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Add --disableLanguageFeature CLI switch and MSBuild property to selectively disable language features #19167

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Merged
T-Gro merged 37 commits into from
Jan 20, 2026
+394 −32

Refactor to use immutable LanguageVersion with reflection-based featu…

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Merged

Add --disableLanguageFeature CLI switch and MSBuild property to selectively disable language features #19167

Refactor to use immutable LanguageVersion with reflection-based featu…
cc29923
Select commit
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Azure Pipelines / fsharp-ci (Build WindowsCompressedMetadata coreclr_release) failed Dec 16, 2025 in 10m 0s

Build WindowsCompressedMetadata coreclr_release failed

3 errors / 1 warnings

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Check failure on line 9 in Build log

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@azure-pipelines azure-pipelines / fsharp-ci (Build WindowsCompressedMetadata coreclr_release)

Build log #L9 

Publishing build artifacts failed with an error: Not found PathtoPublish: D:\a\_work\1\s\artifacts\TestResults\Release

Check failure on line 443 in src\Compiler\Facilities\LanguageFeatures.fs

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@azure-pipelines azure-pipelines / fsharp-ci (Build WindowsCompressedMetadata coreclr_release)

src\Compiler\Facilities\LanguageFeatures.fs#L443 

src\Compiler\Facilities\LanguageFeatures.fs(443,36): error FS3264: (NETCORE_ENGINEERING_TELEMETRY=Build) Nullness warning: Downcasting from 'objnull' into 'LanguageFeature' can introduce unexpected null values. Cast to 'LanguageFeature|null' instead or handle the null before downcasting.

Check failure on line 443 in src\Compiler\Facilities\LanguageFeatures.fs

See this annotation in the file changed.

@azure-pipelines azure-pipelines / fsharp-ci (Build WindowsCompressedMetadata coreclr_release)

src\Compiler\Facilities\LanguageFeatures.fs#L443 

src\Compiler\Facilities\LanguageFeatures.fs(443,36): error FS3264: (NETCORE_ENGINEERING_TELEMETRY=Build) Nullness warning: Downcasting from 'objnull' into 'LanguageFeature' can introduce unexpected null values. Cast to 'LanguageFeature|null' instead or handle the null before downcasting.
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