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Co-authored-by: Daniel Rogozin <daniel.rogozin@serokell.io>
Co-authored-by: Rinat Stryungis <rinat.stryungis@serokell.io>
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It's surprisingly tricky to deal with 'main' (#19397). This
patch does quite bit of refactoring do to it right. Well,
more-right anyway!
The moving parts are documented in GHC.Tc.Module
Note [Dealing with main]
Some other oddments:
* Rename tcRnExports to rnExports; no typechecking here!
* rnExports now uses checkNoErrs rather than failIfErrsM;
the former fails only if rnExports itself finds errors
* Small improvements to tcTyThingCategory, which ultimately
weren't important to the patch, but I've retained as
a minor improvement.
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This implements the BoxedRep proposal, refactoring the `RuntimeRep`
hierarchy from:
```haskell
data RuntimeRep = LiftedPtrRep | UnliftedPtrRep | ...
```
to
```haskell
data RuntimeRep = BoxedRep Levity | ...
data Levity = Lifted | Unlifted
```
Updates binary, haddock submodules.
Closes #17526.
Metric Increase:
T12545
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Add Data.Type.Ord
Add and update tests
Metric Increase:
MultiLayerModules
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Ticket #19364 helpfully points out that we do not currently take
advantage of pushing the result type of an application into the
arguments. This makes error messages notably less good.
The fix is rather easy: move the result-type unification step earlier.
It's even a bit more efficient; in the the checking case we now
do one less zonk.
See Note [Unify with expected type before typechecking arguments]
in GHC.Tc.Gen.App
This change generally improves error messages, but it made one worse:
typecheck/should_fail/T16204c. That led me to the realisation that
a good error can be replaced by a less-good one, which provoked
me to change GHC.Tc.Solver.Interact.inertsCanDischarge. It's
explained in the new Note [Combining equalities]
One other refactoring: I discovered that KindEqOrigin didn't need a
Maybe in its type -- a nice simplification.
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When desugaring large overloaded literals we now avoid
computing the `Rational` value. Instead prefering to
store the significant and exponent as given where
reasonable and possible.
See Note [FractionalLit representation] for details.
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When implementing Quick Look I'd failed to remember that overloaded
labels, like #foo, should be treated as a "head", so that they can be
instantiated with Visible Type Application. This caused #19154.
A very similar ticket covers overloaded literals: #19167.
This patch fixes both problems, but (annoyingly, albeit temporarily)
in two different ways.
Overloaded labels
I dealt with overloaded labels by buying fully into the
Rebindable Syntax approach described in GHC.Hs.Expr
Note [Rebindable syntax and HsExpansion].
There is a good overview in GHC.Rename.Expr
Note [Handling overloaded and rebindable constructs].
That module contains much of the payload for this patch.
Specifically:
* Overloaded labels are expanded in the renamer, fixing #19154.
See Note [Overloaded labels] in GHC.Rename.Expr.
* Left and right sections used to have special code paths in the
typechecker and desugarer. Now we just expand them in the
renamer. This is harder than it sounds. See GHC.Rename.Expr
Note [Left and right sections].
* Infix operator applications are expanded in the typechecker,
specifically in GHC.Tc.Gen.App.splitHsApps. See
Note [Desugar OpApp in the typechecker] in that module
* ExplicitLists are expanded in the renamer, when (and only when)
OverloadedLists is on.
* HsIf is expanded in the renamer when (and only when) RebindableSyntax
is on. Reason: the coverage checker treats HsIf specially. Maybe
we could instead expand it unconditionally, and fix up the coverage
checker, but I did not attempt that.
Overloaded literals
Overloaded literals, like numbers (3, 4.2) and strings with
OverloadedStrings, were not working correctly with explicit type
applications (see #19167). Ideally I'd also expand them in the
renamer, like the stuff above, but I drew back on that because they
can occur in HsPat as well, and I did not want to to do the HsExpanded
thing for patterns.
But they *can* now be the "head" of an application in the typechecker,
and hence something like ("foo" @T) works now. See
GHC.Tc.Gen.Head.tcInferOverLit. It's also done a bit more elegantly,
rather than by constructing a new HsExpr and re-invoking the
typechecker. There is some refactoring around tcShortCutLit.
Ultimately there is more to do here, following the Rebindable Syntax
story.
