summaryrefslogtreecommitdiff
path: root/docs/users_guide
Commit message (Collapse)AuthorAgeFilesLines
* User's Guide: KnownNat evidence is Naturalwip/known-nat-docsVladislav Zavialov2020-06-141-6/+9
| | | | | This bit of documentation got outdated after commit 1fcede43d2b30f33b7505e25eb6b1f321be0407f
* Release Notes: Add news from the pattern-match checker [skip ci]wip/pmcheck-release-notes-8.12Sebastian Graf2020-06-111-0/+13
|
* Fix -fkeep-cafs flag name in users guideÖmer Sinan Ağacan2020-06-102-2/+1
|
* Make GADT constructors adhere to the forall-or-nothing rule properlyRyan Scott2020-06-093-0/+215
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Issue #18191 revealed that the types of GADT constructors don't quite adhere to the `forall`-or-nothing rule. This patch serves to clean up this sad state of affairs somewhat. The main change is not in the code itself, but in the documentation, as this patch introduces two sections to the GHC User's Guide: * A "Formal syntax for GADTs" section that presents a BNF-style grammar for what is and isn't allowed in GADT constructor types. This mostly exists to codify GHC's existing behavior, but it also imposes a new restriction that addresses #18191: the outermost `forall` and/or context in a GADT constructor is not allowed to be surrounded by parentheses. Doing so would make these `forall`s/contexts nested, and GADTs do not support nested `forall`s/contexts at present. * A "`forall`-or-nothing rule" section that describes exactly what the `forall`-or-nothing rule is all about. Surprisingly, there was no mention of this anywhere in the User's Guide up until now! To adhere the new specification in the "Formal syntax for GADTs" section of the User's Guide, the following code changes were made: * A new function, `GHC.Hs.Type.splitLHsGADTPrefixTy`, was introduced. This is very much like `splitLHsSigmaTy`, except that it avoids splitting apart any parentheses, which can be syntactically significant for GADT types. See `Note [No nested foralls or contexts in GADT constructors]` in `GHC.Hs.Type`. * `ConDeclGADTPrefixPs`, an extension constructor for `XConDecl`, was introduced so that `GHC.Parser.PostProcess.mkGadtDecl` can return it when given a prefix GADT constructor. Unlike `ConDeclGADT`, `ConDeclGADTPrefixPs` does not split the GADT type into its argument and result types, as this cannot be done until after the type is renamed (see `Note [GADT abstract syntax]` in `GHC.Hs.Decls` for why this is the case). * `GHC.Renamer.Module.rnConDecl` now has an additional case for `ConDeclGADTPrefixPs` that (1) splits apart the full `LHsType` into its `forall`s, context, argument types, and result type, and (2) checks for nested `forall`s/contexts. Step (2) used to be performed the typechecker (in `GHC.Tc.TyCl.badDataConTyCon`) rather than the renamer, but now the relevant code from the typechecker can simply be deleted. One nice side effect of this change is that we are able to give a more accurate error message for GADT constructors that use visible dependent quantification (e.g., `MkFoo :: forall a -> a -> Foo a`), which improves the stderr in the `T16326_Fail6` test case. Fixes #18191. Bumps the Haddock submodule.
* Simple subsumptionwip/T17775Simon Peyton Jones2020-06-052-14/+55
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This patch simplifies GHC to use simple subsumption. Ticket #17775 Implements GHC proposal #287 https://github.com/ghc-proposals/ghc-proposals/blob/master/ proposals/0287-simplify-subsumption.rst All the motivation is described there; I will not repeat it here. The implementation payload: * tcSubType and friends become noticably simpler, because it no longer uses eta-expansion when checking subsumption. * No deeplyInstantiate or deeplySkolemise That in turn means that some tests fail, by design; they can all be fixed by eta expansion. There is a list of such changes below. Implementing the patch led me into a variety of sticky corners, so the patch includes several othe changes, some quite significant: * I made String wired-in, so that "foo" :: String rather than "foo" :: [Char] This improves error messages, and fixes #15679 * The pattern match checker relies on knowing about in-scope equality constraints, andd adds them to the desugarer's environment using addTyCsDs. But the co_fn in a FunBind was missed, and for some reason simple-subsumption ends up with dictionaries there. So I added a call to addTyCsDs. This is really part of #18049. * I moved the ic_telescope field out of Implication and into ForAllSkol instead. This is a nice win; just expresses the code much better. * There was a bug in GHC.Tc.TyCl.Instance.tcDataFamInstHeader. We called checkDataKindSig inside tc_kind_sig, /before/ solveEqualities and zonking. Obviously wrong, easily fixed. * solveLocalEqualitiesX: there was a whole mess in here, around failing fast enough. I discovered a bad latent bug where we could successfully kind-check a type signature, and use it, but have unsolved constraints that could fill in coercion holes in that signature -- aargh. It's all explained in Note [Failure in local type signatures] in GHC.Tc.Solver. Much better now. * I fixed a serious bug in anonymous type holes. IN f :: Int -> (forall a. a -> _) -> Int that "_" should be a unification variable at the /outer/ level; it cannot be instantiated to 'a'. This was plain wrong. New fields mode_lvl and mode_holes in TcTyMode, and auxiliary data type GHC.Tc.Gen.HsType.HoleMode. This fixes #16292, but makes no progress towards the more ambitious #16082 * I got sucked into an enormous refactoring of the reporting of equality errors in GHC.Tc.Errors, especially in mkEqErr1 mkTyVarEqErr misMatchMsg misMatchMsgOrCND In particular, the very tricky mkExpectedActualMsg function is gone. It took me a full day. But the result is far easier to understand. (Still not easy!) This led to various minor improvements in error output, and an enormous number of test-case error wibbles. One particular point: for occurs-check errors I now just say Can't match 'a' against '[a]' rather than using the intimidating language of "occurs check". * Pretty-printing AbsBinds Tests review * Eta expansions T11305: one eta expansion T12082: one eta expansion (undefined) T13585a: one eta expansion T3102: one eta expansion T3692: two eta expansions (tricky) T2239: two eta expansions T16473: one eta determ004: two eta expansions (undefined) annfail06: two eta (undefined) T17923: four eta expansions (a strange program indeed!) tcrun035: one eta expansion * Ambiguity check at higher rank. Now that we have simple subsumption, a type like f :: (forall a. Eq a => Int) -> Int is no longer ambiguous, because we could write g :: (forall a. Eq a => Int) -> Int g = f and it'd typecheck just fine. But f's type is a bit suspicious, and we might want to consider making the ambiguity check do a check on each sub-term. Meanwhile, these tests are accepted, whereas they were previously rejected as ambiguous: T7220a T15438 T10503 T9222 * Some more interesting error message wibbles T13381: Fine: one error (Int ~ Exp Int) rather than two (Int ~ Exp Int, Exp Int ~ Int) T9834: Small change in error (improvement) T10619: Improved T2414: Small change, due to order of unification, fine T2534: A very simple case in which a change of unification order means we get tow unsolved constraints instead of one tc211: bizarre impredicative tests; just accept this for now Updates Cabal and haddock submodules. Metric Increase: T12150 T12234 T5837 haddock.base Metric Decrease: haddock.compiler haddock.Cabal haddock.base Merge note: This appears to break the `UnliftedNewtypesDifficultUnification` test. It has been marked as broken in the interest of merging. (cherry picked from commit 66b7b195cb3dce93ed5078b80bf568efae904cc5)
* docs: Add more details on InterruptibleFFI.Niklas Hambüchen2020-06-041-7/+34
| | | | | Details from https://gitlab.haskell.org/ghc/ghc/issues/8684 and https://github.com/takano-akio/filelock/pull/7#discussion_r280332430
* Improve parser error messages for TypeApplicationsVladislav Zavialov2020-06-011-4/+11
| | | | | | | | | | | | | | With this patch, we always parse f @t as a type application, thereby producing better error messages. This steals two syntactic forms: * Prefix form of the @-operator in expressions. Since the @-operator is a divergence from the Haskell Report anyway, this is not a major loss. * Prefix form of @-patterns. Since we are stealing loose infix form anyway, might as well sacrifice the prefix form for the sake of much better error messages.
* Fix wording in documentationJeremy Schlatter2020-06-011-1/+0
| | | | | The duplicate "orphan instance" phrase here doesn't make sense, and was probably an accident.
* rts: Drop compatibility shims for Windows VistaBen Gamari2020-05-301-0/+3
| | | | | We can now assume that the thread and processor group interfaces are available.
* users-guide: Note change in getNumProcessors in users guideBen Gamari2020-05-302-3/+8
|
* Fix typo in documentationJeremy Schlatter2020-05-291-1/+1
|
* eventlog: Fix racy flushingBen Gamari2020-05-271-0/+6
| | | | | | | | | | | Previously no attempt was made to avoid multiple threads writing their capability-local eventlog buffers to the eventlog writer simultaneously. This could result in multiple eventlog streams being interleaved. Fix this by documenting that the EventLogWriter's write() and flush() functions may be called reentrantly and fix the default writer to protect its FILE* by a mutex. Fixes #18210.
* Make WorkWrap.Lib.isWorkerSmallEnough aware of the old aritySebastian Graf2020-05-261-3/+4
| | | | | | | | | | We should allow a wrapper with up to 82 parameters when the original function had 82 parameters to begin with. I verified that this made no difference on NoFib, but then again it doesn't use huge records... Fixes #18122.
* users-guide: Clarify meaning of -haddock flagBen Gamari2020-05-231-2/+3
| | | | Fixes #18206.
* Implement cstringLength# and FinalPtrAndrew Martin2020-05-231-0/+12
| | | | | | | | | | | | | | | | | | | | This function and its accompanying rule resolve issue #5218. A future PR to the bytestring library will make the internal Data.ByteString.Internal.unsafePackAddress compute string length with cstringLength#. This will improve the status quo because it is eligible for constant folding. Additionally, introduce a new data constructor to ForeignPtrContents named FinalPtr. This additional data constructor, when used in the IsString instance for ByteString, leads to more Core-to-Core optimization opportunities, fewer runtime allocations, and smaller binaries. Also, this commit re-exports all the functions from GHC.CString (including cstringLength#) in GHC.Exts. It also adds a new test driver. This test driver is used to perform substring matches on Core that is dumped after all the simplifier passes. In this commit, it is used to check that constant folding of cstringLength# works.
* docs: fix formatting and add some linksAdam Sandberg Ericsson2020-05-232-45/+51
| | | | [skip ci]
* Clarify pitfalls of NegativeLiterals; see #18022.Galen Huntington2020-05-211-7/+15
|
* Fix spelling mistakes and typosbuggymcbugfix2020-05-211-1/+1
|
* Update documentation for GHCi :scriptStefan Holdermans2020-05-212-3/+8
| | | | | | | | | This patch adds the fixes that allow for file names containing spaces to be passed to GHCi's ':script' command to the release notes for 8.12 and expands the user-guide documentation for ':script' by mentioning how such file names can be passed. Related to #18027.
* gitlab-ci: Set locale to C.UTF-8.Gleb Popov2020-05-211-1/+1
|
* Refactor linear reg alloc to remember past assignments.Andreas Klebinger2020-05-212-4/+24
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | When assigning registers we now first try registers we assigned to in the past, instead of picking the "first" one. This is in extremely helpful when dealing with loops for which variables are dead for part of the loop. This is important for patterns like this: foo = arg1 loop: use(foo) ... foo = getVal() goto loop; There we: * assign foo to the register of arg1. * use foo, it's dead after this use as it's overwritten after. * do other things. * look for a register to put foo in. If we pick an arbitrary one it might differ from the register the start of the loop expect's foo to be in. To fix this we simply look for past register assignments for the given variable. If we find one and the register is free we use that register. This reduces the need for fixup blocks which match the register assignment between blocks. In the example above between the end and the head of the loop. This patch also moves branch weight estimation ahead of register allocation and adds a flag to control it (cmm-static-pred). * It means the linear allocator is more likely to assign the hotter code paths first. * If it assign these first we are: + Less likely to spill on the hot path. + Less likely to introduce fixup blocks on the hot path. These two measure combined are surprisingly effective. Based on nofib we get in the mean: * -0.9% instructions executed * -0.1% reads/writes * -0.2% code size. * -0.1% compiler allocations. * -0.9% compile time. * -0.8% runtime. Most of the benefits are simply a result of removing redundant moves and spills. Reduced compiler allocations likely are the result of less code being generated. (The added lookup is mostly non-allocating).
* Explicit SpecificityGert-Jan Bottu2020-05-212-0/+84
| | | | | | | | | | | | | | | | | | | | Implementation for Ticket #16393. Explicit specificity allows users to manually create inferred type variables, by marking them with braces. This way, the user determines which variables can be instantiated through visible type application. The additional syntax is included in the parser, allowing users to write braces in type variable binders (type signatures, data constructors etc). This information is passed along through the renamer and verified in the type checker. The AST for type variable binders, data constructors, pattern synonyms, partial signatures and Template Haskell has been updated to include the specificity of type variables. Minor notes: - Bumps haddock submodule - Disables pattern match checking in GHC.Iface.Type with GHC 8.8
* Tweak man page for ghc commandTakenobu Tani2020-05-132-1/+6
| | | | | | | | | | This commit updates the ghc command's man page as followings: * Enable `man_show_urls` to show URL addresses in the `DESCRIPTION` section of ghc.rst, because sphinx currently removes hyperlinks for man pages. * Add a `SEE ALSO` section to point to the GHC homepage
* fix(documentation): Fix the RST links to GHC.PrimHécate2020-05-133-5/+4
|
* doc: Reformulate the opening paragraph of Ch. 4 in User's guideIvan-Yudin2020-05-131-9/+11
| | | | | | | | | Removes mentioning of Hugs (it is not helpful for new users anymore). Changes the wording for the rest of the paragraph. Fixes #18132.
* users-guide: Add discussion of shared object namingBen Gamari2020-05-132-1/+10
| | | | Fixes #18074.
* Fix Haskell98 short description in documentationDenisFrezzato2020-05-051-1/+1
|
* Remove references to -package-keySylvain Henry2020-05-052-14/+3
| | | | | | | | * remove references to `-package-key` which has been removed in 2016 (240ddd7c39536776e955e881d709bbb039b48513) * remove support for `-this-package-key` which has been deprecated at the same time
* Remove custom ExceptionMonad class (#18075) (updating haddock submodule ↵Artem Pelenitsyn2020-05-041-0/+8
| | | | accordingly)
* users guide: Add documentation for non-moving GC eventsBen Gamari2020-05-031-0/+79
|
* users guide: Move eventlog documentation users guideBen Gamari2020-05-033-55/+576
|
* rts: Enable tracing of nonmoving heap census with -lnBen Gamari2020-05-031-0/+4
| | | | | Previously this was not easily available to the user. Fix this. Non-moving collection lifecycle events are now reported with -lg.
* Document BlockArguments/LambdaCase support in arrow notationAlexis King2020-04-302-1/+22
|
* llvmGen: Remove -fast-llvm flagBen Gamari2020-04-221-1/+0
| | | | | | | | | | | | | | | | | | | | | | Issue #18076 drew my attention to the undocumented `-fast-llvm` flag for the LLVM code generator introduced in 22733532171330136d87533d523f565f2a4f102f. Speaking to Moritz about this, the motivation for this flag was to avoid potential incompatibilities between LLVM and the assembler/linker toolchain by making LLVM responsible for machine-code generation. Unfortunately, this cannot possibly work: the LLVM backend's mangler performs a number of transforms on the assembler generated by LLVM that are necessary for correctness. These are currently: * mangling Haskell functions' symbol types to be `object` instead of `function` on ELF platforms (necessary for tables-next-to-code) * mangling AVX instructions to ensure that we don't assume alignment (which LLVM otherwise does) * mangling Darwin's subsections-via-symbols directives Given that these are all necessary I don't believe that we can support `-fast-llvm`. Let's rather remove it.
* Add "ddump-cmm-opt" as alias for "ddump-opt-cmm".Andreas Klebinger2020-04-221-1/+7
|
* Do eager instantation in termsSimon Peyton Jones2020-04-221-0/+10
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This patch implements eager instantiation, a small but critical change to the type inference engine, #17173. The main change is this: When inferring types, always return an instantiated type (for now, deeply instantiated; in future shallowly instantiated) There is more discussion in https://www.tweag.io/posts/2020-04-02-lazy-eager-instantiation.html There is quite a bit of refactoring in this patch: * The ir_inst field of GHC.Tc.Utils.TcType.InferResultk has entirely gone. So tcInferInst and tcInferNoInst have collapsed into tcInfer. * Type inference of applications, via tcInferApp and tcInferAppHead, are substantially refactored, preparing the way for Quick Look impredicativity. * New pure function GHC.Tc.Gen.Expr.collectHsArgs and applyHsArgs are beatifully dual. We can see the zipper! * GHC.Tc.Gen.Expr.tcArgs is now much nicer; no longer needs to return a wrapper * In HsExpr, HsTypeApp now contains the the actual type argument, and is used in desugaring, rather than putting it in a mysterious wrapper. * I struggled a bit with good error reporting in Unify.matchActualFunTysPart. It's a little bit simpler than before, but still not great. Some smaller things * Rename tcPolyExpr --> tcCheckExpr tcMonoExpr --> tcLExpr * tcPatSig moves from GHC.Tc.Gen.HsType to GHC.Tc.Gen.Pat Metric Decrease: T9961 Reduction of 1.6% in comiler allocation on T9961, I think.
* docs: drop note about not supporting shared libraries on unix systemsAdam Sandberg Ericsson2020-04-211-2/+0
| | | | [skip ci]
* Modules (#13009)Sylvain Henry2020-04-181-1/+1
| | | | | | | | | | | | | | * SysTools * Parser * GHC.Builtin * GHC.Iface.Recomp * Settings Update Haddock submodule Metric Decrease: Naperian parsing001
* Use conLikeUserTyVarBinders to quantify field selector typesRyan Scott2020-04-126-2/+162
| | | | | | | | | | | | | This patch: 1. Writes up a specification for how the types of top-level field selectors should be determined in a new section of the GHC User's Guide, and 2. Makes GHC actually implement that specification by using `conLikeUserTyVarBinders` in `mkOneRecordSelector` to preserve the order and specificity of type variables written by the user. Fixes #18023.
* Implement extensible interface filesJosh Meredith2020-04-121-0/+27
|
* Modules: type-checker (#13009)Sylvain Henry2020-04-071-4/+4
| | | | Update Haddock submodule
* Add outputable instances for the types in GHC.Iface.Ext.Types, add -ddump-hieZubin Duggal2020-04-031-0/+6
| | | | | | | | | | | | | | | | | flag to dump pretty printed contents of the .hie file Metric Increase: hie002 Because of the regression on i386: compile_time/bytes allocated increased from i386-linux-deb9 baseline @ HEAD~10: Expected hie002 (normal) compile_time/bytes allocated: 583014888.0 +/-10% Lower bound hie002 (normal) compile_time/bytes allocated: 524713399 Upper bound hie002 (normal) compile_time/bytes allocated: 641316377 Actual hie002 (normal) compile_time/bytes allocated: 877986292 Deviation hie002 (normal) compile_time/bytes allocated: 50.6 % *** unexpected stat test failure for hie002(normal)
* Update "GHC differences to the FFI Chapter" in user guide.Andreas Klebinger2020-03-191-15/+35
| | | | | | | | | The old entry had a heavy focus on how things had been. Which is not what I generally look for in a user guide. I also added a small section on behaviour of nested safe ffi calls. [skip-ci]
* Add release note about fix to #16502.Richard Eisenberg2020-03-181-0/+17
| | | | | | We thought we needed to update the manual, but the fix for #16502 actually brings the implementation in line with the manual. So we just alert users of how to update their code.
* Fix #17021 by checking more return kindsRichard Eisenberg2020-03-171-0/+71
| | | | | | | | | | All the details are in new Note [Datatype return kinds] in TcTyClsDecls. Test case: typecheck/should_fail/T17021{,b} typecheck/should_compile/T17021a Updates haddock submodule
* Document the units of -ddump-timingsMaximilian Tagher2020-03-171-0/+1
| | | | | | | | | | | | | | | | | | | | | | | | Right now, in the output of -ddump-timings to a file, you can't tell what the units are: ``` CodeGen [TemplateTestImports]: alloc=22454880 time=14.597 ``` I believe bytes/milliseconds are the correct units, but confirmation would be appreciated. I'm basing it off of this snippet from `withTiming'`: ``` when (verbosity dflags >= 2 && prtimings == PrintTimings) $ liftIO $ logInfo dflags (defaultUserStyle dflags) (text "!!!" <+> what <> colon <+> text "finished in" <+> doublePrec 2 time <+> text "milliseconds" <> comma <+> text "allocated" <+> doublePrec 3 (realToFrac alloc / 1024 / 1024) <+> text "megabytes") ``` which implies time is in milliseconds, and allocations in bytes (which divided by 1024 would be KB, and again would be MB)
* Add a -no-haddock flag.Judah Jacobson2020-03-152-1/+20
| | | | | | | | This flag undoes the effect of a previous "-haddock" flag. Having both flags makes it easier for build systems to enable Haddock parsing in a set of global flags, but then disable it locally for specific targets (e.g., third-party packages whose comments don't pass the validation in the latest GHC). I added the flag to expected-undocumented-flags.txt since `-haddock` was alreadyin that list.
* Document restriction on SCC pragma syntaxKrzysztof Gogolewski2020-03-151-1/+1
| | | | | | | Currently, the names of cost centres must be quoted or be lowercase identifiers. Fixes #17916.
* Use correct option name (-opti) (fix #17314)Sylvain Henry2020-03-142-8/+4
| | | | s/pgmo/opti
* Fixed a minor typo in codegen.rstGreg Steuck2020-03-111-1/+1
|
View Lorry Controller Status