- Oct 22, 2019
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This fixes #16512. There are lots of parts of this patch: * The main payload is in FamInst. See Note [Coverage condition for injective type families] there for the overview. But it doesn't fix the bug. * We now bump the reduction depth every time we discharge a CFunEqCan. See Note [Flatten when discharging CFunEqCan] in TcInteract. * Exploration of this revealed a new, easy to maintain invariant for CTyEqCans. See Note [Almost function-free] in TcRnTypes. * We also realized that type inference for injectivity was a bit incomplete. This means we exchanged lookupFlattenTyVar for rewriteTyVar. See Note [rewriteTyVar] in TcFlatten. The new function is monadic while the previous one was pure, necessitating some faff in TcInteract. Nothing too bad. * zonkCt did not maintain invariants on CTyEqCan. It's not worth the bother doing so, so we just transmute CTyEqCans to CNonCanonicals. * The pure unifier was finding the fixpoint of the returned substitution, even when doing one-way matching (in tcUnifyTysWithTFs). Fixed now. Test cases: typecheck/should_fail/T16512{a,b}
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- Oct 17, 2019
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This ensures that all testsuite way names given to `omit_ways`, `only_ways`, etc. are known ways.
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Previously `makefile_test` and `run_command` tests could easily end up in a situation where they wouldn't be run if the user used the `only_ways` modifier. The reason is to build the set of a ways to run the test in we first start with a candidate set determined by the test type (e.g. `makefile_test`, `compile_run`, etc.) and then filter that set with the constraints given by the test's modifiers. `makefile_test` and `run_command` tests' candidate sets were simply `{normal}`, and consequently most uses of `only_ways` would result in the test being never run. To avoid this we rather use all ways as the candidate sets for these test types. This may result in a few more testcases than we would like (given that some `run_command` tests are insensitive to way) but this can be fixed by adding modifiers and we would much rather run too many tests than too few. This fixes #16042 and a number of other tests afflicted by the same issue. However, there were a few cases that required special attention: * `T14028` is currently failing and is therefore marked as broken due to #17300 * `T-signals-child` is fragile in the `threaded1` and `threaded2` ways (tracked in #17307)
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- Oct 16, 2019
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Also refactor things a bit to eliminate repetition.
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This introduces three new modules: - basicTypes/Predicate.hs describes predicates, moving this logic out of Type. Predicates don't really exist in Core, and so don't belong in Type. - typecheck/TcOrigin.hs describes the origin of constraints and types. It was easy to remove from other modules and can often be imported instead of other, scarier modules. - typecheck/Constraint.hs describes constraints as used in the solver. It is taken from TcRnTypes. No work other than module splitting is in this patch. This is the first step toward homogeneous equality, which will rely more strongly on predicates. And homogeneous equality is the next step toward a dependently typed core language.
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It came back to life in 381c3ae3 by mistake.
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In #17343 we saw that we didn't handle the pattern guard `!_ <- undefined` correctly: The `undefined` was never evaluated. Indeed, elaboration failed to insert the invisible type aruments to `undefined`. So `undefined` was trivially a normal-form and in turn never entered. The problem is that we used to infer a sigma-type for the RHS of the guard, the leading qualifiers of which will never be useful in a pattern match situation. Hence we infer a rho-type now. Fixes #17343.
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This is a test for the current algorithm of GHCi command name resolution. I add this test in preparation for updating GHCi command name resolution. For the current algorithm, see https://downloads.haskell.org/ghc/latest/docs/html/users_guide/ghci.html#the-ghci-files
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For backends maintaining the CFG during codegen we can now find loops and their nesting level. This is based on the Cmm CFG and dominator analysis. As a result we can estimate edge frequencies a lot better for methods, resulting in far better code layout. Speedup on nofib: ~1.5% Increase in compile times: ~1.9% To make this feasible this commit adds: * Dominator analysis based on the Lengauer-Tarjan Algorithm. * An algorithm estimating global edge frequences from branch probabilities - In CFG.hs A few static branch prediction heuristics: * Expect to take the backedge in loops. * Expect to take the branch NOT exiting a loop. * Expect integer vs constant comparisons to be false. We also treat heap/stack checks special for branch prediction to avoid them being treated as loops.
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- Oct 15, 2019
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Fixes #17351.
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Issue #17355 occurred because the control flow for `TcValidity.check_valid_inst_head` was structured in such a way that whenever it checked a special, built-in class (like `Generic` or `HasField`), it would skip the most important check of all: `checkValidTypePats`, which rejects nonsense like this: ```hs instance Generic (forall a. a) ``` This fixes the issue by carving out `checkValidTypePats` from `check_valid_inst_head` so that `checkValidTypePats` is always invoked. `check_valid_inst_head` has also been renamed to `check_special_inst_head` to reflect its new purpose of _only_ checking for instances headed by special classes. Fixes #17355.
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The latest installment in my quest to clean up the code in `TcDeriv*`. This time, my sights are set on `TcDerivInfer.inferConstraints`, which infers the context for derived instances. This function is a wee bit awkward at the moment: * It's not terribly obvious from a quick glance, but `inferConstraints` is only ever invoked when using the `stock` or `anyclass` deriving strategies, as the code for inferring the context for `newtype`- or `via`-derived instances is located separately in `mk_coerce_based_eqn`. But there's no good reason for things to be this way, so I moved this code from `mk_coerce_based_eqn` to `inferConstraints` so that everything related to inferring instance contexts is located in one place. * In this process, I discovered that the Haddocks for the auxiliary function `inferConstraintsDataConArgs` are completely wrong. It claims that it handles both `stock` and `newtype` deriving, but this is completely wrong, as discussed above—it only handles `stock`. To rectify this, I renamed this function to `inferConstraintsStock` to reflect its actual purpose and created a new `inferConstraintsCoerceBased` function to specifically handle `newtype` (and `via`) deriving. Doing this revealed some opportunities for further simplification: * Removing the context-inference–related code from `mk_coerce_based_eqn` made me realize that the overall structure of the function is basically identical to `mk_originative_eqn`. In fact, I was easily able to combine the two functions into a single `mk_eqn_from_mechanism` function. As part of this merger, I now invoke `atf_coerce_based_error_checks` from `doDerivInstErrorChecks1`. * I discovered that GHC defined this function: ```hs typeToTypeKind = liftedTypeKind `mkVisFunTy` liftedTypeKind ``` No fewer than four times in different modules. I consolidated all of these definitions in a single location in `TysWiredIn`.
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- Oct 14, 2019
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This is a very cheap job and can catch a number of "easy" failure modes (e.g. missing imports in the compiler). Let's run it first.
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The fixes for these issues both have user-facing consequences, so it would be good to mention them in the release notes for GHC 8.10.1. While I'm in town, also mention `UnboxedSums` in the release notes entry related to `-fobject-code`.
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When the users guide fails to build (as in #17346), a `docs/users_guide/.log` file will be generated with contents that look something like this: ``` WARNING: unknown config value 'latex_paper_size' in override, ignoring /home/rgscott/Software/ghc5/docs/users_guide/ghci.rst:3410: WARNING: u'ghc-flag' reference target not found: -pgmo ?option? /home/rgscott/Software/ghc5/docs/users_guide/ghci.rst:3410: WARNING: u'ghc-flag' reference target not found: -pgmo ?port? Encoding error: 'ascii' codec can't encode character u'\u27e8' in position 132: ordinal not in range(128) The full traceback has been saved in /tmp/sphinx-err-rDF2LX.log, if you want to report the issue to the developers. ``` This definitely should not be checked in to version control, so let's add this to `.gitignore`.
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- Oct 13, 2019
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This commit explicitly adds description about double colon command of GHCi. [skip ci]
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Statements can change the basic block in which instructions are placed during instruction selection. We have to keep track of this switch of the current basic block as we need this information in order to properly update the CFG. This commit implements this change and fixes #17334. We do so by having stmtToInstr return the new block id if a statement changed the basic block.
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- Oct 12, 2019
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GHC has a wonderful-but-delicate mechanism for building recursive dictionaries by adding a goal to the "solved dictionaries" before solving the sub-goals. See Note [Solved dictionaries] in TcSMonad Ticket #17267 showed that if you use this mechanism for local /quantified/ constraints you can get a loop -- or even unsafe coerce. This patch fixes the bug. Specifically * Make TcSMonad.addSolvedDict be conditional on using a /top level/ instance, not a quantified one. * Moreover, we /also/ don't want to add a solved dict for equalities (a~b). * Add lots more comments to Note [Solved dictionaries] to explain the above cryptic stuff. * Extend InstanceWhat to identify those strange built-in equality instances. A couple of other things along the way * Delete the unused Type.isIPPred_maybe. * Stop making addSolvedDict conditional on not being an impolicit parameter. This comes from way back. But it's irrelevant now because IP dicts are never solved via an instance.
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GHC is suposed to uphold the principle that an /inferred/ type for a let-binding should obey the rules for that module. E.g. we should only accept an inferred higher rank type if we have RankNTypes on. But we were failing to check this: TcValidity.checkValidType allowed arbitrary rank for inferred types. This patch fixes the bug. It might in principle cause some breakage, but if so that's good: the user should add RankNTypes and/or a manual signature. (And almost every package has explicit user signatures for all top-level things anyway.) Let's see. Fixes #17213. Metric Decrease: T10370 -
Issue #17339 was caused by using a slightly different version of `newDFunName` for derived instances that, confusingly enough, did not take all arguments to the class into account when generating the `DFun` name. I cannot think of any good reason for doing this, so this patch uses `newDFunName` uniformly for both derived instances and manually written instances alike. Fixes #17339.
