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Filename : ripper.rb
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# frozen_string_literal: true

require "ripper"

module Prism
  module Translation
    # This class provides a compatibility layer between prism and Ripper. It
    # functions by parsing the entire tree first and then walking it and
    # executing each of the Ripper callbacks as it goes. To use this class, you
    # treat `Prism::Translation::Ripper` effectively as you would treat the
    # `Ripper` class.
    #
    # Note that this class will serve the most common use cases, but Ripper's
    # API is extensive and undocumented. It relies on reporting the state of the
    # parser at any given time. We do our best to replicate that here, but
    # because it is a different architecture it is not possible to perfectly
    # replicate the behavior of Ripper.
    #
    # The main known difference is that we may omit dispatching some events in
    # some cases. This impacts the following events:
    #
    # - on_assign_error
    # - on_comma
    # - on_ignored_nl
    # - on_ignored_sp
    # - on_kw
    # - on_label_end
    # - on_lbrace
    # - on_lbracket
    # - on_lparen
    # - on_nl
    # - on_op
    # - on_operator_ambiguous
    # - on_rbrace
    # - on_rbracket
    # - on_rparen
    # - on_semicolon
    # - on_sp
    # - on_symbeg
    # - on_tstring_beg
    # - on_tstring_end
    #
    class Ripper < Compiler
      # Parses the given Ruby program read from +src+.
      # +src+ must be a String or an IO or a object with a #gets method.
      def self.parse(src, filename = "(ripper)", lineno = 1)
        new(src, filename, lineno).parse
      end

      # Tokenizes the Ruby program and returns an array of an array,
      # which is formatted like
      # <code>[[lineno, column], type, token, state]</code>.
      # The +filename+ argument is mostly ignored.
      # By default, this method does not handle syntax errors in +src+,
      # use the +raise_errors+ keyword to raise a SyntaxError for an error in +src+.
      #
      #     require "ripper"
      #     require "pp"
      #
      #     pp Ripper.lex("def m(a) nil end")
      #     #=> [[[1,  0], :on_kw,     "def", FNAME    ],
      #          [[1,  3], :on_sp,     " ",   FNAME    ],
      #          [[1,  4], :on_ident,  "m",   ENDFN    ],
      #          [[1,  5], :on_lparen, "(",   BEG|LABEL],
      #          [[1,  6], :on_ident,  "a",   ARG      ],
      #          [[1,  7], :on_rparen, ")",   ENDFN    ],
      #          [[1,  8], :on_sp,     " ",   BEG      ],
      #          [[1,  9], :on_kw,     "nil", END      ],
      #          [[1, 12], :on_sp,     " ",   END      ],
      #          [[1, 13], :on_kw,     "end", END      ]]
      #
      def self.lex(src, filename = "-", lineno = 1, raise_errors: false)
        result = Prism.lex_compat(src, filepath: filename, line: lineno)

        if result.failure? && raise_errors
          raise SyntaxError, result.errors.first.message
        else
          result.value
        end
      end

