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explicitly importing deprecated symbols should elicit the deprecation warning

    • Open Issue created by duncan @trac-duncan

    If we explicitly import but do not use a deprecated function then ghc does not give the deprecation warning.

    module Foo where
{-# DEPRECATED foo "don't use foo please, use ..." #-}
foo = ...
    module Bar where
import Foo (foo)

    This is a bit annoying since it means client packages do not get any notification that some function is going to disappear but they would break if it does disappear. Or to look at it another way, it prevents me removing old deprecated functions because I don't want to break client programs but I have no way of communicating that to the author of a program that is importing but is no longer using the deprecated function.

    My real world example is the Cabal lib and lhs2tex's Setup.hs file. It is importing Distribution.Simple.LocalBuildInfo.mkDataDir (which is deprecated in the current released Cabal version) but the Setup.hs is not actually using it, so the author got no indication that it should not be imported anymore. In the development version of Cabal I'd already removed this deprecated function since I assumed we'd given everyone plenty of warning. I'll have to go add mkDataDir back.

    Trac metadata
    Trac field Value
    Version 6.8.2
    Type FeatureRequest
    TypeOfFailure OtherFailure
    Priority normal
    Resolution Unresolved
    Component Compiler
    Test case
    Differential revisions
    BlockedBy
    Related
    Blocking
    CC
    Operating system Unknown
    Architecture Unknown
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