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
BlockedBy
Related
Blocking
CC	alanz, bgamari
Operating system
Architecture