[commit: ghc] wip/impredicativity: Add lazy instantiation for type classes (d58e17d)

[git at git.haskell.org]

Repository : ssh://git@git.haskell.org/ghc

On branch  : wip/impredicativity
Link       : http://ghc.haskell.org/trac/ghc/changeset/d58e17d2fbae2d424ae5af918fc43c1dafd4cce6/ghc

>---------------------------------------------------------------

commit d58e17d2fbae2d424ae5af918fc43c1dafd4cce6
Author: Alejandro Serrano <trupill at gmail.com>
Date:   Wed Jul 1 13:40:43 2015 +0200

    Add lazy instantiation for type classes
    
    This commit implements the instantiation of type variables when
    they appear in both in an InstanceOf constraint and as an argument
    of a type class constraint that must be inspected to know whether
    an instance applies.
    
    For example, given Eq alpha and InstanceOf (forall b. [b]) alpha, the
    solver will now instantiate alpha to [beta], for a new beta variabe.
    
    The core of the changes are found in two places:
    - compiler/types/Unify.hs, where the matching procedure is enhanced to
      take some extra "lazy equations". These are equations of the form
      type variable ~ type which are available to be used if we do not
      know yet whether a match is successful over that type variable.
      At the end, the matching process returns which of the lazy equations
      were used, from which we can extract information to add the extra
      instantiations to the set of constraints.
    - compiler/typecheck/TcInteract.hs generates lazy equations from the
      InstanceOf constraints in the inert set, and passes them to the
      matching procedure.
    The rest of files had to be changed mostly to accomodate the new
    interface of the matching functions.


>---------------------------------------------------------------

d58e17d2fbae2d424ae5af918fc43c1dafd4cce6
 compiler/specialise/Rules.hs                  |  11 ++-
 compiler/typecheck/FamInst.hs                 |   8 +-
 compiler/typecheck/Inst.hs                    |   4 +-
 compiler/typecheck/TcBinds.hs                 |  13 ++-
 compiler/typecheck/TcErrors.hs                |  10 +--
 compiler/typecheck/TcInteract.hs              |  89 ++++++++++++++-------
 compiler/typecheck/TcSMonad.hs                |  44 ++++++----
 compiler/typecheck/TcSimplify.hs              |   8 +-
 compiler/typecheck/TcTyClsDecls.hs            |  13 +--
 compiler/typecheck/TcValidity.hs              |   6 +-
 compiler/types/Coercion.hs                    |  10 ++-
 compiler/types/FamInstEnv.hs                  | 105 +++++++++++++-----------
 compiler/types/InstEnv.hs                     |  58 ++++++++------
 compiler/types/Unify.hs                       | 111 ++++++++++++++++++--------
 compiler/vectorise/Vectorise/Monad/InstEnv.hs |   4 +-
 compiler/vectorise/Vectorise/Utils/Base.hs    |   2 +-
 16 files changed, 308 insertions(+), 188 deletions(-)

Diff suppressed because of size. To see it, use:

    git diff-tree --root --patch-with-stat --no-color --find-copies-harder --ignore-space-at-eol --cc d58e17d2fbae2d424ae5af918fc43c1dafd4cce6