Error messages have the wrong qualified names

This module:

module Foo where

import Data.ByteString.Lazy (ByteString)
import qualified Data.ByteString.Lazy as BS
import qualified Data.ByteString.Lazy.Char8 as BSC

check :: ByteString -> Bool
check bs = BS.empty bs

produces this type error:

$ ghci -v0 q.hs

q.hs:9:11:
    Couldn't match expected type `ByteString -> Bool'
           against inferred type `ByteString'
    In the expression: BSC.empty bs
    In the definition of `check': check bs = BSC.empty bs

i.e. it claims that the expression is BSC.empty bs, whereas the program text says BS.empty bs.

Similarly, in this module:

module Foo where

import Data.ByteString.Lazy (ByteString)
import qualified Data.ByteString.Lazy as BS
import Data.ByteString.Lazy.Char8

check :: ByteString -> Bool
check bs = BS.empty bs

the qualifier has disappeared completely in the error message:

$ ghci -v0 q.hs

q.hs:9:11:
    Couldn't match expected type `ByteString -> Bool'
           against inferred type `ByteString'
    In the expression: empty bs
    In the definition of `check': check bs = empty bs
Prelude> 

Trac metadata

Trac field	Value
Version	6.11
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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