Dear GHC-ers, It seems I do not quite understand the behaviour of the inliner. Consider these two modules: module Foo.Bar where foo :: Char -> IO () foo = putChar {-# INLINE bar #-} bar :: String -> IO () bar = mapM_ foo module Main where import Foo.Bar main = bar "done" I would expect the inliner to produce at least (considering the pragma) main = mapM_ foo "done" or maybe even main=mapM_ putChar "done" However, when I compile this code, that inlining does not seem to happen: $ ghc -ddump-inlinings -fforce-recomp Main.hs [1 of 2] Compiling Foo.Bar ( Foo/Bar.hs, Foo/Bar.o ) Inlining done: Foo.Bar.foo [2 of 2] Compiling Main ( Main.hs, Main.o ) Linking Main ... Indeed, when I use -ddump-simpl, ghc reports: ==================== Tidy Core ==================== Result size of Tidy Core = {terms: 7, types: 5, coercions: 0} Main.main :: GHC.Types.IO () [GblId, Str=DmdType] Main.main = Foo.Bar.bar (GHC.CString.unpackCString# "done"#) :Main.main :: GHC.Types.IO () [GblId, Str=DmdType] :Main.main = GHC.TopHandler.runMainIO @ () Main.main Can anyone explain why Foo.Bar.bar isn't inlined in Main.main? Regards, Philip