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Support the new functor type syntax MT -> MT#2755

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Julow merged 4 commits intoocaml-ppx:mainfrom
Julow:functor-type-unnamed-arg
Nov 25, 2025
Merged

Support the new functor type syntax MT -> MT#2755
Julow merged 4 commits intoocaml-ppx:mainfrom
Julow:functor-type-unnamed-arg

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@Julow Julow commented Nov 21, 2025

Fix #2646

Support the unnamed functor parameters in module types:

module type F = ARG -> S

The extended parser is changed to preserve the concrete syntax of functor arguments in module types. Notably, these three lines are no longer equivalent and the first two are no longer turned into the third:

module M : (_ : S) -> (_ : S) -> S = N
module M : S -> S -> S = N
module M : (_ : S) (_ : S) -> S = N

Julow added 3 commits November 21, 2025 16:28
@Julow
Support the new functor type syntax MT -> MT
6dcf0b5 
Support the unnamed functor parameters in module types:

    module type F = ARG -> S

The extended parser is changed to preserve the concrete syntax of
functor arguments in module types. Notably, these three lines are no
longer equivalent and the first two are no longer turned into the third:

    module M : (_ : S) -> (_ : S) -> S = N
    module M : S -> S -> S = N
    module M : (_ : S) (_ : S) -> S = N
@Julow
Simplify the parsing rules
e512110
@Julow
Update CHANGES
7926f66
@Julow Julow mentioned this pull request Nov 21, 2025
Closed
@Julow
Remove space in functor[@foo]
16d36f3 
Restore the previous formatting.
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Julow commented Nov 25, 2025

No regressions in test-branch, let's merge !

@Julow Julow merged commit 25d912f into ocaml-ppx:main Nov 25, 2025
11 of 12 checks passed
Julow added a commit to Julow/opam-repository that referenced this pull request Mar 17, 2026
@Julow
[new release] ocamlformat (4 packages) (0.29.0)
f62a590 
CHANGES:

### Highlight

- \* Support OCaml 5.5 syntax
  (ocaml-ppx/ocamlformat#2772, ocaml-ppx/ocamlformat#2774, ocaml-ppx/ocamlformat#2775, ocaml-ppx/ocamlformat#2777, ocaml-ppx/ocamlformat#2780, ocaml-ppx/ocamlformat#2781, ocaml-ppx/ocamlformat#2782, ocaml-ppx/ocamlformat#2783, @Julow)
  The update brings several tiny changes, they are listed below.

- \* Update Odoc's parser to 3.0 (ocaml-ppx/ocamlformat#2757, @Julow)
  The indentation of code-blocks containing OCaml code is reduced by 2 to avoid
  changing the generated documentation. The indentation within code-blocks is
  now significative in Odoc and shows up in generated documentation.

### Added

- Added option `letop-punning` (ocaml-ppx/ocamlformat#2746, @WardBrian) to control whether
  punning is used in extended binding operators.
  For example, the code `let+ x = x in ...` can be formatted as
  `let+ x in ...` when `letop-punning=always`. With `letop-punning=never`, it
  becomes `let+ x = x in ...`. The default is `preserve`, which will
  only use punning when it exists in the source.
  This also applies to `let%ext` bindings (ocaml-ppx/ocamlformat#2747, @WardBrian).

- Support the unnamed functor parameters syntax in module types
  (ocaml-ppx/ocamlformat#2755, ocaml-ppx/ocamlformat#2759, @Julow)
  ```ocaml
  module type F = ARG -> S
  ```
  The following lines are now formatted as they are in the source file:
  ```ocaml
  module M : (_ : S) -> (_ : S) -> S = N
  module M : S -> S -> S = N
  (* The preceding two lines are no longer turned into this: *)
  module M : (_ : S) (_ : S) -> S = N
  ```

### Fixed

- Fix dropped comment in `(function _ -> x (* cmt *))` (ocaml-ppx/ocamlformat#2739, @Julow)

- \* `cases-matching-exp-indent=compact` does not impact `begin end` nodes that
  don't have a match inside. (ocaml-ppx/ocamlformat#2742, @EmileTrotignon)
  ```ocaml
  (* before *)
  begin match () with
  | () -> begin
    f x
  end
  end
  (* after *)
  begin match () with
  | () -> begin
      f x
    end
  end
  ```

- `Ast_mapper` now iterates on *all* locations inside of Longident.t,
  instead of only some.
  (ocaml-ppx/ocamlformat#2737, @v-gb)

- Remove line break in `M with module N = N (* cmt *)` (ocaml-ppx/ocamlformat#2779, @Julow)

### Internal

- Added information on writing tests to `CONTRIBUTING.md` (ocaml-ppx/ocamlformat#2838, @WardBrian)

