Rodrigo Mesquita pushed to branch wip/romes/ast-ohne-faststring at Glasgow Haskell Compiler / GHC Commits: 789bdc71 by Rodrigo Mesquita at 2026-07-01T10:24:46+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 - - - - - 97 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/Backends/Xhtml/Names.hs - utils/haddock/haddock-api/src/Haddock/Convert.hs - utils/haddock/haddock-api/src/Haddock/GhcUtils.hs - utils/haddock/haddock-api/src/Haddock/Interface/AttachInstances.hs - utils/haddock/haddock-api/src/Haddock/Interface/Create.hs - utils/haddock/haddock-api/src/Haddock/Interface/LexParseRn.hs The diff was not included because it is too large. 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