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The CI job fails with: +++ rts/T13676.run/T13676.run.stderr.normalised 2019-10-09 12:27:56.000000000 -0700 @@ -0,0 +1,4 @@ +dyld: Library not loaded: @rpath/libHShaskeline-0.7.5.0-ghc8.9.0.20191009.dylib + Referenced from: /Users/builder/builds/ewzE5N2p/0/ghc/ghc/inplace/lib/bin/ghc + Reason: image not found +*** Exception: readCreateProcess: '/Users/builder/builds/ewzE5N2p/0/ghc/ghc/inplace/lib/bin/ghc' '-B/Users/builder/builds/ewzE5N2p/0/ghc/ghc/inplace/lib' '-e' ''/''$'/'' == '/''/x0024'/''' +RTS '-tT13676.t' (exit -6): failed Unable to reproduce locally.
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- No need to distinguish between gcc-llvm and clang. First of all, gcc-llvm is quite old and surely unmaintained by now. Second of all, none of the code actually care about that distinction! Now, it does make sense to consider C multiple frontends for LLVMs in the form of clang vs clang-cl (same clang, yes, but tweaked interface). But this is better handled in terms of "gccish vs mvscish" and "is LLVM", yielding 4 combinations. Therefore, I don't think it is useful saving the existing code for that. - Get the remaining CC_LLVM_BACKEND, and also TABLES_NEXT_TO_CODE in mk/config.h the normal way, rather than hacking it post-hoc. No point keeping these special cases around for now reason. - Get rid of hand-rolled `die` function and just use `AC_MSG_ERROR`. - Abstract check + flag override for unregisterised and tables next to code. Oh, and as part of the above I also renamed/combined some variables where it felt appropriate. - GccIsClang -> CcLlvmBackend. This is for `AC_SUBST`, like the other Camal case ones. It was never about gcc-llvm, or Apple's renamed clang, to be clear. - llvm_CC_FLAVOR -> CC_LLVM_BACKEND. This is for `AC_DEFINE`, like the other all-caps snake case ones. llvm_CC_FLAVOR was just silly indirection *and* an odd name to boot.
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Fixes #17286.
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Simon realised that the simple language composed of let bindings, bang patterns and flat constructor patterns is enough to capture the semantics of the source pattern language that are important for pattern-match checking. Well, given that the Oracle is smart enough to connect the dots in this less informationally dense form, which it is now. So we transform `translatePat` to return a list of `PmGrd`s relative to an incoming match variable. `pmCheck` then trivially translates each of the `PmGrd`s into constraints that the oracle understands. Since we pass in the match variable, we incidentally fix #15884 (coverage checks for view patterns) through an interaction with !1746.
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- Oct 09, 2019
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If you derive an instance like this: ```hs deriving <...> instance Foo C ``` And the data constructors for `C` aren't in scope, then `doDerivInstErrorChecks1` throws an error. Moreover, it will _only_ throw an error if `<...>` is either `stock` or `newtype`. This is because the code that the `anyclass` or `via` strategies would generate would not require the use of the data constructors for `C`. However, `doDerivInstErrorChecks1` has another purpose. If you write this: ```hs import M (C(MkC1, ..., MkCn)) deriving <...> instance Foo C ``` Then `doDerivInstErrorChecks1` will call `addUsedDataCons` on `MkC1` through `MkCn` to ensure that `-Wunused-imports` does not complain about them. However, `doDerivInstErrorChecks1` was doing this for _every_ deriving strategy, which mean that if `<...>` were `anyclass` or `via`, then the warning about `MkC1` through `MkCn` being unused would be suppressed! The fix is simple enough: only call `addUsedDataCons` when the strategy is `stock` or `newtype`, just like the other code paths in `doDerivInstErrorChecks1`. Fixes #17324.
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This allows the stage1 compiler (which needs to run on the build platform and produce code for the host) to depend upon properties of the target. This is wrong. However, it's no more wrong than it was previously and @Erichson2314 is working on fixing this so I'm going to remove the guard so we can finally bootstrap HEAD with ghc-8.8 (see issue #17146).
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To avoid polluting the macro namespace
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- Oct 08, 2019
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The vanilla COMPLETE set is attached to the representation TyCon of a data family instance, whereas the user-defined COMPLETE sets are attached to the parent data family TyCon itself. Previously, we weren't trying particularly hard to get back to the representation TyCon to the parent data family TyCon, resulting in bugs like #17207. Now we should do much better. Fixes the original issue in #17207, but I found another related bug that isn't so easy to fix.
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