Warning about module abbreviation clashes

Please add the option -fwarn-module-rename-collision that makes GHC to do the following: If GHC encounters an import situation like

module Main where

import qualified Data.A as A
import qualified Control.A as A

then GHC should emit a warning like

Main.hs:3:0:
Main.hs:4:0:
    Warning: Both Data.A and Control.A are renamed to A.
             An identifier like A.ident can only be resolved,
             if it is either in Data.A or Control.A.
             Better rename both modules to different names.

Reason for this warning is, that if 'ident' is from Data.A as of writing Main, and later another variable named 'ident' is added to Control.A, then A.ident can no longer be resolved in Main. That is, by accidental module rename collisions even qualified imports carry the risk of future name collisions.

Related to #4977 (closed)

Trac metadata

Trac field	Value
Version	7.0.1
Type	FeatureRequest
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC	ghc@henning-thielemann.de
Operating system
Architecture