[GHC] #14963: ghci -fdefer-type-errors can't run IO action from another module
GHC
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Mon Jun 4 14:49:22 UTC 2018
#14963: ghci -fdefer-type-errors can't run IO action from another module
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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: |
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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>
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