#14963: ghci -fdefer-type-errors can't run IO action from another module -------------------------------------+------------------------------------- Reporter: elaforge | Owner: tdammers Type: bug | Status: new Priority: high | Milestone: 8.4.2 Component: GHCi | Version: 8.4.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by tdammers): As discussed in Hangouts, the problem is even more specific: it only appears for expressions entered at the GHCi prompt while defer-type-errors is active. Loading modules with defer-type-errors on, then turning it off and *then* evaluating expressions at the prompt works just fine. Hence, the quick fix for 8.6 will be to selectively disable deferred type checking for expressions entered interactively. This way, we will not disrupt any workflows (the error would have appeared right there and then one way or another), while still avoiding the crash. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14963#comment:22 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler