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Remove always-on ImplicitYield language feature flag - #20230
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Remove the dead 'SupportsFeature LanguageFeature.ImplicitYield' guards, whose condition is always true for langversion >= 8.0, across the four Checking/Expressions files. Each guard is collapsed to its enabled branch and the dead branch/binding deleted. Behaviour is unchanged; the flag definition in LanguageFeatures.fs is intentionally left for a later sprint. The now-unused 'cenv' parameter of YieldFree is renamed to '_cenv' (not removed): FSharp.Profiles.props enables --warnon:1182 with WarningsAsErrors, so an unused named binding is a hard build error, and removing the parameter would cascade through IsSimpleSemicolonSequenceElement, TryGetSimpleSemicolonSequenceOfComprehension and the SimpleSemicolonSequence active pattern (all out of scope). The '_' prefix preserves the exact signature and all positional call sites. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
The ImplicitYield feature shipped in F# 4.7 and is permanently enabled (minimum accepted --langversion is 8.0), making the flag dead configuration. Remove the LanguageFeature.ImplicitYield union case, its features-map entry, the GetFeatureString arm, the featureImplicitYield FSComp.txt string, and regenerate the xlf localisation files. The always-on SynExpr.SequentialOrImplicitYield AST machinery is untouched. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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T-Gro
enabled auto-merge (squash)
August 10, 2026 11:24
This was referenced Aug 10, 2026
abonie
approved these changes
Aug 11, 2026
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Fixes#20143
LanguageFeature.ImplicitYieldhas shipped since F# 4.7 and is enabled for every selectable language version (the minimum accepted--langversionis 8.0), so its flag could never be turned off. The flag and itsSupportsFeature/checkLanguageFeatureAndRecoverguards are removed, collapsing each guarded site to its always-enabled behaviour.--disableLanguageFeature:ImplicitYieldis no longer a recognised feature name.The always-on
SynExpr.SequentialOrImplicitYieldAST machinery is untouched.Part of #20139