[GHC] #14833: QuantifiedConstraints: GHC can't deduce (() :: Constraint)?

[GHC]

#14833: QuantifiedConstraints: GHC can't deduce (() :: Constraint)?
-------------------------------------+-------------------------------------
        Reporter:  Iceland_jack      |                Owner:  (none)
            Type:  bug               |               Status:  closed
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.5
      Resolution:  fixed             |             Keywords:
                                     |  QuantifiedConstraints wipT2893
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:  quantified-
                                     |  constraints/T14833
      Blocked By:                    |             Blocking:
 Related Tickets:  #14835            |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------
Changes (by simonpj):

 * testcase:   => quantified-constraints/T14833
 * status:  new => closed
 * resolution:   => fixed


Comment:

 I've fixed this one -- on `wip/T2893` as always.
 ==
 {{{
 commit 60f682407eefdb7884d12ba43d00add0c1ca9245
 Author: Simon Peyton Jones <simonpj at microsoft.com>
 Date:   Tue Feb 27 13:43:26 2018 +0000

     Fix a bunch of buglets in QuantifiedConstraints

     * Freshen tyvars in Inst.instDFunType

     * Freshen tyvars in TcCanonical.solveForAll

     * Define TcSMonad.mightMatchLater, and use it (fixes Trac #14833)

     * Add testsuite directry tests/quantified-constraints/, and start
       to populate it

  compiler/typecheck/Inst.hs                         |  8 ++++++--
  compiler/typecheck/TcCanonical.hs                  | 22
 ++++++++++++++--------
  compiler/typecheck/TcEvidence.hs                   |  2 --
  compiler/typecheck/TcInteract.hs                   | 34
 ++++++++++++++++------------------
  compiler/typecheck/TcSMonad.hs                     | 21
 +++++++++++----------
  compiler/typecheck/TcValidity.hs                   |  3 ++-
  compiler/types/Type.hs                             |  2 +-
  testsuite/tests/quantified-constraints/T14833.hs   | 28
 ++++++++++++++++++++++++++++
  testsuite/tests/quantified-constraints/T2893.hs    | 18
 ++++++++++++++++++
  testsuite/tests/quantified-constraints/T2893a.hs   | 27
 +++++++++++++++++++++++++++
  testsuite/tests/quantified-constraints/T2893b.hs   | 24
 ++++++++++++++++++++++++
  testsuite/tests/quantified-constraints/all.T       |  4 ++++
  testsuite/tests/typecheck/should_compile/T2893.hs  | 18
 ------------------
  testsuite/tests/typecheck/should_compile/T2893a.hs | 27
 ---------------------------
  testsuite/tests/typecheck/should_compile/all.T     |  2 --
  15 files changed, 151 insertions(+), 89 deletions(-)
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14833#comment:4>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler