Apoorv Ingle pushed to branch wip/spj-apporv-Oct24 at Glasgow Haskell Compiler / GHC

Commits:

• fbf98848
  by Apoorv Ingle at 2026-04-01T18:00:17-05:00

  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>
  

114 changed files:

• compiler/GHC.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/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/Parser/HaddockLex.x
• compiler/GHC/Rename/Expr.hs
• compiler/GHC/Rename/Names.hs
• 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/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/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/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/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-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/SrcLoc.hs
• + compiler/GHC/Unit/State.hs-boot
• compiler/GHC/Utils/Binary.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/ghci/prog-mhu001/prog-mhu001c.stdout
• testsuite/tests/indexed-types/should_fail/T2693.stderr
• testsuite/tests/indexed-types/should_fail/T5439.stderr
• 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/plugins/test-defaulting-plugin.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/typecheck/should_compile/ExpansionQLIm.hs
• testsuite/tests/typecheck/should_compile/T14590.stderr
• testsuite/tests/typecheck/should_compile/all.T
• 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/T13311.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

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