Simon Peyton Jones pushed to branch wip/substitution-via-mapper at Glasgow Haskell Compiler / GHC

Commits:

• b25c9866
  by Simon Peyton Jones at 2026-08-03T17:00:50+01:00

  Implement substitution via TyCoMapper
  
  This is a significant bit of refactoring.  The dependencies look like this,
  where each module depends on one above
  
                        Defines               Needs
  ---------------------------------------------------
  GHC.Core.TyCo.Rep     Type, Coercion
                        TyCoFolder
  
  GHC.Core.TyCo.FVs     Free-var finders       TyCoFolder
  
  GHC.Core.TyCo.Make    Lots of mkX functions  Free vars
                        TyCoMapper
  
  GHC.Core.TyCo.Subst   Substitution           TyCoMapper, mkX functions
  
  GHC.Core.Type         coreView, typeKind     Substitution
                        coercionKind
  
  GHC.Core.TyCo.Compare Comparison             coreView
  
  Some `mkX` functions (such as `mkLRCo`, `mkInstCo`, `mkCastTy`) use
  substitution, and so are defined in GHC.Core.Type via a hs-boot import.
  

31 changed files:

• compiler/GHC/Builtin/Types/Prim.hs
• compiler/GHC/Core/Coercion.hs
• compiler/GHC/Core/Coercion.hs-boot
• compiler/GHC/Core/Seq.hs
• compiler/GHC/Core/TyCo/FVs.hs
• + compiler/GHC/Core/TyCo/Make.hs
• + compiler/GHC/Core/TyCo/Make.hs-boot
• compiler/GHC/Core/TyCo/Rep.hs
• compiler/GHC/Core/TyCo/Subst.hs
• compiler/GHC/Core/Type.hs
• compiler/GHC/Core/Type.hs-boot
• compiler/GHC/Driver/Main/Compile.hs
• compiler/GHC/Iface/Syntax.hs
• compiler/GHC/Stg/EnforceEpt/TagSig.hs
• compiler/GHC/Tc/Gen/App.hs
• compiler/GHC/Tc/TyCl.hs
• compiler/GHC/Tc/Utils/Unify.hs
• compiler/GHC/Tc/Zonk/TcType.hs
• compiler/GHC/Tc/Zonk/Type.hs
• compiler/GHC/Types/Arity.hs
• compiler/GHC/Types/Basic.hs
• compiler/GHC/Types/Cpr.hs
• compiler/GHC/Types/Demand.hs
• compiler/GHC/Types/Name/Env.hs
• compiler/GHC/Types/Name/Occurrence.hs
• compiler/GHC/Types/Unique/FM.hs
• compiler/GHC/Types/Unique/Map.hs
• compiler/GHC/Types/Unique/Set.hs
• compiler/GHC/Types/Var/Set.hs
• compiler/GHC/Utils/Binary.hs
• compiler/GHC/Utils/Outputable.hs

The diff was not included because it is too large.