Simon Peyton Jones pushed to branch wip/T26315 at Glasgow Haskell Compiler / GHC

Commits:

• 9e50a25d
  by Simon Peyton Jones at 2025-09-05T17:11:33+01:00

  Solve forall-constraints via an implication, again
  
  In this earlier commit:
  
    commit 953fd8f1dc080f1c56e3a60b4b7157456949be29
    Author: Simon Peyton Jones <simon.peytonjones@gmail.com>
    Date:   Mon Jul 21 10:06:43 2025 +0100
  
    Solve forall-constraints immediately, or not at all
  
  I used a all-or-nothing strategy for quantified constraints
  (aka forall-constraints).  But alas that fell foul of #26315,
  and #26376.
  
  So this MR goes back to solving a quantified constraint by
  turning it into an implication; UNLESS we are simplifying
  constraints from a SPECIALISE pragma, in which case the
  all-or-nothing strategy is great.  See:
  
     Note [Solving a Wanted forall-constraint]
  
  Other stuff in this MR:
  
  * TcSMode becomes a record of flags, rather than an enumeration
    type; much nicer.
  
  * Some fancy footwork to avoid error messages worsening again
    (The above MR made them better; we want to retain that.)
    See `GHC.Tc.Errors.Ppr.pprQCOriginExtra`.
  

44 changed files:

• compiler/GHC/HsToCore/Binds.hs
• compiler/GHC/Tc/Deriv/Utils.hs
• compiler/GHC/Tc/Errors/Ppr.hs
• compiler/GHC/Tc/Gen/Sig.hs
• compiler/GHC/Tc/Solver.hs
• compiler/GHC/Tc/Solver/Default.hs
• compiler/GHC/Tc/Solver/Dict.hs
• compiler/GHC/Tc/Solver/Equality.hs
• compiler/GHC/Tc/Solver/InertSet.hs
• compiler/GHC/Tc/Solver/Monad.hs
• compiler/GHC/Tc/Solver/Solve.hs
• compiler/GHC/Tc/Solver/Solve.hs-boot
• compiler/GHC/Tc/Types/Constraint.hs
• compiler/GHC/Tc/Types/Evidence.hs
• compiler/GHC/Tc/Types/Origin.hs
• compiler/GHC/Tc/Utils/Monad.hs
• compiler/GHC/Tc/Zonk/TcType.hs
• compiler/GHC/Tc/Zonk/Type.hs
• testsuite/tests/backpack/should_fail/bkpfail11.stderr
• testsuite/tests/backpack/should_fail/bkpfail43.stderr
• testsuite/tests/deriving/should_fail/T12768.stderr
• testsuite/tests/deriving/should_fail/T1496.stderr
• testsuite/tests/deriving/should_fail/T21302.stderr
• testsuite/tests/deriving/should_fail/T22696b.stderr
• testsuite/tests/deriving/should_fail/T5498.stderr
• testsuite/tests/deriving/should_fail/T7148.stderr
• testsuite/tests/deriving/should_fail/T7148a.stderr
• testsuite/tests/impredicative/T17332.stderr
• testsuite/tests/quantified-constraints/T19690.stderr
• testsuite/tests/quantified-constraints/T19921.stderr
• testsuite/tests/quantified-constraints/T21006.stderr
• testsuite/tests/roles/should_fail/RolesIArray.stderr
• testsuite/tests/simplCore/should_compile/DsSpecPragmas.hs
• testsuite/tests/simplCore/should_compile/DsSpecPragmas.stderr
• testsuite/tests/typecheck/should_compile/T14434.hs
• + testsuite/tests/typecheck/should_compile/T26376.hs
• testsuite/tests/typecheck/should_compile/all.T
• testsuite/tests/typecheck/should_fail/T15801.stderr
• testsuite/tests/typecheck/should_fail/T19627.stderr
• testsuite/tests/typecheck/should_fail/T20666.stderr
• testsuite/tests/typecheck/should_fail/T20666a.stderr
• testsuite/tests/typecheck/should_fail/T20666b.stderr
• testsuite/tests/typecheck/should_fail/T22912.stderr
• testsuite/tests/typecheck/should_fail/T23427.stderr

The diff was not included because it is too large.