| Commit message (Collapse) | Author | Age | Files | Lines |
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This patch removes the TCvSubst data type and instead uses Subst as
the environment for both term and type level substitution. This
change is partially motivated by the existential type proposal,
which will introduce types that contain expressions and therefore
forces us to carry around an "IdSubstEnv" even when substituting for
types. It also reduces the amount of code because "Subst" and
"TCvSubst" share a lot of common operations. There isn't any
noticeable impact on performance (geo. mean for ghc/alloc is around
0.0% but we have -94 loc and one less data type to worry abount).
Currently, the "TCvSubst" data type for substitution on types is
identical to the "Subst" data type except the former doesn't store
"IdSubstEnv". Using "Subst" for type-level substitution means there
will be a redundant field stored in the data type. However, in cases
where the substitution starts from the expression, using "Subst" for
type-level substitution saves us from having to project "Subst" into a
"TCvSubst". This probably explains why the allocation is mostly even
despite the redundant field.
The patch deletes "TCvSubst" and moves "Subst" and its relevant
functions from "GHC.Core.Subst" into "GHC.Core.TyCo.Subst".
Substitution on expressions is still defined in "GHC.Core.Subst" so we
don't have to expose the definition of "Expr" in the hs-boot file that
"GHC.Core.TyCo.Subst" must import to refer to "IdSubstEnv" (whose
codomain is "CoreExpr"). Most functions named fooTCvSubst are renamed
into fooSubst with a few exceptions (e.g. "isEmptyTCvSubst" is a
distinct function from "isEmptySubst"; the former ignores the
emptiness of "IdSubstEnv"). These exceptions mainly exist for
performance reasons and will go away when "Expr" and "Type" are
mutually recursively defined (we won't be able to take those
shortcuts if we can't make the assumption that expressions don't
appear in types).
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One more step towards the new design of EPA.
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This patch refactors hasFixedRuntimeRep_remainingValArgs, renaming it
to tcRemainingValArgs. The logic is moved to rebuildHsApps, which
ensures consistent behaviour across tcApp and quickLookArg1/tcEValArg.
This patch also refactors the treatment of stupid theta for data
constructors, changing the place we drop stupid theta arguments
from dsConLike to mkDataConRep (now the datacon wrapper drops these
arguments).
We decided not to implement PHASE 2 of the FixedRuntimeRep plan for
these remaining ValArgs. Future directions are outlined on the wiki:
https://gitlab.haskell.org/ghc/ghc/-/wikis/Remaining-ValArgs
Fixes #21544 and #21650
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Replaces uses of `TcRnUnknownMessage` with proper diagnostics
constructors in `GHC.Tc.Gen.Match`, `GHC.Tc.Gen.Pat`, and
`GHC.Tc.Gen.Sig`.
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This commit redefines the structure of Splices in the AST.
We get rid of `HsSplice` which used to represent typed and untyped
splices, quasi quotes, and the result of splicing either an expression,
a type or a pattern.
Instead we have `HsUntypedSplice` which models an untyped splice or a
quasi quoter, which works in practice just like untyped splices.
The `HsExpr` constructor `HsSpliceE` which used to be constructed with
an `HsSplice` is split into `HsTypedSplice` and `HsUntypedSplice`. The
former is directly constructed with an `HsExpr` and the latter now takes
an `HsUntypedSplice`.
Both `HsType` and `Pat` constructors `HsSpliceTy` and `SplicePat` now
take an `HsUntypedSplice` instead of a `HsSplice` (remember only
/untyped splices/ can be spliced as types or patterns).
The result of splicing an expression, type, or pattern is now
comfortably stored in the extension fields `XSpliceTy`, `XSplicePat`,
`XUntypedSplice` as, respectively, `HsUntypedSpliceResult (HsType
GhcRn)`, `HsUntypedSpliceResult (Pat GhcRn)`, and `HsUntypedSpliceResult
(HsExpr GhcRn)`
Overall the TTG extension points are now better used to
make invalid states unrepresentable and model the progression between
stages better.
See Note [Lifecycle of an untyped splice, and PendingRnSplice]
and Note [Lifecycle of an typed splice, and PendingTcSplice] for more
details.
Updates haddock submodule
Fixes #21263
-------------------------
Metric Decrease:
hard_hole_fits
-------------------------
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This patch fixes the unification of concrete type variables.
The subtlety was that unifying concrete metavariables is more subtle
than other metavariables, as decomposition is possible. See the Note
[Unifying concrete metavariables], which explains how we unify a
concrete type variable with a type 'ty' by concretising 'ty', using
the function 'GHC.Tc.Utils.Concrete.concretise'.
This can be used to perform an eager syntactic check for concreteness,
allowing us to remove the IsRefl# special predicate. Instead of emitting
two constraints `rr ~# concrete_tv` and `IsRefl# rr concrete_tv`, we
instead concretise 'rr'. If this succeeds we can fill 'concrete_tv',
and otherwise we directly emit an error message to the typechecker
environment instead of deferring. We still need the error message
to be passed on (instead of directly thrown), as we might benefit from
further unification in which case we will need to zonk the stored types.
To achieve this, we change the 'wc_holes' field of 'WantedConstraints'
to 'wc_errors', which stores general delayed errors. For the moement,
a delayed error is either a hole, or a syntactic equality error.
hasFixedRuntimeRep_MustBeRefl is now hasFixedRuntimeRep_syntactic, and
hasFixedRuntimeRep has been refactored to directly return the most
useful coercion for PHASE 2 of FixedRuntimeRep.
This patch also adds a field ir_frr to the InferResult datatype,
holding a value of type Maybe FRROrigin. When this value is not
Nothing, this means that we must fill the ir_ref field with a type
which has a fixed RuntimeRep.
When it comes time to fill such an ExpType, we ensure that the type
has a fixed RuntimeRep by performing a representation-polymorphism
check with the given FRROrigin
This is similar to what we already do to ensure we fill an Infer
ExpType with a type of the correct TcLevel.
This allows us to properly perform representation-polymorphism checks
on 'Infer' 'ExpTypes'.
The fillInferResult function had to be moved to GHC.Tc.Utils.Unify
to avoid a cyclic import now that it calls hasFixedRuntimeRep.
This patch also changes the code in matchExpectedFunTys to make use
of the coercions, which is now possible thanks to the previous change.
This implements PHASE 2 of FixedRuntimeRep in some situations.
For example, the test cases T13105 and T17536b are now both accepted.
Fixes #21239 and #21325
-------------------------
Metric Decrease:
T18223
T5631
-------------------------
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As #20837 pointed out, `isLiftedType_maybe` returned `Just False` in
many situations where it should return `Nothing`, because it didn't
take into account type families or type variables.
In this patch, we fix this issue. We rename `isLiftedType_maybe` to
`typeLevity_maybe`, which now returns a `Levity` instead of a boolean.
We now return `Nothing` for types with kinds of the form
`TYPE (F a1 ... an)` for a type family `F`, as well as
`TYPE (BoxedRep l)` where `l` is a type variable.
This fix caused several other problems, as other parts of the compiler
were relying on `isLiftedType_maybe` returning a `Just` value, and were
now panicking after the above fix. There were two main situations in
which panics occurred:
1. Issues involving the let/app invariant. To uphold that invariant,
we need to know whether something is lifted or not. If we get an
answer of `Nothing` from `isLiftedType_maybe`, then we don't know
what to do. As this invariant isn't particularly invariant, we
can change the affected functions to not panic, e.g. by behaving
the same in the `Just False` case and in the `Nothing` case
(meaning: no observable change in behaviour compared to before).
2. Typechecking of data (/newtype) constructor patterns. Some programs
involving patterns with unknown representations were accepted, such
as T20363. Now that we are stricter, this caused further issues,
culminating in Core Lint errors. However, the behaviour was
incorrect the whole time; the incorrectness only being revealed by
this change, not triggered by it.
This patch fixes this by overhauling where the representation
polymorphism involving pattern matching are done. Instead of doing
it in `tcMatches`, we instead ensure that the `matchExpected`
functions such as `matchExpectedFunTys`, `matchActualFunTySigma`,
`matchActualFunTysRho` allow return argument pattern types which
have a fixed RuntimeRep (as defined in Note [Fixed RuntimeRep]).
This ensures that the pattern matching code only ever handles types
with a known runtime representation. One exception was that
patterns with an unknown representation type could sneak in via
`tcConPat`, which points to a missing representation-polymorphism
check, which this patch now adds.
This means that we now reject the program in #20363, at least until
we implement PHASE 2 of FixedRuntimeRep (allowing type families in
RuntimeRep positions). The aforementioned refactoring, in which
checks have been moved to `matchExpected` functions, is a first
step in implementing PHASE 2 for patterns.
Fixes #20837
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Co-authored by: Sam Derbyshire
Previously, GHC had three flavours of constraint:
Wanted, Given, and Derived. This removes Derived constraints.
Though serving a number of purposes, the most important role
of Derived constraints was to enable better error messages.
This job has been taken over by the new RewriterSets, as explained
in Note [Wanteds rewrite wanteds] in GHC.Tc.Types.Constraint.
Other knock-on effects:
- Various new Notes as I learned about under-described bits of GHC
- A reshuffling around the AST for implicit-parameter bindings,
with better integration with TTG.
- Various improvements around fundeps. These were caused by the
fact that, previously, fundep constraints were all Derived,
and Derived constraints would get dropped. Thus, an unsolved
Derived didn't stop compilation. Without Derived, this is no
longer possible, and so we have to be considerably more careful
around fundeps.
- A nice little refactoring in GHC.Tc.Errors to center the work
on a new datatype called ErrorItem. Constraints are converted
into ErrorItems at the start of processing, and this allows for
a little preprocessing before the main classification.
- This commit also cleans up the behavior in generalisation around
functional dependencies. Now, if a variable is determined by
functional dependencies, it will not be quantified. This change
is user facing, but it should trim down GHC's strange behavior
around fundeps.
- Previously, reportWanteds did quite a bit of work, even on an empty
WantedConstraints. This commit adds a fast path.
- Now, GHC will unconditionally re-simplify constraints during
quantification. See Note [Unconditionally resimplify constraints when
quantifying], in GHC.Tc.Solver.
Close #18398.
Close #18406.
Solve the fundep-related non-confluence in #18851.
Close #19131.
Close #19137.
Close #20922.
Close #20668.
Close #19665.
-------------------------
Metric Decrease:
LargeRecord
T9872b
T9872b_defer
T9872d
TcPlugin_RewritePerf
-------------------------
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This patch fixes #17469, by improving matters when you use
non-existent field names in a record construction:
data T = MkT { x :: Int }
f v = MkT { y = 3 }
The check is now made in the renamer, in GHC.Rename.Env.lookupRecFieldOcc.
That in turn led to a spurious error in T9975a, which is fixed by
making GHC.Rename.Names.extendGlobalRdrEnvRn fail fast if it finds
duplicate bindings. See Note [Fail fast on duplicate definitions]
in that module for more details.
This patch was originated and worked on by Alex D (@nineonine)
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This was achieved with
git ls-tree --name-only HEAD -r | xargs sed -i -e 's/note \[/Note \[/g'
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The main purpose of this patch is to attach a SkolemInfo directly to
each SkolemTv. This fixes the large number of bugs which have
accumulated over the years where we failed to report errors due to
having "no skolem info" for particular type variables. Now the origin of
each type varible is stored on the type variable we can always report
accurately where it cames from.
Fixes #20969 #20732 #20680 #19482 #20232 #19752 #10946
#19760 #20063 #13499 #14040
The main changes of this patch are:
* SkolemTv now contains a SkolemInfo field which tells us how the
SkolemTv was created. Used when reporting errors.
* Enforce invariants relating the SkolemInfoAnon and level of an implication (ic_info, ic_tclvl)
to the SkolemInfo and level of the type variables in ic_skols.
* All ic_skols are TcTyVars -- Check is currently disabled
* All ic_skols are SkolemTv
* The tv_lvl of the ic_skols agrees with the ic_tclvl
* The ic_info agrees with the SkolInfo of the implication.
These invariants are checked by a debug compiler by
checkImplicationInvariants.
* Completely refactor kcCheckDeclHeader_sig which kept
doing my head in. Plus, it wasn't right because it wasn't skolemising
the binders as it decomposed the kind signature.
The new story is described in Note [kcCheckDeclHeader_sig]. The code
is considerably shorter than before (roughly 240 lines turns into 150
lines).
It still has the same awkward complexity around computing arity as
before, but that is a language design issue.
See Note [Arity inference in kcCheckDeclHeader_sig]
* I added new type synonyms MonoTcTyCon and PolyTcTyCon, and used
them to be clear which TcTyCons have "finished" kinds etc, and
which are monomorphic. See Note [TcTyCon, MonoTcTyCon, and PolyTcTyCon]
* I renamed etaExpandAlgTyCon to splitTyConKind, becuase that's a
better name, and it is very useful in kcCheckDeclHeader_sig, where
eta-expansion isn't an issue.
* Kill off the nasty `ClassScopedTvEnv` entirely.
Co-authored-by: Simon Peyton Jones <simon.peytonjones@gmail.com>
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Previously, it was an error to pattern match on a GADT
without GADTs or TypeFamilies.
This is now allowed. Instead, we check the flag MonoLocalBinds;
if it is not enabled, we issue a warning, controlled by -Wgadt-mono-local-binds.
Also fixes #20485: pattern synonyms are now checked too.
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`Note [The stupid context]` in `GHC.Core.DataCon` talks about stupid contexts
from `DatatypeContexts`, but prior to this commit, it was rather outdated.
This commit spruces it up and references it from places where it is relevant.
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The ghc-exactPrint library has had to re-introduce the relatavise
phase.
This is needed if you change the length of an identifier and want the
layout to be preserved afterwards.
It is not possible to relatavise a bare SrcSpan, so introduce `SrcAnn
NoEpAnns` for them instead.
Updates haddock submodule.
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Close #20443.
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PHASE 1: we never rewrite Concrete# evidence.
This patch migrates all the representation polymorphism checks to
the typechecker, using a new constraint form
Concrete# :: forall k. k -> TupleRep '[]
Whenever a type `ty` must be representation-polymorphic
(e.g. it is the type of an argument to a function), we emit a new
`Concrete# ty` Wanted constraint. If this constraint goes
unsolved, we report a representation-polymorphism error to the user.
The 'FRROrigin' datatype keeps track of the context of the
representation-polymorphism check, for more informative error messages.
This paves the way for further improvements, such as
allowing type families in RuntimeReps and improving the soundness
of typed Template Haskell. This is left as future work (PHASE 2).
fixes #17907 #20277 #20330 #20423 #20426
updates haddock submodule
-------------------------
Metric Decrease:
T5642
-------------------------
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Tickets #20469 and #20470 showed that the current
implementation of arrows is not at all up to the task
of supporting GADTs: GHC produces ill-scoped Core programs
because it doesn't propagate the evidence introduced by a GADT
pattern match.
For the time being, we reject GADT pattern matches in arrow notation.
Hopefully we are able to add proper support for GADTs in arrows
in the future.
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NoGhcTc is removed from HsMatchContext. As a result of this,
HsMatchContext GhcTc is now a valid type that has Id in it,
instead of Name and tcMatchesFun now takes Id instead of Name.
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Fixes #14380, #19997
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This commit tries to untangle the zoo of diagnostic-related functions
in `Tc.Utils.Monad` so that we can have the interfaces mentions only
`TcRnMessage`s while we push the creation of these messages upstream.
It also ports TcRnMessage diagnostics to use the new API, in particular
this commit switch to use TcRnMessage in the external interfaces
of the diagnostic functions, and port the old SDoc to be wrapped
into TcRnUnknownMessage.
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`GHC.Hs.Syn.Type`
The existing `hsPatType`, `hsLPatType` and `hsLitType` functions have also been
moved to this module
This is a less ambitious take on the same problem that !2182 and !3866
attempt to solve. Rather than have the `hsExprType` function attempt to
efficiently compute the `Type` of every subexpression in an `HsExpr`, this
simply computes the overall `Type` of a single `HsExpr`.
- Explicitly forbids the `SplicePat` `HsIPVar`, `HsBracket`, `HsRnBracketOut`
and `HsTcBracketOut` constructors during the typechecking phase by using
`Void` as the TTG extension field
- Also introduces `dataConCantHappen` as a domain specific alternative to `absurd`
to handle cases where the TTG extension points forbid a constructor.
- Turns HIE file generation into a pure function that doesn't need access to the
`DsM` monad to compute types, but uses `hsExprType` instead.
- Computes a few more types during HIE file generation
- Makes GHCi's `:set +c` command also use `hsExprType` instead of going through
the desugarer to compute types.
Updates haddock submodule
Co-authored-by: Zubin Duggal <zubin.duggal@gmail.com>
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This creates new modules GHC.Tc.Solver.InertSet and
GHC.Tc.Solver.Types. The Monad module is still pretty
big, but this is an improvement. Moreover, it means
that GHC.HsToCore.Pmc.Solver.Types no longer depends
on the constraint solver (it now depends on GHC.Tc.Solver.InertSet),
making the error-messages work easier.
This patch thus contributes to #18516.
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This patch is a first step towards a simpler design for exact printing.
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Replace uses of WARN macro with calls to:
warnPprTrace :: Bool -> SDoc -> a -> a
Remove the now unused HsVersions.h
Bump haddock submodule
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There is no reason to use CPP. __LINE__ and __FILE__ macros are now
better replaced with GHC's CallStack. As a bonus, assert error messages
now contain more information (function name, column).
Here is the mapping table (HasCallStack omitted):
* ASSERT: assert :: Bool -> a -> a
* MASSERT: massert :: Bool -> m ()
* ASSERTM: assertM :: m Bool -> m ()
* ASSERT2: assertPpr :: Bool -> SDoc -> a -> a
* MASSERT2: massertPpr :: Bool -> SDoc -> m ()
* ASSERTM2: assertPprM :: m Bool -> SDoc -> m ()
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Metric Increase:
T10370
parsing001
Updates haddock submodule
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This small patch makes pattern synonyms play nicely with CallStack
constraints, using logic explained in GHC.Tc.Gen.Pat
Note [Call-stack tracing of pattern synonyms]
Fixes #19289
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The haddock submodule is also updated so that it understands the changes
to patterns.
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This patch redesigns the flattener to simplify type family applications
directly instead of using flattening meta-variables and skolems. The key new
innovation is the CanEqLHS type and the new CEqCan constraint (Ct). A CanEqLHS
is either a type variable or exactly-saturated type family application; either
can now be rewritten using a CEqCan constraint in the inert set.
Because the flattener no longer reduces all type family applications to
variables, there was some performance degradation if a lengthy type family
application is now flattened over and over (not making progress). To
compensate, this patch contains some extra optimizations in the flattener,
leading to a number of performance improvements.
Close #18875.
