| Commit message (Collapse) | Author | Age | Files | Lines |
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This implements the `DerivingVia` proposal put forth in
https://github.com/ghc-proposals/ghc-proposals/pull/120.
This introduces the `DerivingVia` deriving strategy. This is a
generalization of `GeneralizedNewtypeDeriving` that permits the user
to specify the type to `coerce` from.
The major change in this patch is the introduction of the
`ViaStrategy` constructor to `DerivStrategy`, which takes a type
as a field. As a result, `DerivStrategy` is no longer a simple
enumeration type, but rather something that must be renamed and
typechecked. The process by which this is done is explained more
thoroughly in section 3 of this paper
( https://www.kosmikus.org/DerivingVia/deriving-via-paper.pdf ),
although I have inlined the relevant parts into Notes where possible.
There are some knock-on changes as well. I took the opportunity to
do some refactoring of code in `TcDeriv`, especially the
`mkNewTypeEqn` function, since it was bundling all of the logic for
(1) deriving instances for newtypes and
(2) `GeneralizedNewtypeDeriving`
into one huge broth. `DerivingVia` reuses much of part (2), so that
was factored out as much as possible.
Bumps the Haddock submodule.
Test Plan: ./validate
Reviewers: simonpj, bgamari, goldfire, alanz
Subscribers: alanz, goldfire, rwbarton, thomie, mpickering, carter
GHC Trac Issues: #15178
Differential Revision: https://phabricator.haskell.org/D4684
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Poor DPH and its vectoriser have long been languishing; sadly it seems there is
little chance that the effort will be rekindled. Every few years we discuss
what to do with this mass of code and at least once we have agreed that it
should be archived on a branch and removed from `master`. Here we do just that,
eliminating heaps of dead code in the process.
Here we drop the ParallelArrays extension, the vectoriser, and the `vector` and
`primitive` submodules.
Test Plan: Validate
Reviewers: simonpj, simonmar, hvr, goldfire, alanz
Reviewed By: simonmar
Subscribers: goldfire, rwbarton, thomie, mpickering, carter
Differential Revision: https://phabricator.haskell.org/D4761
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Docstrings don't profit from FastString's interning, so we switch to
a different type that doesn't incur this overhead.
Updates the haddock submodule.
Reviewers: alexbiehl, bgamari
Reviewed By: alexbiehl, bgamari
Subscribers: rwbarton, thomie, mpickering, carter
GHC Trac Issues: #15157
Differential Revision: https://phabricator.haskell.org/D4743
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The warning does not consider the fact that the splice pattern may
very well end up binding variables.
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Summary:
Template Haskell provides a wormhole through which you can
sneak methods that don't belong to a class into an instance for that
class, bypassing the renamer's validity checks. The solution adopted
here is to mirror the treatment for associated type family instances,
which have an additional check in the typechecker which catch
mismatched associated type families that were snuck through using
Template Haskell. I've put a similar check for class methods into
`tcMethods`.
Test Plan: make test TEST=T12387
Reviewers: bgamari, simonpj
Reviewed By: bgamari, simonpj
Subscribers: simonpj, rwbarton, thomie, carter
GHC Trac Issues: #12387
Differential Revision: https://phabricator.haskell.org/D4710
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This patch just pulls out FamInst.loadDependentFamInstModules
as a separate function, and adds better comments.
Provoked by Trac #14759, comment:10.
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Summary:
- remove PostRn/PostTc fields
- remove the HsVect In/Out distinction for Type, Class and Instance
- remove PlaceHolder in favour of NoExt
- Simplify OutputableX constraint
Updates haddock submodule
Test Plan: ./validate
Reviewers: goldfire, bgamari
Subscribers: goldfire, thomie, mpickering, carter
Differential Revision: https://phabricator.haskell.org/D4625
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Summary:
#14710 revealed two unfortunate regressions related to kind
polymorphism that had crept in in recent GHC releases:
1. While GHC was able to catch illegal uses of kind polymorphism
(i.e., if `PolyKinds` wasn't enabled) in limited situations, it
wasn't able to catch kind polymorphism of the following form:
```lang=haskell
f :: forall a. a -> a
f x = const x g
where
g :: Proxy (x :: a)
g = Proxy
```
Note that the variable `a` is being used as a kind variable in the
type signature of `g`, but GHC happily accepts it, even without
the use of `PolyKinds`.
2. If you have `PolyKinds` (but not `TypeInType`) enabled, then GHC
incorrectly accepts the following definition:
```lang=haskell
f :: forall k (a :: k). Proxy a
f = Proxy
```
Even though `k` is explicitly bound and then later used as a kind
variable within the same telescope.
This patch fixes these two bugs as follows:
1. Whenever we rename any `HsTyVar`, we check if the following three
criteria are met:
(a) It's a type variable
(b) It's used at the kind level
(c) `PolyKinds` is not enabled
If so, then we have found an illegal use of kind polymorphism, so
throw an error.
This check replaces the `checkBadKindBndrs` function, which could
only catch illegal uses of kind polymorphism in very limited
situations (when the bad kind variable happened to be implicitly
quantified in the same type signature).
2. In `extract_hs_tv_bndrs`, we must error if `TypeInType` is not
enabled and either of the following criteria are met:
(a) An explicitly bound type variable is used in kind position
in the body of a `forall` type.
(b) An explicitly bound type variable is used in kind position
in the kind of a bound type variable in a `forall` type.
`extract_hs_tv_bndrs` was checking (a), but not (b). Easily fixed.
Test Plan: ./validate
Reviewers: goldfire, simonpj, bgamari, hvr
Reviewed By: simonpj
Subscribers: thomie, carter
GHC Trac Issues: #14710
Differential Revision: https://phabricator.haskell.org/D4554
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Deleting misleading comments, to fix Trac #15047
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Summary:
- Add the balance of the TTG extensions for hsSyn/HsBinds
- Move all the (now orphan) data instances into hsSyn/HsInstances and
use TTG Data instances Plan B
https://ghc.haskell.org/trac/ghc/wiki/ImplementingTreesThatGrow/Instances#PLANB
Updates haddock submodule.
Illustrative numbers
Compiling HsInstances before using Plan B.
Max residency ~ 5G
<<ghc: 629,864,691,176 bytes, 5300 GCs,
321075437/1087762592 avg/max bytes residency (23 samples),
2953M in use, 0.000 INIT (0.000 elapsed),
383.511 MUT (384.986 elapsed), 37.426 GC (37.444 elapsed) :ghc>>
Using Plan B
Max residency 1.1G
<<ghc: 78,832,782,968 bytes, 2884 GCs,
222140352/386470152 avg/max bytes residency (34 samples),
1062M in use, 0.001 INIT (0.001 elapsed),
56.612 MUT (62.917 elapsed), 32.974 GC (32.923 elapsed) :ghc>>
Test Plan: ./validate
Reviewers: shayan-najd, goldfire, bgamari
Subscribers: goldfire, thomie, mpickering, carter
Differential Revision: https://phabricator.haskell.org/D4581
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The following commits were reverted prior to the release of GHC 8.4.1,
because the time to derive Data instances was too long [1].
438dd1cbba13d35f3452b4dcef3f94ce9a216905 Phab:D4147
e3ec2e7ae94524ebd111963faf34b84d942265b4 Phab:D4177
47ad6578ea460999b53eb4293c3a3b3017a56d65 Phab:D4186
The work is continuing, as the minimum bootstrap compiler is now
GHC 8.2.1, and this allows Plan B[2] for instances to be used. This
will land in a following commit.
Updates Haddock submodule
[1] https://ghc.haskell.org/trac/ghc/wiki/ImplementingTreesThatGrow/Instances
[2] https://ghc.haskell.org/trac/ghc/wiki/ImplementingTreesThatGrow/Instances#PLANB
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Updates haddock submodule to match.
