Handle canonical types in constraints checks - #129278

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MichalStrehovsky merged 4 commits into
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MichalStrehovsky:fix126604
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Handle canonical types in constraints checks#129278
MichalStrehovsky merged 4 commits into
dotnet:mainfrom
MichalStrehovsky:fix126604

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Fixes#126604

First commit is a revert of the revert.

The second commit is an update to the casting logic so that we can have both casting logic that treats __Canon as a class __Canon : object and nothing else (this is compatible with how casting in CoreCLR VM works), but also another casting logic that treats __Canon as "some reference type, could be something that does cast". Then update constraints check to use this flavor of the casting logic.

CopilotAI review requested due to automatic review settings June 11, 2026 05:38
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Pull request overview

This PR updates the NativeAOT/CoreCLR shared TypeSystem constraint-checking and casting helpers to correctly account for canonical definition types (__Canon, __UniversalCanon) when validating generic constraints, and wires that behavior into MakeGenericType dataflow so reflected generic instantiations can be preserved correctly under AOT/trimming.

Changes:

  • Introduces canonical-aware casting (CanCastToWithCanon) via a handler-based casting helper split (canon vs non-canon builds).
  • Updates TypeSystemConstraintsHelpers constraint validation to use canonical-aware casting and adds canon-specific handling for special/type constraints.
  • Adds coverage: new canonical constraint validation unit tests, and a NativeAOT trimming smoke test; also normalizes instantiations before constraints checking in MakeGenericType dataflow.

Reviewed changes

Copilot reviewed 13 out of 13 changed files in this pull request and generated 3 comments.

Show a summary per file
FileDescription
src/tests/nativeaot/SmokeTests/TrimmingBehaviors/Dataflow.csAdds a new constrained MakeGenericType + Activator.CreateInstance smoke test.
src/coreclr/tools/ILVerification/ILVerification.projitemsAdds NonCanon helper source inclusions for ILVerification build.
src/coreclr/tools/Common/TypeSystem/Common/TypeSystemConstraintsHelpers.NonCanon.csProvides non-canon stubs for new partial constraint-helper hooks.
src/coreclr/tools/Common/TypeSystem/Common/TypeSystemConstraintsHelpers.csSwitches constraint validation to canonical-aware casting and adds canon-specific fast paths.
src/coreclr/tools/Common/TypeSystem/Common/CastingHelper.NonCanon.csIntended NonCanon implementation of the canonical casting handler.
src/coreclr/tools/Common/TypeSystem/Common/CastingHelper.csRefactors casting logic to support handler-based canon/non-canon behavior; adds CanCastToWithCanon.
src/coreclr/tools/Common/TypeSystem/Canon/TypeSystemConstraintsHelpers.Canon.csImplements canonical-specific constraint logic for __Canon/__UniversalCanon.
src/coreclr/tools/Common/TypeSystem/Canon/CastingHelper.Canon.csImplements canonical matching semantics for casting and generic argument matching.
src/coreclr/tools/aot/ILCompiler.TypeSystem/ILCompiler.TypeSystem.csprojIncludes new canon helper files in the ILCompiler.TypeSystem build.
src/coreclr/tools/aot/ILCompiler.TypeSystem.Tests/CoreTestAssembly/GenericConstraints.csAdds new types used to test invariant interface constraints with canonical args.
src/coreclr/tools/aot/ILCompiler.TypeSystem.Tests/ConstraintsValidationTest.csAdds a new test suite validating canonical type behavior in constraint checking.
src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/Dataflow/HandleCallAction.csNormalizes instantiated types before checking constraints in MakeGenericType dependency computation.
src/coreclr/nativeaot/System.Private.TypeLoader/src/System.Private.TypeLoader.csprojIncludes the canon casting handler to satisfy CanCastToWithCanon usage.

Comment threadsrc/tests/nativeaot/SmokeTests/TrimmingBehaviors/Dataflow.cs
Comment threadsrc/coreclr/tools/Common/TypeSystem/Common/CastingHelper.NonCanon.cs
Comment threadsrc/coreclr/tools/Common/TypeSystem/Common/CastingHelper.cs
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/azp run runtime-nativeaot-outerloop

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Pull request overview

Copilot reviewed 13 out of 13 changed files in this pull request and generated 3 comments.

Comment threadsrc/coreclr/tools/Common/TypeSystem/Common/TypeSystemConstraintsHelpers.NonCanon.cs
Comment threadsrc/coreclr/tools/Common/TypeSystem/Common/CastingHelper.cs
Comment threadsrc/coreclr/tools/aot/ILCompiler.TypeSystem.Tests/ConstraintsValidationTest.cs
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/ba-g windows arm64 timeouts are known

@MichalStrehovsky
MichalStrehovsky merged commit ee2a8a9 into dotnet:mainJun 18, 2026
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MichalStrehovsky deleted the fix126604 branch June 18, 2026 21:53
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@dotnet-milestone-botdotnet-milestone-botBot added this to the 11.0-preview6 milestone Jun 19, 2026
eiriktsarpalis pushed a commit that referenced this pull request Jul 15, 2026
@MichalStrehovsky@eiriktsarpalis
Handle canonical types in constraints checks (#129278)
5acf980
Fixes#126604
First commit is a revert of the revert.
The second commit is an update to the casting logic so that we can have
both casting logic that treats `__Canon` as a `class __Canon : object`
and nothing else (this is compatible with how casting in CoreCLR VM
works), but also another casting logic that treats `__Canon` as "some
reference type, could be something that does cast". Then update
constraints check to use this flavor of the casting logic.
@github-actionsgithub-actionsBot locked and limited conversation to collaborators Jul 20, 2026
Sign up for freeto subscribe to this conversation on GitHub. Already have an account? Sign in.

