMatch did not handle parameterized types like arrays:
string[] vs __Canon[] failed because IsCanonEquivalent checks
Instantiation which is empty for arrays. Add ParameterizedType
structural matching that recursively compares element types.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@MichalStrehovsky
Add regression test for MakeGenericType with constrained canonicals
6f5cf18
Exercises MakeGenericType where the canonical instantiation
(Gen<Atom, __Canon, object>) must pass constraint checking with
__Canon satisfying interface and new() constraints.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
CopilotAI
review requested due to automatic review settings
April 20, 2026 11:27
CopilotAI
reviewed
Apr 20, 2026
View reviewed changes
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Pull request overview
This PR fixes NativeAOT reflection/dataflow constraint validation when generic instantiations are analyzed in canonical form (__Canon / __UniversalCanon), ensuring MakeGenericType sites aren’t incorrectly treated as invalid and therefore skipped for rooting/compilation.
Changes:
  • Normalize instantiated reflected generic types before constraint checking in MakeGenericType dataflow handling.
  • Extend casting and constraint-validation helpers to correctly treat canonical definition types as wildcards/compatible where appropriate (with canon vs non-canon partial implementations).
  • Add unit and smoke tests covering canonical-type constraint scenarios and constrained MakeGenericType dataflow.
Reviewed changes
Copilot reviewed 13 out of 13 changed files in this pull request and generated 4 comments.
Show a summary per file
FileDescription
src/tests/nativeaot/SmokeTests/TrimmingBehaviors/Dataflow.csAdds a new smoke test exercising constrained MakeGenericType rooting during dataflow analysis.
src/coreclr/tools/aot/ILCompiler.TypeSystem/ILCompiler.TypeSystem.csprojIncludes new Canon-specific helper implementations in the TypeSystem build.
src/coreclr/tools/aot/ILCompiler.TypeSystem.Tests/CoreTestAssembly/GenericConstraints.csAdds new generic constraint shapes for canonical constraint tests.
src/coreclr/tools/aot/ILCompiler.TypeSystem.Tests/ConstraintsValidationTest.csAdds a comprehensive canonical-constraint validation test suite.
src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/Dataflow/HandleCallAction.csNormalizes instantiated generic types before constraint validation/rooting.
src/coreclr/tools/ILVerification/ILVerification.projitemsAdds non-canon stub helper files required by the verifier’s non-canon TypeSystem build.
src/coreclr/tools/Common/TypeSystem/Common/TypeSystemConstraintsHelpers.csMakes helpers partial and adds canon-aware special-constraint and type-constraint checks.
src/coreclr/tools/Common/TypeSystem/Common/TypeSystemConstraintsHelpers.NonCanon.csProvides non-canon stub implementations for new partial helpers.
src/coreclr/tools/Common/TypeSystem/Common/CastingHelper.csAdds canon-aware matching hooks into cast logic (interfaces, variance, base chain).
src/coreclr/tools/Common/TypeSystem/Common/CastingHelper.NonCanon.csProvides non-canon stubs for new canon-aware cast helpers.
src/coreclr/tools/Common/TypeSystem/Canon/TypeSystemConstraintsHelpers.Canon.csCanon-specific implementations for wildcard-like canonical constraint handling.
src/coreclr/tools/Common/TypeSystem/Canon/CastingHelper.Canon.csCanon-specific canonical matching logic for casts and type-arg comparisons.
src/coreclr/nativeaot/System.Private.TypeLoader/src/System.Private.TypeLoader.csprojEnsures TypeLoader picks up canon-aware casting helper.
Comment threadsrc/tests/nativeaot/SmokeTests/TrimmingBehaviors/Dataflow.cs
Comment threadsrc/coreclr/tools/aot/ILCompiler.TypeSystem.Tests/ConstraintsValidationTest.cs
Outdated

Comment threadsrc/coreclr/tools/Common/TypeSystem/Common/TypeSystemConstraintsHelpers.NonCanon.cs
Outdated

