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Ryan Scott authored
Summary: We currently permit any and all uses of unsaturated type synonyms and type families in GHCi's `:kind` command, which allows strange interactions like this one: ``` > :set -XTypeFamilies -XPolyKinds > type family Id (a :: k) > type instance Id a = a > type Foo x = Maybe > :kind! Id Foo ``` This is probably a stretch too far, so this patch moves to disallow unsaturated synonyms that aren't at the top level (we still want to allow `:kind Id`, for instance). We do this by augmenting `GhciCtxt` with an additional `Bool` field to indicate if we are at the outermost level of the type being passed to `:kind` or not. See `Note [Unsaturated type synonyms in GHCi]` in `TcValidity` for the full story. Test Plan: make test TEST=T16013 Reviewers: goldfire, bgamari Reviewed By: goldfire Subscribers: simonpj, goldfire, rwbarton, carter GHC Trac Issues: #16013 Differential Revision: https://phabricator.haskell.org/D5471
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