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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 constraints checks - #129278
Merged
MichalStrehovsky merged 4 commits into
dotnet:mainfrom 
MichalStrehovsky:fix126604
Jun 18, 2026
Merged
Handle canonical types in constraints checks#129278
MichalStrehovsky merged 4 commits into
dotnet:mainfrom 
MichalStrehovsky:fix126604
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Fixes#126604
First commit is a revert of the revert.
The second commit is an update to the casting logic so that we can have both casting logic that treats __Canon as a class __Canon : object and nothing else (this is compatible with how casting in CoreCLR VM works), but also another casting logic that treats __Canon as "some reference type, could be something that does cast". Then update constraints check to use this flavor of the casting logic.
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Pull request overview
This PR updates the NativeAOT/CoreCLR shared TypeSystem constraint-checking and casting helpers to correctly account for canonical definition types (__Canon, __UniversalCanon) when validating generic constraints, and wires that behavior into MakeGenericType dataflow so reflected generic instantiations can be preserved correctly under AOT/trimming.
Changes:
  • Introduces canonical-aware casting (CanCastToWithCanon) via a handler-based casting helper split (canon vs non-canon builds).
  • Updates TypeSystemConstraintsHelpers constraint validation to use canonical-aware casting and adds canon-specific handling for special/type constraints.
  • Adds coverage: new canonical constraint validation unit tests, and a NativeAOT trimming smoke test; also normalizes instantiations before constraints checking in MakeGenericType dataflow.
Reviewed changes
Copilot reviewed 13 out of 13 changed files in this pull request and generated 3 comments.
Show a summary per file
FileDescription
src/tests/nativeaot/SmokeTests/TrimmingBehaviors/Dataflow.csAdds a new constrained MakeGenericType + Activator.CreateInstance smoke test.
src/coreclr/tools/ILVerification/ILVerification.projitemsAdds NonCanon helper source inclusions for ILVerification build.
src/coreclr/tools/Common/TypeSystem/Common/TypeSystemConstraintsHelpers.NonCanon.csProvides non-canon stubs for new partial constraint-helper hooks.
src/coreclr/tools/Common/TypeSystem/Common/TypeSystemConstraintsHelpers.csSwitches constraint validation to canonical-aware casting and adds canon-specific fast paths.
src/coreclr/tools/Common/TypeSystem/Common/CastingHelper.NonCanon.csIntended NonCanon implementation of the canonical casting handler.
src/coreclr/tools/Common/TypeSystem/Common/CastingHelper.csRefactors casting logic to support handler-based canon/non-canon behavior; adds CanCastToWithCanon.
src/coreclr/tools/Common/TypeSystem/Canon/TypeSystemConstraintsHelpers.Canon.csImplements canonical-specific constraint logic for __Canon/__UniversalCanon.
src/coreclr/tools/Common/TypeSystem/Canon/CastingHelper.Canon.csImplements canonical matching semantics for casting and generic argument matching.
src/coreclr/tools/aot/ILCompiler.TypeSystem/ILCompiler.TypeSystem.csprojIncludes new canon helper files in the ILCompiler.TypeSystem build.
src/coreclr/tools/aot/ILCompiler.TypeSystem.Tests/CoreTestAssembly/GenericConstraints.csAdds new types used to test invariant interface constraints with canonical args.
src/coreclr/tools/aot/ILCompiler.TypeSystem.Tests/ConstraintsValidationTest.csAdds a new test suite validating canonical type behavior in constraint checking.
src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/Dataflow/HandleCallAction.csNormalizes instantiated types before checking constraints in MakeGenericType dependency computation.
src/coreclr/nativeaot/System.Private.TypeLoader/src/System.Private.TypeLoader.csprojIncludes the canon casting handler to satisfy CanCastToWithCanon usage.
Comment threadsrc/tests/nativeaot/SmokeTests/TrimmingBehaviors/Dataflow.cs
Comment threadsrc/coreclr/tools/Common/TypeSystem/Common/CastingHelper.NonCanon.cs
Comment threadsrc/coreclr/tools/Common/TypeSystem/Common/CastingHelper.cs

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/azp run runtime-nativeaot-outerloop
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Pull request overview
Copilot reviewed 13 out of 13 changed files in this pull request and generated 3 comments.
Comment threadsrc/coreclr/tools/Common/TypeSystem/Common/TypeSystemConstraintsHelpers.NonCanon.cs
Comment threadsrc/coreclr/tools/Common/TypeSystem/Common/CastingHelper.cs
Comment threadsrc/coreclr/tools/aot/ILCompiler.TypeSystem.Tests/ConstraintsValidationTest.cs
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/ba-g windows arm64 timeouts are known
@MichalStrehovsky
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merged commit ee2a8a9
into
dotnet:mainJun 18, 2026

132 of 140 checks passed

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deleted the

fix126604

branch
June 18, 2026 21:53
@dotnet-maestrodotnet-maestroBot
mentioned this pull request
Jun 19, 2026
 Merged

@dotnet-milestone-botdotnet-milestone-botBot
added this to the 11.0-preview6 milestone
Jun 19, 2026
eiriktsarpalis pushed a commit
that referenced
this pull request
Jul 15, 2026
@MichalStrehovsky@eiriktsarpalis
Handle canonical types in constraints checks (#129278)
5acf980
Fixes#126604
First commit is a revert of the revert.
The second commit is an update to the casting logic so that we can have
both casting logic that treats `__Canon` as a `class __Canon : object`
and nothing else (this is compatible with how casting in CoreCLR VM
works), but also another casting logic that treats `__Canon` as "some
reference type, could be something that does cast". Then update
constraints check to use this flavor of the casting logic.
@github-actionsgithub-actionsBot
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Jul 20, 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("// 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");
}
} catch(__e) { console.warn('[Userscript:GitHub Dark Mode README Fix]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
Handle canonical types in constraints checks - #129278
Merged
MichalStrehovsky merged 4 commits into
dotnet:mainfrom 
MichalStrehovsky:fix126604
Jun 18, 2026
Merged
Handle canonical types in constraints checks#129278
MichalStrehovsky merged 4 commits into
dotnet:mainfrom 
MichalStrehovsky:fix126604
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Fixes#126604
First commit is a revert of the revert.
The second commit is an update to the casting logic so that we can have both casting logic that treats __Canon as a class __Canon : object and nothing else (this is compatible with how casting in CoreCLR VM works), but also another casting logic that treats __Canon as "some reference type, could be something that does cast". Then update constraints check to use this flavor of the casting logic.
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Pull request overview
This PR updates the NativeAOT/CoreCLR shared TypeSystem constraint-checking and casting helpers to correctly account for canonical definition types (__Canon, __UniversalCanon) when validating generic constraints, and wires that behavior into MakeGenericType dataflow so reflected generic instantiations can be preserved correctly under AOT/trimming.
Changes:
  • Introduces canonical-aware casting (CanCastToWithCanon) via a handler-based casting helper split (canon vs non-canon builds).
  • Updates TypeSystemConstraintsHelpers constraint validation to use canonical-aware casting and adds canon-specific handling for special/type constraints.
  • Adds coverage: new canonical constraint validation unit tests, and a NativeAOT trimming smoke test; also normalizes instantiations before constraints checking in MakeGenericType dataflow.
Reviewed changes
Copilot reviewed 13 out of 13 changed files in this pull request and generated 3 comments.
Show a summary per file
FileDescription
src/tests/nativeaot/SmokeTests/TrimmingBehaviors/Dataflow.csAdds a new constrained MakeGenericType + Activator.CreateInstance smoke test.
src/coreclr/tools/ILVerification/ILVerification.projitemsAdds NonCanon helper source inclusions for ILVerification build.
src/coreclr/tools/Common/TypeSystem/Common/TypeSystemConstraintsHelpers.NonCanon.csProvides non-canon stubs for new partial constraint-helper hooks.
src/coreclr/tools/Common/TypeSystem/Common/TypeSystemConstraintsHelpers.csSwitches constraint validation to canonical-aware casting and adds canon-specific fast paths.
src/coreclr/tools/Common/TypeSystem/Common/CastingHelper.NonCanon.csIntended NonCanon implementation of the canonical casting handler.
src/coreclr/tools/Common/TypeSystem/Common/CastingHelper.csRefactors casting logic to support handler-based canon/non-canon behavior; adds CanCastToWithCanon.
src/coreclr/tools/Common/TypeSystem/Canon/TypeSystemConstraintsHelpers.Canon.csImplements canonical-specific constraint logic for __Canon/__UniversalCanon.
src/coreclr/tools/Common/TypeSystem/Canon/CastingHelper.Canon.csImplements canonical matching semantics for casting and generic argument matching.
src/coreclr/tools/aot/ILCompiler.TypeSystem/ILCompiler.TypeSystem.csprojIncludes new canon helper files in the ILCompiler.TypeSystem build.
src/coreclr/tools/aot/ILCompiler.TypeSystem.Tests/CoreTestAssembly/GenericConstraints.csAdds new types used to test invariant interface constraints with canonical args.
src/coreclr/tools/aot/ILCompiler.TypeSystem.Tests/ConstraintsValidationTest.csAdds a new test suite validating canonical type behavior in constraint checking.
src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/Dataflow/HandleCallAction.csNormalizes instantiated types before checking constraints in MakeGenericType dependency computation.
src/coreclr/nativeaot/System.Private.TypeLoader/src/System.Private.TypeLoader.csprojIncludes the canon casting handler to satisfy CanCastToWithCanon usage.
Comment threadsrc/tests/nativeaot/SmokeTests/TrimmingBehaviors/Dataflow.cs
Comment threadsrc/coreclr/tools/Common/TypeSystem/Common/CastingHelper.NonCanon.cs
Comment threadsrc/coreclr/tools/Common/TypeSystem/Common/CastingHelper.cs

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Pull request overview
Copilot reviewed 13 out of 13 changed files in this pull request and generated 3 comments.
Comment threadsrc/coreclr/tools/Common/TypeSystem/Common/TypeSystemConstraintsHelpers.NonCanon.cs
Comment threadsrc/coreclr/tools/Common/TypeSystem/Common/CastingHelper.cs
Comment threadsrc/coreclr/tools/aot/ILCompiler.TypeSystem.Tests/ConstraintsValidationTest.cs
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/ba-g windows arm64 timeouts are known
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merged commit ee2a8a9
into
dotnet:mainJun 18, 2026

132 of 140 checks passed

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deleted the

fix126604

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@dotnet-maestrodotnet-maestroBot
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added this to the 11.0-preview6 milestone
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eiriktsarpalis pushed a commit
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Jul 15, 2026
@MichalStrehovsky@eiriktsarpalis
Handle canonical types in constraints checks (#129278)
5acf980
Fixes#126604
First commit is a revert of the revert.
The second commit is an update to the casting logic so that we can have
both casting logic that treats `__Canon` as a `class __Canon : object`
and nothing else (this is compatible with how casting in CoreCLR VM
works), but also another casting logic that treats `__Canon` as "some
reference type, could be something that does cast". Then update
constraints check to use this flavor of the casting logic.
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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("// 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('^' + ".*" + '

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Handle canonical types in constraints checks - #129278
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MichalStrehovsky:fix126604
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Handle canonical types in constraints checks#129278
MichalStrehovsky merged 4 commits into
dotnet:mainfrom 
MichalStrehovsky:fix126604
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Fixes#126604
First commit is a revert of the revert.
The second commit is an update to the casting logic so that we can have both casting logic that treats __Canon as a class __Canon : object and nothing else (this is compatible with how casting in CoreCLR VM works), but also another casting logic that treats __Canon as "some reference type, could be something that does cast". Then update constraints check to use this flavor of the casting logic.
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Pull request overview
This PR updates the NativeAOT/CoreCLR shared TypeSystem constraint-checking and casting helpers to correctly account for canonical definition types (__Canon, __UniversalCanon) when validating generic constraints, and wires that behavior into MakeGenericType dataflow so reflected generic instantiations can be preserved correctly under AOT/trimming.
Changes:
  • Introduces canonical-aware casting (CanCastToWithCanon) via a handler-based casting helper split (canon vs non-canon builds).
  • Updates TypeSystemConstraintsHelpers constraint validation to use canonical-aware casting and adds canon-specific handling for special/type constraints.
  • Adds coverage: new canonical constraint validation unit tests, and a NativeAOT trimming smoke test; also normalizes instantiations before constraints checking in MakeGenericType dataflow.
Reviewed changes
Copilot reviewed 13 out of 13 changed files in this pull request and generated 3 comments.
Show a summary per file
FileDescription
src/tests/nativeaot/SmokeTests/TrimmingBehaviors/Dataflow.csAdds a new constrained MakeGenericType + Activator.CreateInstance smoke test.
src/coreclr/tools/ILVerification/ILVerification.projitemsAdds NonCanon helper source inclusions for ILVerification build.
src/coreclr/tools/Common/TypeSystem/Common/TypeSystemConstraintsHelpers.NonCanon.csProvides non-canon stubs for new partial constraint-helper hooks.
src/coreclr/tools/Common/TypeSystem/Common/TypeSystemConstraintsHelpers.csSwitches constraint validation to canonical-aware casting and adds canon-specific fast paths.
src/coreclr/tools/Common/TypeSystem/Common/CastingHelper.NonCanon.csIntended NonCanon implementation of the canonical casting handler.
src/coreclr/tools/Common/TypeSystem/Common/CastingHelper.csRefactors casting logic to support handler-based canon/non-canon behavior; adds CanCastToWithCanon.
src/coreclr/tools/Common/TypeSystem/Canon/TypeSystemConstraintsHelpers.Canon.csImplements canonical-specific constraint logic for __Canon/__UniversalCanon.
src/coreclr/tools/Common/TypeSystem/Canon/CastingHelper.Canon.csImplements canonical matching semantics for casting and generic argument matching.
src/coreclr/tools/aot/ILCompiler.TypeSystem/ILCompiler.TypeSystem.csprojIncludes new canon helper files in the ILCompiler.TypeSystem build.
src/coreclr/tools/aot/ILCompiler.TypeSystem.Tests/CoreTestAssembly/GenericConstraints.csAdds new types used to test invariant interface constraints with canonical args.
src/coreclr/tools/aot/ILCompiler.TypeSystem.Tests/ConstraintsValidationTest.csAdds a new test suite validating canonical type behavior in constraint checking.
src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/Dataflow/HandleCallAction.csNormalizes instantiated types before checking constraints in MakeGenericType dependency computation.
src/coreclr/nativeaot/System.Private.TypeLoader/src/System.Private.TypeLoader.csprojIncludes the canon casting handler to satisfy CanCastToWithCanon usage.
Comment threadsrc/tests/nativeaot/SmokeTests/TrimmingBehaviors/Dataflow.cs
Comment threadsrc/coreclr/tools/Common/TypeSystem/Common/CastingHelper.NonCanon.cs
Comment threadsrc/coreclr/tools/Common/TypeSystem/Common/CastingHelper.cs

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Pull request overview
Copilot reviewed 13 out of 13 changed files in this pull request and generated 3 comments.
Comment threadsrc/coreclr/tools/Common/TypeSystem/Common/TypeSystemConstraintsHelpers.NonCanon.cs
Comment threadsrc/coreclr/tools/Common/TypeSystem/Common/CastingHelper.cs
Comment threadsrc/coreclr/tools/aot/ILCompiler.TypeSystem.Tests/ConstraintsValidationTest.cs
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/ba-g windows arm64 timeouts are known
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merged commit ee2a8a9
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fix126604

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@MichalStrehovsky@eiriktsarpalis
Handle canonical types in constraints checks (#129278)
5acf980
Fixes#126604
First commit is a revert of the revert.
The second commit is an update to the casting logic so that we can have
both casting logic that treats `__Canon` as a `class __Canon : object`
and nothing else (this is compatible with how casting in CoreCLR VM
works), but also another casting logic that treats `__Canon` as "some
reference type, could be something that does cast". Then update
constraints check to use this flavor of the casting logic.
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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("// 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" + '

