Spurious warning about incomplete pattern with PatternSynonyms

{-# LANGUAGE ViewPatterns #-}
{-# LANGUAGE PatternSynonyms #-}

module Test where

f :: Int -> Bool
f (id -> a) = True

pattern X a <- (id -> a)

g :: Int -> Bool
g (X a) = True

When compiling with -Wincomplete-patterns, this code produces an (incorrect) warning for g, but not for f. The only difference is that g uses a pattern synonym.

K.hs:12:1: warning: [-Wincomplete-patterns]
    Pattern match(es) are non-exhaustive
    In an equation for ‘g’: Patterns not matched: _
   |
12 | g (X a) = True
   | ^^^^^^^^^^^^^^

Trac metadata

Trac field	Value
Version	8.6.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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