#1722: Code using type synonym families requires workarounds to compile
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Reporter: [EMAIL PROTECTED] | Owner: chak
Type: bug | Status: closed
Priority: normal | Milestone: 6.10 branch
Component: Compiler (Type checker) | Version: 6.8
Severity: normal | Resolution: fixed
Keywords: | Difficulty: Unknown
Testcase: indexed-types/should_compile/GADT12 | Architecture: Unknown
Os: Unknown |
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Changes (by chak):
* testcase: => indexed-types/should_compile/GADT12
* status: new => closed
* resolution: => fixed
Comment:
As expected, the replacement of GADT refinement with equality constraints
fixed this bug. More precisely, the test cases `Bug1`, `Bug2A`, and
`Bug2B` are working now. The module Bug3 is still rejected:
{{{
Code:
module Bug3 where
import Defs
bug :: Expr Typed a -> ()
bug (Var2 "x" (TypeList TypeBool :: Type [Bool])) = ()
bug e = ()
Compilation:
[1 of 2] Compiling Defs ( Defs.hs, Defs.o )
[2 of 2] Compiling Bug3 ( Bug3.hs, Bug3.o )
Bug3.hs:13:15:
Couldn't match expected type `a2' against inferred type `[Bool]'
`a2' is a rigid type variable bound by
the constructor `Var2' at Bug3.hs:13:5
Expected type: TU Typed (Type a2)
Inferred type: Type [Bool]
In the pattern: TypeList TypeBool :: Type [Bool]
In the pattern: Var2 "x" (TypeList TypeBool :: Type [Bool])
}}}
However, I believe this program is actually incorrect; i.e., GHC
rightfully rejects it.
Interestingly, the test cases that I added to the regression test suite
does trigger a corelint failure. This is however a different bug; hence,
I am closing this one.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/1722#comment:4>
GHC <http://www.haskell.org/ghc/>
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