#14794: -Weverything should not enable -Wmissing-exported-signatures -------------------------------------+------------------------------------- Reporter: MaxGabriel | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Incorrect Unknown/Multiple | error/warning at compile-time Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- The `-Weverything` compiler flag enables every compiler warning. That includes `-Wmissing-exported-signatures`, which disables `-Wmissing- signatures` (With `-Wmissing-signatures`, every top-level binding without a signature generates a warning, with `-Wmissing-exported-signatures`, only exported bindings generate a warning). While technically "every warning" includes `-Wmissing-exported- signatures`, I don't think this matches how people use `-Weverything`. At least personally I think of it as "`-Wall` isn't enough, give me the strictest possible warning settings", but actually `-Weverything` can have ''fewer'' warnings than `-Wall` because of `-Wmissing-exported- signatures`. Example reproduction case: {{{ -- Main.hs {-# LANGUAGE Safe #-} module Main (main) where import Prelude (IO, putStrLn, show, ($)) import Foo (foo) main :: IO () main = putStrLn $ show foo }}} {{{ -- Foo.hs {-# LANGUAGE Safe #-} module Foo (foo) where import Prelude (Integer) foo :: Integer foo = bar bar = (1 :: Integer) }}} Expected: when compiling with `-Weverything`, I get a superset of `-Wall`'s warnings. Actual: Actual `-Wall`: {{{ maximiliantagher@Maximilians-MacBook-Pro ~/D/C/H/ghc-warning> ghc -Wall Main.hs Foo.hs [1 of 2] Compiling Foo ( Foo.hs, Foo.o ) Foo.hs:10:1: warning: [-Wmissing-signatures] Top-level binding with no type signature: bar :: Integer | 10 | bar = (1 :: Integer) | ^^^ [2 of 2] Compiling Main ( Main.hs, Main.o ) Linking Main ... }}} Actual `-Weverything` (note: you should remove run `rm main.o main.hi main Foo.o Foo.hi` in between invocations of the ghc to avoid it using something pre-built): {{{ maximiliantagher@Maximilians-MacBook-Pro ~/D/C/H/ghc-warning> ghc -Weverything Main.hs Foo.hs [1 of 2] Compiling Foo ( Foo.hs, Foo.o ) <no location info>: warning: [-Wsafe] ‘Foo’ has been inferred as safe! [2 of 2] Compiling Main ( Main.hs, Main.o ) <no location info>: warning: [-Wsafe] ‘Main’ has been inferred as safe! Linking Main ... }}} (I'm not familiar enough with Safe Haskell to get those warnings to go away—I tried the SafeHaskell pragma but that didn't seem to work. In any case, unrelated to this issue) I tested with these versions: * GHC: The Glorious Glasgow Haskell Compilation System, version 8.2.1 * OS Version: Mac OS 10.13.3 (17D47) (High Sierra) -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14794 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler