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Ryan Scott authored
`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
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