Test Plan : Validate
Differential Revision: https://phabricator.haskell.org/D4199
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Summary:
At its core, this patch is a simple tweak that allows a user
to write:
```lang=haskell
deriving instance _ => Eq (Foo a)
```
Which is functionally equivalent to:
```lang=haskell
data Foo a = ...
deriving Eq
```
But with the added flexibility that `StandaloneDeriving` gives you
(namely, the ability to use it anywhere, not just in the same module
that `Foo` was declared in). This fixes #13324, and should hopefully
address a use case brought up in #10607.
Currently, only the use of a single, extra-constraints wildcard is
permitted in a standalone deriving declaration. Any other wildcard
is rejected, so things like
`deriving instance (Eq a, _) => Eq (Foo a)` are currently forbidden.
There are quite a few knock-on changes brought on by this change:
* The `HsSyn` type used to represent standalone-derived instances
was previously `LHsSigType`, which isn't sufficient to hold
wildcard types. This needed to be changed to `LHsSigWcType` as a
result.
* Previously, `DerivContext` was a simple type synonym for
`Maybe ThetaType`, under the assumption that you'd only ever be in
the `Nothing` case if you were in a `deriving` clause. After this
patch, that assumption no longer holds true, as you can also be
in this situation with standalone deriving when an
extra-constraints wildcard is used.
As a result, I changed `DerivContext` to be a proper datatype that
reflects the new wrinkle that this patch adds, and plumbed this
through the relevant parts of `TcDeriv` and friends.
* Relatedly, the error-reporting machinery in `TcErrors` also assumed
that if you have any unsolved constraints in a derived instance,
then you should be able to fix it by switching over to standalone
deriving. This was always sound advice before, but with this new
feature, it's possible to have unsolved constraints even when
you're standalone-deriving something!
To rectify this, I tweaked some constructors of `CtOrigin` a bit
to reflect this new subtlety.
This requires updating the Haddock submodule. See my fork at
https://github.com/RyanGlScott/haddock/commit/067d52fd4be15a1842cbb05f42d9d482de0ad3a7
Test Plan: ./validate
Reviewers: simonpj, goldfire, bgamari
Reviewed By: simonpj
Subscribers: goldfire, rwbarton, thomie, mpickering, carter
GHC Trac Issues: #13324
Differential Revision: https://phabricator.haskell.org/D4383
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Pretty-print unused imported names unqualified unconditionally to
make the warning message consistent for ambiguous/unambiguous
identifiers.
Signed-off-by: HE, Tao <sighingnow@gmail.com>
Test Plan: make test TEST="T14881"
Reviewers: bgamari, simonpj
Reviewed By: simonpj
Subscribers: simonpj, rwbarton, thomie, carter
GHC Trac Issues: #14881
Differential Revision: https://phabricator.haskell.org/D4461
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This patch is preparatory for the main fix for Trac #13324
Here, we simplify rnLHsInstType so that it does not try
to figure out the class name. This turns out to have a good
(rather than bad) effect on error messages, and it prepares
the way for the main event.
Plus, less code!
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Comment:4 in Trac #14808 explains why I'm unhappy with the current
state of affairs -- at least the lack of documentation.
This smallpatch does nothing major:
* adds comments
* uses existing type synonyms more (notably FreeKiTyVarsWithDups)
* adds another test case to T14808
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Previously, we were extracting the free variables from a
GADT constructor in an incorrect order, which caused the type
variables for the constructor's type signature to end up in
non-toposorted order. Thankfully, rearranging the order of types
during renaming makes swift work of this bug.
This fixes a regression introduced in commit
fa29df02a1b0b926afb2525a258172dcbf0ea460.
For whatever reason, that commit also commented out a
significant portion of the `T13123` test. This code appears
to work, so I've opted to uncomment it.
Test Plan: make test TEST=T14808
Reviewers: simonpj, bgamari
Reviewed By: bgamari
Subscribers: rwbarton, thomie, carter
GHC Trac Issues: #14808
Differential Revision: https://phabricator.haskell.org/D4413
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I've explained most of the rationale in a new Note.
I'd happily add a test for this, but the difference is only
visible in run time, allocations remain more or less the same.
FWIW running `generateModules` from #14693 with DEPTH=16, WIDTH=30
finishes in `23s` before, and `11s` after.
