#3163: GADTs should not allow polymorphism in return type
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Reporter: Scott Turner | Owner:
Type: bug | Status: new
Priority: normal | Milestone:
Component: Compiler (Type checker) | Version: 6.10.1
Severity: normal | Resolution:
Keywords: | Difficulty: Unknown
Testcase: | Os: Linux
Architecture: x86 |
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Changes (by simonpj):
* difficulty: => Unknown
* summary: quantified types fail to match in GADT case => GADTs should
not allow polymorphism in return type
Comment:
GADTs shouldn't allow for-all types in the return type, even with
`-XImpredicativeTypes`, I'm afraid. It's hard enough doing the equality
reasoning over monotypes, and I have no idea what additional complications
are introduced by polytypes.
So I'll re-title this ticket!
Simon
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Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/3163#comment:1>
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