bad/wrong warning by ghc?

Main.hs

{-# LANGUAGE GADTs #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE DataKinds #-}
{-# LANGUAGE TypeOperators #-}
{-# OPTIONS_GHC -Wall #-}

module Main where

data HList :: [*] -> * where
  HNil :: HList '[]
  (:+:) :: x -> HList xs -> HList (x ': xs)

main :: IO ()
main = do
  let x :: HList '[Bool]
      x = True :+: HNil
  case x of
    (b :+: HNil) -> print b -- Pattern match(es) are non-exhaustive ...  Patterns not matched: _ :+: (_ :+: _)