#2905: require -XGADTs in order to pattern-match GADTs
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Reporter: guest | Owner:
Type: proposal | Status: new
Priority: normal | Milestone:
Component: Compiler (Type checker) | Version: 6.10.1
Severity: normal | Resolution:
Keywords: | Testcase:
Os: Unknown/Multiple | Architecture: Unknown/Multiple
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Comment (by int-e):
I also support requiring {{{-XGADTs}}} for pattern matching against GADT
constructors - and I'd include the case where the GADT is really a plain
data type or existential, because that makes the behaviour much easier to
explain: "You used GADT syntax to define it, you need -XGADTs to pattern
match against it."
Merely mentioning GADTs in type signatures should work without the
extension.
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Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/2905#comment:2>
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