Test Plan: ./validate
Reviewers: simonpj, simonmar, bgamari
Reviewed By: simonpj
Subscribers: rwbarton, thomie, carter
GHC Trac Issues: #14693
Differential Revision: https://phabricator.haskell.org/D4369
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This is a pure refactoring. Use HsConDetails to implement
HsPatSynDetails, instead of defining a whole new data type.
Less code, fewer types, all good.
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This patch refactors HsDecls.ConDecl. Specifically
* ConDeclGADT was horrible, with all the information hidden
inside con_res_ty. Now it's kept separate, as it should be.
* ConDeclH98: use [LHsTyVarBndr] instead of LHsQTyVars for the
existentials. There is no implicit binding here.
* Add a field con_forall to both ConDeclGADT and ConDeclH98
which says if there is an explicit user-written forall.
* Field renamings in ConDecl
con_cxt to con_mb_cxt
con_details to con_args
There is an accompanying submodule update to Haddock.
Also the following change turned out to remove a lot of clutter:
* add a smart constructor for HsAppsTy, namely mkHsAppsTy,
and use it consistently. This avoids a lot of painful pattern
matching for the common singleton case.
Two api-annotation tests (T10278, and T10399) are broken, hence marking
them as expect_broken(14529). Alan is going to fix them, probably by
changing the con_forall field to
con_forall :: Maybe SrcSpan
instead of Bool
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Summary:
Suppose that you are typechecking A.hs, which transitively imports,
via B.hs, A.hs-boot. When we poke on B.hs and discover that it
has a reference to a type from A, what TyThing should we wire
it up with? Clearly, if we have already typechecked A, we
should use the most up-to-date TyThing: the one we freshly
generated when we typechecked A. But what if we haven't typechecked
it yet?
For the longest time, GHC adopted the policy that this was
*an error condition*; that you MUST NEVER poke on B.hs's reference
to a thing defined in A.hs until A.hs has gotten around to checking
this. However, actually ensuring this is the case has proven
to be a bug farm. The problem was especially poignant with
type family consistency checks, which eagerly happen before
any typechecking takes place.
This patch takes a different strategy: if we ever try to access
an entity from A which doesn't exist, we just fall back on the
definition of A from the hs-boot file. This means that you may
end up with a mix of A.hs and A.hs-boot TyThings during the
course of typechecking.
Signed-off-by: Edward Z. Yang <ezyang@fb.com>
Test Plan: validate
Reviewers: simonpj, bgamari, austin, goldfire
Subscribers: thomie, rwbarton
GHC Trac Issues: #14396
Differential Revision: https://phabricator.haskell.org/D4154
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As documented in #14490, the Data instances currently blow up
compilation time by too much to stomach. Alan will continue working on
this in a branch and we will perhaps merge to 8.2 before 8.2.1 to avoid
having to perform painful cherry-picks in 8.2 minor releases.
Reverts haddock submodule.
This reverts commit 47ad6578ea460999b53eb4293c3a3b3017a56d65.
This reverts commit e3ec2e7ae94524ebd111963faf34b84d942265b4.
This reverts commit 438dd1cbba13d35f3452b4dcef3f94ce9a216905.
This reverts commit 0ff152c9e633accca48815e26e59d1af1fe44ceb.
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* Document requirement to use the same binaries.
* Fix some code comments.
Test Plan: ./validate
Reviewers: bgamari, mboes, hvr
Reviewed By: bgamari, mboes
Subscribers: rwbarton, thomie
Differential Revision: https://phabricator.haskell.org/D4172
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Further progress on implementing Trees that Grow on hsSyn AST.
