#1783: FD leads to non-termination of type checker
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Reporter: chak | Owner:
Type: bug | Status: closed
Priority: normal | Milestone:
Component: Compiler (Type checker) | Version: 6.9
Severity: normal | Resolution: fixed
Keywords: | Difficulty: Unknown
Os: Unknown | Testcase: FD2
Architecture: Unknown |
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Changes (by simonpj):
* status: new => closed
* resolution: => fixed
Comment:
When we have fundeps working using equality constraints in their full
glory, this program might typecheck. But meanwhile I have restored the
old behaviour: it's rejected but the typechecker doesn't loop:
{{{
FD2.hs:26:35:
Couldn't match expected type `e' against inferred type `e1'
`e' is a rigid type variable bound by
the type signature for `foldr1' at FD2.hs:21:19
`e1' is a rigid type variable bound by
the type signature for `mf' at FD2.hs:24:24
In the first argument of `f', namely `x'
In the first argument of `Just', namely `(f x y)'
In the expression: Just (f x y)
}}}
Thanks for reporting it. It's an interesting example, and helped avoid us
shipping a n embarassing bug in 6.8.
Simon
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/1783#comment:2>
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