[GHC] #14880: GHC panic: updateRole
GHC
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Thu Apr 26 15:52:17 UTC 2018
#14880: GHC panic: updateRole
-------------------------------------+-------------------------------------
Reporter: RyanGlScott | Owner: goldfire
Type: bug | Status: new
Priority: normal | Milestone:
Component: Compiler (Type | Version: 8.2.2
checker) |
Resolution: | Keywords: TypeInType
Operating System: Unknown/Multiple | Architecture:
Type of failure: Compile-time | Unknown/Multiple
crash or panic | Test Case:
Blocked By: | Blocking:
Related Tickets: #15076 | Differential Rev(s):
Wiki Page: |
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Comment (by simonpj):
> The trouble is that MkBar has an implicit forall's variable a, whose
kind mentions an explicit type variable arg.
Richard and I discussed this on Monday. Our conclusions
* `Inferred` variables should always precede `Specified` ones. That is,
do not top-sort
* Idea: simply refrain from quantifying any inferred variables that
mention specified ones. They'll get defaulted to `Any` which is probably
fine. This refraining can readily be done in `candidatesQTyVarsOfType`.
* Also came up: close over kinds once in `tyCoVarsOfType` instead of at
every leaf. This is not just an efficiency issue: consider
{{{
tyCoVarsOfType (forall a. b::a)
}}}
Richard is on the job
--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14880#comment:10>
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