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Handle canonical types in constraints checks - #129278
Merged
MichalStrehovsky merged 4 commits into
dotnet:mainfrom 
MichalStrehovsky:fix126604
Jun 18, 2026
Merged
Handle canonical types in constraints checks#129278
MichalStrehovsky merged 4 commits into
dotnet:mainfrom 
MichalStrehovsky:fix126604
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Fixes#126604
First commit is a revert of the revert.
The second commit is an update to the casting logic so that we can have both casting logic that treats __Canon as a class __Canon : object and nothing else (this is compatible with how casting in CoreCLR VM works), but also another casting logic that treats __Canon as "some reference type, could be something that does cast". Then update constraints check to use this flavor of the casting logic.
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Pull request overview
This PR updates the NativeAOT/CoreCLR shared TypeSystem constraint-checking and casting helpers to correctly account for canonical definition types (__Canon, __UniversalCanon) when validating generic constraints, and wires that behavior into MakeGenericType dataflow so reflected generic instantiations can be preserved correctly under AOT/trimming.
Changes:
  • Introduces canonical-aware casting (CanCastToWithCanon) via a handler-based casting helper split (canon vs non-canon builds).
  • Updates TypeSystemConstraintsHelpers constraint validation to use canonical-aware casting and adds canon-specific handling for special/type constraints.
  • Adds coverage: new canonical constraint validation unit tests, and a NativeAOT trimming smoke test; also normalizes instantiations before constraints checking in MakeGenericType dataflow.
Reviewed changes
Copilot reviewed 13 out of 13 changed files in this pull request and generated 3 comments.
Show a summary per file
FileDescription
src/tests/nativeaot/SmokeTests/TrimmingBehaviors/Dataflow.csAdds a new constrained MakeGenericType + Activator.CreateInstance smoke test.
src/coreclr/tools/ILVerification/ILVerification.projitemsAdds NonCanon helper source inclusions for ILVerification build.
src/coreclr/tools/Common/TypeSystem/Common/TypeSystemConstraintsHelpers.NonCanon.csProvides non-canon stubs for new partial constraint-helper hooks.
src/coreclr/tools/Common/TypeSystem/Common/TypeSystemConstraintsHelpers.csSwitches constraint validation to canonical-aware casting and adds canon-specific fast paths.
src/coreclr/tools/Common/TypeSystem/Common/CastingHelper.NonCanon.csIntended NonCanon implementation of the canonical casting handler.
src/coreclr/tools/Common/TypeSystem/Common/CastingHelper.csRefactors casting logic to support handler-based canon/non-canon behavior; adds CanCastToWithCanon.
src/coreclr/tools/Common/TypeSystem/Canon/TypeSystemConstraintsHelpers.Canon.csImplements canonical-specific constraint logic for __Canon/__UniversalCanon.
src/coreclr/tools/Common/TypeSystem/Canon/CastingHelper.Canon.csImplements canonical matching semantics for casting and generic argument matching.
src/coreclr/tools/aot/ILCompiler.TypeSystem/ILCompiler.TypeSystem.csprojIncludes new canon helper files in the ILCompiler.TypeSystem build.
src/coreclr/tools/aot/ILCompiler.TypeSystem.Tests/CoreTestAssembly/GenericConstraints.csAdds new types used to test invariant interface constraints with canonical args.
src/coreclr/tools/aot/ILCompiler.TypeSystem.Tests/ConstraintsValidationTest.csAdds a new test suite validating canonical type behavior in constraint checking.
src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/Dataflow/HandleCallAction.csNormalizes instantiated types before checking constraints in MakeGenericType dependency computation.
src/coreclr/nativeaot/System.Private.TypeLoader/src/System.Private.TypeLoader.csprojIncludes the canon casting handler to satisfy CanCastToWithCanon usage.
Comment threadsrc/tests/nativeaot/SmokeTests/TrimmingBehaviors/Dataflow.cs
Comment threadsrc/coreclr/tools/Common/TypeSystem/Common/CastingHelper.NonCanon.cs
Comment threadsrc/coreclr/tools/Common/TypeSystem/Common/CastingHelper.cs

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/azp run runtime-nativeaot-outerloop
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Pull request overview
Copilot reviewed 13 out of 13 changed files in this pull request and generated 3 comments.
Comment threadsrc/coreclr/tools/Common/TypeSystem/Common/TypeSystemConstraintsHelpers.NonCanon.cs
Comment threadsrc/coreclr/tools/Common/TypeSystem/Common/CastingHelper.cs
Comment threadsrc/coreclr/tools/aot/ILCompiler.TypeSystem.Tests/ConstraintsValidationTest.cs
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/ba-g windows arm64 timeouts are known
@MichalStrehovsky
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merged commit ee2a8a9
into
dotnet:mainJun 18, 2026

132 of 140 checks passed

@MichalStrehovsky
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deleted the

fix126604

branch
June 18, 2026 21:53
@dotnet-maestrodotnet-maestroBot
mentioned this pull request
Jun 19, 2026
 Merged

@dotnet-milestone-botdotnet-milestone-botBot
added this to the 11.0-preview6 milestone
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eiriktsarpalis pushed a commit
that referenced
this pull request
Jul 15, 2026
@MichalStrehovsky@eiriktsarpalis
Handle canonical types in constraints checks (#129278)
5acf980
Fixes#126604
First commit is a revert of the revert.
The second commit is an update to the casting logic so that we can have
both casting logic that treats `__Canon` as a `class __Canon : object`
and nothing else (this is compatible with how casting in CoreCLR VM
works), but also another casting logic that treats `__Canon` as "some
reference type, could be something that does cast". Then update
constraints check to use this flavor of the casting logic.
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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@sbomer

, '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 constraints checks - #129278
Merged
MichalStrehovsky merged 4 commits into
dotnet:mainfrom 
MichalStrehovsky:fix126604
Jun 18, 2026
Merged
Handle canonical types in constraints checks#129278
MichalStrehovsky merged 4 commits into
dotnet:mainfrom 
MichalStrehovsky:fix126604
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Fixes#126604
First commit is a revert of the revert.
The second commit is an update to the casting logic so that we can have both casting logic that treats __Canon as a class __Canon : object and nothing else (this is compatible with how casting in CoreCLR VM works), but also another casting logic that treats __Canon as "some reference type, could be something that does cast". Then update constraints check to use this flavor of the casting logic.
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Pull request overview
This PR updates the NativeAOT/CoreCLR shared TypeSystem constraint-checking and casting helpers to correctly account for canonical definition types (__Canon, __UniversalCanon) when validating generic constraints, and wires that behavior into MakeGenericType dataflow so reflected generic instantiations can be preserved correctly under AOT/trimming.
Changes:
  • Introduces canonical-aware casting (CanCastToWithCanon) via a handler-based casting helper split (canon vs non-canon builds).
  • Updates TypeSystemConstraintsHelpers constraint validation to use canonical-aware casting and adds canon-specific handling for special/type constraints.
  • Adds coverage: new canonical constraint validation unit tests, and a NativeAOT trimming smoke test; also normalizes instantiations before constraints checking in MakeGenericType dataflow.
Reviewed changes
Copilot reviewed 13 out of 13 changed files in this pull request and generated 3 comments.
Show a summary per file
FileDescription
src/tests/nativeaot/SmokeTests/TrimmingBehaviors/Dataflow.csAdds a new constrained MakeGenericType + Activator.CreateInstance smoke test.
src/coreclr/tools/ILVerification/ILVerification.projitemsAdds NonCanon helper source inclusions for ILVerification build.
src/coreclr/tools/Common/TypeSystem/Common/TypeSystemConstraintsHelpers.NonCanon.csProvides non-canon stubs for new partial constraint-helper hooks.
src/coreclr/tools/Common/TypeSystem/Common/TypeSystemConstraintsHelpers.csSwitches constraint validation to canonical-aware casting and adds canon-specific fast paths.
src/coreclr/tools/Common/TypeSystem/Common/CastingHelper.NonCanon.csIntended NonCanon implementation of the canonical casting handler.
src/coreclr/tools/Common/TypeSystem/Common/CastingHelper.csRefactors casting logic to support handler-based canon/non-canon behavior; adds CanCastToWithCanon.
src/coreclr/tools/Common/TypeSystem/Canon/TypeSystemConstraintsHelpers.Canon.csImplements canonical-specific constraint logic for __Canon/__UniversalCanon.
src/coreclr/tools/Common/TypeSystem/Canon/CastingHelper.Canon.csImplements canonical matching semantics for casting and generic argument matching.
src/coreclr/tools/aot/ILCompiler.TypeSystem/ILCompiler.TypeSystem.csprojIncludes new canon helper files in the ILCompiler.TypeSystem build.
src/coreclr/tools/aot/ILCompiler.TypeSystem.Tests/CoreTestAssembly/GenericConstraints.csAdds new types used to test invariant interface constraints with canonical args.
src/coreclr/tools/aot/ILCompiler.TypeSystem.Tests/ConstraintsValidationTest.csAdds a new test suite validating canonical type behavior in constraint checking.
src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/Dataflow/HandleCallAction.csNormalizes instantiated types before checking constraints in MakeGenericType dependency computation.
src/coreclr/nativeaot/System.Private.TypeLoader/src/System.Private.TypeLoader.csprojIncludes the canon casting handler to satisfy CanCastToWithCanon usage.
Comment threadsrc/tests/nativeaot/SmokeTests/TrimmingBehaviors/Dataflow.cs
Comment threadsrc/coreclr/tools/Common/TypeSystem/Common/CastingHelper.NonCanon.cs
Comment threadsrc/coreclr/tools/Common/TypeSystem/Common/CastingHelper.cs

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/azp run runtime-nativeaot-outerloop
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Pull request overview
Copilot reviewed 13 out of 13 changed files in this pull request and generated 3 comments.
Comment threadsrc/coreclr/tools/Common/TypeSystem/Common/TypeSystemConstraintsHelpers.NonCanon.cs
Comment threadsrc/coreclr/tools/Common/TypeSystem/Common/CastingHelper.cs
Comment threadsrc/coreclr/tools/aot/ILCompiler.TypeSystem.Tests/ConstraintsValidationTest.cs
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/ba-g windows arm64 timeouts are known
@MichalStrehovsky
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merged commit ee2a8a9
into
dotnet:mainJun 18, 2026

132 of 140 checks passed

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deleted the

fix126604

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June 18, 2026 21:53
@dotnet-maestrodotnet-maestroBot
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added this to the 11.0-preview6 milestone
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eiriktsarpalis pushed a commit
that referenced
this pull request
Jul 15, 2026
@MichalStrehovsky@eiriktsarpalis
Handle canonical types in constraints checks (#129278)
5acf980
Fixes#126604
First commit is a revert of the revert.
The second commit is an update to the casting logic so that we can have
both casting logic that treats `__Canon` as a `class __Canon : object`
and nothing else (this is compatible with how casting in CoreCLR VM
works), but also another casting logic that treats `__Canon` as "some
reference type, could be something that does cast". Then update
constraints check to use this flavor of the casting logic.
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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@sbomer