      # This contains a table of all of the parser events and their
      # corresponding arity.
      PARSER_EVENT_TABLE = {
        BEGIN: 1,
        END: 1,
        alias: 2,
        alias_error: 2,
        aref: 2,
        aref_field: 2,
        arg_ambiguous: 1,
        arg_paren: 1,
        args_add: 2,
        args_add_block: 2,
        args_add_star: 2,
        args_forward: 0,
        args_new: 0,
        array: 1,
        aryptn: 4,
        assign: 2,
        assign_error: 2,
        assoc_new: 2,
        assoc_splat: 1,
        assoclist_from_args: 1,
        bare_assoc_hash: 1,
        begin: 1,
        binary: 3,
        block_var: 2,
        blockarg: 1,
        bodystmt: 4,
        brace_block: 2,
        break: 1,
        call: 3,
        case: 2,
        class: 3,
        class_name_error: 2,
        command: 2,
        command_call: 4,
        const_path_field: 2,
        const_path_ref: 2,
        const_ref: 1,
        def: 3,
        defined: 1,
        defs: 5,
        do_block: 2,
        dot2: 2,
        dot3: 2,
        dyna_symbol: 1,
        else: 1,
        elsif: 3,
        ensure: 1,
        excessed_comma: 0,
        fcall: 1,
        field: 3,
        fndptn: 4,
        for: 3,
        hash: 1,
        heredoc_dedent: 2,
        hshptn: 3,
        if: 3,
        if_mod: 2,
        ifop: 3,
        in: 3,
        kwrest_param: 1,
        lambda: 2,
        magic_comment: 2,
        massign: 2,
        method_add_arg: 2,
        method_add_block: 2,
        mlhs_add: 2,
        mlhs_add_post: 2,
        mlhs_add_star: 2,
        mlhs_new: 0,
        mlhs_paren: 1,
        module: 2,
        mrhs_add: 2,
        mrhs_add_star: 2,
        mrhs_new: 0,
        mrhs_new_from_args: 1,
        next: 1,
        nokw_param: 1,
        opassign: 3,
        operator_ambiguous: 2,
        param_error: 2,
        params: 7,
        paren: 1,
        parse_error: 1,
        program: 1,
        qsymbols_add: 2,
        qsymbols_new: 0,
        qwords_add: 2,
        qwords_new: 0,
        redo: 0,
        regexp_add: 2,
        regexp_literal: 2,
        regexp_new: 0,
        rescue: 4,
        rescue_mod: 2,
        rest_param: 1,
        retry: 0,
        return: 1,
        return0: 0,
        sclass: 2,
        stmts_add: 2,
        stmts_new: 0,
        string_add: 2,
        string_concat: 2,
        string_content: 0,
        string_dvar: 1,
        string_embexpr: 1,
        string_literal: 1,
        super: 1,
        symbol: 1,
        symbol_literal: 1,
        symbols_add: 2,
        symbols_new: 0,
        top_const_field: 1,
        top_const_ref: 1,
        unary: 2,
        undef: 1,
        unless: 3,
        unless_mod: 2,
        until: 2,
        until_mod: 2,
        var_alias: 2,
        var_field: 1,
        var_ref: 1,
        vcall: 1,
        void_stmt: 0,
        when: 3,
        while: 2,
        while_mod: 2,
        word_add: 2,
        word_new: 0,
        words_add: 2,
        words_new: 0,
        xstring_add: 2,
        xstring_literal: 1,
        xstring_new: 0,
        yield: 1,
        yield0: 0,
        zsuper: 0
      }

      # This contains a table of all of the scanner events and their
      # corresponding arity.
      SCANNER_EVENT_TABLE = {
        CHAR: 1,
        __end__: 1,
        backref: 1,
        backtick: 1,
        comma: 1,
        comment: 1,
        const: 1,
        cvar: 1,
        embdoc: 1,
        embdoc_beg: 1,
        embdoc_end: 1,
        embexpr_beg: 1,
        embexpr_end: 1,
        embvar: 1,
        float: 1,
        gvar: 1,
        heredoc_beg: 1,
        heredoc_end: 1,
        ident: 1,
        ignored_nl: 1,
        imaginary: 1,
        int: 1,
        ivar: 1,
        kw: 1,
        label: 1,
        label_end: 1,
        lbrace: 1,
        lbracket: 1,
        lparen: 1,
        nl: 1,
        op: 1,
        period: 1,
        qsymbols_beg: 1,
        qwords_beg: 1,
        rational: 1,
        rbrace: 1,
        rbracket: 1,
        regexp_beg: 1,
        regexp_end: 1,
        rparen: 1,
        semicolon: 1,
        sp: 1,
        symbeg: 1,
        symbols_beg: 1,
        tlambda: 1,
        tlambeg: 1,
        tstring_beg: 1,
        tstring_content: 1,
        tstring_end: 1,
        words_beg: 1,
        words_sep: 1,
        ignored_sp: 1
      }

      # This array contains name of parser events.
      PARSER_EVENTS = PARSER_EVENT_TABLE.keys

      # This array contains name of scanner events.
      SCANNER_EVENTS = SCANNER_EVENT_TABLE.keys

      # This array contains name of all ripper events.
      EVENTS = PARSER_EVENTS + SCANNER_EVENTS

      # A list of all of the Ruby keywords.
      KEYWORDS = [
        "alias",
        "and",
        "begin",
        "BEGIN",
        "break",
        "case",
        "class",
        "def",
        "defined?",
        "do",
        "else",
        "elsif",
        "end",
        "END",
        "ensure",
        "false",
        "for",
        "if",
        "in",
        "module",
        "next",
        "nil",
        "not",
        "or",
        "redo",
        "rescue",
        "retry",
        "return",
        "self",
        "super",
        "then",
        "true",
        "undef",
        "unless",
        "until",
        "when",
        "while",
        "yield",
        "__ENCODING__",
        "__FILE__",
        "__LINE__"
      ]

      # A list of all of the Ruby binary operators.
      BINARY_OPERATORS = [
        :!=,
        :!~,
        :=~,
        :==,
        :===,
        :<=>,
        :>,
        :>=,
        :<,
        :<=,
        :&,
        :|,
        :^,
        :>>,
        :<<,
        :-,
        :+,
        :%,
        :/,
        :*,
        :**
      ]

      private_constant :KEYWORDS, :BINARY_OPERATORS

      # Parses +src+ and create S-exp tree.
      # Returns more readable tree rather than Ripper.sexp_raw.
      # This method is mainly for developer use.
      # The +filename+ argument is mostly ignored.
      # By default, this method does not handle syntax errors in +src+,
      # returning +nil+ in such cases. Use the +raise_errors+ keyword
      # to raise a SyntaxError for an error in +src+.
      #
      #     require "ripper"
      #     require "pp"
      #
      #     pp Ripper.sexp("def m(a) nil end")
      #       #=> [:program,
      #            [[:def,
      #             [:@ident, "m", [1, 4]],
      #             [:paren, [:params, [[:@ident, "a", [1, 6]]], nil, nil, nil, nil, nil, nil]],
      #             [:bodystmt, [[:var_ref, [:@kw, "nil", [1, 9]]]], nil, nil, nil]]]]
      #
      def self.sexp(src, filename = "-", lineno = 1, raise_errors: false)
        builder = SexpBuilderPP.new(src, filename, lineno)
        sexp = builder.parse
        if builder.error?
          if raise_errors
            raise SyntaxError, builder.error
          end
        else
          sexp
        end
      end

      # Parses +src+ and create S-exp tree.
      # This method is mainly for developer use.
      # The +filename+ argument is mostly ignored.
      # By default, this method does not handle syntax errors in +src+,
      # returning +nil+ in such cases. Use the +raise_errors+ keyword
      # to raise a SyntaxError for an error in +src+.
      #
      #     require "ripper"
      #     require "pp"
      #
      #     pp Ripper.sexp_raw("def m(a) nil end")
      #       #=> [:program,
      #            [:stmts_add,
      #             [:stmts_new],
      #             [:def,
      #              [:@ident, "m", [1, 4]],
      #              [:paren, [:params, [[:@ident, "a", [1, 6]]], nil, nil, nil]],
      #              [:bodystmt,
      #               [:stmts_add, [:stmts_new], [:var_ref, [:@kw, "nil", [1, 9]]]],
      #               nil,
      #               nil,
      #               nil]]]]
      #
      def self.sexp_raw(src, filename = "-", lineno = 1, raise_errors: false)
        builder = SexpBuilder.new(src, filename, lineno)
        sexp = builder.parse
        if builder.error?
          if raise_errors
            raise SyntaxError, builder.error
          end
        else
          sexp
        end
      end

      autoload :SexpBuilder, "prism/translation/ripper/sexp"
      autoload :SexpBuilderPP, "prism/translation/ripper/sexp"

      # The source that is being parsed.
      attr_reader :source

      # The filename of the source being parsed.
      attr_reader :filename

      # The current line number of the parser.
      attr_reader :lineno

      # The current column number of the parser.
      attr_reader :column

      # Create a new Translation::Ripper object with the given source.
      def initialize(source, filename = "(ripper)", lineno = 1)
        @source = source
        @filename = filename
        @lineno = lineno
        @column = 0
        @result = nil
      end

      ##########################################################################
      # Public interface
      ##########################################################################

      # True if the parser encountered an error during parsing.
      def error?
        result.failure?
      end

      # Parse the source and return the result.
      def parse
        result.comments.each do |comment|
          location = comment.location
          bounds(location)

          if comment.is_a?(InlineComment)
            on_comment(comment.slice)
          else
            offset = location.start_offset
            lines = comment.slice.lines

            lines.each_with_index do |line, index|
              bounds(location.copy(start_offset: offset))

              if index == 0
                on_embdoc_beg(line)
              elsif index == lines.size - 1
                on_embdoc_end(line)
              else
                on_embdoc(line)
              end

              offset += line.bytesize
            end
          end
        end

        result.magic_comments.each do |magic_comment|
          on_magic_comment(magic_comment.key, magic_comment.value)
        end

        unless result.data_loc.nil?
          on___end__(result.data_loc.slice.each_line.first)
        end

        result.warnings.each do |warning|
          bounds(warning.location)

          if warning.level == :default
            warning(warning.message)
          else
            case warning.type
            when :ambiguous_first_argument_plus
              on_arg_ambiguous("+")
            when :ambiguous_first_argument_minus
              on_arg_ambiguous("-")
            when :ambiguous_slash
              on_arg_ambiguous("/")
            else
              warn(warning.message)
            end
          end
        end

        if error?
          result.errors.each do |error|
            location = error.location
            bounds(location)

            case error.type
            when :alias_argument
              on_alias_error("can't make alias for the number variables", location.slice)
            when :argument_formal_class
              on_param_error("formal argument cannot be a class variable", location.slice)
            when :argument_format_constant
              on_param_error("formal argument cannot be a constant", location.slice)
            when :argument_formal_global
              on_param_error("formal argument cannot be a global variable", location.slice)
            when :argument_formal_ivar
              on_param_error("formal argument cannot be an instance variable", location.slice)
            when :class_name, :module_name
              on_class_name_error("class/module name must be CONSTANT", location.slice)
            else
              on_parse_error(error.message)
            end
          end

          nil
        else
          result.value.accept(self)
        end
      end

      ##########################################################################
      # Visitor methods
      ##########################################################################

      # alias foo bar
      # ^^^^^^^^^^^^^
      def visit_alias_method_node(node)
        new_name = visit(node.new_name)
        old_name = visit(node.old_name)

        bounds(node.location)
        on_alias(new_name, old_name)
      end

      # alias $foo $bar
      # ^^^^^^^^^^^^^^^
      def visit_alias_global_variable_node(node)
        new_name = visit_alias_global_variable_node_value(node.new_name)
        old_name = visit_alias_global_variable_node_value(node.old_name)

        bounds(node.location)
        on_var_alias(new_name, old_name)
      end

      # Visit one side of an alias global variable node.
      private def visit_alias_global_variable_node_value(node)
        bounds(node.location)

        case node
        when BackReferenceReadNode
          on_backref(node.slice)
        when GlobalVariableReadNode
          on_gvar(node.name.to_s)
        else
          raise
        end
      end

      # foo => bar | baz
      #        ^^^^^^^^^
      def visit_alternation_pattern_node(node)
        left = visit_pattern_node(node.left)
        right = visit_pattern_node(node.right)

        bounds(node.location)
        on_binary(left, :|, right)
      end

      # Visit a pattern within a pattern match. This is used to bypass the
      # parenthesis node that can be used to wrap patterns.
      private def visit_pattern_node(node)
        if node.is_a?(ParenthesesNode)
          visit(node.body)
        else
          visit(node)
        end
      end

      # a and b
      # ^^^^^^^
      def visit_and_node(node)
        left = visit(node.left)
        right = visit(node.right)

        bounds(node.location)
        on_binary(left, node.operator.to_sym, right)
      end

      # []
      # ^^
      def visit_array_node(node)
        case (opening = node.opening)
        when /^%w/
          opening_loc = node.opening_loc
          bounds(opening_loc)
          on_qwords_beg(opening)

          elements = on_qwords_new
          previous = nil

          node.elements.each do |element|
            visit_words_sep(opening_loc, previous, element)

            bounds(element.location)
            elements = on_qwords_add(elements, on_tstring_content(element.content))

            previous = element
          end

          bounds(node.closing_loc)
          on_tstring_end(node.closing)
        when /^%i/
          opening_loc = node.opening_loc
          bounds(opening_loc)
          on_qsymbols_beg(opening)

          elements = on_qsymbols_new
          previous = nil

          node.elements.each do |element|
            visit_words_sep(opening_loc, previous, element)

            bounds(element.location)
            elements = on_qsymbols_add(elements, on_tstring_content(element.value))

            previous = element
          end

          bounds(node.closing_loc)
          on_tstring_end(node.closing)
        when /^%W/
          opening_loc = node.opening_loc
          bounds(opening_loc)
          on_words_beg(opening)

          elements = on_words_new
          previous = nil

          node.elements.each do |element|
            visit_words_sep(opening_loc, previous, element)

            bounds(element.location)
            elements =
              on_words_add(
                elements,
                if element.is_a?(StringNode)
                  on_word_add(on_word_new, on_tstring_content(element.content))
                else
                  element.parts.inject(on_word_new) do |word, part|
                    word_part =
                      if part.is_a?(StringNode)
                        bounds(part.location)
                        on_tstring_content(part.content)
                      else
                        visit(part)
                      end

                    on_word_add(word, word_part)
                  end
                end
              )

            previous = element
          end

          bounds(node.closing_loc)
          on_tstring_end(node.closing)
        when /^%I/
          opening_loc = node.opening_loc
          bounds(opening_loc)
          on_symbols_beg(opening)

          elements = on_symbols_new
          previous = nil

          node.elements.each do |element|
            visit_words_sep(opening_loc, previous, element)

            bounds(element.location)
            elements =
              on_symbols_add(
                elements,
                if element.is_a?(SymbolNode)
                  on_word_add(on_word_new, on_tstring_content(element.value))
                else
                  element.parts.inject(on_word_new) do |word, part|
                    word_part =
                      if part.is_a?(StringNode)
                        bounds(part.location)
                        on_tstring_content(part.content)
                      else
                        visit(part)
                      end

                    on_word_add(word, word_part)
                  end
                end
              )

            previous = element
          end

          bounds(node.closing_loc)
          on_tstring_end(node.closing)
        else
          bounds(node.opening_loc)
          on_lbracket(opening)

          elements = visit_arguments(node.elements) unless node.elements.empty?

          bounds(node.closing_loc)
          on_rbracket(node.closing)
        end

        bounds(node.location)
        on_array(elements)
      end

      # Dispatch a words_sep event that contains the space between the elements
      # of list literals.
      private def visit_words_sep(opening_loc, previous, current)
        end_offset = (previous.nil? ? opening_loc : previous.location).end_offset
        start_offset = current.location.start_offset

        if end_offset != start_offset
          bounds(current.location.copy(start_offset: end_offset))
          on_words_sep(source.byteslice(end_offset...start_offset))
        end
      end

      # Visit a list of elements, like the elements of an array or arguments.
      private def visit_arguments(elements)
        bounds(elements.first.location)
        elements.inject(on_args_new) do |args, element|
          arg = visit(element)
          bounds(element.location)

          case element
          when BlockArgumentNode
            on_args_add_block(args, arg)
          when SplatNode
            on_args_add_star(args, arg)
          else
            on_args_add(args, arg)
          end
        end
      end

      # foo => [bar]
      #        ^^^^^
      def visit_array_pattern_node(node)
        constant = visit(node.constant)
        requireds = visit_all(node.requireds) if node.requireds.any?
        rest =
          if (rest_node = node.rest).is_a?(SplatNode)
            if rest_node.expression.nil?
              bounds(rest_node.location)
              on_var_field(nil)
            else
              visit(rest_node.expression)
            end
          end

        posts = visit_all(node.posts) if node.posts.any?