See https://ghc.haskell.org/trac/ghc/wiki/ImplementingTreesThatGrow
Trees that grow extension points are added for
- Rest of HsExpr.hs
Updates haddock submodule
Test Plan: ./validate
Reviewers: bgamari, shayan-najd, goldfire
Subscribers: goldfire, rwbarton, thomie, mpickering
Differential Revision: https://phabricator.haskell.org/D4186
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See https://ghc.haskell.org/trac/ghc/wiki/ImplementingTreesThatGrow
Trees that grow extension points are added for
- HsExpr
Updates haddock submodule
Test Plan: ./validate
Reviewers: bgamari, goldfire
Subscribers: rwbarton, thomie, shayan-najd, mpickering
Differential Revision: https://phabricator.haskell.org/D4177
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See https://ghc.haskell.org/trac/ghc/wiki/ImplementingTreesThatGrow
Trees that grow extension points are added for
- ValBinds
- HsPat
- HsLit
- HsOverLit
- HsType
- HsTyVarBndr
- HsAppType
- FieldOcc
- AmbiguousFieldOcc
Updates haddock submodule
Test Plan: ./validate
Reviewers: shayan-najd, simonpj, austin, goldfire, bgamari
Subscribers: goldfire, rwbarton, thomie, mpickering
Differential Revision: https://phabricator.haskell.org/D4147
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This reverts commit 0ff152c9e633accca48815e26e59d1af1fe44ceb.
Sadly this broke when bootstrapping with 8.0.2 due to #14396.
Reverts haddock submodule.
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See https://ghc.haskell.org/trac/ghc/wiki/ImplementingTreesThatGrow
Trees that grow extension points are added for
- ValBinds
- HsPat
- HsLit
- HsOverLit
- HsType
- HsTyVarBndr
- HsAppType
- FieldOcc
- AmbiguousFieldOcc
Updates haddock submodule
Test Plan: ./validate
Reviewers: shayan-najd, simonpj, austin, goldfire, bgamari
Subscribers: goldfire, rwbarton, thomie, mpickering
Differential Revision: https://phabricator.haskell.org/D4147
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Summary:
It's simple to treat BodyStmt just like a BindStmt with a wildcard
pattern, which is enough to fix #12143 without going all the way to
using `<*` and `*>` (#10892).
Test Plan:
* new test cases in `ado004.hs`
* validate
Reviewers: niteria, simonpj, bgamari, austin, erikd
Subscribers: rwbarton, thomie
GHC Trac Issues: #12143
Differential Revision: https://phabricator.haskell.org/D4128
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Trac #14331 showed that in a data type decl like
data D = D deriving (C (a :: k))
we were quantifying D over the 'k' in the deriving clause. Yikes.
Easily fixed, by deleting code in RnTypes.extractDataDefnKindVars
See the discussion on the ticket, esp comment:8.
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Summary:
#10816 surfaced because we were renaming top-level fixity
declarations with a different code path (`rnSrcFixityDecl`) than
the code path for fixity declarations inside of type classes, which
is not privy to names that exist in the type namespace. Luckily, the
fix is simple: use `rnSrcFixityDecl` in both places.
Test Plan: make test TEST=T10816
Reviewers: austin, bgamari, simonpj
Reviewed By: simonpj
Subscribers: simonpj, rwbarton, thomie
GHC Trac Issues: #10816
Differential Revision: https://phabricator.haskell.org/D4077
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In investigating something else (Trac #14307) I encountered the
wonders of TcRnExports.lookupChildrenExport, and the data
type ChildLookupResult.
I managed to remove the NameErr constructor from ChildLookupResult,
and simplify the code significantly at the same time.
This is just refactoring; no change in behaviour.
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this is a remains from supporting Result Type Signaturs in the ancient
past.
Differential Revision: https://phabricator.haskell.org/D4066
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When a record contruction or pattern uses a data constructor
that isn't in scope, we may produce spurious ambiguous-field
errors (Trac #14307). E.g.
f (A { fld = x }) = e
where 'A' is not in scope. We want to draw attention to the
out-of-scope data constructor first; once that is fixed we
can think about the fields.
This patch suppresses the field errors if the data con is out
of scope.
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This switches the compiler/ component to get compiled with
-XNoImplicitPrelude and a `import GhcPrelude` is inserted in all
modules.