Close #18910.
There are many extra parts of the compiler that had to be affected in writing
this patch:
* The family-application cache (formerly the flat-cache) sometimes stores
coercions built from Given inerts. When these inerts get kicked out, we must
kick out from the cache as well. (This was, I believe, true previously, but
somehow never caused trouble.) Kicking out from the cache requires adding a
filterTM function to TrieMap.
* This patch obviates the need to distinguish "blocking" coercion holes from
non-blocking ones (which, previously, arose from CFunEqCans). There is thus
some simplification around coercion holes.
* Extra commentary throughout parts of the code I read through, to preserve
the knowledge I gained while working.
* A change in the pure unifier around unifying skolems with other types.
Unifying a skolem now leads to SurelyApart, not MaybeApart, as documented
in Note [Binding when looking up instances] in GHC.Core.InstEnv.
* Some more use of MCoercion where appropriate.
* Previously, class-instance lookup automatically noticed that e.g. C Int was
a "unifier" to a target [W] C (F Bool), because the F Bool was flattened to
a variable. Now, a little more care must be taken around checking for
unifying instances.
* Previously, tcSplitTyConApp_maybe would split (Eq a => a). This is silly,
because (=>) is not a tycon in Haskell. Fixed now, but there are some
knock-on changes in e.g. TrieMap code and in the canonicaliser.
* New function anyFreeVarsOf{Type,Co} to check whether a free variable
satisfies a certain predicate.
* Type synonyms now remember whether or not they are "forgetful"; a forgetful
synonym drops at least one argument. This is useful when flattening; see
flattenView.
* The pattern-match completeness checker invokes the solver. This invocation
might need to look through newtypes when checking representational equality.
Thus, the desugarer needs to keep track of the in-scope variables to know
what newtype constructors are in scope. I bet this bug was around before but
never noticed.
* Extra-constraints wildcards are no longer simplified before printing.
See Note [Do not simplify ConstraintHoles] in GHC.Tc.Solver.
* Whether or not there are Given equalities has become slightly subtler.
See the new HasGivenEqs datatype.
* Note [Type variable cycles in Givens] in GHC.Tc.Solver.Canonical
explains a significant new wrinkle in the new approach.
* See Note [What might match later?] in GHC.Tc.Solver.Interact, which
explains the fix to #18910.
* The inert_count field of InertCans wasn't actually used, so I removed
it.
Though I (Richard) did the implementation, Simon PJ was very involved
in design and review.
This updates the Haddock submodule to avoid #18932 by adding
a type signature.
-------------------------
Metric Decrease:
T12227
T5030
T9872a
T9872b
T9872c
Metric Increase:
T9872d
-------------------------
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This refactors the GHC AST to remove `HsImplicitBndrs` and replace it with
`HsOuterTyVarBndrs`, a type which records whether the outermost quantification
in a type is explicit (i.e., with an outermost, invisible `forall`) or
implicit. As a result of this refactoring, it is now evident in the AST where
the `forall`-or-nothing rule applies: it's all the places that use
`HsOuterTyVarBndrs`. See the revamped `Note [forall-or-nothing rule]` in
`GHC.Hs.Type` (previously in `GHC.Rename.HsType`).
Moreover, the places where `ScopedTypeVariables` brings lexically scoped type
variables into scope are a subset of the places that adhere to the
`forall`-or-nothing rule, so this also makes places that interact with
`ScopedTypeVariables` easier to find. See the revamped
`Note [Lexically scoped type variables]` in `GHC.Hs.Type` (previously in
`GHC.Tc.Gen.Sig`).
`HsOuterTyVarBndrs` are used in type signatures (see `HsOuterSigTyVarBndrs`)
and type family equations (see `HsOuterFamEqnTyVarBndrs`). The main difference
between the former and the latter is that the former cares about specificity
but the latter does not.