        bounds(node.location)
        on_aryptn(constant, requireds, rest, posts)
      end

      # foo(bar)
      #     ^^^
      def visit_arguments_node(node)
        arguments, _ = visit_call_node_arguments(node, nil, false)
        arguments
      end

      # { a: 1 }
      #   ^^^^
      def visit_assoc_node(node)
        key = visit(node.key)
        value = visit(node.value)

        bounds(node.location)
        on_assoc_new(key, value)
      end

      # def foo(**); bar(**); end
      #                  ^^
      #
      # { **foo }
      #   ^^^^^
      def visit_assoc_splat_node(node)
        value = visit(node.value)

        bounds(node.location)
        on_assoc_splat(value)
      end

      # $+
      # ^^
      def visit_back_reference_read_node(node)
        bounds(node.location)
        on_backref(node.slice)
      end

      # begin end
      # ^^^^^^^^^
      def visit_begin_node(node)
        clauses = visit_begin_node_clauses(node.begin_keyword_loc, node, false)

        bounds(node.location)
        on_begin(clauses)
      end

      # Visit the clauses of a begin node to form an on_bodystmt call.
      private def visit_begin_node_clauses(location, node, allow_newline)
        statements =
          if node.statements.nil?
            on_stmts_add(on_stmts_new, on_void_stmt)
          else
            body = node.statements.body
            body.unshift(nil) if void_stmt?(location, node.statements.body[0].location, allow_newline)

            bounds(node.statements.location)
            visit_statements_node_body(body)
          end

        rescue_clause = visit(node.rescue_clause)
        else_clause =
          unless (else_clause_node = node.else_clause).nil?
            else_statements =
              if else_clause_node.statements.nil?
                [nil]
              else
                body = else_clause_node.statements.body
                body.unshift(nil) if void_stmt?(else_clause_node.else_keyword_loc, else_clause_node.statements.body[0].location, allow_newline)
                body
              end

            bounds(else_clause_node.location)
            visit_statements_node_body(else_statements)
          end
        ensure_clause = visit(node.ensure_clause)

        bounds(node.location)
        on_bodystmt(statements, rescue_clause, else_clause, ensure_clause)
      end

      # Visit the body of a structure that can have either a set of statements
      # or statements wrapped in rescue/else/ensure.
      private def visit_body_node(location, node, allow_newline = false)
        case node
        when nil
          bounds(location)
          on_bodystmt(visit_statements_node_body([nil]), nil, nil, nil)
        when StatementsNode
          body = [*node.body]
          body.unshift(nil) if void_stmt?(location, body[0].location, allow_newline)
          stmts = visit_statements_node_body(body)

          bounds(node.body.first.location)
          on_bodystmt(stmts, nil, nil, nil)
        when BeginNode
          visit_begin_node_clauses(location, node, allow_newline)
        else
          raise
        end
      end

      # foo(&bar)
      #     ^^^^
      def visit_block_argument_node(node)
        visit(node.expression)
      end

      # foo { |; bar| }
      #          ^^^
      def visit_block_local_variable_node(node)
        bounds(node.location)
        on_ident(node.name.to_s)
      end

      # Visit a BlockNode.
      def visit_block_node(node)
        braces = node.opening == "{"
        parameters = visit(node.parameters)

        body =
          case node.body
          when nil
            bounds(node.location)
            stmts = on_stmts_add(on_stmts_new, on_void_stmt)

            bounds(node.location)
            braces ? stmts : on_bodystmt(stmts, nil, nil, nil)
          when StatementsNode
            stmts = node.body.body
            stmts.unshift(nil) if void_stmt?(node.parameters&.location || node.opening_loc, node.body.location, false)
            stmts = visit_statements_node_body(stmts)

            bounds(node.body.location)
            braces ? stmts : on_bodystmt(stmts, nil, nil, nil)
          when BeginNode
            visit_body_node(node.parameters&.location || node.opening_loc, node.body)
          else
            raise
          end

        if braces
          bounds(node.location)
          on_brace_block(parameters, body)
        else
          bounds(node.location)
          on_do_block(parameters, body)
        end
      end

