#14342: ghci fails to start with RebindableSyntax and OverloadedStrings ---------------------------------+---------------------------------------- Reporter: NeilMitchell | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: GHCi | Version: 8.2.1 Resolution: | Keywords: Operating System: Windows | Architecture: Unknown/Multiple Type of failure: GHCi crash | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | ---------------------------------+---------------------------------------- Changes (by NeilMitchell): * cc: ndmitchell@… (added) -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14342#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#14342: ghci fails to start with RebindableSyntax and OverloadedStrings ---------------------------------+---------------------------------------- Reporter: NeilMitchell | Owner: (none) Type: bug | Status: patch Priority: normal | Milestone: Component: GHCi | Version: 8.2.1 Resolution: | Keywords: RebindableSyntax Operating System: Windows | Architecture: Unknown/Multiple Type of failure: GHCi crash | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D4086 Wiki Page: | ---------------------------------+---------------------------------------- Comment (by Ryan Scott ): In [changeset:"e023e78bc13ffae168f00a52324fc406a146b40f/ghc" e023e78/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="e023e78bc13ffae168f00a52324fc406a146b40f" Disable -XRebindableSyntax when running internal GHCi expressions Summary: It's well known that `-XRebindableSyntax` doesn't play nicely with some of the internal expressions that GHCi runs. #13385 was one example where this problem arose, which was fixed at the time by simply avoiding the use of `do`-notation in these internal GHCi expressions. That seemed to work, but it was a technique that proved not to scale, as #14342 demonstrated //another// example where `-XRebindableSyntax` can bite. Instead of delicately arranging the internal GHCi expressions to avoid anything that might be covered under `-XRebindableSyntax`, this patch takes the much more direct approach of disabling `-XRebindableSyntax` entirely when running any internal GHCi expression. This shouldn't hurt, since nothing internal to GHCi was taking advantage of the extension in the first place, and moreover, we can have greater confidence that some other obscure `-XRebindableSyntax` corner case won't pop up in the future. As an added bonus, this lets us once again use `do`-notation in the code that had to be changed when #13385 was (hackily) fixed before. Test Plan: make test TEST=T14342 Reviewers: bgamari, austin Subscribers: rwbarton, thomie GHC Trac Issues: #14342 Differential Revision: https://phabricator.haskell.org/D4086 }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14342#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler