#15708: Cross-module SPECIALZE pragmas aren't typechecked in -O0 -------------------------------------+------------------------------------- Reporter: regnat | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.6.1 (Type checker) | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: GHC accepts Unknown/Multiple | invalid program Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- If a module defines a `SPECIALIZE` pragma for a value defined in another module, then the signature of this pragma won't be typecheck by `ghc -O0` (but it will be if the `SPECIALIZE` pragma is in the same module as the value). For example, given {{{#!hs -- Foo.hs module Foo where foo :: a -> a foo = id ---------- -- Bar.hs module Bar where import Foo {-# SPECIALIZE foo :: Int -> Bool #-} }}} running `ghc --make Bar.hs` will run fine, while `ghc --make -O2 Bar.hs` will complain: {{{ Bar.hs:5:1: error: • Couldn't match type ‘Bool’ with ‘Int’ Expected type: Int -> Int Actual type: Int -> Bool • In the SPECIALISE pragma {-# SPECIALIZE foo :: Int -> Bool #-} | 5 | {-# SPECIALIZE foo :: Int -> Bool #-} | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ }}} Tested on ghc 8.6.1 and 8.4.3 -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15708 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler