Ast_iterator(3)

💖 Ast_iterator(3) 💖

okay bestie, welcome to the Ast_iterator(3) page from the OCaml library manual — this one is all about AST inspection energy ✨

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🌸 NAME 🌸

Ast_iterator — Ast_iterator.iterator enables AST inspection using open recursion. 🫶

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🧚 MODULE 🧚

Module: Ast_iterator

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✨ DOCUMENTATION ✨

Here’s the module signature line, untouched and iconic:

Module Ast_iterator : sig end

Ast_iterator.iterator enables AST inspection using open recursion. A typical mapper would be based on Ast_iterator.default_iterator — a trivial iterator — and will fall back on it for handling the syntax it does not modify. No cap, that’s the whole vibe. 💅

🚨 Warning: this module is unstable and part of Compiler_libs.

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🦋 A generic Parsetree iterator 🦋

Type time, bestie — here’s the full iterator record, every field in its rightful place:

type iterator = {
  attribute : iterator -> Parsetree.attribute -> unit ;
  attributes : iterator -> Parsetree.attribute list -> unit ;
  binding_op : iterator -> Parsetree.binding_op -> unit ;
  case : iterator -> Parsetree.case -> unit ;
  cases : iterator -> Parsetree.case list -> unit ;
  class_declaration : iterator -> Parsetree.class_declaration -> unit ;
  class_description : iterator -> Parsetree.class_description -> unit ;
  class_expr : iterator -> Parsetree.class_expr -> unit ;
  class_field : iterator -> Parsetree.class_field -> unit ;
  class_signature : iterator -> Parsetree.class_signature -> unit ;
  class_structure : iterator -> Parsetree.class_structure -> unit ;
  class_type : iterator -> Parsetree.class_type -> unit ;
  class_type_declaration : iterator -> Parsetree.class_type_declaration -> unit ;
  class_type_field : iterator -> Parsetree.class_type_field -> unit ;
  constructor_declaration : iterator -> Parsetree.constructor_declaration -> unit ;
  directive_argument : iterator -> Parsetree.directive_argument -> unit ;
  expr : iterator -> Parsetree.expression -> unit ;
  extension : iterator -> Parsetree.extension -> unit ;
  extension_constructor : iterator -> Parsetree.extension_constructor -> unit ;
  include_declaration : iterator -> Parsetree.include_declaration -> unit ;
  include_description : iterator -> Parsetree.include_description -> unit ;
  label_declaration : iterator -> Parsetree.label_declaration -> unit ;
  location : iterator -> Location.t -> unit ;
  module_binding : iterator -> Parsetree.module_binding -> unit ;
  module_declaration : iterator -> Parsetree.module_declaration -> unit ;
  module_substitution : iterator -> Parsetree.module_substitution -> unit ;
  module_expr : iterator -> Parsetree.module_expr -> unit ;
  module_type : iterator -> Parsetree.module_type -> unit ;
  module_type_declaration : iterator -> Parsetree.module_type_declaration -> unit ;
  open_declaration : iterator -> Parsetree.open_declaration -> unit ;
  open_description : iterator -> Parsetree.open_description -> unit ;
  package_type : iterator -> Parsetree.package_type -> unit ;
  pat : iterator -> Parsetree.pattern -> unit ;
  payload : iterator -> Parsetree.payload -> unit ;
  signature : iterator -> Parsetree.signature -> unit ;
  signature_item : iterator -> Parsetree.signature_item -> unit ;
  structure : iterator -> Parsetree.structure -> unit ;
  structure_item : iterator -> Parsetree.structure_item -> unit ;
  toplevel_directive : iterator -> Parsetree.toplevel_directive -> unit ;
  toplevel_phrase : iterator -> Parsetree.toplevel_phrase -> unit ;
  typ : iterator -> Parsetree.core_type -> unit ;
  row_field : iterator -> Parsetree.row_field -> unit ;
  object_field : iterator -> Parsetree.object_field -> unit ;
  type_declaration : iterator -> Parsetree.type_declaration -> unit ;
  type_extension : iterator -> Parsetree.type_extension -> unit ;
  type_exception : iterator -> Parsetree.type_exception -> unit ;
  type_kind : iterator -> Parsetree.type_kind -> unit ;
  value_binding : iterator -> Parsetree.value_binding -> unit ;
  value_description : iterator -> Parsetree.value_description -> unit ;
  with_constraint : iterator -> Parsetree.with_constraint -> unit ;
}

An iterator record implements one “method” per syntactic category, using an open recursion style: each method takes as its first argument the iterator to be applied to children in the syntax tree. Literally so organized. 🌈

val default_iterator : iterator

A default iterator, which implements a “do not do anything” mapping. It’s the chill default — lowkey iconic. 🫶

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Source/version: OCamldoc · date: 2026-06-22 · page: Ast_iterator(3) — bye bestie, go traverse something cute 💅💖✨