Comment threadsrc/coreclr/tools/Common/TypeSystem/Canon/TypeSystemConstraintsHelpers.Canon.cs
Outdated


This was referenced Apr 20, 2026

Open


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@MichalStrehovsky
Apply suggestions from code review
8289ab1
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
CopilotAI
review requested due to automatic review settings
April 21, 2026 00:48
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Pull request overview
Copilot reviewed 13 out of 13 changed files in this pull request and generated 1 comment.
Comment threadsrc/coreclr/tools/Common/TypeSystem/Common/TypeSystemConstraintsHelpers.NonCanon.cs
@build-analysisbuild-analysisBot
mentioned this pull request
Apr 21, 2026

Open

@MichalStrehovsky
MichalStrehovsky
merged commit 7bba220
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dotnet:mainApr 21, 2026

139 of 144 checks passed

@MichalStrehovsky
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deleted the

fix126604

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April 21, 2026 09:50
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This was referenced Apr 21, 2026
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@MichalStrehovsky
Revert "Handle canonical types in casting logic" (#127301)
9619cf5
Resolves#127259
Reverts #127146
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Successfully merging this pull request may close these issues.

NativeAOT MakeGenericType fails to activate reflected generic type when generic parameter has self-referential interface constraint


4 participants

@MichalStrehovsky@jkoritzinsky@jkotas

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Universal Dark Mode - works on any site\n(function() {\n var enabled = true;\n \n function applyDarkMode() {\n if (!enabled) return;\n \n // Create style element if it doesn't exist\n var style = document.getElementById('universal-dark-mode-style');\n if (!style) {\n style = document.createElement('style');\n style.id = 'universal-dark-mode-style';\n document.head.appendChild(style);\n }\n \n // Dark mode CSS - inverts colors but preserves images/video\n style.textContent = '\n /* Invert everything except media */\n html {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #1a1a2e !important;\n }\n \n /* Restore images, videos, iframes, canvas */\n img, video, iframe, canvas, svg, picture, [style*=\"background-image\"] {\n filter: invert(1) hue-rotate(180deg) !important;\n }\n \n /* Preserve specific elements that should not be inverted */\n .no-dark-mode, .no-dark-mode *,\n [data-theme=\"light\"], [data-theme=\"light\"],\n .ace_editor, .ace_editor *,\n .CodeMirror, .CodeMirror *,\n .monaco-editor, .monaco-editor *,\n .markdown-body pre, .markdown-body pre *,\n .highlight, .highlight *,\n pre code, pre code * {\n filter: none !important;\n }\n \n /* Fix common UI elements */\n .modal, .popup, .dropdown-menu, .tooltip, .popover {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #2d2d44 !important;\n border-color: #444 !important;\n }\n \n /* Scrollbars */\n ::-webkit-scrollbar { background: #1a1a2e !important; }\n ::-webkit-scrollbar-thumb { background: #444 !important; }\n ::-webkit-scrollbar-thumb:hover { background: #555 !important; }\n \n /* Selection */\n ::selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ::-moz-selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ';\n }\n \n function removeDarkMode() {\n var style = document.getElementById('universal-dark-mode-style');\n if (style) style.remove();\n }\n \n // Toggle with Alt+Shift+D\n document.addEventListener('keydown', function(e) {\n if (e.altKey && e.shiftKey && e.key === 'D') {\n e.preventDefault();\n enabled = !enabled;\n if (enabled) {\n applyDarkMode();\n console.log('[Universal Dark Mode] Enabled');\n } else {\n removeDarkMode();\n console.log('[Universal Dark Mode] Disabled');\n }\n }\n });\n \n // Apply on load\n applyDarkMode();\n \n // Re-apply on dynamic content\n var observer = new MutationObserver(function(mutations) {\n if (enabled && !document.getElementById('universal-dark-mode-style')) {\n applyDarkMode();\n }\n });\n observer.observe(document.head, { childList: true });\n \n console.log('[Universal Dark Mode] Loaded - Press Alt+Shift+D to toggle');\n})();", "Universal Dark Mode");
}
} catch(__e) { console.warn('[Userscript:Universal Dark Mode]', __e); }
})();
})();

Skip to content
Handle canonical types in casting logic - #127146
Merged
MichalStrehovsky merged 5 commits into
dotnet:mainfrom 
MichalStrehovsky:fix126604
Apr 21, 2026
Merged
Handle canonical types in casting logic#127146
MichalStrehovsky merged 5 commits into
dotnet:mainfrom 
MichalStrehovsky:fix126604
Conversation
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@MichalStrehovskyMichalStrehovsky
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Apr 20, 2026

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Fixes#126604.
When we're doing dataflow analysis of MakeGenericXXX calls, we run constraint validation to ensure we don't precompile something invalid. However, because most reflection analysis within the compiler happens with canonical types, we can end up in a situation where a constraint check is necessary but all we have are canonical types. Constraint checking and CanCastTo logic was treating this a class __Canon : object { } case, but this is not that.
Cc @dotnet/ilc-contrib
MichalStrehovskyand others
added 4 commits
April 20, 2026 16:04
@MichalStrehovsky
Make constraint checking canon-aware for type constraints
c74f22b
The AOT compiler's CheckConstraints was rejecting valid canonical
instantiations because CanCastTo has no awareness of canonical types.
When MakeGenericType produces canonical forms like GenericType<TestRequest,
__Canon>, type constraints (interface/base-type) would fail because e.g.
IRequest<TestRequest, string> doesn't match IRequest<TestRequest, __Canon>.
Add CanCastToConstraintWithCanon to TypeSystemConstraintsHelpers that
handles canonical types in constraint checking:
- __Canon/__UniversalCanon as the instantiation param: wildcard, accepts
any type constraint (runtime validates with concrete types).
- __Canon/__UniversalCanon as the constraint type itself: __Canon accepts
reference types, __UniversalCanon accepts anything.
- Canonical subtypes in constraint type args: uses ConvertToCanonForm to
compare canonicalized forms, with variance support for variant positions.
- Universal canon fallback for nested __UniversalCanon under Specific
canonicalization.
Split into Canon/NonCanon partial files following the existing pattern
for IsSpecialTypeMeetingConstraint. Add NormalizeInstantiation call in
HandleCallAction's MakeGenericTypeSite.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@MichalStrehovsky
Move canon awareness from constraint helpers into CastingHelper
bb84090
Move IsCanonicalTypeArgMatch and IsCanonEquivalent from
TypeSystemConstraintsHelpers.Canon.cs into CastingHelper.Canon.cs so
that CanCastTo naturally handles canonical types. This eliminates the
duplicated interface-walking, base-chain-walking, and variance logic
that was in CanCastToConstraintWithCanon.
Key changes to CastingHelper:
- IsCanonicalCastTarget in CanCastToInternal: __Canon accepts any
reference type as a cast source, __UniversalCanon accepts any type.
This makes array covariance (string[] -> __Canon[]) work naturally.
- IsCanonicalTypeArgMatch in CanCastByVarianceToInterfaceOrDelegate:
handles invariant positions where type args differ by canonicalization.
- IsCanonEquivalent in CanCastToNonVariantInterface and CanCastToClass:
handles non-variant interfaces and base types with canon type args.
CanCastToConstraintWithCanon is simplified to only handle wildcard cases
where the param or constraint IS __Canon/__UniversalCanon directly.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@MichalStrehovsky
Handle parameterized types in canonical type arg matching
3fe978a
IsCanonicalTypeArgMatch did not handle parameterized types like arrays:
string[] vs __Canon[] failed because IsCanonEquivalent checks
Instantiation which is empty for arrays. Add ParameterizedType
structural matching that recursively compares element types.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@MichalStrehovsky
Add regression test for MakeGenericType with constrained canonicals
6f5cf18
Exercises MakeGenericType where the canonical instantiation
(Gen<Atom, __Canon, object>) must pass constraint checking with
__Canon satisfying interface and new() constraints.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Pull request overview
This PR fixes NativeAOT reflection/dataflow constraint validation when generic instantiations are analyzed in canonical form (__Canon / __UniversalCanon), ensuring MakeGenericType sites aren’t incorrectly treated as invalid and therefore skipped for rooting/compilation.
Changes:
  • Normalize instantiated reflected generic types before constraint checking in MakeGenericType dataflow handling.
  • Extend casting and constraint-validation helpers to correctly treat canonical definition types as wildcards/compatible where appropriate (with canon vs non-canon partial implementations).
  • Add unit and smoke tests covering canonical-type constraint scenarios and constrained MakeGenericType dataflow.
Reviewed changes
Copilot reviewed 13 out of 13 changed files in this pull request and generated 4 comments.
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FileDescription
src/tests/nativeaot/SmokeTests/TrimmingBehaviors/Dataflow.csAdds a new smoke test exercising constrained MakeGenericType rooting during dataflow analysis.
src/coreclr/tools/aot/ILCompiler.TypeSystem/ILCompiler.TypeSystem.csprojIncludes new Canon-specific helper implementations in the TypeSystem build.
src/coreclr/tools/aot/ILCompiler.TypeSystem.Tests/CoreTestAssembly/GenericConstraints.csAdds new generic constraint shapes for canonical constraint tests.
src/coreclr/tools/aot/ILCompiler.TypeSystem.Tests/ConstraintsValidationTest.csAdds a comprehensive canonical-constraint validation test suite.
src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/Dataflow/HandleCallAction.csNormalizes instantiated generic types before constraint validation/rooting.
src/coreclr/tools/ILVerification/ILVerification.projitemsAdds non-canon stub helper files required by the verifier’s non-canon TypeSystem build.
src/coreclr/tools/Common/TypeSystem/Common/TypeSystemConstraintsHelpers.csMakes helpers partial and adds canon-aware special-constraint and type-constraint checks.
src/coreclr/tools/Common/TypeSystem/Common/TypeSystemConstraintsHelpers.NonCanon.csProvides non-canon stub implementations for new partial helpers.
src/coreclr/tools/Common/TypeSystem/Common/CastingHelper.csAdds canon-aware matching hooks into cast logic (interfaces, variance, base chain).
src/coreclr/tools/Common/TypeSystem/Common/CastingHelper.NonCanon.csProvides non-canon stubs for new canon-aware cast helpers.
src/coreclr/tools/Common/TypeSystem/Canon/TypeSystemConstraintsHelpers.Canon.csCanon-specific implementations for wildcard-like canonical constraint handling.
src/coreclr/tools/Common/TypeSystem/Canon/CastingHelper.Canon.csCanon-specific canonical matching logic for casts and type-arg comparisons.
src/coreclr/nativeaot/System.Private.TypeLoader/src/System.Private.TypeLoader.csprojEnsures TypeLoader picks up canon-aware casting helper.
Comment threadsrc/tests/nativeaot/SmokeTests/TrimmingBehaviors/Dataflow.cs
Comment threadsrc/coreclr/tools/aot/ILCompiler.TypeSystem.Tests/ConstraintsValidationTest.cs
Outdated

Comment threadsrc/coreclr/tools/Common/TypeSystem/Common/TypeSystemConstraintsHelpers.NonCanon.cs
Outdated

Comment threadsrc/coreclr/tools/Common/TypeSystem/Canon/TypeSystemConstraintsHelpers.Canon.cs
Outdated


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Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
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Pull request overview
Copilot reviewed 13 out of 13 changed files in this pull request and generated 1 comment.
Comment threadsrc/coreclr/tools/Common/TypeSystem/Common/TypeSystemConstraintsHelpers.NonCanon.cs
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@MichalStrehovsky
Revert "Handle canonical types in casting logic" (#127301)
9619cf5
Resolves#127259
Reverts #127146
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NativeAOT MakeGenericType fails to activate reflected generic type when generic parameter has self-referential interface constraint


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