GHC thinks pattern match is exhaustive
{-# OPTIONS_GHC -Werror #-}
module Lib where
data Value = Finite Integer | Infinity
deriving (Eq)
instance Num Value where
(+) = undefined
(*) = undefined
abs = undefined
signum = undefined
negate = undefined
fromInteger = Finite
isSpecial :: Value -> Bool
isSpecial Infinity = True
isSpecial 0 = True
isSpecial 1 = True
isSpecial _ = False
> ghc Lib.hs
[1 of 1] Compiling Lib ( Lib.hs, Lib.o )
Lib.hs:19:1: error: [-Woverlapping-patterns, -Werror=overlapping-patterns]
Pattern match is redundant
In an equation for ‘isSpecial’: isSpecial 1 = ...
|
19 | isSpecial 1 = True
| ^^^^^^^^^^^^^^^^^^^^^^^^^
Lib.hs:20:1: error: [-Woverlapping-patterns, -Werror=overlapping-patterns]
Pattern match is redundant
In an equation for ‘isSpecial’: isSpecial _ = ...
|
20 | isSpecial _ = False
| ^^^^^^^^^^^^^^^^^^^^^^^^^^
Trac metadata
Trac field |
Value |
Version |
8.6.3 |
Type |
Bug |
TypeOfFailure |
OtherFailure |
Priority |
normal |
Resolution |
Unresolved |
Component |
Compiler |
Test case |
|
Differential revisions |
|
BlockedBy |
|
Related |
|
Blocking |
|
CC |
|
Operating system |
|
Architecture |
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