#3700: Being instance of Monoid is not checked
------------------------+---------------------------------------------------
Reporter: boris | Owner:
Type: bug | Status: new
Priority: normal | Component: Compiler (Type checker)
Version: 6.10.3 | Keywords: Monoid, Writer
Os: Windows | Testcase:
Architecture: x86 | Failure: Other
------------------------+---------------------------------------------------
It is possible pass not only instances of Monoid to tell function and load
the file with GHCi. GHCi shows type f :: (MonadWriter ((a -> b) -> [a] ->
[b]) m) => t -> m ()
{{{
f _ = tell map
}}}
However, if code is
{{{
f = tell map
}}}
GHCi shows type error(no instance) as expected.
It seems very strange that type correctness depends on number of
parameters for function that is not used anywhere.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/3700>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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