[GHC] #14968: QuantifiedConstraints: Can't be RHS of type family instances
GHC
ghc-devs at haskell.org
Sat Mar 24 15:31:17 UTC 2018
#14968: QuantifiedConstraints: Can't be RHS of type family instances
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Reporter: josef | Owner: (none)
Type: bug | Status: new
Priority: normal | Milestone:
Component: Compiler (Type | Version: 8.5
checker) | Keywords:
Resolution: | QuantifiedConstraints
Operating System: Unknown/Multiple | Architecture:
| Unknown/Multiple
Type of failure: None/Unknown | Test Case:
Blocked By: | Blocking:
Related Tickets: #9269 | Differential Rev(s):
Wiki Page: |
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Comment (by RyanGlScott):
I'm not sure what the return kind has anything to do with this.
Ultimately, the issue is impredicativity, which is going to be a problem
regardless of whether you're working over `*`, `Constraint` (as in your
example), `Bool` (as in the example in
https://ghc.haskell.org/trac/ghc/ticket/9269#comment:1), or something
else.
--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14968#comment:3>
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