Matthew Pickering pushed to branch wip/splice-imports-2025 at Glasgow Haskell Compiler / GHC Commits: 6e59256e by Matthew Pickering at 2025-04-16T16:26:54+01:00 Move -fno-code note into Downsweep module This note was left behind when all the code which referred to it was moved into the GHC.Driver.Downsweep module - - - - - c8365be9 by Matthew Pickering at 2025-04-16T16:30:03+01:00 Implement Explicit Level Imports for Template Haskell This commit introduces the `ExplicitLevelImports` and `ImplicitStagePersistence` language extensions as proposed in GHC Proposal #682. Key Features ------------ - `ExplicitLevelImports` adds two new import modifiers - `splice` and `quote` - allowing precise control over the level at which imported identifiers are available - `ImplicitStagePersistence` (enabled by default) preserves existing path-based cross-stage persistence behavior - `NoImplicitStagePersistence` disables implicit cross-stage persistence, requiring explicit level imports Benefits -------- - Improved compilation performance by reducing unnecessary code generation - Enhanced IDE experience with faster feedback in `-fno-code` mode - Better dependency tracking by distinguishing compile-time and runtime dependencies - Foundation for future cross-compilation improvements This implementation enables the separation of modules needed at compile-time from those needed at runtime, allowing for more efficient compilation pipelines and clearer code organization in projects using Template Haskell. Implementation Notes -------------------- The level which a name is availble at is stored in the 'GRE', in the normal GlobalRdrEnv. The function `greLevels` returns the levels which a specific GRE is imported at. The level information for a 'Name' is computed by `getStageAndBindLevel`. The level validity is checked by `checkCrossStageLifting`. Instances are checked by `checkWellStagedDFun`, which computes the level an instance by calling `checkWellStagedInstanceWhat`, which sees what is available at by looking at the module graph. Modifications to downsweep -------------------------- Code generation is now only enabled for modules which are needed at compile time. See the Note [-fno-code mode] for more information. Uniform error messages for level errors --------------------------------------- All error messages to do with levels are now reported uniformly using the `TcRnBadlyStaged` constructor. Lift derivation changed ----------------------- Derived lift instances will now not generate code with expression quotations. Before: ``` data A = A Int deriving Lift => lift (A x) = [| A $(lift x) |] ``` After: ``` lift (A x) = conE 'A `appE` (lift x) ``` This is because if you attempt to derive `Lift` in a module where `NoImplicitStagePersistence` is enabled, you would get an infinite loop where a constructor was attempted to be persisted using the instance you are currently defining. GHC API Changes --------------- The ModuleGraph now contains additional information about the type of the edges (normal, quote or splice) between modules. This is abstracted using the `ModuleGraphEdge` data type. Fixes #25828 - - - - - 75cb7d70 by Matthew Pickering at 2025-04-16T17:33:46+01:00 Start on docs - - - - - 209 changed files: - compiler/GHC.hs - compiler/GHC/Data/Graph/Directed/Reachability.hs - compiler/GHC/Driver/Backpack.hs - compiler/GHC/Driver/Downsweep.hs - compiler/GHC/Driver/DynFlags.hs - compiler/GHC/Driver/Flags.hs - compiler/GHC/Driver/Make.hs - compiler/GHC/Driver/MakeFile.hs - compiler/GHC/Driver/Pipeline.hs - compiler/GHC/Driver/Pipeline/Execute.hs - compiler/GHC/Hs/ImpExp.hs - compiler/GHC/Iface/Recomp.hs - compiler/GHC/Iface/Tidy.hs - compiler/GHC/Parser.y - compiler/GHC/Parser/Header.hs - compiler/GHC/Parser/Lexer.x - compiler/GHC/Rename/Env.hs - compiler/GHC/Rename/Expr.hs - compiler/GHC/Rename/Names.hs - compiler/GHC/Rename/Splice.hs - compiler/GHC/Runtime/Loader.hs - compiler/GHC/Tc/Deriv/Generate.hs - compiler/GHC/Tc/Errors/Ppr.hs - compiler/GHC/Tc/Errors/Types.hs - compiler/GHC/Tc/Gen/Head.hs - compiler/GHC/Tc/Plugin.hs - compiler/GHC/Tc/Solver/Monad.hs - compiler/GHC/Tc/Types.hs - compiler/GHC/Tc/Types/LclEnv.hs - compiler/GHC/Tc/Utils/Backpack.hs - compiler/GHC/Tc/Utils/Env.hs - compiler/GHC/Tc/Utils/Monad.hs - compiler/GHC/Types/Name/Reader.hs - compiler/GHC/Unit/Home/PackageTable.hs - compiler/GHC/Unit/Module/Deps.hs - compiler/GHC/Unit/Module/Graph.hs - compiler/GHC/Unit/Module/Imported.hs - compiler/GHC/Unit/Module/ModSummary.hs - + compiler/GHC/Unit/Module/Stage.hs - compiler/GHC/Unit/Types.hs - compiler/GHC/Utils/Binary.hs - compiler/GHC/Utils/Outputable.hs - compiler/Language/Haskell/Syntax/ImpExp.hs - compiler/ghc.cabal.in - docs/users_guide/exts/control.rst - docs/users_guide/exts/template_haskell.rst - libraries/base/tests/IO/Makefile - libraries/ghc-internal/src/GHC/Internal/LanguageExtensions.hs - testsuite/tests/ado/ado004.stderr - testsuite/tests/annotations/should_fail/annfail03.stderr - testsuite/tests/annotations/should_fail/annfail04.stderr - testsuite/tests/annotations/should_fail/annfail06.stderr - testsuite/tests/annotations/should_fail/annfail09.stderr - 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testsuite/tests/partial-sigs/should_compile/Meltdown.stderr - testsuite/tests/partial-sigs/should_compile/MonoLocalBinds.stderr - testsuite/tests/partial-sigs/should_compile/NamedTyVar.stderr - testsuite/tests/partial-sigs/should_compile/NamedWildcardInDataFamilyInstanceLHS.stderr - testsuite/tests/partial-sigs/should_compile/NamedWildcardInTypeFamilyInstanceLHS.stderr - testsuite/tests/partial-sigs/should_compile/ParensAroundContext.stderr - testsuite/tests/partial-sigs/should_compile/PatBind.stderr - testsuite/tests/partial-sigs/should_compile/PatBind2.stderr - testsuite/tests/partial-sigs/should_compile/PatternSig.stderr - testsuite/tests/partial-sigs/should_compile/Recursive.stderr - testsuite/tests/partial-sigs/should_compile/ScopedNamedWildcards.stderr - testsuite/tests/partial-sigs/should_compile/ScopedNamedWildcardsGood.stderr - testsuite/tests/partial-sigs/should_compile/ShowNamed.stderr - testsuite/tests/partial-sigs/should_compile/SimpleGen.stderr - testsuite/tests/partial-sigs/should_compile/SkipMany.stderr - 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testsuite/tests/showIface/DocsInHiFile1.stdout - testsuite/tests/showIface/DocsInHiFileTH.stdout - testsuite/tests/showIface/HaddockIssue849.stdout - testsuite/tests/showIface/HaddockOpts.stdout - testsuite/tests/showIface/HaddockSpanIssueT24378.stdout - testsuite/tests/showIface/LanguageExts.stdout - testsuite/tests/showIface/MagicHashInHaddocks.stdout - testsuite/tests/showIface/NoExportList.stdout - testsuite/tests/showIface/PragmaDocs.stdout - testsuite/tests/showIface/ReExports.stdout - + testsuite/tests/splice-imports/ClassA.hs - + testsuite/tests/splice-imports/InstanceA.hs - + testsuite/tests/splice-imports/Makefile - + testsuite/tests/splice-imports/SI01.hs - + testsuite/tests/splice-imports/SI01A.hs - + testsuite/tests/splice-imports/SI02.hs - + testsuite/tests/splice-imports/SI03.hs - + testsuite/tests/splice-imports/SI03.stderr - + testsuite/tests/splice-imports/SI04.hs - + testsuite/tests/splice-imports/SI05.hs - + testsuite/tests/splice-imports/SI05.stderr - + testsuite/tests/splice-imports/SI05A.hs - 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utils/check-exact/ExactPrint.hs - utils/count-deps/Main.hs - utils/haddock/haddock-api/src/Haddock/Backends/Hyperlinker/Parser.hs The diff was not included because it is too large. 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