#13600: surprising error message with bang pattern -------------------------------------+------------------------------------- Reporter: andrewufrank | Owner: v0d1ch Type: bug | Status: patch Priority: normal | Milestone: Component: Compiler | Version: 8.0.2 Resolution: | Keywords: BangPatterns, | newcomer Operating System: Unknown/Multiple | Architecture: Type of failure: Poor/confusing | Unknown/Multiple error message | Test Case: Blocked By: | Blocking: Related Tickets: #15166, #15458 | Differential Rev(s): Phab:D5040 Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonpj): It's not just a parsing thing. That definition of `go` really might be defining `(!)`, as if you'd written {{{ let (!) go t | T.null t = ... | otherwise = ... }}} We could simply discourage infix definitions of `(!)` (which is used for array indexing anyway), by issuing a warning and asking the user to write their definition prefix (as I have done above) to avoid the potential ambiguity with bang-patterns. Or, maybe only warn if there is no space between the `!` and the argument (comment:2). I dunno. This is user-facing, so a GHC proposal (a very small one!) might be indicated. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13600#comment:14 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler