| Commit message (Collapse) | Author | Age | Files | Lines |
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* Users can define their own (~) type operator
* Haddock can display documentation for the built-in (~)
* New transitional warnings implemented:
-Wtype-equality-out-of-scope
-Wtype-equality-requires-operators
Updates the haddock submodule.
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As the `hlint` executable is only available in the linters image.
Fixes #21146.
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The default instance leads to an infinite loop.
bisequenceA is defined in terms of bisquence which is defined in terms
of bitraverse.
```
bitraverse f g
= (defn of bitraverse)
bisequenceA . bimap f g
= (defn of bisequenceA)
bitraverse id id . bimap f g
= (defn of bitraverse)
...
```
Any instances defined without an explicitly implementation are currently
broken, therefore removing it will alert users to an issue in their
code.
CLC issue: https://github.com/haskell/core-libraries-committee/issues/47
Fixes #20329 #18901
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fix #18963
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It is unclear what `TestEquality` is for. There are 3 possible choices.
Assuming
```haskell
data Tag a where
TagInt1 :: Tag Int
TagInt2 :: Tag Int
```
Weakest -- type param equality semi-decidable
---------------------------------------------
`Just Refl` merely means the type params are equal, the values being compared might not be.
`Nothing` means the type params may or may not be not equal.
```haskell
instance TestEquality Tag where
testEquality TagInt1 TagInt1 = Nothing -- oopsie is allowed
testEquality TagInt1 TagInt2 = Just Refl
testEquality TagInt2 TagInt1 = Just Refl
testEquality TagInt2 TagInt2 = Just Refl
```
This option is better demonstrated with a different type:
```haskell
data Tag' a where
TagInt1 :: Tag Int
TagInt2 :: Tag a
```
```haskell
instance TestEquality Tag' where
testEquality TagInt1 TagInt1 = Just Refl
testEquality TagInt1 TagInt2 = Nothing -- can't be sure
testEquality TagInt2 TagInt1 = Nothing -- can't be sure
testEquality TagInt2 TagInt2 = Nothing -- can't be sure
```
Weaker -- type param equality decidable
---------------------------------------
`Just Refl` merely means the type params are equal, the values being compared might not be.
`Nothing` means the type params are not equal.
```haskell
instance TestEquality Tag where
testEquality TagInt1 TagInt1 = Just Refl
testEquality TagInt1 TagInt2 = Just Refl
testEquality TagInt2 TagInt1 = Just Refl
testEquality TagInt2 TagInt2 = Just Refl
```
Strong -- Like `Eq`
-------------------
`Just Refl` means the type params are equal, and the values are equal according to `Eq`.
```haskell
instance TestEquality Tag where
testEquality TagInt1 TagInt1 = Just Refl
testEquality TagInt2 TagInt2 = Just Refl
testEquality _ _ = Nothing
```
Strongest -- unique value concrete type
---------------------------------------
`Just Refl` means the type params are equal, and the values are equal, and the class assume if the type params are equal the values must also be equal. In other words, the type is a singleton type when the type parameter is a closed term.
```haskell
-- instance TestEquality -- invalid instance because two variants for `Int`
```
------
The discussion in
https://github.com/haskell/core-libraries-committee/issues/21 has
decided on the "Weaker" option (confusingly formerly called the
"Weakest" option). So that is what is implemented.
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In addition to providing stack traces, the scary HasCallStack will
hopefully make people think whether they want to use these functions,
i.e. act as a documentation hint that something weird might happen.
A single metric increased, which doesn't visibly
use any method with `HasCallStack`.
-------------------------
Metric Decrease:
T9630
Metric Decrease:
T19695
T9630
-------------------------
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* Make 'mtimesDefault' use 'stimes' for the underlying monoid
rather than the default 'stimes'.
* Explain in the documentation why one might use `mtimesDefault`.
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Amazing nobody had reported the "Foldabla" typo. :-(
The Traversable docs got overhauled, leaving a stale
link in Foldable to a section that got replaced. Gave
the new section an anchor and updated the link.
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While a *strict* (i.e. constant space) right-fold on lists is not
possible, the default `foldr'` is optimised for structures like
`Seq`, that support efficient access to the right-most elements.
The original default implementation seems to have a better
constant factor for lists, so we add a monomorphic implementation
in GHC.List.
Should this be re-exported from `Data.List`? That would be a
user-visible change if both `Data.Foldable` and `Data.List` are
imported unqualified...
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This reverts commit bddecda1a4c96da21e3f5211743ce5e4c78793a2.
This implements the first step in the plan formulated in #20025 to
improve the communication and migration strategy for the proposed
changes to Data.List.
Requires changing the haddock submodule to update the test output.
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We can inline a bit earlier than the previous pragmas said. I think
they dated from an era in which the InitialPhase did no inlining.
I don't think this patch will have much effect, but it's
a bit cleaner.
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Haddock doesn't know how to render SAKS, so the only current way to make
the documentation show the kind is to write what it should say into the
type family declaration.
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- Fix cut/paste error by adding missing `c` pattern in `Vec3`
traversable instance.
- Add a bit of contextual prose above the Vec2/Vec3 instance
sample code.
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It seems more clear to think of lines as LF-terminated rather than
LF-separated.
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This is a writeup of the state of play for better than linear `elem` via
a helper type class.
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- Add link to laws from the class head
- Simplify wording of left/right associativity intro paragraph
- Avoid needless mention of "endomorphisms"
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Fixes #20009
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ie `succ (0000) == 0001` -- (not 1001)
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* The `Solo` type is intended to be the canonical lifted
unary tuple. Up until now, it has only been available from
`GHC.Tuple` in `ghc-prim`. Export it from `Data.Tuple` in
`base`.
I proposed this on the libraries list in December, 2020.
https://mail.haskell.org/pipermail/libraries/2020-December/031061.html
Responses from chessai
https://mail.haskell.org/pipermail/libraries/2020-December/031062.html
and George Wilson
https://mail.haskell.org/pipermail/libraries/2021-January/031077.html
were positive. There were no other responses.
* Add Haddock documentation for Solo.
* Give `Solo` a single field, `getSolo`, a custom `Show` instance that
does *not* use record syntax, and a `Read` instance that accepts
either record syntax or non-record syntax.
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We detect insoluble Givens by making getInertInsols
take into account TypeError constraints, on top of insoluble equalities
such as Int ~ Bool (which it already took into account).
This allows pattern matches with insoluble contexts to be reported
as redundant (tyOracle calls tcCheckGivens which calls getInertInsols).
As a bonus, we get to remove a workaround in Data.Typeable.Internal:
we can directly use a NotApplication type family, as opposed to
needing to cook up an insoluble equality constraint.
Fixes #11503 #14141 #16377 #20180
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This makes the implementations of:
- mapAccumL
- mapAccumR
- fmapDefault
- foldMapDefault
more uniform and match the approach in the overview.
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(generic Functor, Applicative, Alternative, Eq1, Ord1 instances) to GHC.Generics.
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- Remove fstName, sndName, fstIdKey, sndIdKey - no longer used,
removed from basicKnownKeyNames
- Remove breakpointId, breakpointCondId, opaqueTyCon, unknownTyCon -
they were used in the old implementation of the GHCi debugger
- Fix typos in comments
- Remove outdated comment in Lint.hs
- Use 'LitRubbish' instead of 'RubbishLit' for consistency
- Remove comment about subkinding - superseded by
Note [Kind Constraint and kind Type]
- Mention ticket ID in a linear types error message
- Fix formatting in using-warnings.rst and linear-types.rst
- Remove comment about 'Any' in Dynamic.hs - Dynamic
now uses Typeable + existential instead of Any
- Remove codeGen/should_compile/T13233.hs
This was added by accident, it is not used and T13233 is already in
should_fail
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The sequencing of monadic effects in foldlM and foldrM was described as
respectively right-associative and left-associative, but this could be
confusing, as in essence we're just composing Kleisli arrows, whose
composition is simply associative.
What matters therefore is the order of sequencing of effects, which
can be described more clearly without dragging in associativity as
such.
This avoids describing these folds as being both left-to-right and
right-to-left depending on whether we're tracking effects or operator
application. The new text should be easier to understand.
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This gives a more precise type signature to `magicDict` as proposed in #16646.
In addition, this replaces the constant-folding rule for `magicDict` in
`GHC.Core.Opt.ConstantFold` with a special case in the desugarer in
`GHC.HsToCore.Expr.dsHsWrapped`. I have also renamed `magicDict` to `withDict`
in light of the discussion in
https://mail.haskell.org/pipermail/ghc-devs/2021-April/019833.html.
All of this has the following benefits:
* `withDict` is now more type safe than before. Moreover, if a user applies
`withDict` at an incorrect type, the special-casing in `dsHsWrapped` will
now throw an error message indicating what the user did incorrectly.
* `withDict` can now work with classes that have multiple type arguments, such
as `Typeable @k a`. This means that `Data.Typeable.Internal.withTypeable` can
now be implemented in terms of `withDict`.
* Since the special-casing for `withDict` no longer needs to match on the
structure of the expression passed as an argument to `withDict`, it no
longer cares about the presence or absence of `Tick`s. In effect, this
obsoletes the fix for #19667.
The new `T16646` test case demonstrates the new version of `withDict` in
action, both in terms of `base` functions defined in terms of `withDict`
as well as in terms of functions from the `reflection` and `singletons`
libraries. The `T16646Fail` test case demonstrates the error message that GHC
throws when `withDict` is applied incorrectly.
This fixes #16646. By adding more tests for `withDict`, this also
fixes #19673 as a side effect.
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