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* Bump template-haskell version to 2.17.0.0Ryan Scott2020-04-141-1/+1
| | | | | | | | | | | | | | | | | | This requires bumping the `exceptions` and `text` submodules to bring in commits that bump their respective upper version bounds on `template-haskell`. Fixes #17645. Fixes #17696. Note that the new `text` commit includes a fair number of additions to the Haddocks in that library. As a result, Haddock has to do more work during the `haddock.Cabal` test case, increasing the number of allocations it requires. Therefore, ------------------------- Metric Increase: haddock.Cabal -------------------------
* Change zipWith to zipWithEqual in a few placesKrzysztof Gogolewski2020-04-1412-21/+28
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* Use conLikeUserTyVarBinders to quantify field selector typesRyan Scott2020-04-124-21/+100
| | | | | | | | | | | | | 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 Meredith2020-04-125-7/+195
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* Significant refactor of LintSimon Peyton Jones2020-04-122-518/+532
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This refactoring of Lint was triggered by #17923, which is fixed by this patch. The main change is this. Instead of lintType :: Type -> LintM LintedKind we now have lintType :: Type -> LintM LintedType Previously, all of typeKind was effectively duplicate in lintType. Moreover, since we have an ambient substitution, we still had to apply the substition here and there, sometimes more than once. It was all very tricky, in the end, and made my head hurt. Now, lintType returns a fully linted type, with all substitutions performed on it. This is much simpler. The same thing is needed for Coercions. Instead of lintCoercion :: OutCoercion -> LintM (LintedKind, LintedKind, LintedType, LintedType, Role) we now have lintCoercion :: Coercion -> LintM LintedCoercion Much simpler! The code is shorter and less bug-prone. There are a lot of knock on effects. But life is now better. Metric Decrease: T1969
* DmdAnal: No need to attach a StrictSig to DataCon workersSebastian Graf2020-04-095-33/+28
| | | | | | | | | | In GHC.Types.Id.Make we were giving a strictness signature to every data constructor wrapper Id that we weren't looking at in demand analysis anyway. We used to use its CPR info, but that has its own CPR signature now. `Note [Data-con worker strictness]` then felt very out of place, so I moved it to GHC.Core.DataCon.
* Special case `isConstraintKindCon` on `AlgTyCon`Sebastian Graf2020-04-093-4/+11
| | | | | | | | | | | | Previously, the `tyConUnique` record selector would unfold into a huge case expression that would be inlined in all call sites, such as the `INLINE`-annotated `coreView`, see #18026. `constraintKindTyConKey` only occurs as the `Unique` of an `AlgTyCon` anyway, so we can make the code a lot more compact, but have to move it to GHC.Core.TyCon. Metric Decrease: T12150 T12234
* Handle promoted data constructors in typeToLHsType correctlyRyan Scott2020-04-081-1/+6
| | | | | | | | Instead of using `nlHsTyVar`, which hardcodes `NotPromoted`, have `typeToLHsType` pick between `Promoted` and `NotPromoted` by checking if a type constructor is promoted using `isPromotedDataCon`. Fixes #18020.
* Make NoExtCon fields strictwip/strict-NoExtConRyan Scott2020-04-0755-692/+106
| | | | | | | | | | | | | | | | This changes every unused TTG extension constructor to be strict in its field so that the pattern-match coverage checker is smart enough any such constructors are unreachable in pattern matches. This lets us remove nearly every use of `noExtCon` in the GHC API. The only ones we cannot remove are ones underneath uses of `ghcPass`, but that is only because GHC 8.8's and 8.10's coverage checkers weren't smart enough to perform this kind of reasoning. GHC HEAD's coverage checker, on the other hand, _is_ smart enough, so we guard these uses of `noExtCon` with CPP for now. Bumps the `haddock` submodule. Fixes #17992.
* Modules: type-checker (#13009)Sylvain Henry2020-04-07181-1709/+1745
| | | | Update Haddock submodule
* simplifier: Kill off ufKeenessFactorBen Gamari2020-04-072-20/+24
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | We used to have another factor, ufKeenessFactor, which would scale the discounts before they were subtracted from the size. This was justified with the following comment: -- We multiple the raw discounts (args_discount and result_discount) -- ty opt_UnfoldingKeenessFactor because the former have to do with -- *size* whereas the discounts imply that there's some extra -- *efficiency* to be gained (e.g. beta reductions, case reductions) -- by inlining. However, this is highly suspect since it means that we subtract a *scaled* size from an absolute size, resulting in crazy (e.g. negative) scores in some cases (#15304). We consequently killed off ufKeenessFactor and bumped up the ufUseThreshold to compensate. Adjustment of unfolding use threshold ===================================== Since this removes a discount from our inlining heuristic, I revisited our default choice of -funfolding-use-threshold to minimize the change in overall inlining behavior. Specifically, I measured runtime allocations and executable size of nofib and the testsuite performance tests built using compilers (and core libraries) built with several values of -funfolding-use-threshold. This comes as a result of a quantitative comparison of testsuite performance and code size as a function of ufUseThreshold, comparing GHC trees using values of 50, 60, 70, 80, 90, and 100. The test set consisted of nofib and the testsuite performance tests. A full summary of these measurements are found in the description of !2608 Comparing executable sizes (relative to the base commit) across all nofib tests, we see that sizes are similar to the baseline: gmean min max median thresh 50 -6.36% -7.04% -4.82% -6.46% 60 -5.04% -5.97% -3.83% -5.11% 70 -2.90% -3.84% -2.31% -2.92% 80 -0.75% -2.16% -0.42% -0.73% 90 +0.24% -0.41% +0.55% +0.26% 100 +1.36% +0.80% +1.64% +1.37% baseline +0.00% +0.00% +0.00% +0.00% Likewise, looking at runtime allocations we see that 80 gives slightly better optimisation than the baseline: gmean min max median thresh 50 +0.16% -0.16% +4.43% +0.00% 60 +0.09% -0.00% +3.10% +0.00% 70 +0.04% -0.09% +2.29% +0.00% 80 +0.02% -1.17% +2.29% +0.00% 90 -0.02% -2.59% +1.86% +0.00% 100 +0.00% -2.59% +7.51% -0.00% baseline +0.00% +0.00% +0.00% +0.00% Finally, I had to add a NOINLINE in T4306 to ensure that `upd` is worker-wrappered as the test expects. This makes me wonder whether the inlining heuristic is now too liberal as `upd` is quite a large function. The same measure was taken in T12600. Wall clock time compiling Cabal with -O0 thresh 50 60 70 80 90 100 baseline build-Cabal 93.88 89.58 92.59 90.09 100.26 94.81 89.13 Also, this change happens to avoid the spurious test output in `plugin-recomp-change` and `plugin-recomp-change-prof` (see #17308). Metric Decrease: hie002 T12234 T13035 T13719 T14683 T4801 T5631 T5642 T9020 T9872d T9961 Metric Increase: T12150 T12425 T13701 T14697 T15426 T1969 T3064 T5837 T6048 T9203 T9872a T9872b T9872c T9872d haddock.Cabal haddock.base haddock.compiler
* Refactoring onlySimon Peyton Jones2020-04-061-25/+36
| | | | | This refactors DictBinds into a data type rather than a pair. No change in behaviour, just better code
* Fix an tricky specialiser loopSimon Peyton Jones2020-04-061-123/+206
| | | | | | | | | | | | | | Issue #17151 was a very tricky example of a bug in which the specialiser accidentally constructs a recurive dictionary, so that everything turns into bottom. I have fixed variants of this bug at least twice before: see Note [Avoiding loops]. It was a bit of a struggle to isolate the problem, greatly aided by the work that Alexey Kuleshevich did in distilling a test case. Once I'd understood the problem, it was not difficult to fix, though it did lead me a bit of refactoring in specImports.
* Don't override proc CafInfos in ticky buildsÖmer Sinan Ağacan2020-04-062-5/+37
| | | | | | | | | | | | | | | | | | | | | | | | | Fixes #17947 When we have a ticky label for a proc, IdLabels for the ticky counter and proc entry share the same Name. This caused overriding proc CafInfos with the ticky CafInfos (i.e. NoCafRefs) during SRT analysis. We now ignore the ticky labels when building SRTMaps. This makes sense because: - When building the current module they don't need to be in SRTMaps as they're initialized as non-CAFFY (see mkRednCountsLabel), so they don't take part in the dependency analysis and they're never added to SRTs. (Reminder: a "dependency" in the SRT analysis is a CAFFY dependency, non-CAFFY uses are not considered as dependencies for the algorithm) - They don't appear in the interfaces as they're not exported, so it doesn't matter for cross-module concerns whether they're in the SRTMap or not. See also the new Note [Ticky labels in SRT analysis].
* Enable ImpredicativeTypes internally when typechecking selector bindingsRyan Scott2020-04-041-0/+28
| | | | | | | | This is necessary for certain record selectors with higher-rank types, such as the examples in #18005. See `Note [Impredicative record selectors]` in `TcTyDecls`. Fixes #18005.
* Revert accidental change in 9462452Ömer Sinan Ağacan2020-04-031-2/+0
| | | | [ci skip]
* Major improvements to the specialiserSimon Peyton Jones2020-04-034-389/+528
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This patch is joint work of Alexis King and Simon PJ. It does some significant refactoring of the type-class specialiser. Main highlights: * We can specialise functions with types like f :: Eq a => a -> Ord b => b => blah where the classes aren't all at the front (#16473). Here we can correctly specialise 'f' based on a call like f @Int @Bool dEqInt x dOrdBool This change really happened in an earlier patch commit 2d0cf6252957b8980d89481ecd0b79891da4b14b Author: Sandy Maguire <sandy@sandymaguire.me> Date: Thu May 16 12:12:10 2019 -0400 work that this new patch builds directly on that work, and refactors it a bit. * We can specialise functions with implicit parameters (#17930) g :: (?foo :: Bool, Show a) => a -> String Previously we could not, but now they behave just like a non-class argument as in 'f' above. * We can specialise under-saturated calls, where some (but not all of the dictionary arguments are provided (#17966). For example, we can specialise the above 'f' based on a call map (f @Int dEqInt) xs even though we don't (and can't) give Ord dictionary. This may sound exotic, but #17966 is a program from the wild, and showed significant perf loss for functions like f, if you need saturation of all dictionaries. * We fix a buglet in which a floated dictionary had a bogus demand (#17810), by using zapIdDemandInfo in the NonRec case of specBind. * A tiny side benefit: we can drop dead arguments to specialised functions; see Note [Drop dead args from specialisations] * Fixed a bug in deciding what dictionaries are "interesting"; see Note [Keep the old dictionaries interesting] This is all achieved by by building on Sandy Macguire's work in defining SpecArg, which mkCallUDs uses to describe the arguments of the call. Main changes: * Main work is in specHeader, which marched down the [InBndr] from the function definition and the [SpecArg] from the call site, together. * specCalls no longer has an arity check; the entire mechanism now handles unders-saturated calls fine. * mkCallUDs decides on an argument-by-argument basis whether to specialise a particular dictionary argument; this is new. See mk_spec_arg in mkCallUDs. It looks as if there are many more lines of code, but I think that all the extra lines are comments!
* Refactor CmmStaticsSylvain Henry2020-04-0326-127/+101
| | | | | | | | | | In !2959 we noticed that there was some redundant code (in GHC.Cmm.Utils and GHC.Cmm.StgToCmm.Utils) used to deal with `CmmStatics` datatype (before SRT generation) and `RawCmmStatics` datatype (after SRT generation). This patch removes this redundant code by using a single GADT for (Raw)CmmStatics.
* Move blob handling into StgToCmmSylvain Henry2020-04-0311-39/+59
| | | | | | | Move handling of big literal strings from CmmToAsm to StgToCmm. It avoids the use of `sdocWithDynFlags` (cf #10143). We might need to move this handling even higher in the pipeline in the future (cf #17960): this patch will make it easier.
* Improve and refactor StgToCmm codegen for DataCons.Andreas Klebinger2020-04-031-77/+170
| | | | | | | | | | | | | | | | We now differentiate three cases of constructor bindings: 1)Bindings which we can "replace" with a reference to an existing closure. Reference the replacement closure when accessing the binding. 2)Bindings which we can "replace" as above. But we still generate a closure which will be referenced by modules importing this binding. 3)For any other binding generate a closure. Then reference it. Before this patch 1) did only apply to local bindings and we didn't do 2) at all.
* Add outputable instances for the types in GHC.Iface.Ext.Types, add -ddump-hieZubin Duggal2020-04-035-47/+101
| | | | | | | | | | | | | | | | | 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)
* Fix two ASSERT buglets in reifyDataConRyan Scott2020-04-021-2/+2
| | | | | | | | | | | | | | | | | | | Two `ASSERT`s in `reifyDataCon` were always using `arg_tys`, but `arg_tys` is not meaningful for GADT constructors. In fact, it's worse than non-meaningful, since using `arg_tys` when reifying a GADT constructor can lead to failed `ASSERT`ions, as #17305 demonstrates. This patch applies the simplest possible fix to the immediate problem. The `ASSERT`s now use `r_arg_tys` instead of `arg_tys`, as the former makes sure to give something meaningful for GADT constructors. This makes the panic go away at the very least. There is still an underlying issue with the way the internals of `reifyDataCon` work, as described in https://gitlab.haskell.org/ghc/ghc/issues/17305#note_227023, but we leave that as future work, since fixing the underlying issue is much trickier (see https://gitlab.haskell.org/ghc/ghc/issues/17305#note_227087).
* Session: Memoize stderrSupportsAnsiColorsBen Gamari2020-04-022-4/+11
| | | | | Not only is this a reasonable efficiency measure but it avoids making reentrant calls into ncurses, which is not thread-safe. See #17922.
* Preserve precise exceptions in strictness analysisSebastian Graf2020-04-023-21/+57
| | | | | | | | | | | Fix #13380 and #17676 by 1. Changing `raiseIO#` to have `topDiv` instead of `botDiv` 2. Give it special treatment in `Simplifier.Util.mkArgInfo`, treating it as if it still had `botDiv`, to recover dead code elimination. This is the first commit of the plan outlined in https://gitlab.haskell.org/ghc/ghc/-/merge_requests/2525#note_260886.
* Re-engineer the binder-swap transformationSimon Peyton Jones2020-04-0215-622/+636
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The binder-swap transformation is implemented by the occurrence analyser -- see Note [Binder swap] in OccurAnal. However it had a very nasty corner in it, for the case where the case scrutinee was a GlobalId. This led to trouble and hacks, and ultimately to #16296. This patch re-engineers how the occurrence analyser implements the binder-swap, by actually carrying out a substitution rather than by adding a let-binding. It's all described in Note [The binder-swap substitution]. I did a few other things along the way * Fix a bug in StgCse, which could allow a loop breaker to be CSE'd away. See Note [Care with loop breakers] in StgCse. I think it can only show up if occurrence analyser sets up bad loop breakers, but still. * Better commenting in SimplUtils.prepareAlts * A little refactoring in CoreUnfold; nothing significant e.g. rename CoreUnfold.mkTopUnfolding to mkFinalUnfolding * Renamed CoreSyn.isFragileUnfolding to hasCoreUnfolding * Move mkRuleInfo to CoreFVs We observed respectively 4.6% and 5.9% allocation decreases for the following tests: Metric Decrease: T9961 haddock.base
* PmCheck: Adjust recursion depth for inhabitation testSebastian Graf2020-04-011-9/+33
| | | | | | | | | | | | | In #17977, we ran into the reduction depth limit of the typechecker. That was only a symptom of a much broader issue: The recursion depth of the coverage checker for trying to instantiate strict fields in the `nonVoid` test was far too high (100, the `defaultMaxTcBound`). As a result, we were performing quite poorly on `T17977`. Short of a proper termination analysis to prove emptyness of a type, we just arbitrarily default to a much lower recursion limit of 3. Fixes #17977.
* Kill wORDS_BIGENDIAN and replace it with platformByteOrder (#17957)Sylvain Henry2020-04-015-83/+80
| | | | | | Metric Decrease: T13035 T1969
* Clean up "Eta reduction for data families" NotesRyan Scott2020-04-017-21/+31
| | | | | | | | | | | | Before, there were two distinct Notes named "Eta reduction for data families". This renames one of them to "Implementing eta reduction for data families" to disambiguate the two and fixes references in other parts of the codebase to ensure that they are pointing to the right place. Fixes #17313. [ci skip]
* Simplify stderrSupportsAnsiColorsÖmer Sinan Ağacan2020-03-311-13/+6
| | | | | The combinator andM is used only once, and the code is shorter and simpler if you inline it.
* Require GHC 8.8 as the minimum compiler for bootstrappingRyan Scott2020-03-3111-48/+9
| | | | | | | | This allows us to remove several bits of CPP that are either always true or no longer reachable. As an added bonus, we no longer need to worry about importing `Control.Monad.Fail.fail` qualified to avoid clashing with `Control.Monad.fail`, since the latter is now the same as the former.
* Minor cleanupKrzysztof Gogolewski2020-03-2910-53/+53
| | | | | | | - Simplify mkBuildExpr, the function newTyVars was called only on a one-element list. - TTG: use noExtCon in more places. This is more future-proof. - In zonkExpr, panic instead of printing a warning.
* Run checkNewDataCon before constraint-solving newtype constructorsRyan Scott2020-03-291-4/+8
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | Within `checkValidDataCon`, we used to run `checkValidType` on the argument types of a newtype constructor before running `checkNewDataCon`, which ensures that the user does not attempt non-sensical things such as newtypes with multiple arguments or constraints. This works out in most situations, but this falls over on a corner case revealed in #17955: ```hs newtype T = Coercible () T => T () ``` `checkValidType`, among other things, peforms an ambiguity check on the context of a data constructor, and that it turn invokes the constraint solver. It turns out that there is a special case in the constraint solver for representational equalities (read: `Coercible` constraints) that causes newtypes to be unwrapped (see `Note [Unwrap newtypes first]` in `TcCanonical`). This special case does not know how to cope with an ill formed newtype like `T`, so it ends up panicking. The solution is surprisingly simple: just invoke `checkNewDataCon` before `checkValidType` to ensure that the illicit newtype constructor context is detected before the constraint solver can run amok with it. Fixes #17955.
* Store ComponentId detailsSylvain Henry2020-03-2913-91/+168
| | | | | | | | | | | | | | | | As far as GHC is concerned, installed package components ("units") are identified by an opaque ComponentId string provided by Cabal. But we don't want to display it to users (as it contains a hash) so GHC queries the database to retrieve some infos about the original source package (name, version, component name). This patch caches these infos in the ComponentId itself so that we don't need to provide DynFlags (which contains installed package informations) to print a ComponentId. In the future we want GHC to support several independent package states (e.g. for plugins and for target code), hence we need to avoid implicitly querying a single global package state.
* Demand analysis: simplify the demand for a RHSSimon Peyton Jones2020-03-293-96/+117
| | | | | | | | | | | | | | | | | | | | | Ticket #17932 showed that we were using a stupid demand for the RHS of a let-binding, when the result is a product. This was the result of a "fix" in 2013, which (happily) turns out to no longer be necessary. So I just deleted the code, which simplifies the demand analyser, and fixes #17932. That in turn uncovered that the anticipation of worker/wrapper in CPR analysis was inaccurate, hence the logic that decides whether to unbox an argument in WW was extracted into a function `wantToUnbox`, now consulted by CPR analysis. I tried nofib, and got 0.0% perf changes. All this came up when messing about with !2873 (ticket #17917), but is idependent of it. Unfortunately, this patch regresses #4267 and realised that it is now blocked on #16335.
* Merge GHC.Types.CostCentre.Init into GHC.Driver.CodeOutputSylvain Henry2020-03-294-67/+56
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* Remove GHC.Types.Unique.Map moduleSylvain Henry2020-03-292-207/+0
| | | | This module isn't used anywhere in GHC.
* Modules: Types (#13009)Sylvain Henry2020-03-29410-2293/+2322
| | | | | | | Update Haddock submodule Metric Increase: haddock.compiler
* Use run-time tablesNextToCode in compiler exclusively (#15548)Joachim Breitner2020-03-262-9/+3
| | | | | | | | | | | | | | | | | Summary: - There is no more use of the TABLES_NEXT_TO_CODE CPP macro in `compiler/`. GHCI_TABLES_NEXT_TO_CODE is also removed entirely. The field within `PlatformMisc` within `DynFlags` is used instead. - The field is still not exposed as a CLI flag. We might consider some way to ensure the right RTS / libraries are used before doing that. Original reviewers: Original subscribers: TerrorJack, rwbarton, carter Original Differential Revision: https://phabricator.haskell.org/D5082
* Remove unused `ghciTablesNextToCode` from compiler properJohn Ericson2020-03-261-8/+0
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* DynFlags refactoring IIISylvain Henry2020-03-2545-921/+946
| | | | | | | | | | | | | Use Platform instead of DynFlags when possible: * `tARGET_MIN_INT` et al. replaced with `platformMinInt` et al. * no more DynFlags in PreRules: added a new `RuleOpts` datatype * don't use `wORD_SIZE` in the compiler * make `wordAlignment` use `Platform` * make `dOUBLE_SIZE` a constant Metric Decrease: T13035 T1969
* Do not panic on linker errorsPeter Trommler2020-03-251-3/+5
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* Remove -fkill-absence and -fkill-one-shot flagsSebastian Graf2020-03-253-41/+3
| | | | | They seem to be a benchmarking vestige of the Cardinality paper and probably shouldn't have been merged to HEAD in the first place.
* Use export list of Main module in function TcRnDriver.hs:check_main (Fix #16453)Roland Senn2020-03-252-45/+164
| | | | | | | | | | | | - Provide the export list of the `Main` module as parameter to the `compiler/typecheck/TcRnDriver.hs:check_main` function. - Instead of `lookupOccRn_maybe` call the function `lookupInfoOccRn`. It returns the list `mains_all` of all the main functions in scope. - Select from this list `mains_all` all `main` functions that are in the export list of the `Main` module. - If this new list contains exactly one single `main` function, then typechecking continues. - Otherwise issue an appropriate error message.
* Fix ApplicativeDo regression #17835Josef Svenningsson2020-03-232-19/+36
| | | | | | | A previous fix for #15344 made sure that monadic 'fail' is used properly when translating ApplicativeDo. However, it didn't properly account for when a 'fail' will be inserted which resulted in some programs failing with a type error.
* Fix event message in withTiming'Sergej Jaskiewicz2020-03-201-1/+1
| | | | This typo caused generating 'end' events without the corresponding 'begin' events.
* Update core spec to reflect changes to Core.Richard Eisenberg2020-03-205-12/+65
| | | | | | | | | | | | Key changes: * Adds a new rule for forall-coercions over coercion variables, which was implemented but conspicuously missing from the spec. * Adds treatment for FunCo. * Adds treatment for ForAllTy over coercion variables. * Improves commentary (including restoring a Note lost in 03d4852658e1b7407abb4da84b1b03bfa6f6db3b) in the source. No changes to running code.
* Simplify treatment of heterogeneous equalityRichard Eisenberg2020-03-2017-412/+537
| | | | | | | | | | | | | | | | | | | | | | | | | | Previously, if we had a [W] (a :: k1) ~ (rhs :: k2), we would spit out a [D] k1 ~ k2 and part the W as irreducible, hoping for a unification. But we needn't do this. Instead, we now spit out a [W] co :: k2 ~ k1 and then use co to cast the rhs of the original Wanted. This means that we retain the connection between the spat-out constraint and the original. The problem with this new approach is that we cannot use the casted equality for substitution; it's too like wanteds-rewriting- wanteds. So, we forbid CTyEqCans that mention coercion holes. All the details are in Note [Equalities with incompatible kinds] in TcCanonical. There are a few knock-on effects, documented where they occur. While debugging an error in this patch, Simon and I ran into infelicities in how patterns and matches are printed; we made small improvements. This patch includes mitigations for #17828, which causes spurious pattern-match warnings. When #17828 is fixed, these lines should be removed.
* FastString: fix eager reading of string ptr in hashStrÖmer Sinan Ağacan2020-03-191-7/+13
| | | | | | | | | | | | | | | | | | | | | | | This read causes NULL dereferencing when len is 0. Fixes #17909 In the reproducer in #17909 this bug is triggered as follows: - SimplOpt.dealWithStringLiteral is called with a single-char string ("=" in #17909) - tailFS gets called on the FastString of the single-char string. - tailFS checks the length of the string, which is 1, and calls mkFastStringByteString on the tail of the ByteString, which is an empty ByteString as the original ByteString has only one char. - ByteString's unsafeUseAsCStringLen returns (NULL, 0) for the empty ByteString, which is passed to mkFastStringWith. - mkFastStringWith gets hash of the NULL pointer via hashStr, which fails on empty strings because of this bug.
* Refactoring: use Platform instead of DynFlags when possibleSylvain Henry2020-03-1960-2318/+2530
| | | | | | | | Metric Decrease: ManyConstructors T12707 T13035 T1969
* PmCheck: Use ConLikeSet to model negative infoSebastian Graf2020-03-192-17/+45
| | | | | | | | | | | | In #17911, Simon recognised many warnings stemming from over-long list unions while coverage checking Cabal's `LicenseId` module. This patch introduces a new `PmAltConSet` type which uses a `UniqDSet` instead of an association list for `ConLike`s. For `PmLit`s, it will still use an assocation list, though, because a similar map data structure would entail a lot of busy work. Fixes #17911.
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