There are a lot of knock-on effects:
* HsOverLabel and ExplicitList no longer need funny (Maybe SyntaxExpr)
fields to support rebindable syntax -- good!
* HsOverLabel, OpApp, SectionL, SectionR all become impossible in the
output of the typecheker, GhcTc; so we set their extension fields to
Void. See GHC.Hs.Expr Note [Constructor cannot occur]
* Template Haskell quotes for HsExpanded is a bit tricky. See
Note [Quotation and rebindable syntax] in GHC.HsToCore.Quote.
* In GHC.HsToCore.Match.viewLExprEq, which groups equal HsExprs for the
purpose of pattern-match overlap checking, I found that dictionary
evidence for the same type could have two different names. Easily
fixed by comparing types not names.
* I did quite a bit of annoying fiddling around in GHC.Tc.Gen.Head and
GHC.Tc.Gen.App to get error message locations and contexts right,
esp in splitHsApps, and the HsExprArg type. Tiresome and not very
illuminating. But at least the tricky, higher order, Rebuilder
function is gone.
* Some refactoring in GHC.Tc.Utils.Monad around contexts and locations
for rebindable syntax.
* Incidentally fixes #19346, because we now print renamed, rather than
typechecked, syntax in error mesages about applications.
The commit removes the vestigial module GHC.Builtin.RebindableNames,
and thus triggers a 2.4% metric decrease for test MultiLayerModules
(#19293).
Metric Decrease:
MultiLayerModules
T12545
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They have no effect since 2011 (GHC 7.2/7.4),
commits cb698570b2b and 49dbe60558.
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When combining
Inert: [W] C ty1 ty2
Work item: [D] C ty1 ty2
we were simply discarding the Derived one. Not good! We should turn
the inert back into [WD] or keep both. E.g. fundeps work only on
Derived (see isImprovable).
This little patch fixes it. The bug is hard to tickle, but #19315 did so.
The fix is a little messy (see Note [KeepBoth] plus the change in
addDictCt), but I am disinclined to refine it further because it'll
all be swept away when we Kill Deriveds.
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Co-authored-by: Rinat Stryungis <rinat.stryungis@serokell.io>
Implement GHC Proposal #387
* Parse char literals 'x' at the type level
* New built-in type families CmpChar, ConsSymbol, UnconsSymbol
* New KnownChar class (cf. KnownSymbol and KnownNat)
* New SomeChar type (cf. SomeSymbol and SomeNat)
* CharTyLit support in template-haskell
Updated submodules: binary, haddock.
Metric Decrease:
T5205
haddock.base
Metric Increase:
Naperian
T13035
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This commit also consolidates documentation in the user
manual around UndecidableSuperClasses, UndecidableInstances,
and FlexibleContexts.
Close #19186.
Close #19187.
Test case: typecheck/should_compile/T19186,
typecheck/should_fail/T19187{,a}
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The `Applicative` instance is the most important one (for
array/vector/sequence indexing purposes), but it deserves
all the usual ones.
T12545 does silly 1% wibbles both ways, it seems, maybe depending
on architecture.
Metric Increase:
T12545
Metric Decrease:
T12545
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This has two fixes:
1. Take TyVarTvs into account in matchableGivens. This
fixes #19106.
2. Don't allow unifying alpha ~ Maybe alpha. This fixes
#19107.
This patch also removes a redundant Note and redirects
references to a better replacement.
Also some refactoring/improvements around the BindFun
in the pure unifier, which now can take the RHS type
into account.
Close #19106.
Close #19107.
Test case: partial-sigs/should_compile/T19106,
typecheck/should_compile/T19107
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This commit fixes 19 tests which were failing due to the use of
`consBag` / `snocBag`, which have been now replaced by `addMessage`.
This means that now GHC would output things in different order but
only for /diagnostics on the same line/, so this is just reflecting
that. The "normal" order of messages is still guaranteed.
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As #19142 showed, with -fdefer-type-errors we were allowing
compilation to proceed despite a fatal kind error. This patch
fixes it, as described in the new note in GHC.Tc.Solver,
Note [Wrapping failing kind equalities]
Also fixes #19158
Also when checking
default( ty1, ty2, ... )
only consider a possible default (C ty2) if ty2 is kind-compatible
with C. Previously we could form kind-incompatible constraints, with
who knows what kind of chaos resulting. (Actually, no chaos results,
but that's only by accident. It's plain wrong to form the constraint
(Num Either) for example.) I just happened to notice
this during fixing #19142.
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This patch delays the detection of missing fields in record creation
after type-checking. This gives us better error messages (see updated
test outputs).
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See Note [Error on unconstrained meta-variables] in TcMType.
Close #17301
Close #17567
Close #17562
Close #15474
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This patch establishes invariant (GivenInv) from GHC.Tc.Utils.TcType
Note [TcLevel invariants]. (GivenInv) says that unification variables
from level 'n' should not appear in the Givens for level 'n'. See
Note [GivenInv] in teh same module.
This invariant was already very nearly true, but a dark corner of
partial type signatures made it false. The patch re-jigs partial type
signatures a bit to avoid the problem, and documents the invariant
much more thorughly
Fixes #18646 along the way: see Note [Extra-constraints wildcards]
in GHC.Tc.Gen.Bind
I also simplified the interface to tcSimplifyInfer slightly, so that
it /emits/ the residual constraint, rather than /returning/ it.
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Allow INLINE and NOINLINE pragmas to be used for patterns.
Those are applied to both the builder and matcher (where applicable).
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Previously, we let-bound an identifier to use to carry
the erroring evidence for an out-of-scope variable. But
this failed for levity-polymorphic out-of-scope variables,
leading to a panic (#17812). The new plan is to use
a mutable update to just write the erroring expression directly
where it needs to go.
Close #17812.
Test case: typecheck/should_compile/T17812
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patterns
Fixes #19109.
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This patch delivers on #17656, by entirel killing off the complex
floatEqualities mechanism. Previously, floatEqualities would float an
equality out of an implication, so that it could be solved at an outer
level. But now we simply do unification in-place, without floating the
constraint, relying on level numbers to determine untouchability.
There are a number of important new Notes:
* GHC.Tc.Utils.Unify Note [Unification preconditions]
describes the preconditions for unification, including both
skolem-escape and touchability.
* GHC.Tc.Solver.Interact Note [Solve by unification]
describes what we do when we do unify
* GHC.Tc.Solver.Monad Note [The Unification Level Flag]
describes how we control solver iteration under this new scheme
* GHC.Tc.Solver.Monad Note [Tracking Given equalities]
describes how we track when we have Given equalities
* GHC.Tc.Types.Constraint Note [HasGivenEqs]
is a new explanation of the ic_given_eqs field of an implication
A big raft of subtle Notes in Solver, concerning floatEqualities,
disappears.
Main code changes:
* GHC.Tc.Solver.floatEqualities disappears entirely
* GHC.Tc.Solver.Monad: new fields in InertCans, inert_given_eq_lvl
and inert_given_eq, updated by updateGivenEqs
See Note [Tracking Given equalities].
* In exchange for updateGivenEqa, GHC.Tc.Solver.Monad.getHasGivenEqs
is much simpler and more efficient
* I found I could kill of metaTyVarUpdateOK entirely
One test case T14683 showed a 5.1% decrease in compile-time
allocation; and T5631 was down 2.2%. Other changes were small.
Metric Decrease:
T14683
T5631
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This fixes test Linear14. The code in Unify.hs was always using
multiplicity Many instead of a new metavariable.
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See Note [Infinitary substitution in lookup] in GHC.Core.InstEnv
and Note [Unification result] in GHC.Core.Unify.
Test case: typecheck/should_compile/T190{44,52}
Close #19044
Close #19052
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See commentary in tcCheckUsage.
Close #18998.
Test case: typecheck/should_compile/T18998
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This was inadvertently merged.
This reverts commit 6c2eb2232b39ff4720fda0a4a009fb6afbc9dcea.
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This implements the BoxedRep proposal, refacoring the `RuntimeRep`
hierarchy from:
```haskell
data RuntimeRep = LiftedPtrRep | UnliftedPtrRep | ...
```
to
```haskell
data RuntimeRep = BoxedRep Levity | ...
data Levity = Lifted | Unlifted
```
Closes #17526.
