[Git][ghc/ghc][wip/T18891] Fix kind inference for data types. Again.

[Simon Peyton Jones]

Simon Peyton Jones pushed to branch wip/T18891 at Glasgow Haskell Compiler / GHC


Commits:
1a9e9996 by Simon Peyton Jones at 2020-12-04T22:06:53+00:00
Fix kind inference for data types. Again.

This patch fixes several aspects of kind inference for data type
declarations, especially data /instance/ declarations

Specifically

1. In kcConDecls/kcConDecl make it clear that the tc_res_kind argument
   is only used in the H98 case; and in that case there is no result
   kind signature; and hence no need for the disgusting splitPiTys in
   kcConDecls (now thankfully gone).

   The GADT case is a bit different to before, and much nicer.
   This is what fixes #18891.

   See Note [kcConDecls: kind-checking data type decls]

2. Do not look at the constructor decls of a data/newtype instance
   in tcDataFamInstanceHeader. See GHC.Tc.TyCl.Instance
   Note [Kind inference for data family instances].  This was a
   new realisation that arose when doing (1)

   This causes a few knock-on effects in the tests suite, because
   we require more information than before in the instance /header/.

   New user-manual material about this in "Kind inference in data type
   declarations" and "Kind inference for data/newtype instance
   declarations".

3. Minor improvement in kcTyClDecl, combining GADT and H98 cases

4. Fix #14111 and #8707 by allowing the header of a data instance
   to affect kind inferece for the the data constructor signatures;
   as described at length in Note [GADT return types] in GHC.Tc.TyCl

   This led to a modest refactoring of the arguments (and argument
   order) of tcConDecl/tcConDecls.

5. Fix #19000 by inverting the sense of the test in new_locs
   in GHC.Tc.Solver.Canonical.canDecomposableTyConAppOK.

- - - - -


30 changed files:

- compiler/GHC/Hs/Extension.hs
- compiler/GHC/Tc/Gen/HsType.hs
- compiler/GHC/Tc/Solver/Canonical.hs
- compiler/GHC/Tc/TyCl.hs
- compiler/GHC/Tc/TyCl/Instance.hs
- docs/users_guide/9.2.1-notes.rst
- docs/users_guide/exts/poly_kinds.rst
- testsuite/tests/dependent/should_fail/T13780a.stderr
- testsuite/tests/deriving/should_compile/T11416.hs
- testsuite/tests/deriving/should_compile/T9359.hs
- + testsuite/tests/gadt/SynDataRec.hs
- testsuite/tests/gadt/all.T
- + testsuite/tests/indexed-types/should_compile/T14111.hs
- + testsuite/tests/indexed-types/should_compile/T8707.hs
- testsuite/tests/indexed-types/should_compile/all.T
- testsuite/tests/indexed-types/should_fail/T8368.stderr
- testsuite/tests/indexed-types/should_fail/T8368a.stderr
- testsuite/tests/patsyn/should_fail/T15685.stderr
- testsuite/tests/polykinds/T13659.stderr
- testsuite/tests/polykinds/T16221a.stderr
- testsuite/tests/th/T11145.stderr
- testsuite/tests/th/T9692.hs
- + testsuite/tests/typecheck/should_compile/T18891.hs
- testsuite/tests/typecheck/should_compile/UnliftedNewtypesUnassociatedFamily.hs
- testsuite/tests/typecheck/should_compile/UnliftedNewtypesUnifySig.hs
- testsuite/tests/typecheck/should_compile/all.T
- + testsuite/tests/typecheck/should_fail/T18891a.hs
- + testsuite/tests/typecheck/should_fail/T18891a.stderr
- testsuite/tests/typecheck/should_fail/UnliftedNewtypesFamilyKindFail2.stderr
- + testsuite/tests/typecheck/should_fail/UnliftedNewtypesUnassociatedFamilyFail.hs


The diff was not included because it is too large.


View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/1a9e9996e17f73b40fcdfc18f0a3d4dd39c2f187

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View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/1a9e9996e17f73b40fcdfc18f0a3d4dd39c2f187
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