#5691: Crash: strange interaction of ScopedTypeVariables extension with type
class
name resolution
------------------------------------------+---------------------------------
Reporter: dominiquedevriese | Owner:
Type: bug | Status: closed
Priority: normal | Milestone:
Component: Compiler (Type checker) | Version: 7.0.4
Resolution: fixed | Keywords:
ScopedTypeVariables, type classes
Os: Unknown/Multiple | Architecture: Unknown/Multiple
Failure: Compile-time crash | Difficulty: Unknown
Testcase: typecheck/should_fail/T5691 | Blockedby:
Blocking: | Related:
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Changes (by simonpj):
* status: new => closed
* difficulty: => Unknown
* resolution: => fixed
* testcase: => typecheck/should_fail/T5691
Comment:
Interesting! Indeed with 7.0.3 I get
{{{
simonpj@cam-04-unx:~/tmp$ ghc-7.0.3 -c T5691.hs -dcore-lint
*** Core Lint errors : in result of Desugar ***
<no location info>:
In the coercion `co_alI'
co_alI is out of scope
*** Offending Program ***
...snip...
}}}
But with HEAD I get
{{{
T5691.hs:15:24:
Couldn't match type `p' with `PrintRuleInterp'
Expected type: PrintRuleInterp a
Actual type: p a
In the first argument of `printRule_', namely `f'
In the second argument of `($)', namely `printRule_ f'
In the expression: MkPRI $ printRule_ f
T5691.hs:24:10:
No instance for (Monad RecDecParser)
arising from the superclasses of an instance declaration
Possible fix: add an instance declaration for (Monad RecDecParser)
In the instance declaration for `MonadPlus RecDecParser'
}}}
both of which are correct. Rather than investigate further, I'll mark
this as fixed, but I'll add it to the test suite.
Thanks
simon
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5691#comment:2>
GHC <http://www.haskell.org/ghc/>
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