Simon Peyton Jones pushed to branch wip/T26868 at Glasgow Haskell Compiler / GHC

Commits:

• 18d3e6b1
  by Simon Peyton Jones at 2026-03-27T17:26:59+00:00

  Major refactor of free-variable functions
  
  For some time we have had two free-variable mechanims for types:
  
  * The "FV" mechanism, embodied in GHC.Utils.FV, which worked OK, but
    was fragile where eta-expansion was concerned.
  
  * The TyCoFolder mechanism, using a one-shot EndoOS accumulator
  
  I finally got tired of this and refactored the whole thing, thereby
  addressing #27080.   Now we have
  
  * `GHC.Types.Var.FV`, which has a composable free-variable result type,
    very much in the spirit of the old `FV`, but much more robust.
    (It uses the "one shot trick".)
  
  * GHC.Core.TyCo.FVs now has just one technology for free variables.
  
  All this led to a lot of renaming.
  
  There are couple of error-message changes.  The change in T18451
  makes an already-poor error message even more mysterious.  But
  it really needs a separate look.
  

81 changed files:

• compiler/GHC/Core/Coercion.hs
• compiler/GHC/Core/FVs.hs
• compiler/GHC/Core/Opt/DmdAnal.hs
• compiler/GHC/Core/Opt/SetLevels.hs
• compiler/GHC/Core/Opt/Specialise.hs
• compiler/GHC/Core/Rules.hs
• compiler/GHC/Core/Subst.hs
• compiler/GHC/Core/TyCo/FVs.hs
• compiler/GHC/Core/TyCo/Rep.hs
• compiler/GHC/Core/Type.hs
• compiler/GHC/Core/Unify.hs
• compiler/GHC/Hs/Utils.hs
• compiler/GHC/HsToCore/Binds.hs
• compiler/GHC/HsToCore/Ticks.hs
• compiler/GHC/Iface/Ext/Ast.hs
• compiler/GHC/Iface/Syntax.hs
• compiler/GHC/Rename/Bind.hs
• compiler/GHC/Rename/Env.hs
• compiler/GHC/Rename/Expr.hs
• compiler/GHC/Rename/Expr.hs-boot
• compiler/GHC/Rename/HsType.hs
• compiler/GHC/Rename/Lit.hs
• compiler/GHC/Rename/Module.hs
• compiler/GHC/Rename/Pat.hs
• compiler/GHC/Rename/Splice.hs
• compiler/GHC/Rename/Splice.hs-boot
• compiler/GHC/Rename/Utils.hs
• compiler/GHC/Tc/Deriv.hs
• compiler/GHC/Tc/Errors.hs
• compiler/GHC/Tc/Errors/Hole.hs
• compiler/GHC/Tc/Gen/App.hs
• compiler/GHC/Tc/Instance/Family.hs
• compiler/GHC/Tc/Instance/FunDeps.hs
• compiler/GHC/Tc/Module.hs
• compiler/GHC/Tc/TyCl/Utils.hs
• compiler/GHC/Tc/Types/Constraint.hs
• compiler/GHC/Tc/Types/Evidence.hs
• compiler/GHC/Tc/Utils/TcType.hs
• compiler/GHC/Tc/Utils/Unify.hs
• compiler/GHC/Tc/Validity.hs
• compiler/GHC/Types/Name/Set.hs
• + compiler/GHC/Types/Var/FV.hs
• compiler/GHC/Types/Var/Set.hs
• compiler/GHC/Utils/EndoOS.hs
• − compiler/GHC/Utils/FV.hs
• compiler/ghc.cabal.in
• testsuite/tests/count-deps/CountDepsAst.stdout
• testsuite/tests/count-deps/CountDepsParser.stdout
• testsuite/tests/cpranal/should_compile/T18401.stderr
• testsuite/tests/deriving/should_fail/deriving-via-fail4.stderr
• testsuite/tests/indexed-types/should_fail/T2693.stderr
• testsuite/tests/interface-stability/base-exports.stdout
• testsuite/tests/partial-sigs/should_compile/T10403.stderr
• testsuite/tests/partial-sigs/should_compile/T12844.stderr
• testsuite/tests/partial-sigs/should_compile/T15039a.stderr
• testsuite/tests/partial-sigs/should_compile/T15039b.stderr
• testsuite/tests/partial-sigs/should_compile/T15039c.stderr
• testsuite/tests/partial-sigs/should_compile/T15039d.stderr
• testsuite/tests/partial-sigs/should_fail/T10999.stderr
• testsuite/tests/partial-sigs/should_fail/T12634.stderr
• testsuite/tests/polykinds/T15789.stderr
• testsuite/tests/polykinds/T18451.stderr
• testsuite/tests/polykinds/T7328.stderr
• testsuite/tests/simplCore/should_compile/DsSpecPragmas.stderr
• testsuite/tests/simplCore/should_compile/T24229a.stderr
• testsuite/tests/simplCore/should_compile/T24229b.stderr
• testsuite/tests/simplCore/should_compile/T24359a.stderr
• testsuite/tests/simplCore/should_compile/T26116.stderr
• testsuite/tests/simplCore/should_compile/T4908.stderr
• testsuite/tests/simplCore/should_compile/spec-inline.stderr
• testsuite/tests/typecheck/no_skolem_info/T20063.stderr
• testsuite/tests/typecheck/should_compile/T25180.stderr
• testsuite/tests/typecheck/should_compile/free_monad_hole_fits.stderr
• testsuite/tests/typecheck/should_fail/T10971d.stderr
• testsuite/tests/typecheck/should_fail/T12589.stderr
• testsuite/tests/typecheck/should_fail/T13311.stderr
• testsuite/tests/typecheck/should_fail/T17773.stderr
• testsuite/tests/typecheck/should_fail/T2846b.stderr
• testsuite/tests/typecheck/should_fail/T7851.stderr
• testsuite/tests/typecheck/should_fail/T8603.stderr
• utils/haddock/haddock-api/src/Haddock/GhcUtils.hs

The diff was not included because it is too large.