#13988: GADT constructor with kind equality constraint quantifies unused existential type variables -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: patch Priority: normal | Milestone: Component: Compiler (Type | Version: 8.0.1 checker) | Resolution: | Keywords: TypeInType Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect result | Unknown/Multiple at runtime | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D3872 Wiki Page: | -------------------------------------+------------------------------------- Changes (by RyanGlScott): * status: new => patch * differential: => Phab:D3872 Comment: I ended up needing to fix this as a part of an unrelated patch, Phab:D3872. (Note that I borrowed the solution for this particular issue from Richard, so the credit should go to him.) -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13988#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#13988: GADT constructor with kind equality constraint quantifies unused existential type variables -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: patch Priority: normal | Milestone: Component: Compiler (Type | Version: 8.0.1 checker) | Resolution: | Keywords: TypeInType Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect result | Unknown/Multiple at runtime | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D3872 Wiki Page: | -------------------------------------+------------------------------------- Changes (by RyanGlScott): * status: new => patch * differential: => Phab:D3872 Comment: ...and now Phab:D3872 is back! Re-setting the Differential revision. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13988#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#13988: GADT constructor with kind equality constraint quantifies unused existential type variables -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: patch Priority: normal | Milestone: Component: Compiler (Type | Version: 8.0.1 checker) | Resolution: | Keywords: TypeInType Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect result | Unknown/Multiple at runtime | Test Case: Blocked By: | Blocking: 14131 Related Tickets: | Differential Rev(s): Phab:D3902 Wiki Page: | -------------------------------------+------------------------------------- Comment (by Ben Gamari ): In [changeset:"b9ac9e05b29c58efc93b78bf7fca43d61ead50c7/ghc" b9ac9e0/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="b9ac9e05b29c58efc93b78bf7fca43d61ead50c7" Fix egregious duplication of vars in RnTypes `RnTypes` contains a fairly intricate algorithm to extract the kind and type variables of an HsType. This algorithm carefully maintains the separation between type variables and kind variables so that the difference between `-XPolyKinds` and `-XTypeInType` can be respected. But after doing all this, `rmDupsInRdrTyVars` stupidly just concatenated the lists of type and kind variables at the end. If a variable were used as both a type and a kind, the algorithm would produce *both*! This led to all kinds of problems, including #13988. This is mostly Richard Eisenberg's patch. The only original contribution I made was adapting call sites of `rnImplicitBndrs` to work with the new definition of `rmDupsInRdrTyVars`. That is, `rnImplicitBndrs` checks for variables that are illegally used in both type and kind positions without using `-XTypeInType`, but in order to check this, one cannot have filtered duplicate variables out before passing them to `rnImplicitBndrs`. To accommodate for this, I needed to concoct variations on the existing `extract-` functions in `RnTypes` which do not remove duplicates, and use those near `rnImplicitBndrs` call sites. test case: ghci/scripts/T13988 Test Plan: make test TEST=T13988 Reviewers: goldfire, simonpj, austin, bgamari Reviewed By: goldfire, simonpj Subscribers: rwbarton, thomie GHC Trac Issues: #13988 Differential Revision: https://phabricator.haskell.org/D3902 }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13988#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#13988: GADT constructor with kind equality constraint quantifies unused existential type variables -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: patch Priority: normal | Milestone: Component: Compiler (Type | Version: 8.0.1 checker) | Resolution: | Keywords: TypeInType Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: Incorrect result | Test Case: at runtime | ghci/scripts/T13988 Blocked By: | Blocking: 14131 Related Tickets: | Differential Rev(s): Phab:D3902 Wiki Page: | -------------------------------------+------------------------------------- Changes (by simonpj): * testcase: => ghci/scripts/T13988 -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13988#comment:7 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler