#10117: Change the scheme for reporting redundant imports -------------------------------------+------------------------------------- Reporter: simonpj | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.4 Resolution: | Keywords: deprecate | warning Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect | Unknown/Multiple warning at compile-time | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by ezyang): Your first bullet point is exactly right. To refine the old principle, I think this is good enough: an import is unused if it can be deleted without changing the meaning of the program, EXCEPT if the import explicitly brings x into scope (e.g., `import A (x)`), and the only other ways x was brought into scope are implicit (e.g., `import B`), AND each such implicit import is of a different module (e.g., `import A (x)` is still redundant if we `import A`). I've expanded the wikipage on this point, and I also streamlined the proposed algorithm so that we don't need a textual subsumption check anymore: I'm just a bit choosier about what import-items I mark as used when I hit a RdrName. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10117#comment:8 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler