Changelog#

Unreleased#

Compiler#

• The compiler now supports list prepending in constants. For example:

  pub const viviparous_mammals = ["dog", "cat", "human"]
  
  pub const all_mammals = ["platypus", "echidna", ..viviparous_mammals]
  

  (Surya Rose)

Build tool#

• When publishing, the package manager now uses the full term instead of the shorthand "MFA" in the prompt and error message. (Luka Ivanović)

Language server#

• The "extract variable" code action can now pick better names for variables in case branches and blocks, ignoring unrelated names of variables in other branches. (Giacomo Cavalieri)

• The language server now has a code action to replace a _ in a type annotation with the corresponding type. For example:

  pub fn load_user(id: Int) -> Result(_, Error) {
    //                                ^
    //      Triggering the code action here
    sql.find_by_id(id)
    |> result.map_error(CannotLoadUser)
  }
  

  Triggering the code action over the _ will result in the following code:

  pub fn load_user(id: Int) -> Result(User, Error) {
    sql.find_by_id(id)
    |> result.map_error(CannotLoadUser)
  }
  

  (Giacomo Cavalieri)

Formatter#

Bug fixes#

• Fixed a bug where the compiler would crash when trying to read the cache for modules containing large constants. (Surya Rose)

• Fixed a bug where BitArray$BitArray$data constructed a DataView with incorrect byte length instead of the slice's actual size, causing sliced bit arrays to include extra bytes from the underlying buffer on JavaScript. (John Downey)

• The compiler now parses UTF-8 source files with a byte-order mark correctly, instead of raising an error. (Lucy McPhail)

v1.15.1 - 2026-03-17#

Bug fixes#

• Fixed a bug where BitArray$BitArray$data constructed a DataView with offset 0 instead of the slice's actual byte offset, causing sliced bit arrays to read from the wrong position in the underlying buffer on JavaScript. (John Downey)

• Fixed a bug where the "Add missing type parameter" code action could be triggered on types that do not exist instead of type variables. (Giacomo Cavalieri)