      # def foo(&bar); end
      #         ^^^^
      def visit_block_parameter_node(node)
        if node.name_loc.nil?
          bounds(node.location)
          on_blockarg(nil)
        else
          bounds(node.name_loc)
          name = visit_token(node.name.to_s)

          bounds(node.location)
          on_blockarg(name)
        end
      end

      # A block's parameters.
      def visit_block_parameters_node(node)
        parameters =
          if node.parameters.nil?
            on_params(nil, nil, nil, nil, nil, nil, nil)
          else
            visit(node.parameters)
          end

        locals =
          if node.locals.any?
            visit_all(node.locals)
          else
            false
          end

        bounds(node.location)
        on_block_var(parameters, locals)
      end

      # break
      # ^^^^^
      #
      # break foo
      # ^^^^^^^^^
      def visit_break_node(node)
        if node.arguments.nil?
          bounds(node.location)
          on_break(on_args_new)
        else
          arguments = visit(node.arguments)

          bounds(node.location)
          on_break(arguments)
        end
      end

      # foo
      # ^^^
      #
      # foo.bar
      # ^^^^^^^
      #
      # foo.bar() {}
      # ^^^^^^^^^^^^
      def visit_call_node(node)
        if node.call_operator_loc.nil?
          case node.name
          when :[]
            receiver = visit(node.receiver)
            arguments, block = visit_call_node_arguments(node.arguments, node.block, trailing_comma?(node.arguments&.location || node.location, node.closing_loc))

            bounds(node.location)
            call = on_aref(receiver, arguments)

            if block.nil?
              call
            else
              bounds(node.location)
              on_method_add_block(call, block)
            end
          when :[]=
            receiver = visit(node.receiver)

            *arguments, last_argument = node.arguments.arguments
            arguments << node.block if !node.block.nil?

            arguments =
              if arguments.any?
                args = visit_arguments(arguments)

                if !node.block.nil?
                  args
                else
                  bounds(arguments.first.location)
                  on_args_add_block(args, false)
                end
              end

            bounds(node.location)
            call = on_aref_field(receiver, arguments)
            value = visit_write_value(last_argument)

            bounds(last_argument.location)
            on_assign(call, value)
          when :-@, :+@, :~
            receiver = visit(node.receiver)

            bounds(node.location)
            on_unary(node.name, receiver)
          when :!
            if node.message == "not"
              receiver =
                if !node.receiver.is_a?(ParenthesesNode) || !node.receiver.body.nil?
                  visit(node.receiver)
                end

              bounds(node.location)
              on_unary(:not, receiver)
            else
              receiver = visit(node.receiver)

              bounds(node.location)
              on_unary(:!, receiver)
            end
          when *BINARY_OPERATORS
            receiver = visit(node.receiver)
            value = visit(node.arguments.arguments.first)

            bounds(node.location)
            on_binary(receiver, node.name, value)
          else
            bounds(node.message_loc)
            message = visit_token(node.message, false)

            if node.variable_call?
              on_vcall(message)
            else
              arguments, block = visit_call_node_arguments(node.arguments, node.block, trailing_comma?(node.arguments&.location || node.location, node.closing_loc || node.location))
              call =
                if node.opening_loc.nil? && arguments&.any?
                  bounds(node.location)
                  on_command(message, arguments)
                elsif !node.opening_loc.nil?
                  bounds(node.location)
                  on_method_add_arg(on_fcall(message), on_arg_paren(arguments))
                else
                  bounds(node.location)
                  on_method_add_arg(on_fcall(message), on_args_new)
                end

              if block.nil?
                call
              else
                bounds(node.block.location)
                on_method_add_block(call, block)
              end
            end
          end
        else
          receiver = visit(node.receiver)

          bounds(node.call_operator_loc)
          call_operator = visit_token(node.call_operator)

          message =
            if node.message_loc.nil?
              :call
            else
              bounds(node.message_loc)
              visit_token(node.message, false)
            end

