1. 26 Sep, 2020 1 commit
  2. 24 Sep, 2020 1 commit
    • Simon Peyton Jones's avatar
      Improve kind generalisation, error messages · 9fa26aa1
      Simon Peyton Jones authored and  Marge Bot's avatar Marge Bot committed
      This patch does two things:
      
      * It refactors GHC.Tc.Errors a bit.  In debugging Quick Look I was
        forced to look in detail at error messages, and ended up doing a bit
        of refactoring, esp in mkTyVarEqErr'.  It's still quite a mess, but
        a bit better, I think.
      
      * It makes a significant improvement to the kind checking of type and
        class declarations. Specifically, we now ensure that if kind
        checking fails with an unsolved constraint, all the skolems are in
        scope.  That wasn't the case before, which led to some obscure error
        messages; and occasional failures with "no skolem info" (eg #16245).
      
      Both of these, and the main Quick Look patch itself, affect a /lot/ of
      error messages, as you can see from the number of files changed.  I've
      checked them all; I think they are as good or better than before.
      
      Smaller things
      
      * I documented the various instances of VarBndr better.
        See Note [The VarBndr tyep and its uses] in GHC.Types.Var
      
      * Renamed GHC.Tc.Solver.simpl_top to simplifyTopWanteds
      
      * A bit of refactoring in bindExplicitTKTele, to avoid the
        footwork with Either.  Simpler now.
      
      * Move promoteTyVar from GHC.Tc.Solver to GHC.Tc.Utils.TcMType
      
      Fixes #16245 (comment 211369), memorialised as
        typecheck/polykinds/T16245a
      Also fixes the three bugs in #18640
      9fa26aa1
  3. 17 Jun, 2020 1 commit
    • Krzysztof Gogolewski's avatar
      Linear types (#15981) · 40fa237e
      Krzysztof Gogolewski authored and Ben Gamari's avatar Ben Gamari committed
      This is the first step towards implementation of the linear types proposal
      (https://github.com/ghc-proposals/ghc-proposals/pull/111).
      
      It features
      
      * A language extension -XLinearTypes
      * Syntax for linear functions in the surface language
      * Linearity checking in Core Lint, enabled with -dlinear-core-lint
      * Core-to-core passes are mostly compatible with linearity
      * Fields in a data type can be linear or unrestricted; linear fields
        have multiplicity-polymorphic constructors.
        If -XLinearTypes is disabled, the GADT syntax defaults to linear fields
      
      The following items are not yet supported:
      
      * a # m -> b syntax (only prefix FUN is supported for now)
      * Full multiplicity inference (multiplicities are really only checked)
      * Decent linearity error messages
      * Linear let, where, and case expressions in the surface language
        (each of these currently introduce the unrestricted variant)
      * Multiplicity-parametric fields
      * Syntax for annotating lambda-bound or let-bound with a multiplicity
      * Syntax for non-linear/multiple-field-multiplicity records
      * Linear projections for records with a single linear field
      * Linear pattern synonyms
      * Multiplicity coercions (test LinearPolyType)
      
      A high-level description can be found at
      https://ghc.haskell.org/trac/ghc/wiki/LinearTypes/Implementation
      Following the link above you will find a description of the changes made to Core.
      This commit has been authored by
      
      * Richard Eisenberg
      * Krzysztof Gogolewski
      * Matthew Pickering
      * Arnaud Spiwack
      
      With contributions from:
      
      * Mark Barbone
      * Alexander Vershilov
      
      Updates haddock submodule.
      40fa237e