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During the compilation of programs GHC very frequently deals with
the `Type` type, which is a synonym of `TYPE 'LiftedRep`. This patch
teaches GHC to avoid expanding the `Type` synonym (and other nullary
type synonyms) during type comparisons, saving a good amount of work.
This optimisation is described in `Note [Comparing nullary type
synonyms]`.
To maximize the impact of this optimisation, we introduce a few
special-cases to reduce `TYPE 'LiftedRep` to `Type`. See
`Note [Prefer Type over TYPE 'LiftedPtrRep]`.
Closes #17958.
Metric Decrease:
T18698b
T1969
T12227
T12545
T12707
T14683
T3064
T5631
T5642
T9020
T9630
T9872a
T13035
haddock.Cabal
haddock.base
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This was inadvertently merged.
This reverts commit 7e9debd4ceb068effe8ac81892d2cabcb8f55850.
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During the compilation of programs GHC very frequently deals with
the `Type` type, which is a synonym of `TYPE 'LiftedRep`. This patch
teaches GHC to avoid expanding the `Type` synonym (and other nullary
type synonyms) during type comparisons, saving a good amount of work.
This optimisation is described in `Note [Comparing nullary type
synonyms]`.
To maximize the impact of this optimisation, we introduce a few
special-cases to reduce `TYPE 'LiftedRep` to `Type`. See
`Note [Prefer Type over TYPE 'LiftedPtrRep]`.
Closes #17958.
Metric Decrease:
T18698b
T1969
T12227
T12545
T12707
T14683
T3064
T5631
T5642
T9020
T9630
T9872a
T13035
haddock.Cabal
haddock.base
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The haddock submodule is also updated so that it understands the changes
to patterns.
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This patch fixes several aspects of kind inference for data type
declarations, especially data /instance/ declarations
Specifically
1. In kcConDecls/kcConDecl make it clear that the tc_res_kind argument
is only used in the H98 case; and in that case there is no result
kind signature; and hence no need for the disgusting splitPiTys in
kcConDecls (now thankfully gone).
The GADT case is a bit different to before, and much nicer.
This is what fixes #18891.
See Note [kcConDecls: kind-checking data type decls]
2. Do not look at the constructor decls of a data/newtype instance
in tcDataFamInstanceHeader. See GHC.Tc.TyCl.Instance
Note [Kind inference for data family instances]. This was a
new realisation that arose when doing (1)
This causes a few knock-on effects in the tests suite, because
we require more information than before in the instance /header/.
New user-manual material about this in "Kind inference in data type
declarations" and "Kind inference for data/newtype instance
declarations".
3. Minor improvement in kcTyClDecl, combining GADT and H98 cases
4. Fix #14111 and #8707 by allowing the header of a data instance
to affect kind inferece for the the data constructor signatures;
as described at length in Note [GADT return types] in GHC.Tc.TyCl
This led to a modest refactoring of the arguments (and argument
order) of tcConDecl/tcConDecls.
5. Fix #19000 by inverting the sense of the test in new_locs
in GHC.Tc.Solver.Canonical.canDecomposableTyConAppOK.
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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 replaces all Word<N> = W<N># Word# and Int<N> = I<N># Int# with
Word<N> = W<N># Word<N># and Int<N> = I<N># Int<N>#, thus providing us
with properly sized primitives in the codegenerator instead of pretending
they are all full machine words.
This came up when implementing darwinpcs for arm64. The darwinpcs reqires
us to pack function argugments in excess of registers on the stack. While
most procedure call standards (pcs) assume arguments are just passed in
8 byte slots; and thus the caller does not know the exact signature to make
the call, darwinpcs requires us to adhere to the prototype, and thus have
the correct sizes. If we specify CInt in the FFI call, it should correspond
to the C int, and not just be Word sized, when it's only half the size.
This does change the expected output of T16402 but the new result is no
less correct as it eliminates the narrowing (instead of the `and` as was
previously done).
Bumps the array, bytestring, text, and binary submodules.
Co-Authored-By: Ben Gamari <ben@well-typed.com>
Metric Increase:
T13701
T14697
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This issue was fixed at some point between GHC 8.0 and 8.2. Let's add a
regression test to ensure that it stays fixed.
Fixes #10504.
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The use of `tcSplitForAllTyVars` in `tcDataFamInstHeader` was the immediate
cause of #18939, and replacing it with a new `tcSplitForAllInvisTyVars`
function (which behaves like `tcSplitForAllTyVars` but only splits invisible
type variables) fixes the issue. However, this led me to realize that _most_
uses of `tcSplitForAllTyVars` in GHC really ought to be
`tcSplitForAllInvisTyVars` instead. While I was in town, I opted to replace
most uses of `tcSplitForAllTys` with `tcSplitForAllTysInvis` to reduce the
likelihood of such bugs in the future.
I say "most uses" above since there is one notable place where we _do_ want
to use `tcSplitForAllTyVars`: in `GHC.Tc.Validity.forAllTyErr`, which produces
the "`Illegal polymorphic type`" error message if you try to use a higher-rank
`forall` without having `RankNTypes` enabled. Here, we really do want to split
all `forall`s, not just invisible ones, or we run the risk of giving an
inaccurate error message in the newly added `T18939_Fail` test case.
I debated at some length whether I wanted to name the new function
`tcSplitForAllInvisTyVars` or `tcSplitForAllTyVarsInvisible`, but in the end,
I decided that I liked the former better. For consistency's sake, I opted to
rename the existing `splitPiTysInvisible` and `splitPiTysInvisibleN` functions
to `splitInvisPiTys` and `splitPiTysInvisN`, respectively, so that they use the
same naming convention. As a consequence, this ended up requiring a `haddock`
submodule bump.
Fixes #18939.
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This got fixed sometime recently; not worth it trying to
figure out which commit.
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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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Commit f594a68a5500696d94ae36425bbf4d4073aca3b2
(`Use level numbers for generalisation`) ended up fixing #18920. Let's add a
regression test to ensure that it stays fixed.
Fixes #18920.
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Previously, `can_eq_nc'` would equate `ForAllTy`s regardless of their
`ArgFlag`, including `forall i -> i -> Type` and `forall i. i -> Type`! To fix
this, `can_eq_nc'` now uses the `sameVis` function to first check if the
`ArgFlag`s are equal modulo specificity. I have also updated `tcEqType`'s
implementation to match this behavior. For more explanation on the "modulo
specificity" part, see the new `Note [ForAllTy and typechecker equality]`
in `GHC.Tc.Solver.Canonical`.
While I was in town, I fixed some related documentation issues:
* I added `Note [Typechecker equality]` to `GHC.Tc.Utils.TcType` to describe
what exactly distinguishes `can_eq_nc'` and `tcEqType` (which implement
typechecker equality) from `eqType` (which implements definitional equality,
which does not care about the `ArgFlags` of `ForAllTy`s at all).
* The User's Guide had some outdated prose on the specified/inferred
distinction being different for types and kinds, a holdover from #15079. This
is no longer the case on today's GHC, so I removed this prose, added some new
prose to take its place, and added a regression test for the programs in
#15079.
* The User's Guide had some _more_ outdated prose on inferred type variables
not being allowed in `default` type signatures for class methods, which is no
longer true as of the resolution of #18432.
* The related `Note [Deferred Unification]` was being referenced as
`Note [Deferred unification]` elsewhere, which made it harder to `grep`
for. I decided to change the name of the Note to `Deferred unification`
for consistency with the capitalization style used for most other Notes.
Fixes #18863.
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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 fixes two problems in the constraint solver.
* An actual bug #18555: we were floating out a constraint to eagerly,
and that was ultimately fatal. It's explained in
Note [Do not float blocked constraints] in GHC.Core.Constraint.
This is all very delicate, but it's all going to become irrelevant
when we stop floating constraints (#17656).
* A major performance infelicity in the flattener. When flattening
(ty |> co) we *never* generated Refl, even when there was nothing
at all to do. Result: we would gratuitously rewrite the constraint
to exactly the same thing, wasting work. Described in #18413, and
came up again in #18855.
Solution: exploit the special case by calling the new function
castCoercionKind1. See Note [castCoercionKind1] in
GHC.Core.Coercion
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Also bumps upper bounds on base in boot libraries (incl. submodules).
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This patch implements two related warnings:
-Woperator-whitespace-ext-conflict
warns on uses of infix operators that would be parsed
differently were a particular GHC extension enabled
-Woperator-whitespace
warns on prefix, suffix, and tight infix uses of infix
operators
Updates submodules: haddock, containers.
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