[GHC] #15248: Coercions from plugins cannot be stopped from floating out
#15248: Coercions from plugins cannot be stopped from floating out -------------------------------------+------------------------------------- Reporter: goldfire | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 8.4.3 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Suppose we have {{{#!hs type family (a :: Nat) http://ghc.haskell.org/trac/ghc/ticket/15248 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#15248: Coercions from plugins cannot be stopped from floating out -------------------------------------+------------------------------------- Reporter: goldfire | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 8.4.3 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: | -------------------------------------+------------------------------------- Changes (by adamgundry): * cc: adamgundry (added) Comment: In this case, in principle, shouldn't the evidence produced for the plugin directly depend on the evidence for the assumptions? That is, rather than "proving" `(a a True) }}} by `UnivCo` and then instantiate it with your evidence for `(a http://ghc.haskell.org/trac/ghc/ticket/15248#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#15248: Coercions from plugins cannot be stopped from floating out -------------------------------------+------------------------------------- Reporter: goldfire | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 8.4.3 Resolution: | Keywords: | TypeCheckerPlugins Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by adamgundry): * keywords: => TypeCheckerPlugins -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15248#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#15248: Coercions from plugins cannot be stopped from floating out -------------------------------------+------------------------------------- Reporter: goldfire | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 8.4.3 Resolution: | Keywords: | TypeCheckerPlugins 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 goldfire): But comment:1 seems to require a constrained type in the `~` relation, which is generally not allowed. I suppose nothing stops a plugin from producing such things (and GHC might even consume them correctly), but I don't think that's explicitly a supported feature. (You can't say that in source Haskell, for example. Even with quantified constraints.) -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15248#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#15248: Coercions from plugins cannot be stopped from floating out -------------------------------------+------------------------------------- Reporter: goldfire | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 8.4.3 Resolution: | Keywords: | TypeCheckerPlugins 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 simonpj): Yes: see comment:15 on #8095, and the discussion on Phab:D4766. `PlugInProv` should have a `TyCoVarSet` just as the (upcoming) `ZappedProv` does, and for the same reasons. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15248#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
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