#12920: Overzealous unused-top-binds -------------------------------------+------------------------------------- Reporter: crockeea | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.2-rc1 Resolution: | 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: | -------------------------------------+------------------------------------- Comment (by RyanGlScott): I just ran into this issue in a somewhat different context: {{{#!hs {-# OPTIONS_GHC -Wunused-top-binds #-} module Bug () where type A = Int type B = A type C = B a, b, c :: Int a = 42 b = a c = b }}} {{{ GHCi, version 8.6.3: http://www.haskell.org/ghc/ :? for help Loaded GHCi configuration from /home/rgscott/.ghci [1 of 1] Compiling Bug ( Bug2.hs, interpreted ) Bug2.hs:6:1: warning: [-Wunused-top-binds] Defined but not used: type constructor or class ‘C’ | 6 | type C = B | ^^^^^^^^^^ Bug2.hs:9:1: warning: [-Wunused-top-binds] Defined but not used: ‘a’ | 9 | a = 42 | ^ Bug2.hs:10:1: warning: [-Wunused-top-binds] Defined but not used: ‘b’ | 10 | b = a | ^ Bug2.hs:11:1: warning: [-Wunused-top-binds] Defined but not used: ‘c’ | 11 | c = b | ^ Ok, one module loaded. }}} It appears that `-Wunused-top-binds` has different transitivity behavior when it comes to functions vs. type synonyms: the former has transitive behavior, whereas the latter does not. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12920#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler