Rodrigo Mesquita pushed to branch wip/romes/ast-ohne-faststring at Glasgow Haskell Compiler / GHC

Commits:

• 225fc61a
  by Rodrigo Mesquita at 2026-07-01T10:45:41+01:00

  ttg: Using Text over FastString in the AST
  
  To make the AST independent of GHC, this commit replaces usages of
  `FastString` with `HText` in the AST, killing the last edge from
  Language.Haskell.* to GHC.* modules.
  
  Even though we /do/ want to use FastStrings in general -- critically in
  Names or Ids -- there is no particular reason for the FastStrings that
  occur in the AST proper to be FastStrings. Strings in the AST are
  typically unique and don't benefit particularly from being interned
  FastStrings with Uniques for fast comparison.
  
  `HText` is a newtype string wrapper around `Text` which uses GHC's
  Modified UTF-8 encoding exclusively. It is an opaque type, to ensure it
  is only modified and converted in ways which preserve the Modified UTF-8
  encoding in a way that roundtrips (as opposed to losing information,
  which would happen if using bare `Text`).
  
  Modified UTF-8 must be used to represent the Haskell AST because the
  Haskell Report allows surrogate code points. `Text` operations use UTF-8
  proper and replaces surrogates with a placeholder value, thus is
  unsuitable for the AST directly. See the `Language.Haskell.Syntax.Text`
  module header for more details.
  
  Final progress towards #21592
  

94 changed files:

• compiler/GHC/Builtin/Utils.hs
• compiler/GHC/Cmm/CLabel.hs
• compiler/GHC/Core/Ppr.hs
• compiler/GHC/Core/TyCon.hs
• compiler/GHC/Data/FastString.hs
• compiler/GHC/Data/StringBuffer.hs
• compiler/GHC/Driver/Errors/Ppr.hs
• compiler/GHC/Driver/Session.hs
• compiler/GHC/Hs/Decls.hs
• compiler/GHC/Hs/Expr.hs
• compiler/GHC/Hs/Lit.hs
• compiler/GHC/Hs/Type.hs
• compiler/GHC/Hs/Utils.hs
• compiler/GHC/HsToCore.hs
• compiler/GHC/HsToCore/Errors/Types.hs
• compiler/GHC/HsToCore/Expr.hs
• compiler/GHC/HsToCore/Foreign/C.hs
• compiler/GHC/HsToCore/Foreign/JavaScript.hs
• compiler/GHC/HsToCore/Foreign/Wasm.hs
• compiler/GHC/HsToCore/Match.hs
• compiler/GHC/HsToCore/Match/Literal.hs
• compiler/GHC/HsToCore/Pmc/Desugar.hs
• compiler/GHC/HsToCore/Pmc/Solver/Types.hs
• compiler/GHC/HsToCore/Quote.hs
• compiler/GHC/Iface/Syntax.hs
• compiler/GHC/Parser.y
• compiler/GHC/Parser/Errors/Ppr.hs
• compiler/GHC/Parser/Errors/Types.hs
• compiler/GHC/Parser/HaddockLex.x
• compiler/GHC/Parser/Lexer.x
• compiler/GHC/Parser/PostProcess.hs
• compiler/GHC/Rename/Bind.hs
• compiler/GHC/Rename/Env.hs
• compiler/GHC/Rename/HsType.hs
• compiler/GHC/Rename/Module.hs
• compiler/GHC/Rename/Names.hs
• compiler/GHC/Rename/Splice.hs
• compiler/GHC/Rename/Utils.hs
• compiler/GHC/StgToByteCode.hs
• compiler/GHC/StgToCmm/Foreign.hs
• compiler/GHC/StgToCmm/Prim.hs
• compiler/GHC/StgToJS/FFI.hs
• compiler/GHC/Tc/Deriv/Generate.hs
• compiler/GHC/Tc/Deriv/Generics.hs
• compiler/GHC/Tc/Errors.hs
• compiler/GHC/Tc/Errors/Ppr.hs
• compiler/GHC/Tc/Gen/Bind.hs
• compiler/GHC/Tc/Gen/Expr.hs
• compiler/GHC/Tc/Gen/HsType.hs
• 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/Solver/Dict.hs
• compiler/GHC/Tc/TyCl.hs
• compiler/GHC/Tc/TyCl/Utils.hs
• compiler/GHC/Tc/Types/Origin.hs
• compiler/GHC/Tc/Validity.hs
• compiler/GHC/ThToHs.hs
• compiler/GHC/Types/Basic.hs
• compiler/GHC/Types/Error.hs
• compiler/GHC/Types/FieldLabel.hs
• compiler/GHC/Types/ForeignCall.hs
• compiler/GHC/Types/Literal.hs
• compiler/GHC/Types/PkgQual.hs
• compiler/GHC/Types/SourceText.hs
• compiler/GHC/Unit/Module/Warnings.hs
• compiler/GHC/Utils/Binary.hs
• compiler/GHC/Utils/Outputable.hs
• compiler/Language/Haskell/Syntax/Basic.hs
• compiler/Language/Haskell/Syntax/Decls.hs
• compiler/Language/Haskell/Syntax/Decls/Foreign.hs
• compiler/Language/Haskell/Syntax/Expr.hs
• compiler/Language/Haskell/Syntax/Lit.hs
• compiler/Language/Haskell/Syntax/Module/Name.hs
• + compiler/Language/Haskell/Syntax/Text.hs
• compiler/Language/Haskell/Syntax/Type.hs
• compiler/ghc.cabal.in
• testsuite/tests/parser/should_compile/DumpParsedAst.stderr
• testsuite/tests/parser/should_compile/DumpParsedAstComments.stderr
• testsuite/tests/parser/should_compile/DumpRenamedAst.stderr
• testsuite/tests/parser/should_compile/DumpTypecheckedAst.stderr
• + testsuite/tests/parser/should_run/StringStartsWithNull.hs
• + testsuite/tests/parser/should_run/StringStartsWithNull.stdout
• testsuite/tests/parser/should_run/all.T
• testsuite/tests/perf/compiler/hard_hole_fits.stderr
• utils/check-exact/ExactPrint.hs
• utils/check-exact/check-exact.cabal
• utils/haddock/haddock-api/haddock-api.cabal
• utils/haddock/haddock-api/src/Haddock.hs
• utils/haddock/haddock-api/src/Haddock/Backends/Hyperlinker/Parser.hs
• utils/haddock/haddock-api/src/Haddock/Convert.hs
• utils/haddock/haddock-api/src/Haddock/Interface/Create.hs
• utils/haddock/haddock-api/src/Haddock/Interface/LexParseRn.hs

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