This is motivated by the upcoming "Prelude" re-export of
`Semigroup((<>))` which would cause lots of name clashes in every
modulewhich imports also `Outputable`
Reviewers: austin, goldfire, bgamari, alanz, simonmar
Reviewed By: bgamari
Subscribers: goldfire, rwbarton, thomie, mpickering, bgamari
Differential Revision: https://phabricator.haskell.org/D3989
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Summary:
Trying to use `static` expressions without the `-XStaticPointers`
extension enabled can lead to runtime errors. Normally, such a situation isn't
possible, but Template Haskell provides a backdoor that allows it to happen,
as shown in #14204.
To prevent this, we ensure that `-XStaticPointers` is enabled when renaming
`static` expressions.
Test Plan: make test TEST=T14204
Reviewers: facundominguez, austin, bgamari, simonpj
Reviewed By: facundominguez, simonpj
Subscribers: simonpj, rwbarton, thomie
GHC Trac Issues: #14204
Differential Revision: https://phabricator.haskell.org/D3931
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The renamer wasn't able to deal with more than a couple strict
patterns in a row with `ApplicativeDo` when using the heuristic
splitter. Update it to work with them properly.
Reviewers: simonmar, austin, bgamari, hvr
Reviewed By: simonmar
Subscribers: RyanGlScott, lippling, rwbarton, thomie
GHC Trac Issues: #14163
Differential Revision: https://phabricator.haskell.org/D3900
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Summary:
Before, there was a discrepancy in how GHC renamed type synonyms as
opposed to type family instances. That is, GHC would accept definitions like
this one:
```lang=haskell
type T = (Nothing :: Maybe a)
```
However, it would not accept a very similar type family instance:
```lang=haskell
type family T :: Maybe a
type instance T = (Nothing :: Maybe a)
```
The primary goal of this patch is to bring the renaming of type family
instances up to par with that of type synonyms, causing the latter definition
to be accepted, and fixing #14131.
In particular, we now allow kind variables on the right-hand sides of type
(and data) family instances to be //implicitly// bound by LHS type (or kind)
patterns (as opposed to type variables, which must always be explicitly
bound by LHS type patterns only). As a consequence, this allows programs
reported in #7938 and #9574 to typecheck, whereas before they would
have been rejected.
Implementation-wise, there isn't much trickery involved in making this happen.
We simply need to bind additional kind variables from the RHS of a type family
in the right place (in particular, see `RnSource.rnFamInstEqn`, which has
undergone a minor facelift).
While doing this has the upside of fixing #14131, it also made it easier to
trigger #13985, so I decided to fix that while I was in town. This was
accomplished by a careful blast of `reportFloatingKvs` in `tcFamTyPats`.
Test Plan: ./validate
Reviewers: simonpj, goldfire, austin, bgamari
Reviewed By: simonpj
Subscribers: rwbarton, thomie
GHC Trac Issues: #13985, #14131
Differential Revision: https://phabricator.haskell.org/D3872
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`RnTypes` contains a fairly intricate algorithm to extract
the kind and type variables of an HsType. This algorithm carefully
maintains the separation between type variables and kind variables
so that the difference between `-XPolyKinds` and `-XTypeInType` can
be respected.
But after doing all this, `rmDupsInRdrTyVars` stupidly just
concatenated the lists of type and kind variables at the end. If a
variable were used as both a type and a kind, the algorithm would
produce *both*! This led to all kinds of problems, including #13988.
This is mostly Richard Eisenberg's patch. The only original
contribution I made was adapting call sites of `rnImplicitBndrs` to
work with the new definition of `rmDupsInRdrTyVars`. That is,
`rnImplicitBndrs` checks for variables that are illegally used in
both type and kind positions without using `-XTypeInType`, but in
order to check this, one cannot have filtered duplicate variables out
before passing them to `rnImplicitBndrs`. To accommodate for this, I
needed to concoct variations on the existing `extract-` functions in
`RnTypes` which do not remove duplicates, and use those near
`rnImplicitBndrs` call sites.
test case: ghci/scripts/T13988
Test Plan: make test TEST=T13988
Reviewers: goldfire, simonpj, austin, bgamari
Reviewed By: goldfire, simonpj
Subscribers: rwbarton, thomie
GHC Trac Issues: #13988
Differential Revision: https://phabricator.haskell.org/D3902
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This is a pre-requisite for implementing the Semigroup/Monoid proposal.
