#9127: Don't warn about pattern-bindings of the form `let !_ = rhs` -------------------------------------+------------------------------------ Reporter: refold | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Unknown/Multiple Type of failure: None/Unknown | Difficulty: Unknown Test Case: | Blocked By: Blocking: | Related Tickets: -------------------------------------+------------------------------------ Comment (by igloo): Ah, well, it'll ''probably'' do what you want. But if, for example, at a usage site GHC can see the expression that has been put in `rqPostParams` and thinks that it is cheap, then it may evaluate a copy of it rather than sharing the value. #2273 is an example of something similar. To be sure, I think you'd need something like: {{{ foo :: RequestBuilder foo = do rq <- rGet let !rqPostParams' = rqPostParams rq ... rPut $! (rq { rqPostParams = rqPostParams' }) }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9127#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler