#10890: Incorrect redundant import warning for type classes -------------------------------------+------------------------------------- Reporter: quchen | Owner: Type: bug | Status: new Priority: normal | Milestone: 8.0.1 Component: Compiler | Version: 7.10.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Revisions: -------------------------------------+------------------------------------- Comment (by osa1): Here's more stuff: GHC actually doesn't even consider `has` as an used symbol(i.e. internally it doesn't add it to the set of symbols used in a module, `tcg_used_rdrnames` of `TcGblEnv`), so in this case it only considers importing `AClass` and `BClass`. (that why in my second example it prints warnings about both `has`) `BClass` is exported by both `Base` and `Extends`. Now let's say we have this: {{{#!haskell import Base import Extends }}} Which one should be used for importing `BClass`? GHC makes the choice based on their locations in the source file. That is, it imports it from `Base` and not from `Extends`. But if I change imports like this: {{{#!haskell import Extends import Base }}} Now GHC imports `BClass` from `Extends` because it comes first in the source code, so no warnings here. Long story short, I think the problem is that GHC doesn't consider `has` a used symbol. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10890#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler