Fix: suppress "Use guards" under RebindableSyntax (fixes #1559)#1688
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Fix: suppress "Use guards" under RebindableSyntax (fixes #1559)#1688mgajda wants to merge 1 commit into
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…ell#1559) When `RebindableSyntax` is on, `if-then-else` desugars through the user-defined `ifThenElse` and may accept non-`Bool` conditions, while pattern guards always require `Bool`. Rewriting a chain of `if` into guards therefore changes semantics and can break compilation. Thread a `rebindableSyntax` flag through `patternHint` / `hints` and skip the `"Use guards"` branch when the extension is in scope.
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Summary
Fixes #1559. With
RebindableSyntax,if-then-elsedesugars via theuser's
ifThenElse, which may accept non-Boolconditions. Patternguards, however, always require
Bool, so rewritingif a then x else if b then y else zinto the guards form changes semantics and can breakcompilation — as reproduced in the original issue.
The fix threads a
rebindableSyntaxflag throughpatternHintand skipsthe
"Use guards"branch when the extension is enabled. The otherPatternhints (Redundant guard,Redundant where,Use otherwise)are unaffected.