#7010: Type error in one function causes wrong type error report in another
function when using type families
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Reporter: Lemming | Owner:
Type: bug | Status: new
Priority: normal | Component: Compiler
Version: 7.4.1 | Keywords:
Os: Unknown/Multiple | Architecture:
Unknown/Multiple
Failure: Incorrect warning at compile-time | Testcase:
Blockedby: | Blocking:
Related: |
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This ticket is very similar to #5978, but this time it is about type
families. If I load the attached module I get the two error messages:
{{{
TypeCheck7_4_1_TF_IncorrectMsg.hs:27:21:
Couldn't match type `Float' with `Serial Float'
Expected type: (ValueTuple Vector, ValueTuple Vector)
Actual type: (Serial Float, Serial Float)
In the first argument of `processIO', namely `stereoFromMono'
In the expression: processIO stereoFromMono
TypeCheck7_4_1_TF_IncorrectMsg.hs:42:27:
Couldn't match type `IO' with `Serial'
Expected type: (Float, ValueTuple Vector)
Actual type: (Float, ValueTuple Float)
In the first argument of `withArgs', namely `plug'
In the expression: withArgs plug
}}}
If I uncomment 'filterFormant', that is, only the second one of the two
criticized parts, then the module is accepted.
These two error messages are very confusing because in the original module
'phoneme' was a complex definition and it was not immediately clear that
it is actually correct. Trying hard to fix it does not succeed because it
is not broken.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7010>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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