The instances have been introduced in a way to minimise warnings.
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These comments clarify the details of:
commit 0257dacf228024d0cc6ba247c707130637a25580
Author: Simon Peyton Jones <simonpj@microsoft.com>
Date: Mon Aug 28 14:20:02 2017 +0100
Refactor bindHsQTyVars and friends
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I added these when investigating Trac #14163, but they'll be
useful anyway.
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This implements @simonpj's suggested refactoring of the abstract syntax
for type/data family instances (from
https://ghc.haskell.org/trac/ghc/ticket/14131#comment:9). This combines
the previously separate `TyFamEqn` and `DataFamInstDecl` types into a
single `FamEqn` datatype. This also factors the `HsImplicitBndrs` out of
`HsTyPats` in favor of putting them just outside of `FamEqn` (as opposed
to before, where all of the implicit binders were embedded inside of
`TyFamEqn`/`DataFamInstDecl`). Finally, along the way I noticed that
`dfid_fvs` and `tfid_fvs` were completely unused, so I removed them.
Aside from some changes in parser test output, there is no change in
behavior.
Requires a Haddock submodule commit from my fork (at
https://github.com/RyanGlScott/haddock/commit/815d2deb9c0222c916becccf84
64b740c26255fd)
Test Plan: ./validate
Reviewers: simonpj, austin, goldfire, bgamari, alanz
Reviewed By: bgamari
Subscribers: mpickering, goldfire, rwbarton, thomie, simonpj
GHC Trac Issues: #14131
Differential Revision: https://phabricator.haskell.org/D3881
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This work was triggered by Trac #13738, which revealed to me that
the code RnTypes.bindHsQTyVars and bindLHsTyVarBndrs was a huge
tangled mess -- and outright wrong on occasion as the ticket showed.
The big problem was that bindLHsTyVarBndrs (which is invoked at every
HsForAll, including nested higher rank ones) was attempting to bind
implicit kind variables, which it has absolutely no busineess doing.
Imlicit kind quantification is done at the outside only, in fact
precisely where we have HsImplicitBndrs or LHsQTyVars (which also
has implicit binders).
Achieving this move was surprisingly hard, because more and more
barnacles had accreted aroud the original mistake. It's much
much better now.
Summary of changes. Almost all the action is in RnTypes.
* Implicit kind variables are bound only by
- By bindHsQTyVars, which deals with LHsQTyVars
- By rnImplicitBndrs, which deals with HsImplicitBndrs
* bindLHsTyVarBndrs, and bindLHsTyVarBndr are radically simplified.
They simply does far less, and have lots their forest of
incomprehensible accumulating parameters. (To be fair, some of
the code in bindLHsTyVarBndrs just moved to bindHsQTyVars, but
in much more perspicuous form.)
* The code that checks if a variable appears in both a kind and
a type (triggering RnTypes.mixedVarsErr) was bizarre. E.g.
we had this in RnTypes.extract_hs_tv_bndrs
; check_for_mixed_vars bndr_kvs acc_tvs
; check_for_mixed_vars bndr_kvs body_tvs
; check_for_mixed_vars body_tvs acc_kvs
; check_for_mixed_vars body_kvs acc_tvs
; check_for_mixed_vars locals body_kvs
I cleaned all this up; now we check for mixed use at binding
sites only.
* Checks for "Variable used as a kind before being bound", like
data T (a :: k) k = rhs
now just show up straightforwardly as "k is not in scope".
See Note [Kind variable ordering]
* There are some knock-on simplifications in RnSource.
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Summary:
Because we weren't checking for duplicate variables on the right-hand
sides of pattern synonyms, bogus definitions like this one passed the renamer:
```lang=haskell
pattern Foo a <- (a,a)
```
Luckily, the fix is simple.
Test Plan: make test TEST=T14114
Reviewers: mpickering, austin, bgamari, simonpj
Reviewed By: simonpj
Subscribers: simonpj, rwbarton, thomie
GHC Trac Issues: #14114
Differential Revision: https://phabricator.haskell.org/D3866
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