There are a number of knock-on consequences:
* There is now a dedicated `HsSigType` type, which is the combination of
`HsOuterSigTyVarBndrs` and `HsType`. `LHsSigType` is now an alias for an
`XRec` of `HsSigType`.
* Working out the details led us to a substantial refactoring of
the handling of explicit (user-written) and implicit type-variable
bindings in `GHC.Tc.Gen.HsType`.
Instead of a confusing family of higher order functions, we now
have a local data type, `SkolemInfo`, that controls how these
binders are kind-checked.
It remains very fiddly, not fully satisfying. But it's better
than it was.
Fixes #16762. Bumps the Haddock submodule.
Co-authored-by: Simon Peyton Jones <simonpj@microsoft.com>
Co-authored-by: Richard Eisenberg <rae@richarde.dev>
Co-authored-by: Zubin Duggal <zubin@cmi.ac.in>
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This fixes #18723 by:
* Moving the existing `GHC.Tc.Gen.HsType.bigConstraintTuple` validity
check to `GHC.Rename.Utils.checkCTupSize` for consistency with
`GHC.Rename.Utils.checkTupSize`, and
* Using `check(C)TupSize` when checking tuple _types_, in addition
to checking names, expressions, and patterns.
Note that I put as many of these checks as possible in the typechecker so
that GHC can properly distinguish between boxed and constraint tuples. The
exception to this rule is checking names, which I perform in the renamer
(in `GHC.Rename.Env`) so that we can rule out `(,, ... ,,)` and
`''(,, ... ,,)` alike in one fell swoop.
While I was in town, I also removed the `HsConstraintTuple` and
`HsBoxedTuple` constructors of `HsTupleSort`, which are functionally
unused. This requires a `haddock` submodule bump.
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This patch implements Quick Look impredicativity (#18126), sticking
very closely to the design in
A quick look at impredicativity, Serrano et al, ICFP 2020
The main change is that a big chunk of GHC.Tc.Gen.Expr has been
extracted to two new modules
GHC.Tc.Gen.App
GHC.Tc.Gen.Head
which deal with typechecking n-ary applications, and the head of
such applications, respectively. Both contain a good deal of
documentation.
Three other loosely-related changes are in this patch:
* I implemented (partly by accident) points (2,3)) of the accepted GHC
proposal "Clean up printing of foralls", namely
https://github.com/ghc-proposals/ghc-proposals/blob/
master/proposals/0179-printing-foralls.rst
(see #16320).
In particular, see Note [TcRnExprMode] in GHC.Tc.Module
- :type instantiates /inferred/, but not /specified/, quantifiers
- :type +d instantiates /all/ quantifiers
- :type +v is killed off
That completes the implementation of the proposal,
since point (1) was done in
commit df08468113ab46832b7ac0a7311b608d1b418c4d
Author: Krzysztof Gogolewski <krzysztof.gogolewski@tweag.io>
Date: Mon Feb 3 21:17:11 2020 +0100
Always display inferred variables using braces
* HsRecFld (which the renamer introduces for record field selectors),
is now preserved by the typechecker, rather than being rewritten
back to HsVar. This is more uniform, and turned out to be more
convenient in the new scheme of things.
* The GHCi debugger uses a non-standard unification that allows the
unification variables to unify with polytypes. We used to hack
this by using ImpredicativeTypes, but that doesn't work anymore
so I introduces RuntimeUnkTv. See Note [RuntimeUnkTv] in
GHC.Runtime.Heap.Inspect
Updates haddock submodule.
WARNING: this patch won't validate on its own. It was too
hard to fully disentangle it from the following patch, on
type errors and kind generalisation.
Changes to tests
* Fixes #9730 (test added)
* Fixes #7026 (test added)
* Fixes most of #8808, except function `g2'` which uses a
section (which doesn't play with QL yet -- see #18126)
Test added
* Fixes #1330. NB Church1.hs subsumes Church2.hs, which is now deleted
* Fixes #17332 (test added)
* Fixes #4295
* This patch makes typecheck/should_run/T7861 fail.
But that turns out to be a pre-existing bug: #18467.
So I have just made T7861 into expect_broken(18467)
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- put panic related functions into GHC.Utils.Panic
- put trace related functions using DynFlags in GHC.Driver.Ppr
One step closer making Outputable fully independent of DynFlags.
Bump haddock submodule
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This patch (due to Richard Eisenberg) improves
documentation of the wrapper returned by tcSubMult
(see Note [Wrapper returned from tcSubMult] in
GHC.Tc.Utils.Unify).
And, more substantially, it cleans up the multiplicity
handling in the typechecking of NPlusKPat
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As #18412 points out, it should be OK for multiple case alternatives
to have a higher rank type, provided they are all the same.
This patch implements that change. It sweeps away
GHC.Tc.Gen.Match.tauifyMultipleBranches, and friends, replacing it
with an enhanced version of fillInferResult.
The basic change to fillInferResult is to permit the case in which
another case alternative has already filled in the result; and in
that case simply unify. It's very simple actually.
See the new Note [fillInferResult] in TcMType
Other refactoring:
- Move all the InferResult code to one place, in GHC.Tc.Utils.TcMType
(previously some of it was in Unify)
- Move tcInstType and friends from TcMType to Instantiate, where it
more properly belongs. (TCMType was getting very long.)
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GHC.Hs.Extension had
type GhcPs = GhcPass 'Parsed
type GhcRn = GhcPass 'Renamed
type GhcTc = GhcPass 'Typechecked
type GhcTcId = GhcTc
The last of these, GhcTcId, is a vestige of the past.
This patch expunges it from GHC.
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This is the first step towards implementation of the linear types proposal
(https://github.com/ghc-proposals/ghc-proposals/pull/111).
It features
* A language extension -XLinearTypes
* Syntax for linear functions in the surface language
* Linearity checking in Core Lint, enabled with -dlinear-core-lint
* Core-to-core passes are mostly compatible with linearity
* Fields in a data type can be linear or unrestricted; linear fields
have multiplicity-polymorphic constructors.
If -XLinearTypes is disabled, the GADT syntax defaults to linear fields
The following items are not yet supported:
* a # m -> b syntax (only prefix FUN is supported for now)
* Full multiplicity inference (multiplicities are really only checked)
* Decent linearity error messages
* Linear let, where, and case expressions in the surface language
(each of these currently introduce the unrestricted variant)
* Multiplicity-parametric fields
* Syntax for annotating lambda-bound or let-bound with a multiplicity
* Syntax for non-linear/multiple-field-multiplicity records
* Linear projections for records with a single linear field
* Linear pattern synonyms
* Multiplicity coercions (test LinearPolyType)
A high-level description can be found at
https://ghc.haskell.org/trac/ghc/wiki/LinearTypes/Implementation
Following the link above you will find a description of the changes made to Core.
This commit has been authored by
* Richard Eisenberg
* Krzysztof Gogolewski
* Matthew Pickering
* Arnaud Spiwack
With contributions from:
* Mark Barbone
* Alexander Vershilov
Updates haddock submodule.
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This updates comments only.
This patch replaces leaf module names according to new module
hierarchy [1][2] as followings:
* Expand leaf names to easily find the module path:
for instance, `Id.hs` to `GHC.Types.Id`.
* Modify leaf names according to new module hierarchy:
for instance, `Convert.hs` to `GHC.ThToHs`.
* Fix typo:
for instance, `GHC.Core.TyCo.Rep.hs` to `GHC.Core.TyCo.Rep`
See also !3375
[1]: https://gitlab.haskell.org/ghc/ghc/-/wikis/Make-GHC-codebase-more-modular
[2]: https://gitlab.haskell.org/ghc/ghc/issues/13009
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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)
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In GHC, not in the code being compiled!
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