#2204: Improve 'patterns not matched' warnings
-------------------------+--------------------------------------------------
Reporter: Deewiant | Owner:
Type: proposal | Status: new
Priority: normal | Component: Compiler
Version: 6.8.2 | Severity: trivial
Keywords: | Testcase:
Architecture: Multiple | Os: Multiple
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Compiling the following with `-fwarn-incomplete-patterns`:
{{{
module Asdf where
f :: String -> Int
f "0" = 0
g :: Int -> Int
g 0 = 0
}}}
Yields:
{{{
asdf.hs:4:0:
Warning: Pattern match(es) are non-exhaustive
In the definition of `f':
Patterns not matched:
[]
(GHC.Base.C# #x) : _ with #x `notElem` ['0']
(GHC.Base.C# '0') : (_ : _)
asdf.hs:7:0:
Warning: Pattern match(es) are non-exhaustive
In the definition of `g':
Patterns not matched: GHC.Base.I# #x with #x `notElem`
[0#]
}}}
Losing the 'GHC.Base' stuff along with the various octothorpes would make
the error messages a lot nicer. Ideally it'd be something like `Patterns
not matched: x where x `notElem` [0]` for the second case, for instance.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/2204>
GHC <http://www.haskell.org/ghc/>
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