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This is an automated preview release. Get the latest stable release here.

New features:

• Move the closed record update optimization (#4489 by @rhendric)

  For consumers of CoreFn like alternate backends, the optimization of replacing a closed record update with an object literal has now been moved to the point of desugaring CoreFn into JS. The ObjectUpdate expression constructor now contains a Maybe field holding a list of record labels to be copied as-is, for backends that want to perform this optimization also.

• Allow instances that require Fail to be empty (#4490 by @rhendric)

  A class instance declaration that has Prim.TypeError.Fail as a constraint will never be used. In light of this, such instances are now allowed to have empty bodies even if the class has members.

  (Such instances are still allowed to declare all of their members, and it is still an error to specify some but not all members.)

Bugfixes:

• Stop emitting warnings for wildcards in Visible Type Applications (#4492 by @JordanMartinez)

  Previously, the below usage of a wildcard (i.e. _) would incorrectly cause the compiler to emit a warning.

  f :: forall @a. a -> a
  f = identity
  
  x :: { x :: Int }
  x = f @{ x :: _ } { x: 42 }
  

• Infer types using VTA inside a record (#4501 by @JordanMartinez)

  Previously, use would fail to compile because the v type variable would not be inferred to String. Now the below code compiles:

  reflect :: forall @t v . Reflectable t v => v
  reflect = reflectType (Proxy @t)
  
  use :: String
  use = show { asdf: reflect @"asdf" }
  

Internal:

• Use gh for release artifacts (#4493 by @rhendric, #4509 by @JordanMartinez)

• Stop triggering CI on non-code-related changes (e.g. Readme) (#4502 by @JordanMartinez)

Please use 0.15.12 instead of this release. There was an issue with the Linux build. This release's notes were moved into 0.15.12's release notes.

This is an automated preview release. Get the latest stable release here.

This is an automated preview release. Get the latest stable release here.

This is an automated preview release. Get the latest stable release here.

This is an automated preview release. Get the latest stable release here.

New features:

• Implement visible type applications

  The compiler now supports visible type applications, allowing the user to instantiate one or more "visible" type variables to a specific type.

  A "visible" type variable is a type variable in a forall binder that appears prefixed with an @, like the following example:

  id :: forall @a. a -> a  -- or with kinds: `forall (@a :: Type). a -> a`
  id a = a
  

  We can then use type application syntax to instantiate this binding to a specific type:

  idInt :: Int -> Int
  idInt = id @Int
  
  example :: Int
  example = id @Int 0
  

  Type variables appearing in class or data are automatically visible, meaning that they do not require annotations:

  data Maybe a = Just a | Nothing
  
  nothingInt :: Maybe Int
  nothingInt = Nothing @Int
  
  class Identity a where
    identity :: a -> a
  
  instance Identity Int where
    identity a = a
  
  identityInt = identity @Int
  
  -- This throws a `NoInstanceFound` error.
  identityNumber = identity @Number
  

  Lastly, visible type variables can also be skipped with a wildcard (i.e. _)

  data Either a b = Left a | Right b
  
  example = Left @_ @Number 0
  

  Note that performing a type application with a type that has no visible type variables throws an error:

  module Main where
  
  id :: forall a. a -> a
  id a = a
  
  idInt = id @Int
  
  {-
  Error found:
  in module Main
  at Main.purs:6:9 - 6:16 (line 6, column 9 - line 6, column 16)
  
    An expression of polymorphic type
    with the invisible type variable a:
  
      forall a. a -> a
  
    cannot be applied to:
  
      Int
  
  
  while inferring the type of id
  in value declaration idInt
  
  See https://github.com/purescript/documentation/blob/master/errors/CannotApplyExpressionOfTypeOnType.md for more information,
  or to contribute content related to this error.
  -}
  

  Similarly, monomorphic types also cannot be used for type applications:

  module Main where
  
  idInt :: Int -> Int
  idInt a = a
  
  example = idInt @Int
  
  {-
  Error found:
  in module Main
  at Main.purs:6:11 - 6:21 (line 6, column 11 - line 6, column 21)
  
    An expression of monomorphic type:
  
      Int -> Int
  
    cannot be applied to:
  
      Int
  
  
  while inferring the type of idInt
  in value declaration example
  
  See https://github.com/purescript/documentation/blob/master/errors/CannotApplyExpressionOfTypeOnType.md for more information,
  or to contribute content related to this error.
  -}
  

• Exclude files from compiler input (#4480 by @i-am-the-slime)

  The compiler now supports excluding files from the globs given to it as input. This means there's now a new option for purs compile, namely --exclude-files (or the short version -x):

  > purs compile --help
  Usage: purs compile [FILE] [-x|--exclude-files ARG] [-o|--output ARG] ...
  
    Compile PureScript source files
  
  Available options:
    -h,--help                Show this help text
    FILE                     The input .purs file(s).
    -x,--exclude-files ARG   Glob of .purs files to exclude from the supplied
                            files.
    ...
  

  This allows you to keep related files closer together (that is, colocate them).

  Consider a setup like the following:

  src/
      Main.purs
      View/
          LoginPage.purs
          LoginPageTest.purs
          LoginPageStories.purs
  

  In order to exclude the files in the example above you can now invoke purs like this and it will only compile LoginPage.purs:

  purs compile "src/**/*.purs" --exclude-files "src/**/*Stories.purs" -x "src/**/*Test.purs"
  

  With spago, the equivalent command is:

  spago build --purs-args '-x "src/**/*Test.purs" -x "src/**/*Stories.purs"'
  

This is an automated preview release. Get the latest stable release here.

This is an automated preview release. Get the latest stable release here.