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

Commits:

• 58009c14
  by Apoorv Ingle at 2026-04-02T09:51:24+01:00

  Streamline expansions using HsExpansion (#25001)
  
  Notes added [Error Context Stack] [Typechecking by expansion: overview]
  Notes updated Note [Expanding HsDo with XXExprGhcRn] [tcApp: typechecking applications]
  
  -------------------------
  Metric Decrease:
      T9020
  -------------------------
  
  There are 2 key changes:
  
  1. `HsExpand` datatype mediates between expansions
  2. Replace `ErrCtxtM` to a simpler `HsCtxt` that does not depend on a `TidyEnv`
  
  This has some consequences detailed below:
  
  1. `HsExpand` datatype mediates between expansions
     * Simplifies the implementations of `tcExpr` to work on `XExpr`
     * Removes `VACtxt` (and its associated `VAExpansion` and `VACall`) datatype, it is subsumed by simply a `SrcSpan`.
     * Removes the function `addHeadCtxt` as it is now mearly setting a location
     * The function `tcValArgs` does its own argument number management
     * move `splitHsTypes` out of `tcApp`
     * Removes special case of tcBody from `tcLambdaMatches`
     * Removes special case of `dsExpr` for `ExpandedThingTc`
     * Renames `tcMonoExpr` -> `tcMonoLExpr`, `tcMonoExprNC` -> `tcMonoLExpr`
     * Renames `EValArg`, `EValArgQL` fields: `ea_ctxt` -> `ea_loc_span` and `eaql_ctx` -> `eaql_loc_span`
     * Remove `PopErrCtxt` from `XXExprGhcRn`
     * `fun_orig` in tcInstFun depends on the SrcSpan of the head of the application chain (similar to addArgCtxt)
       - it references the application chain head if it is user located, or
        uses the error context stack  as a fallback if it's a generated
        location
     * Make a new variant `GeneratedSrcSpan` in `SrcSpan` for HIEAst Nodes
      - Expressions wrapped around `GeneratedSrcSpan` are ignored and never added to the error context stack
      - In Explicit list expansion `fromListN` is wrapped with a `GeneratedSrcSpan` with `GeneratedSrcSpanDetails` field to store the original srcspan
  
  2. Replace `ErrCtxtM` to a simpler `HsCtxt` that does not depend on a `TidyEnv`
     * Merge `HsThingRn` to `HsCtxt`
     * Landmark Error messages are now just computed on the fly
     * Make HsExpandedRn and HsExpandedTc payload a located HsExpr GhcRn
     * `HsCtxt` are tidied and zonked at the end right before printing
  
  Co-authored-by: simonpj <simon.peytonjones@gmail.com>
  

• bc4b4487
  by Zubin Duggal at 2026-04-03T14:22:27-04:00

  driver: recognise .dyn_o as a valid object file to link if passed on the command line.
  This allows plugins compiled with this suffix to run.
  
  Fixes #24486
  

• 5ebb9121
  by Simon Jakobi at 2026-04-03T14:23:11-04:00

  Add regression test for #16145
  
  Closes #16145.
  

• 3ec86aeb
  by Simon Peyton Jones at 2026-04-03T19:43:08+01:00

  Add Invariant (NoTypeShadowing) to Core
  
  This commit addresses #26868, by adding
  a new invariant (NoTypeShadowing) to Core.
  
  See Note [No type-shadowing in Core] in GHC.Core
  

• 33ecfbb5
  by Simon Peyton Jones at 2026-04-03T20:56:12+01:00

  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.
  
  We also now traverse the AST in a different order leading to a different
  but still deterministic order for FVs and test output has been adjusted
  accordingly.
  

196 changed files:

• compiler/GHC.hs
• compiler/GHC/Core.hs
• compiler/GHC/Core/Coercion.hs
• compiler/GHC/Core/FVs.hs
• compiler/GHC/Core/Lint.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/TyCo/Subst.hs
• compiler/GHC/Core/Type.hs
• compiler/GHC/Core/Unify.hs
• compiler/GHC/Driver/Phases.hs
• compiler/GHC/Hs/DocString.hs
• compiler/GHC/Hs/Expr.hs
• compiler/GHC/Hs/Expr.hs-boot
• compiler/GHC/Hs/Instances.hs
• compiler/GHC/Hs/Syn/Type.hs
• compiler/GHC/Hs/Utils.hs
• compiler/GHC/HsToCore/Binds.hs
• compiler/GHC/HsToCore/Expr.hs
• compiler/GHC/HsToCore/Match.hs
• compiler/GHC/HsToCore/Monad.hs
• compiler/GHC/HsToCore/Pmc.hs
• compiler/GHC/HsToCore/Quote.hs
• compiler/GHC/HsToCore/Ticks.hs
• compiler/GHC/Iface/Ext/Ast.hs
• compiler/GHC/Iface/Ext/Utils.hs
• compiler/GHC/Iface/Syntax.hs
• compiler/GHC/Parser/HaddockLex.x
• 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/Names.hs
• compiler/GHC/Rename/Pat.hs
• compiler/GHC/Rename/Splice.hs
• compiler/GHC/Rename/Splice.hs-boot
• compiler/GHC/Rename/Utils.hs
• compiler/GHC/Runtime/Debugger/Breakpoints.hs
• compiler/GHC/Tc/Deriv.hs
• compiler/GHC/Tc/Deriv/Infer.hs
• compiler/GHC/Tc/Deriv/Utils.hs
• compiler/GHC/Tc/Errors.hs
• compiler/GHC/Tc/Errors/Hole.hs
• compiler/GHC/Tc/Errors/Ppr.hs
• compiler/GHC/Tc/Errors/Types.hs
• compiler/GHC/Tc/Gen/App.hs
• compiler/GHC/Tc/Gen/Bind.hs
• compiler/GHC/Tc/Gen/Do.hs
• + compiler/GHC/Tc/Gen/Expand.hs
• compiler/GHC/Tc/Gen/Export.hs
• compiler/GHC/Tc/Gen/Expr.hs
• compiler/GHC/Tc/Gen/Expr.hs-boot
• compiler/GHC/Tc/Gen/Head.hs
• compiler/GHC/Tc/Gen/HsType.hs
• compiler/GHC/Tc/Gen/Match.hs
• compiler/GHC/Tc/Gen/Match.hs-boot
• compiler/GHC/Tc/Gen/Pat.hs
• compiler/GHC/Tc/Gen/Sig.hs
• compiler/GHC/Tc/Gen/Splice.hs
• compiler/GHC/Tc/Instance/Class.hs
• compiler/GHC/Tc/Instance/Family.hs
• compiler/GHC/Tc/Instance/FunDeps.hs
• compiler/GHC/Tc/Module.hs
• compiler/GHC/Tc/Solver/Solve.hs
• compiler/GHC/Tc/TyCl.hs
• compiler/GHC/Tc/TyCl/Class.hs
• compiler/GHC/Tc/TyCl/Instance.hs
• compiler/GHC/Tc/TyCl/PatSyn.hs
• compiler/GHC/Tc/TyCl/Utils.hs
• compiler/GHC/Tc/Types.hs
• compiler/GHC/Tc/Types/BasicTypes.hs
• compiler/GHC/Tc/Types/Constraint.hs
• compiler/GHC/Tc/Types/CtLoc.hs
• compiler/GHC/Tc/Types/ErrCtxt.hs
• compiler/GHC/Tc/Types/Evidence.hs
• compiler/GHC/Tc/Types/LclEnv.hs
• compiler/GHC/Tc/Types/Origin.hs
• compiler/GHC/Tc/Types/Origin.hs-boot
• compiler/GHC/Tc/Utils/Instantiate.hs
• compiler/GHC/Tc/Utils/Monad.hs
• compiler/GHC/Tc/Utils/TcMType.hs
• compiler/GHC/Tc/Utils/TcType.hs
• compiler/GHC/Tc/Utils/TcType.hs-boot
• compiler/GHC/Tc/Utils/Unify.hs
• compiler/GHC/Tc/Validity.hs
• compiler/GHC/Tc/Zonk/TcType.hs
• compiler/GHC/Tc/Zonk/Type.hs
• compiler/GHC/Types/Error.hs
• + compiler/GHC/Types/Error.hs-boot
• compiler/GHC/Types/Hint/Ppr.hs
• compiler/GHC/Types/Name/Reader.hs
• compiler/GHC/Types/Name/Set.hs
• compiler/GHC/Types/SrcLoc.hs
• + compiler/GHC/Types/Var/FV.hs
• compiler/GHC/Types/Var/Set.hs
• + compiler/GHC/Unit/State.hs-boot
• compiler/GHC/Utils/Binary.hs
• compiler/GHC/Utils/EndoOS.hs
• − compiler/GHC/Utils/FV.hs
• compiler/GHC/Utils/Logger.hs
• compiler/ghc.cabal.in
• ghc/GHCi/UI.hs
• ghc/GHCi/UI/Info.hs
• 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/ghci/prog-mhu001/prog-mhu001c.stdout
• testsuite/tests/indexed-types/should_fail/T2693.stderr
• testsuite/tests/indexed-types/should_fail/T5439.stderr
• testsuite/tests/interface-stability/base-exports.stdout
• testsuite/tests/interface-stability/base-exports.stdout-javascript-unknown-ghcjs
• testsuite/tests/interface-stability/base-exports.stdout-mingw32
• testsuite/tests/interface-stability/base-exports.stdout-ws-32
• testsuite/tests/monadfail/MonadFailErrors.stderr
• testsuite/tests/overloadedrecflds/should_fail/T26480b.stderr
• testsuite/tests/parser/should_fail/RecordDotSyntaxFail10.stderr
• testsuite/tests/parser/should_fail/RecordDotSyntaxFail11.stderr
• testsuite/tests/parser/should_fail/RecordDotSyntaxFail9.stderr
• testsuite/tests/partial-sigs/should_compile/SplicesUsed.stderr
• 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/plugins/Makefile
• + testsuite/tests/plugins/T24486-plugin/Makefile
• + testsuite/tests/plugins/T24486-plugin/Setup.hs
• + testsuite/tests/plugins/T24486-plugin/T24486-plugin.cabal
• + testsuite/tests/plugins/T24486-plugin/T24486_Plugin.hs
• + testsuite/tests/plugins/T24486.hs
• + testsuite/tests/plugins/T24486_Helper.hs
• testsuite/tests/plugins/all.T
• testsuite/tests/plugins/test-defaulting-plugin.stderr
• testsuite/tests/polykinds/T15789.stderr
• testsuite/tests/polykinds/T18451.stderr
• testsuite/tests/polykinds/T7328.stderr
• testsuite/tests/printer/T17697.stderr
• testsuite/tests/profiling/should_run/callstack001.stdout
• testsuite/tests/rebindable/rebindable6.stderr
• testsuite/tests/rep-poly/RepPolyRecordUpdate.stderr
• testsuite/tests/runghc/Makefile
• + testsuite/tests/runghc/T16145.hs
• + testsuite/tests/runghc/T16145.stdout
• + testsuite/tests/runghc/T16145_aux.hs
• testsuite/tests/runghc/all.T
• 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/ExpansionQLIm.hs
• testsuite/tests/typecheck/should_compile/T14590.stderr
• testsuite/tests/typecheck/should_compile/T25180.stderr
• testsuite/tests/typecheck/should_compile/all.T
• testsuite/tests/typecheck/should_compile/free_monad_hole_fits.stderr
• testsuite/tests/typecheck/should_compile/valid_hole_fits.stderr
• testsuite/tests/typecheck/should_fail/DoExpansion1.stderr
• testsuite/tests/typecheck/should_fail/DoExpansion2.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/T3323.stderr
• testsuite/tests/typecheck/should_fail/T3613.stderr
• testsuite/tests/typecheck/should_fail/T6069.stderr
• testsuite/tests/typecheck/should_fail/T7851.stderr
• testsuite/tests/typecheck/should_fail/T7857.stderr
• testsuite/tests/typecheck/should_fail/T8603.stderr
• testsuite/tests/typecheck/should_fail/T9612.stderr
• testsuite/tests/typecheck/should_fail/tcfail102.stderr
• testsuite/tests/typecheck/should_fail/tcfail128.stderr
• testsuite/tests/typecheck/should_fail/tcfail140.stderr
• testsuite/tests/typecheck/should_fail/tcfail181.stderr
• utils/check-exact/ExactPrint.hs
• utils/check-exact/Parsers.hs
• utils/check-exact/Transform.hs
• utils/check-exact/Utils.hs
• utils/haddock/haddock-api/src/Haddock/Backends/Hyperlinker/Parser.hs
• utils/haddock/haddock-api/src/Haddock/Backends/Xhtml/Utils.hs
• utils/haddock/haddock-api/src/Haddock/GhcUtils.hs

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