, '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('^' + ".*" + '

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Handle canonical types in constraints checks - #129278
Merged
MichalStrehovsky merged 4 commits into
dotnet:mainfrom 
MichalStrehovsky:fix126604
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Merged
Handle canonical types in constraints checks#129278
MichalStrehovsky merged 4 commits into
dotnet:mainfrom 
MichalStrehovsky:fix126604
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Fixes#126604
First commit is a revert of the revert.
The second commit is an update to the casting logic so that we can have both casting logic that treats __Canon as a class __Canon : object and nothing else (this is compatible with how casting in CoreCLR VM works), but also another casting logic that treats __Canon as "some reference type, could be something that does cast". Then update constraints check to use this flavor of the casting logic.
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Pull request overview
This PR updates the NativeAOT/CoreCLR shared TypeSystem constraint-checking and casting helpers to correctly account for canonical definition types (__Canon, __UniversalCanon) when validating generic constraints, and wires that behavior into MakeGenericType dataflow so reflected generic instantiations can be preserved correctly under AOT/trimming.
Changes:
  • Introduces canonical-aware casting (CanCastToWithCanon) via a handler-based casting helper split (canon vs non-canon builds).
  • Updates TypeSystemConstraintsHelpers constraint validation to use canonical-aware casting and adds canon-specific handling for special/type constraints.
  • Adds coverage: new canonical constraint validation unit tests, and a NativeAOT trimming smoke test; also normalizes instantiations before constraints checking in MakeGenericType dataflow.
Reviewed changes
Copilot reviewed 13 out of 13 changed files in this pull request and generated 3 comments.
Show a summary per file
FileDescription
src/tests/nativeaot/SmokeTests/TrimmingBehaviors/Dataflow.csAdds a new constrained MakeGenericType + Activator.CreateInstance smoke test.
src/coreclr/tools/ILVerification/ILVerification.projitemsAdds NonCanon helper source inclusions for ILVerification build.
src/coreclr/tools/Common/TypeSystem/Common/TypeSystemConstraintsHelpers.NonCanon.csProvides non-canon stubs for new partial constraint-helper hooks.
src/coreclr/tools/Common/TypeSystem/Common/TypeSystemConstraintsHelpers.csSwitches constraint validation to canonical-aware casting and adds canon-specific fast paths.
src/coreclr/tools/Common/TypeSystem/Common/CastingHelper.NonCanon.csIntended NonCanon implementation of the canonical casting handler.
src/coreclr/tools/Common/TypeSystem/Common/CastingHelper.csRefactors casting logic to support handler-based canon/non-canon behavior; adds CanCastToWithCanon.
src/coreclr/tools/Common/TypeSystem/Canon/TypeSystemConstraintsHelpers.Canon.csImplements canonical-specific constraint logic for __Canon/__UniversalCanon.
src/coreclr/tools/Common/TypeSystem/Canon/CastingHelper.Canon.csImplements canonical matching semantics for casting and generic argument matching.
src/coreclr/tools/aot/ILCompiler.TypeSystem/ILCompiler.TypeSystem.csprojIncludes new canon helper files in the ILCompiler.TypeSystem build.
src/coreclr/tools/aot/ILCompiler.TypeSystem.Tests/CoreTestAssembly/GenericConstraints.csAdds new types used to test invariant interface constraints with canonical args.
src/coreclr/tools/aot/ILCompiler.TypeSystem.Tests/ConstraintsValidationTest.csAdds a new test suite validating canonical type behavior in constraint checking.
src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/Dataflow/HandleCallAction.csNormalizes instantiated types before checking constraints in MakeGenericType dependency computation.
src/coreclr/nativeaot/System.Private.TypeLoader/src/System.Private.TypeLoader.csprojIncludes the canon casting handler to satisfy CanCastToWithCanon usage.
Comment threadsrc/tests/nativeaot/SmokeTests/TrimmingBehaviors/Dataflow.cs
Comment threadsrc/coreclr/tools/Common/TypeSystem/Common/CastingHelper.NonCanon.cs
Comment threadsrc/coreclr/tools/Common/TypeSystem/Common/CastingHelper.cs

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/azp run runtime-nativeaot-outerloop
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Pull request overview
Copilot reviewed 13 out of 13 changed files in this pull request and generated 3 comments.
Comment threadsrc/coreclr/tools/Common/TypeSystem/Common/TypeSystemConstraintsHelpers.NonCanon.cs
Comment threadsrc/coreclr/tools/Common/TypeSystem/Common/CastingHelper.cs
Comment threadsrc/coreclr/tools/aot/ILCompiler.TypeSystem.Tests/ConstraintsValidationTest.cs
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/ba-g windows arm64 timeouts are known
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@MichalStrehovsky@eiriktsarpalis
Handle canonical types in constraints checks (#129278)
5acf980
Fixes#126604
First commit is a revert of the revert.
The second commit is an update to the casting logic so that we can have
both casting logic that treats `__Canon` as a `class __Canon : object`
and nothing else (this is compatible with how casting in CoreCLR VM
works), but also another casting logic that treats `__Canon` as "some
reference type, could be something that does cast". Then update
constraints check to use this flavor of the casting logic.
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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("// 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); }
})();
})();