### Changed

- indentation of the `end` keyword in a match-case is now always at least 2. (ocaml-ppx/ocamlformat#2742, @EmileTrotignon)
  ```ocaml
  (* before *)
  begin match () with
  | () -> begin
    match () with
    | () -> ()
  end
  end
  (* after *)
  begin match () with
  | () -> begin
    match () with
    | () -> ()

- \* use shortcut `begin end` in `match` cases and `if then else` body. (ocaml-ppx/ocamlformat#2744, @EmileTrotignon)
  ```ocaml
  (* before *)
  match () with
  | () -> begin
      match () with
      | () ->
    end
  end
  (* after *)
  match () with
  | () ->
    begin match () with
      | () ->
    end
  end
  ```

- \* Set the `ocaml-version` to `5.4` by default (ocaml-ppx/ocamlformat#2750, @EmileTrotignon)
  The main difference is that the `effect` keyword is recognized without having
  to add `ocaml-version=5.3` to the configuration.
  In exchange, code that use `effect` as an identifier must use
  `ocaml-version=5.2`.

- The work to support OCaml 5.5 come with several improvements:
  + Improve the indentation of `let structure-item` with the
    `[@ocamlformat "disable"]` attribute.
    `let structure-item` means `let module`, `let open`, `let include` and
    `let exception`.
  + `(let open M in e)[@A]` is turned into `let[@A] open M in e`.
  + Long `let open ... in` no longer exceed the margin.
  + Improve indentation of `let structure-item` within parentheses:
    ```ocaml
    (* before *)
    (let module M = M in
    M.foo)
    (* after *)
    (let module M = M in
     M.foo)
    ```
Julow added a commit to Julow/opam-repository that referenced this pull request Mar 17, 2026
@Julow
[new release] ocamlformat (4 packages) (0.29.0)
e67854d 
CHANGES:

### Highlight

- \* Support OCaml 5.5 syntax
  (ocaml-ppx/ocamlformat#2772, ocaml-ppx/ocamlformat#2774, ocaml-ppx/ocamlformat#2775, ocaml-ppx/ocamlformat#2777, ocaml-ppx/ocamlformat#2780, ocaml-ppx/ocamlformat#2781, ocaml-ppx/ocamlformat#2782, ocaml-ppx/ocamlformat#2783, @Julow)
  The update brings several tiny changes, they are listed below.

- \* Update Odoc's parser to 3.0 (ocaml-ppx/ocamlformat#2757, @Julow)
  The indentation of code-blocks containing OCaml code is reduced by 2 to avoid
  changing the generated documentation. The indentation within code-blocks is
  now significative in Odoc and shows up in generated documentation.

### Added

- Added option `letop-punning` (ocaml-ppx/ocamlformat#2746, @WardBrian) to control whether
  punning is used in extended binding operators.
  For example, the code `let+ x = x in ...` can be formatted as
  `let+ x in ...` when `letop-punning=always`. With `letop-punning=never`, it
  becomes `let+ x = x in ...`. The default is `preserve`, which will
  only use punning when it exists in the source.
  This also applies to `let%ext` bindings (ocaml-ppx/ocamlformat#2747, @WardBrian).

- Support the unnamed functor parameters syntax in module types
  (ocaml-ppx/ocamlformat#2755, ocaml-ppx/ocamlformat#2759, @Julow)
  ```ocaml
  module type F = ARG -> S
  ```
  The following lines are now formatted as they are in the source file:
  ```ocaml
  module M : (_ : S) -> (_ : S) -> S = N
  module M : S -> S -> S = N
  (* The preceding two lines are no longer turned into this: *)
  module M : (_ : S) (_ : S) -> S = N
  ```

### Fixed

- Fix dropped comment in `(function _ -> x (* cmt *))` (ocaml-ppx/ocamlformat#2739, @Julow)

- \* `cases-matching-exp-indent=compact` does not impact `begin end` nodes that
  don't have a match inside. (ocaml-ppx/ocamlformat#2742, @EmileTrotignon)
  ```ocaml
  (* before *)
  begin match () with
  | () -> begin
    f x
  end
  end
  (* after *)
  begin match () with
  | () -> begin
      f x
    end
  end
  ```

- `Ast_mapper` now iterates on *all* locations inside of Longident.t,
  instead of only some.
  (ocaml-ppx/ocamlformat#2737, @v-gb)

- Remove line break in `M with module N = N (* cmt *)` (ocaml-ppx/ocamlformat#2779, @Julow)

### Internal

- Added information on writing tests to `CONTRIBUTING.md` (ocaml-ppx/ocamlformat#2838, @WardBrian)

### Changed

- indentation of the `end` keyword in a match-case is now always at least 2. (ocaml-ppx/ocamlformat#2742, @EmileTrotignon)
  ```ocaml
  (* before *)
  begin match () with
  | () -> begin
    match () with
    | () -> ()
  end
  end
  (* after *)
  begin match () with
  | () -> begin
    match () with
    | () -> ()

- \* use shortcut `begin end` in `match` cases and `if then else` body. (ocaml-ppx/ocamlformat#2744, @EmileTrotignon)
  ```ocaml
  (* before *)
  match () with
  | () -> begin
      match () with
      | () ->
    end
  end
  (* after *)
  match () with
  | () ->
    begin match () with
      | () ->
    end
  end
  ```

- \* Set the `ocaml-version` to `5.4` by default (ocaml-ppx/ocamlformat#2750, @EmileTrotignon)
  The main difference is that the `effect` keyword is recognized without having
  to add `ocaml-version=5.3` to the configuration.
  In exchange, code that use `effect` as an identifier must use
  `ocaml-version=5.2`.

- The work to support OCaml 5.5 come with several improvements:
  + Improve the indentation of `let structure-item` with the
    `[@ocamlformat "disable"]` attribute.
    `let structure-item` means `let module`, `let open`, `let include` and
    `let exception`.
  + `(let open M in e)[@A]` is turned into `let[@A] open M in e`.
  + Long `let open ... in` no longer exceed the margin.
  + Improve indentation of `let structure-item` within parentheses:
    ```ocaml
    (* before *)
    (let module M = M in
    M.foo)
    (* after *)
    (let module M = M in
     M.foo)
    ```
@Julow Julow mentioned this pull request Mar 17, 2026
Merged
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Bug: Incorrectly added any-pattern into signature of functor

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@Julow