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Remove redundant Storable constraints #394

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merged 1 commit into from
Jul 24, 2021
Merged

Remove redundant Storable constraints #394

merged 1 commit into from
Jul 24, 2021

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lehins
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@lehins lehins commented Jul 24, 2021 •
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These redundant constraints can get in a way on rare occasions. Consider

data Buffer a = BA Int ByteArray | FP Int (ForeignPtr a)

toVector :: Buffer a -> Either (VP.Vector a) (VS.Vector a)
toVector (BA size ba) = Left (VP.Vector 0 size ba)
toVector (FP size fp) = Right (VS.unsafeFromForeignPtr0 fp size)

This function will not compile because it needs Storable, but it doesn't need Prim.

@Bodigrim Bodigrim merged commit 6e4d613 into master Jul 24, 2021
@lehins lehins deleted the remove-redundant-storable branch July 25, 2021 12:59
This was referenced Jul 29, 2022
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netbsd-srcmastr pushed a commit to NetBSD/pkgsrc that referenced this pull request Aug 19, 2022
@0-wiz-0
hs-vector: update to 0.13.0.0.
0986fd5 
# Changes in version 0.13.0.0

 * `mkType` from `Data.Vector.Generic` is deprecated in favor of
   `Data.Data.mkNoRepType`
 * The role signatures on several `Vector` types were too permissive, so they
   have been tightened up:
   * The role signature for `Data.Vector.Mutable.MVector` is now
     `type role MVector nominal representational` (previously, both arguments
     were `phantom`). [#224](haskell/vector#224)
   * The role signature for `Data.Vector.Primitive.Vector` is now
     `type role Vector nominal` (previously, it was `phantom`).
     The role signature for `Data.Vector.Primitive.Mutable.MVector` is now
     `type role MVector nominal nominal` (previously, both arguments were
     `phantom`). [#316](haskell/vector#316)
   * The role signature for `Data.Vector.Storable.Vector` is now
     `type role Vector nominal` (previous, it was `phantom`), and the signature
     for `Data.Vector.Storable.Mutable.MVector` is now
     `type role MVector nominal nominal` (previous, both arguments were
     `phantom`). [#235](haskell/vector#235)

     We pick `nominal` for the role of the last argument instead of
     `representational` since the internal structure of a `Storable` vector is
     determined by the `Storable` instance of the element type, and it is not
     guaranteed that the `Storable` instances between two representationally
     equal types will preserve this internal structure.  One consequence of this
     choice is that it is no longer possible to `coerce` between
     `Storable.Vector a` and `Storable.Vector b` if `a` and `b` are nominally
     distinct but representationally equal types. We now provide
     `unsafeCoerce{M}Vector` and `unsafeCast` functions to allow this (the onus
     is on the user to ensure that no `Storable` invariants are broken when
     using these functions).
 * Methods of type classes `Data.Vector.Generic.Mutable.MVector` and
   `Data.Vector.Generic.Vector` use concrete monads (`ST`, etc) istead of being
   polymorphic (`PrimMonad`, etc). [#335](haskell/vector#335).
   This makes it possible to derive `Unbox` with:
   * `GeneralizedNewtypeDeriving`
   * via `UnboxViaPrim` and `Prim` instance
   * via `As` and `IsoUnbox` instance: [#378](haskell/vector#378)
 * Add `MonadFix` instance for boxed vectors: [#312](haskell/vector#312)
 * Re-export `PrimMonad` and `RealWorld` from mutable vectors:
   [#320](haskell/vector#320)
 * Add `maximumOn` and `minimumOn`: [#356](haskell/vector#356)
 * The functions `scanl1`, `scanl1'`, `scanr1`, and `scanr1'` for immutable
   vectors are now defined when given empty vectors as arguments,
   in which case they return empty vectors. This new behavior is consistent
   with the one of the corresponding functions in `Data.List`.
   Prior to this change, applying an empty vector to any of those functions
   resulted in an error. This change was introduced in:
   [#382](haskell/vector#382)
 * Change allocation strategy for `unfoldrN`: [#387](haskell/vector#387)
 * Remove `CPP` driven error reporting in favor of `HasCallStack`:
   [#397](haskell/vector#397)
 * Remove redundant `Storable` constraints on to/from `ForeignPtr` conversions:
   [#394](haskell/vector#394)
 * Add `unsafeCast` to `Primitive` vectors: [#401](haskell/vector#401)
 * Make `(!?)` operator strict: [#402](haskell/vector#402)
 * Add `readMaybe`: [#425](haskell/vector#425)
 * Add `groupBy` and `group` for `Data.Vector.Generic` and the specialized
   version in `Data.Vector`, `Data.Vector.Unboxed`, `Data.Vector.Storable` and
   `Data.Vector.Primitive`. [#427](haskell/vector#427)
 * Add `toArraySlice` and `unsafeFromArraySlice` functions for conversion to and
   from the underlying boxed `Array`: [#434](haskell/vector#434)
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@Bodigrim Bodigrim Bodigrim approved these changes

@Shimuuar Shimuuar Shimuuar approved these changes

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@lehins @Shimuuar @Bodigrim