Module Compiler Warnings

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#1

Is there a way to just have ghc emit a warning when compiling a module after CPP?

I have resorted to just making up an undefined pragma like

#2

You can do it with template Haskell:

{-# LANGUAGE TemplateHaskell #-}
import Language.Haskell.TH

$([] <$ reportWarning "foo")

Or you could create a module with a module warning:

-- in FooWarning.hs
module FooWarning {-# WARNING "foo" #-} where

-- in MonoTraversable.hs
#else
import FooWarning
#endif
1 Like
#3

I was trying with the module warning but it was warning on the compilation of modules that imported it rather than the module itself which may be better but created a large number of warnings when anything imported was used.

#4

Yeah, I meant that you could make one empty module that is just for the warning and then import it only in your CPP blocks where you want the warning to appear.