[Git][ghc/ghc][wip/24279] 16 commits: Preserve user-written kinds in data declarations

Simon Peyton Jones pushed to branch wip/24279 at Glasgow Haskell Compiler / GHC Commits: 3c2f4bb4 by sheaf at 2025-11-11T11:47:28-05:00 Preserve user-written kinds in data declarations This commit ensures that we preserve the user-written kind for data declarations, e.g. in type T2T = Type -> Type type D :: T2T data D a where { .. } that we preserve the user-written kind of D as 'T2T', instead of expanding the type synonym 'T2T' during kind checking. We do this by storing 'tyConKind' separately from 'tyConResKind'. This means that 'tyConKind' is not necessarily equal to 'mkTyConKind binders res_kind', as e.g. in the above example the former is 'T2T' while the latter is 'Type -> Type'. This is explained in Note [Preserve user-written TyCon kind] in GHC.Core.TyCon. This is particularly important for Haddock, as the kinds stored in interface files affect the generated documentation, and we want to preserve the user-written types as much as possible. - - - - - 19859584 by sheaf at 2025-11-11T11:47:28-05:00 Store user-written datacon tvs in interface files This commit ensures we store the user-written quantified type variables of data constructors in interface files, e.g. in data D a where MkD1 :: forall x. x -> D x MkD2 :: forall u v. u -> v -> D v The previous behaviour was to rename the universal variables to match the universal variables of the data constructor. This was undesirable because the names that end up in interface files end up mattering for generated Haddock documentation; it's better to preserve the user-written type variables. Moreover, the universal variables may not have been user-written at all, e.g. in an example such as: type T2T = Type -> Type data G :: T2T where MkG :: forall x. D x Here GHC will invent the type variable name 'a' for the first binder of the TyCon G. We really don't want to then rename the user-written 'x' into the generated 'a'. - - - - - 034b2056 by sheaf at 2025-11-11T11:47:28-05:00 DataCon univ_tvs names: pick TyCon over inferred This commit changes how we compute the names of universal type variables in GADT data constructors. This augments the existing logic that chose which type variable name to use, in GHC.Tc.TyCl.mkGADTVars. We continue to prefer DataCon tv names for user-written binders, but we now prefer TyCon tv names for inferred (non-user-written) DataCon binders. This makes a difference in examples such as: type (:~~:) :: k1 -> k2 -> Type data a :~~: b where HRefl :: a :~~: a Before this patch, we ended up giving HRefl the type: forall {k2}. forall (a :: k2). a :~~: a whereas we now give it the type: forall {k1}. forall (a :: k1). a :~~: a The important part isn't really 'k1' or 'k2', but more that the inferred type variable names of the DataCon can be arbitrary/unpredictable (as they are chosen by GHC and depend on how unification proceeds), so it's much better to use the more predictable TyCon type variable names. - - - - - 95078d00 by sheaf at 2025-11-11T11:47:28-05:00 Backpack Rename: use explicit record construction This commit updates the Backpack boilerplate in GHC.Iface.Rename to use explicit record construction rather than record update. This makes sure that the code stays up to date when the underlying constructors change (e.g. new fields are added). The rationale is further explained in Note [Prefer explicit record construction]. - - - - - 2bf36263 by sheaf at 2025-11-11T11:47:28-05:00 Store # eta binders in TyCon and use for Haddock This commit stores the number of TyCon binders that were introduced by eta-expansion (by the function GHC.Tc.Gen.HsType.splitTyConKind). This is then used to pretty-print the TyCon as the user wrote it, e.g. for type Effect :: (Type -> Type) -> Type -> Type data State s :: Effect where {..} -- arity 3 GHC will eta-expand the data declaration to data State s a b where {..} but also store in the 'TyCon' that the number of binders introduced by this eta expansion is 2. This allows us, in 'Haddock.Convert.synifyTyConKindSig', to recover the original user-written syntax, preserving the user's intent in Haddock documentation. See Note [Inline kind signatures with GADTSyntax] in Haddock.Convert. - - - - - 6c91582f by Matthew Pickering at 2025-11-11T11:48:12-05:00 driver: Properly handle errors during LinkNode steps Previously we were not properly catching errors during the LinkNode step (see T9930fail test). This is fixed by wrapping the `LinkNode` action in `wrapAction`, the same handler which is used for module compilation. Fixes #26496 - - - - - e1e1eb32 by Matthew Pickering at 2025-11-11T11:48:54-05:00 driver: Remove unecessary call to hscInsertHPT This call was left-over from e9445c013fbccf9318739ca3d095a3e0a2e1be8a If you follow the functions which call `upsweep_mod`, they immediately add the interface to the HomePackageTable when `upsweep_mod` returns. - - - - - b22777d4 by ARATA Mizuki at 2025-11-11T11:49:44-05:00 LLVM backend: Pass the +evex512 attribute to LLVM 18+ if -mavx512f is set The newer LLVM requires the +evex512 attribute to enable use of ZMM registers. LLVM exhibits a backward-compatible behavior if the cpu is `x86-64`, but not if `penryn`. Therefore, on macOS, where the cpu is set to `penryn`, we need to explicitly pass +evex512. Fixes #26410 - - - - - 6ead7d06 by Vladislav Zavialov at 2025-11-11T11:50:26-05:00 Comments only in GHC.Parser.PostProcess.Haddock Remove outdated Note [Register keyword location], as the issue it describes was addressed by commit 05eb50dff2fcc78d025e77b9418ddb369db49b9f. - - - - - 43fa8be8 by sheaf at 2025-11-11T11:51:18-05:00 localRegistersConflict: account for assignment LHS This commit fixes a serious oversight in GHC.Cmm.Sink.conflicts, specifically the code that computes which local registers conflict between an assignment and a Cmm statement. If we have: assignment: = <expr> node: = then clearly the two conflict, because we cannot move one statement past the other, as they assign two different values to the same local register. (Recall that 'conflicts (local_reg,expr) node' is False if and only if the assignment 'local_reg = expr' can be safely commuted past the statement 'node'.) The fix is to update 'GHC.Cmm.Sink.localRegistersConflict' to take into account the following two situations: (1) 'node' defines the LHS local register of the assignment, (2) 'node' defines a local register used in the RHS of the assignment. The bug is precisely that we were previously missing condition (1). Fixes #26550 - - - - - 79dfcfe0 by sheaf at 2025-11-11T11:51:18-05:00 Update assigned register format when spilling When we come to spilling a register to put new data into it, in GHC.CmmToAsm.Reg.Linear.allocRegsAndSpill_spill, we need to: 1. Spill the data currently in the register. That is, do a spill with a format that matches what's currently in the register. 2. Update the register assignment, allocating a virtual register to this real register, but crucially **updating the format** of this assignment. Due to shadowing in the Haskell code for allocRegsAndSpill_spill, we were mistakenly re-using the old format. This could lead to a situation where: a. We were using xmm6 to store a Double#. b. We want to store a DoubleX2# into xmm6, so we spill the current content of xmm6 to the stack using a scalar move (correct). c. We update the register assignment, but we fail to update the format of the assignment, so we continue to think that xmm6 stores a Double# and not a DoubleX2#. d. Later on, we need to spill xmm6 because it is getting clobbered by another instruction. We then decide to only spill the lower 64 bits of the register, because we still think that xmm6 only stores a Double# and not a DoubleX2#. Fixes #26542 - - - - - aada5db9 by ARATA Mizuki at 2025-11-11T11:52:07-05:00 Fix the order of spill/reload instructions The AArch64 NCG could emit multiple instructions for a single spill/reload, but their order was not consistent between the definition and a use. Fixes #26537 Co-authored-by: sheaf - - - - - 64ec82ff by Andreas Klebinger at 2025-11-11T11:52:48-05:00 Add hpc to release script - - - - - 741da00c by Ben Gamari at 2025-11-12T03:38:20-05:00 template-haskell: Better describe getQ semantics Clarify that the state is a type-indexed map, as suggested by #26484. - - - - - 8b080e04 by ARATA Mizuki at 2025-11-12T03:39:11-05:00 Fix incorrect markups in the User's Guide * Correct markup for C--: "C-\-" in reST * Fix internal links * Fix code highlighting * Fix inline code: Use ``code`` rather than `code` * Remove extra backslashes Fixes #16812 Co-authored-by: sheaf - - - - - a00840ea by Simon Peyton Jones at 2025-11-14T15:23:56+00:00 Make TYPE and CONSTRAINT apart again This patch finally fixes #24279. * The story started with #11715 * Then #21623 articulated a plan, which made Type and Constraint not-apart; a horrible hack but it worked. The main patch was commit 778c6adca2c995cd8a1b84394d4d5ca26b915dac Author: Simon Peyton Jones Date: Wed Nov 9 10:33:22 2022 +0000 Type vs Constraint: finally nailed * #24279 reported a bug in the above big commit; this small patch fixes it commit af6932d6c068361c6ae300d52e72fbe13f8e1f18 Author: Simon Peyton Jones Date: Mon Jan 8 10:49:49 2024 +0000 Make TYPE and CONSTRAINT not-apart Issue #24279 showed up a bug in the logic in GHC.Core.Unify.unify_ty which is supposed to make TYPE and CONSTRAINT be not-apart. * Then !10479 implemented "unary classes". * That change in turn allows us to make Type and Constraint apart again, cleaning up the compiler and allowing a little bit more expressiveness. It fixes the original hope in #24279, namely that `Type` and `Constraint` should be distinct throughout. - - - - - 121 changed files: - .gitlab/rel_eng/upload_ghc_libs.py - compiler/GHC/Builtin/Types.hs - compiler/GHC/Builtin/Types/Literals.hs - compiler/GHC/Builtin/Types/Prim.hs - compiler/GHC/Cmm/Sink.hs - compiler/GHC/CmmToAsm/Reg/Linear.hs - compiler/GHC/CmmToAsm/Reg/Liveness.hs - compiler/GHC/Core/Coercion.hs - compiler/GHC/Core/Lint.hs - compiler/GHC/Core/RoughMap.hs - compiler/GHC/Core/TyCon.hs - compiler/GHC/Core/Type.hs - compiler/GHC/Core/Unify.hs - compiler/GHC/Driver/Make.hs - compiler/GHC/Driver/Pipeline/Execute.hs - compiler/GHC/Iface/Decl.hs - compiler/GHC/Iface/Rename.hs - compiler/GHC/Iface/Syntax.hs - compiler/GHC/IfaceToCore.hs - compiler/GHC/Parser/PostProcess/Haddock.hs - compiler/GHC/Tc/Gen/HsType.hs - compiler/GHC/Tc/Instance/Class.hs - compiler/GHC/Tc/TyCl.hs - compiler/GHC/Tc/TyCl/Build.hs - compiler/GHC/Tc/TyCl/Instance.hs - docs/users_guide/9.16.1-notes.rst - docs/users_guide/bugs.rst - docs/users_guide/debug-info.rst - docs/users_guide/debugging.rst - docs/users_guide/extending_ghc.rst - docs/users_guide/exts/arrows.rst - docs/users_guide/exts/derive_any_class.rst - docs/users_guide/exts/deriving_extra.rst - docs/users_guide/exts/deriving_inferred.rst - docs/users_guide/exts/deriving_strategies.rst - docs/users_guide/exts/gadt.rst - docs/users_guide/exts/generics.rst - docs/users_guide/exts/overloaded_labels.rst - docs/users_guide/exts/overloaded_strings.rst - docs/users_guide/exts/pattern_synonyms.rst - docs/users_guide/exts/poly_kinds.rst - docs/users_guide/exts/primitives.rst - docs/users_guide/exts/rank_polymorphism.rst - docs/users_guide/exts/rebindable_syntax.rst - docs/users_guide/exts/required_type_arguments.rst - docs/users_guide/exts/scoped_type_variables.rst - docs/users_guide/exts/standalone_deriving.rst - docs/users_guide/exts/template_haskell.rst - docs/users_guide/exts/tuple_sections.rst - docs/users_guide/exts/type_data.rst - 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