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Handle canonical types in constraints checks - #129278
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MichalStrehovsky:fix126604
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Handle canonical types in constraints checks#129278
MichalStrehovsky merged 4 commits into
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MichalStrehovsky:fix126604
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Fixes#126604
First commit is a revert of the revert.
The second commit is an update to the casting logic so that we can have both casting logic that treats __Canon as a class __Canon : object and nothing else (this is compatible with how casting in CoreCLR VM works), but also another casting logic that treats __Canon as "some reference type, could be something that does cast". Then update constraints check to use this flavor of the casting logic.
CopilotAI
review requested due to automatic review settings
June 11, 2026 05:38
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Tagging subscribers to this area: @agocke, @dotnet/ilc-contrib

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Pull request overview
This PR updates the NativeAOT/CoreCLR shared TypeSystem constraint-checking and casting helpers to correctly account for canonical definition types (__Canon, __UniversalCanon) when validating generic constraints, and wires that behavior into MakeGenericType dataflow so reflected generic instantiations can be preserved correctly under AOT/trimming.
Changes:
  • Introduces canonical-aware casting (CanCastToWithCanon) via a handler-based casting helper split (canon vs non-canon builds).
  • Updates TypeSystemConstraintsHelpers constraint validation to use canonical-aware casting and adds canon-specific handling for special/type constraints.
  • Adds coverage: new canonical constraint validation unit tests, and a NativeAOT trimming smoke test; also normalizes instantiations before constraints checking in MakeGenericType dataflow.
Reviewed changes
Copilot reviewed 13 out of 13 changed files in this pull request and generated 3 comments.
Show a summary per file
FileDescription
src/tests/nativeaot/SmokeTests/TrimmingBehaviors/Dataflow.csAdds a new constrained MakeGenericType + Activator.CreateInstance smoke test.
src/coreclr/tools/ILVerification/ILVerification.projitemsAdds NonCanon helper source inclusions for ILVerification build.
src/coreclr/tools/Common/TypeSystem/Common/TypeSystemConstraintsHelpers.NonCanon.csProvides non-canon stubs for new partial constraint-helper hooks.
src/coreclr/tools/Common/TypeSystem/Common/TypeSystemConstraintsHelpers.csSwitches constraint validation to canonical-aware casting and adds canon-specific fast paths.
src/coreclr/tools/Common/TypeSystem/Common/CastingHelper.NonCanon.csIntended NonCanon implementation of the canonical casting handler.
src/coreclr/tools/Common/TypeSystem/Common/CastingHelper.csRefactors casting logic to support handler-based canon/non-canon behavior; adds CanCastToWithCanon.
src/coreclr/tools/Common/TypeSystem/Canon/TypeSystemConstraintsHelpers.Canon.csImplements canonical-specific constraint logic for __Canon/__UniversalCanon.
src/coreclr/tools/Common/TypeSystem/Canon/CastingHelper.Canon.csImplements canonical matching semantics for casting and generic argument matching.
src/coreclr/tools/aot/ILCompiler.TypeSystem/ILCompiler.TypeSystem.csprojIncludes new canon helper files in the ILCompiler.TypeSystem build.
src/coreclr/tools/aot/ILCompiler.TypeSystem.Tests/CoreTestAssembly/GenericConstraints.csAdds new types used to test invariant interface constraints with canonical args.
src/coreclr/tools/aot/ILCompiler.TypeSystem.Tests/ConstraintsValidationTest.csAdds a new test suite validating canonical type behavior in constraint checking.
src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/Dataflow/HandleCallAction.csNormalizes instantiated types before checking constraints in MakeGenericType dependency computation.
src/coreclr/nativeaot/System.Private.TypeLoader/src/System.Private.TypeLoader.csprojIncludes the canon casting handler to satisfy CanCastToWithCanon usage.
Comment threadsrc/tests/nativeaot/SmokeTests/TrimmingBehaviors/Dataflow.cs
Comment threadsrc/coreclr/tools/Common/TypeSystem/Common/CastingHelper.NonCanon.cs
Comment threadsrc/coreclr/tools/Common/TypeSystem/Common/CastingHelper.cs

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/azp run runtime-nativeaot-outerloop
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Pull request overview
Copilot reviewed 13 out of 13 changed files in this pull request and generated 3 comments.
Comment threadsrc/coreclr/tools/Common/TypeSystem/Common/TypeSystemConstraintsHelpers.NonCanon.cs
Comment threadsrc/coreclr/tools/Common/TypeSystem/Common/CastingHelper.cs
Comment threadsrc/coreclr/tools/aot/ILCompiler.TypeSystem.Tests/ConstraintsValidationTest.cs
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/ba-g windows arm64 timeouts are known
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merged commit ee2a8a9
into
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132 of 140 checks passed

@MichalStrehovsky
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fix126604

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@dotnet-maestrodotnet-maestroBot
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 Merged

@dotnet-milestone-botdotnet-milestone-botBot
added this to the 11.0-preview6 milestone
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eiriktsarpalis pushed a commit
that referenced
this pull request
Jul 15, 2026
@MichalStrehovsky@eiriktsarpalis
Handle canonical types in constraints checks (#129278)
5acf980
Fixes#126604
First commit is a revert of the revert.
The second commit is an update to the casting logic so that we can have
both casting logic that treats `__Canon` as a `class __Canon : object`
and nothing else (this is compatible with how casting in CoreCLR VM
works), but also another casting logic that treats `__Canon` as "some
reference type, could be something that does cast". Then update
constraints check to use this flavor of the casting logic.
@github-actionsgithub-actionsBot
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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@sbomer