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  • Glasgow Haskell CompilerGlasgow Haskell Compiler
  • GHCGHC
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  • #15884
Closed
Open
Issue created Nov 09, 2018 by Shayan-Najd@trac-Shayan-Najd

Completeness of View Patterns With a Complete Set of Output Patterns

For example, the code

{-# OPTIONS_GHC -Wall #-}
{-# LANGUAGE ViewPatterns #-}
f :: Maybe a -> Bool
f (id->Nothing)  = False
f (id->(Just _)) = True

mistakenly returns the warning

warning: [-Wincomplete-patterns]
    Pattern match(es) are non-exhaustive
    In an equation for ‘f’: Patterns not matched: _
  |
4 | f (id->Nothing)  = False
  | ^^^^^^^^^^^^^^^^^^^^^^^^...
Trac metadata
Trac field Value
Version 8.6.2
Type Bug
TypeOfFailure OtherFailure
Priority normal
Resolution Unresolved
Component Compiler
Test case
Differential revisions
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Blocking
CC alanz, bgamari
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