# Changelog

## v1.14.0-rc1 - 2025-12-15

### Compiler

- The output of `echo` when printing atoms has been updated to use
  `atom.create("...")` instead of `atom.create_from_string("...")`.
  ([Patrick Dewey](https://github.com/ptdewey))

- Patterns aliasing a string prefix have been optimised to generate faster code
  on the Erlang target.
  ([Giacomo Cavalieri](https://github.com/giacomocavalieri))

- Type inference for constants is now fault tolerant, meaning the compiler won't
  stop at the first error as it is typing constants.
  ([Giacomo Cavalieri](https://github.com/giacomocavalieri))

- Analysis is now fault tolerant in the presence of errors in field definitions
  of custom type variants.
  ([Adi Salimgereyev](https://github.com/abs0luty))

- The compiler now emits a warning when a module contains no public definitions
  and prevents publishing packages with empty modules to Hex.
  ([Vitor Souza](https://github.com/vit0rr))

- The `@external` annotation is now supported for external types. It allows
  users to point an external type definition to a specific Erlang or TypeScript
  type. For example, the `dict.Dict` type from the standard library can now be
  written as the following:

  ```gleam
  @external(erlang, "erlang", "map")
  @external(javascript, "../dict.d.mts", "Dict")
  pub type Dict(key, value)
  ```

  ([Surya Rose](https://github.com/GearsDatapacks))

- When matching the wrong number of subjects, the compiler now pinpoints the
  error location instead of marking the entire branch.

  ```
  case wibble {
    0, _ -> 1
    ^^^^ Expected 1 pattern, got 2
    0 |  -> 1
      ^ I was expecting a pattern after this
  }
  ```

  ([fruno](https://github.com/fruno-bulax/))

- Missing patterns in error messages and the "Add missing patterns" code action
  are no longer sorted lexicographically. Instead, they now consider the order
  in which variants were defined. As programmers often group "related" variants
  together, this should mean less reshuffling after inserting missing patterns!
  ([fruno](https://github.com/fruno-bulax/))

- The performance of `==` and `!=` has been improved for fieldless custom type
  variants when compiling to JavaScript. This was done by generating comparison
  code specific to the custom type rather than using the generic equality check
  code.
  ([Nafi](https://github.com/re-masashi))

- The lowercase bool pattern error is no longer a syntax error, but instead a
  part of the analysis step. This allows the entire module to be analyzed,
  rather than stopping at the syntax error.
  ([mxtthias](https://github.com/mxtthias))

- Exhaustiveness checks for ints and floats now correctly handle unreachable
  cases in which the numbers contain underscores (i.e. `10` and `1_0`).
  Float exhaustiveness checks also now correctly identify unreachable cases
  containing scientific notation or trailing zeros (i.e. `100` and `1e2`).
  ([ptdewey](https://github.com/ptdewey))

- The compiler now emits a warning when a doc comment is not attached to a
  definition due to a regular comment in between. For example, in the following
  code:

  ```gleam
  /// This documentation is not attached
  // This is not a doc comment
  /// This is actual documentation
  pub fn wibble() {
    todo
  }
  ```

  Will now produce the following warning:

  ```txt
    warning: Detached doc comment
    ┌─ src/main.gleam:1:4
    │
  1 │ /// This documentation is not attached
    │    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ This is not attached to a definition

  This doc comment is followed by a regular comment so it is not attached to
  any definition.
  Hint: Move the comment above the doc comment
  ```

  ([Surya Rose](https://github.com/GearsDatapacks))

- The [interference-based pruning](https://gleam.run/news/formalising-external-apis/#Improved-bit-array-exhaustiveness-checking)
  from 1.13 has been extended to int segments!
  Aside from the various performance improvements, this allows the compiler to
  mark more branches as unreachable.

  ```gleam
  case bits {
    <<"a">> -> 0
    <<97>> -> 1
    // ^- This branch is unreachable because it's equal to "a".

    <<0b1:1, _:1>> -> 2
    <<0b11:2>> -> 3
    // ^- This branch is unreachable because the branch before it already covers it.

    _ -> 99
  }
  ```

  ([fruno](https://github.com/fruno-bulax/))

- Comparison of record constructors with non-zero arity always produces `False`,
  because under the hood during code generation they become anonymous functions:

  ```gleam
  pub type Wibble {
    Wobble(String)
  }

  pub fn main() {
    echo Wobble == Wobble // False
  }
  ```

  Previously compiler produced false-positive redundant comparison warning, which
  is now removed:

  ([Adi Salimgereyev](https://github.com/abs0luty))

- Record update syntax can now be used in constant definitions. For example:

  ```gleam
  pub const base_http_config = HttpConfig(
    host: "0.0.0.0",
    port: 8080,
    use_tls: False,
    log_level: Info,
  )

  pub const dev_http_config = HttpConfig(
    ..base_http_config,
    port: 4000,
    log_level: Debug,
  )

  pub const prod_http_config = HttpConfig(
    ..base_http_config,
    port: 80,
    use_tls: True,
    log_level: Warn,
  )
  ```

  ([Adi Salimgereyev](https://github.com/abs0luty))

### Build tool

- The help text displayed by `gleam dev --help`, `gleam test --help`, and
  `gleam run --help` has been improved: now each one states which function it's
  going to run.
  ([Giacomo Cavalieri](https://github.com/giacomocavalieri))

- The `--invert` and `--package` options of `gleam deps tree` are now mutually
  exclusive; if both options are given the command will fail. Previously,
  `--invert` would be silently ignored if given together with `--package`.
  ([Evan Silberman](https://github.com/silby))

- Updated to use the latest Elixir API, so a warning would not be shown when
  compiling Elixir file in a Gleam project.
  ([Andrey Kozhev](https://github.com/ankddev))

- The build tool now has a new `gleam deps outdated` command that shows outdated
  versions for dependencies. For example:

  ```sh
  $ gleam deps outdated
  Package  Current  Latest
  -------  -------  ------
  wibble   1.4.0    1.4.1
  wobble   1.0.1    2.3.0
  ```

  ([Vladislav Shakitskiy](https://github.com/vshakitskiy))

- The format used for `gleam deps list` and the notice of available major
  version upgrades has been improved.
  ([Louis Pilfold](https://github.com/lpil))

- `gleam new` now creates the project directory using the confirmed project
  name when a suggested rename is accepted.
  ([Adi Salimgereyev](https://github.com/abs0luty))

- The build tool now provides better error message when trying to build Git
  dependencies without Git installed. Previously, it would show this error:

  ```txt
  error: Shell command failure

  There was a problem when running the shell command `git`.

  The error from the shell command library was:

      Could not find the stdio stream
  ```

  Now it will show:

  ```txt
  error: Program not found

  The program `git` was not found. Is it installed?

  Documentation for installing Git can be viewed here:
  https://git-scm.com/book/en/v2/Getting-Started-Installing-Git
  ```

  ([Andrey Kozhev](https://github.com/ankddev))

### Language server

- The language server can now offer a code action to merge case clauses with
  the same body. For example:

  ```gleam
  case user {
    Admin(name:, ..) -> todo
  //^^^^^^^^^^^^^^^^^^^^^^^^
    Guest(name:, ..) -> todo
  //^^^^^^^^^^^^^^^^ Selecting these two branches you can
  //                 trigger the "Merge case branches" code action
    _ -> todo
  }
  ```

  Triggering the code action would result in the following code:

  ```gleam
  case user {
    Admin(name:, ..) | Guest(name:, ..) -> todo
    _ -> todo
  }
  ```

  ([Giacomo Cavalieri](https://github.com/giacomocavalieri))

- The "generate function" code action can now pick better names for arguments
  that use the record access syntax. For example:

  ```gleam
  pub type User {
    User(id: Int, name: String)
  }

  pub fn go(user: User) {
    authenticate(user.id, user.name)
    todo
  }
  ```

  Having the language server generate the missing `authenticate` function will
  produce the following code:

  ```gleam
  pub fn authenticate(id: Int, name: String) {
    todo
  }
  ```

  ([Giacomo Cavalieri](https://github.com/giacomocavalieri))

- The "inline variable" code action can now trigger when used over the `let`
  keyword of a variable to inline.
  ([Giacomo Cavalieri](https://github.com/giacomocavalieri))

- The "add omitted labels" code action can now be used in function calls where
  some of the labels have been provided already.
  ([Giacomo Cavalieri](https://github.com/giacomocavalieri))

- The "generate function" code action can now trigger when used over constant
  values as well.
  ([Giacomo Cavalieri](https://github.com/giacomocavalieri))

- Grouping of related diagnostics should now work across more editors.
  Warnings will display together with their hints and you no longer have
  "go to next diagnostic" twice in a row. Zedlings rejoice!
  ([fruno](https://github.com/fruno-bulax/))

- The "pattern match on variable" code action can now pick better names when
  used on tuples.
  ([Giacomo Cavalieri](https://github.com/giacomocavalieri))

- When renaming, if the new name is invalid, the language server will produce an
  error message instead of silently doing nothing.
  ([Giacomo Cavalieri](https://github.com/giacomocavalieri))

- When providing autocomplete suggestions, the language server will now
  prioritise values which match the expected type of the value being completed.
  ([Surya Rose](https://github.com/GearsDatapacks))

- The language server now offers code action to add type annotations to all
  functions and constants. For example,

  ```gleam
  pub const answer = 42

  pub fn add(x, y) {
    x + y
  }

  pub fn add_one(thing) {
    //     ^ Triggering "Annotate all top level definitions" code action here
    let result = add(thing, 1)
    result
  }
  ```

  Triggering the "Annotate all top level definitions" code action over
  the name of function `add_one` would result in following code:

  ```gleam
  pub const answer: Int = 42

  pub fn add(x: Int, y: Int) -> Int {
    x + y
  }

  pub fn add_one(thing: Int) -> Int {
    let result = add(thing, 1)
    result
  }
  ```

  ([Andrey Kozhev](https://github.com/ankddev))

- Qualify and unqualify code actions can now trigger when used over constant
  values as well.
  ([Vladislav Shakitskiy](https://github.com/vshakitskiy))

### Formatter

### Bug fixes

- Fixed two bugs that made gleam not update the manifest correctly, causing
  it to hit hex for version resolution on every operation and quickly reach
  request limits in large projects.
  ([fruno](https://github.com/fruno-bulax/))

- Fixed a bug where renaming a variable from an alternative pattern would not
  rename all its occurrences.
  ([Giacomo Cavalieri](https://github.com/giacomocavalieri))

- The compiler now reports an error for literal floats that are outside the
  floating point representable range on both targets. Previously it would only
  do that when compiling on the Erlang target.
  ([Giacomo Cavalieri](https://github.com/giacomocavalieri))

- Fixed a typo in the error message emitted when trying to run a module that
  does not have a main function.
  ([Louis Pilfold](https://github.com/lpil))

- Fixed a bug where the "Generate function" code action would be incorrectly
  offered when calling a function unsupported by the current target, leading to
  invalid code if the code action was accepted.
  ([Surya Rose](https://github.com/GearsDatapacks))

- Fixed a bug where the formatter would not remove the right number of double
  negations from literal integers.
  ([Giacomo Cavalieri](https://github.com/giacomocavalieri))

- Fixed a typo for the "Invalid number of patterns" error.
  ([Giacomo Cavalieri](https://github.com/giacomocavalieri))

- Fixed a stack overflow when type checking some case expressions with
  thousands of branches.
  ([fruno](https://github.com/fruno-bulax/))

- The "add omitted label" code action no longer adds labels to arguments
  being piped in or the callbacks of `use`.
  ([fruno](https://github.com/fruno-bulax))

- Fixed a bug that caused the compiler to incorrectly optimise away runtime
  size checks in bit array patterns on the javascript target if they used
  calculations in the size of a segment (`_:size(wibble - wobble)`).
  ([fruno](https://github.com/fruno-bulax/))

- Add a missing BitArray constructor return type in the prelude's TypeScript
  definitions.
  ([Richard Viney](https://github.com/richard-viney))

- Fixed a bug where the BEAM would be shut down abruptly once the program had
  successfully finished running.
  ([Louis Pilfold](https://github.com/lpil))

- Fixed a bug where the "pattern match on variable" code action would generate
  invalid code when applied on a list's tail.
  ([Giacomo Cavalieri](https://github.com/giacomocavalieri))

- Fixed a bug where the "pattern match on variable" code action would generate
  invalid patterns by repeating a variable name already used in the same
  pattern.
  ([Giacomo Cavalieri](https://github.com/giacomocavalieri))

- Fixed a bug where the "generate function" code action would pop up for
  variants.
  ([Giacomo Cavalieri](https://github.com/giacomocavalieri))

- Fixed a bug where useless comparison warnings for floats compared literal
  strings, claiming for example that `1.0 == 1.` was always false.
  ([fruno](https://github.com/fruno-bulax/))

- Fixed a bug where pattern variables in case clause guards would incorrectly
  shadow outer scope variables in other branches when compiling to JavaScript.
  ([Elias Haider](https://github.com/EliasDerHai))

- Fix invalid TypeScript definition being generated for variant constructors
  with long names that take no arguments.
  ([Richard Viney](https://github.com/richard-viney))

- Fixed a bug where the formatter would remove the `@deprecated` attribute from
  constants.
  ([Surya Rose](https://github.com/GearsDatapacks))

- Fixed a bug where invalid code would be generated on the JavaScript target in
  cases where an underscore followed the decimal point in a float literal.
  ([Patrick Dewey](https://github.com/ptdewey))

- Typos in the error message shown when trying to install a non-existent package
  have been fixed.
  ([Ioan Clarke](https://github.com/ioanclarke))

- Fixed a bug where the compiler would generate invalid Erlang and TypeScript
  code for unused opaque types referencing private types.
  ([Surya Rose](https://github.com/GearsDatapacks))

- Fixed a bug where the type checker would allow invalid programs when a large
  group of functions were all mutually recursive.
  ([Surya Rose](https://github.com/GearsDatapacks))

- The compiler now provides a clearer error message when a function's return type
  is mistakenly declared using `:` instead of `->`.
  ([Gurvir Singh](https://github.com/baraich))

- Fixed a bug where the data generated for searching documentation was in the
  wrong format, preventing it from being used by Hexdocs search.
  ([Surya Rose](https://github.com/GearsDatapacks))

- Fixed a bug where the "collapse nested case" code action would produce invalid
  code on a list tail pattern.
  ([Matias Carlander](https://github.com/matiascr))

- Fixed two bugs that made gleam not update the manifest correctly, causing
  it to hit hex for version resolution on every operation and quickly reach
  request limits in large projects.
  ([fruno](https://github.com/fruno-bulax/))