          if node.name.end_with?("=") && !node.message.end_with?("=") && !node.arguments.nil? && node.block.nil?
            value = visit_write_value(node.arguments.arguments.first)

            bounds(node.location)
            on_assign(on_field(receiver, call_operator, message), value)
          else
            arguments, block = visit_call_node_arguments(node.arguments, node.block, trailing_comma?(node.arguments&.location || node.location, node.closing_loc || node.location))
            call =
              if node.opening_loc.nil?
                bounds(node.location)

                if node.arguments.nil? && !node.block.is_a?(BlockArgumentNode)
                  on_call(receiver, call_operator, message)
                else
                  on_command_call(receiver, call_operator, message, arguments)
                end
              else
                bounds(node.opening_loc)
                arguments = on_arg_paren(arguments)

                bounds(node.location)
                on_method_add_arg(on_call(receiver, call_operator, message), arguments)
              end

            if block.nil?
              call
            else
              bounds(node.block.location)
              on_method_add_block(call, block)
            end
          end
        end
      end

      # Visit the arguments and block of a call node and return the arguments
      # and block as they should be used.
      private def visit_call_node_arguments(arguments_node, block_node, trailing_comma)
        arguments = arguments_node&.arguments || []
        block = block_node

        if block.is_a?(BlockArgumentNode)
          arguments << block
          block = nil
        end

        [
          if arguments.length == 1 && arguments.first.is_a?(ForwardingArgumentsNode)
            visit(arguments.first)
          elsif arguments.any?
            args = visit_arguments(arguments)

            if block_node.is_a?(BlockArgumentNode) || arguments.last.is_a?(ForwardingArgumentsNode) || command?(arguments.last) || trailing_comma
              args
            else
              bounds(arguments.first.location)
              on_args_add_block(args, false)
            end
          end,
          visit(block)
        ]
      end

      # Returns true if the given node is a command node.
      private def command?(node)
        node.is_a?(CallNode) &&
          node.opening_loc.nil? &&
          (!node.arguments.nil? || node.block.is_a?(BlockArgumentNode)) &&
          !BINARY_OPERATORS.include?(node.name)
      end

      # foo.bar += baz
      # ^^^^^^^^^^^^^^^
      def visit_call_operator_write_node(node)
        receiver = visit(node.receiver)

        bounds(node.call_operator_loc)
        call_operator = visit_token(node.call_operator)

        bounds(node.message_loc)
        message = visit_token(node.message)

        bounds(node.location)
        target = on_field(receiver, call_operator, message)

        bounds(node.binary_operator_loc)
        operator = on_op("#{node.binary_operator}=")
        value = visit_write_value(node.value)

        bounds(node.location)
        on_opassign(target, operator, value)
      end

      # foo.bar &&= baz
      # ^^^^^^^^^^^^^^^
      def visit_call_and_write_node(node)
        receiver = visit(node.receiver)

        bounds(node.call_operator_loc)
        call_operator = visit_token(node.call_operator)

        bounds(node.message_loc)
        message = visit_token(node.message)

        bounds(node.location)
        target = on_field(receiver, call_operator, message)

        bounds(node.operator_loc)
        operator = on_op("&&=")
        value = visit_write_value(node.value)

        bounds(node.location)
        on_opassign(target, operator, value)
      end

      # foo.bar ||= baz
      # ^^^^^^^^^^^^^^^
      def visit_call_or_write_node(node)
        receiver = visit(node.receiver)

        bounds(node.call_operator_loc)
        call_operator = visit_token(node.call_operator)

        bounds(node.message_loc)
        message = visit_token(node.message)

        bounds(node.location)
        target = on_field(receiver, call_operator, message)

        bounds(node.operator_loc)
        operator = on_op("||=")
        value = visit_write_value(node.value)

        bounds(node.location)
        on_opassign(target, operator, value)
      end

      # foo.bar, = 1
      # ^^^^^^^
      def visit_call_target_node(node)
        if node.call_operator == "::"
          receiver = visit(node.receiver)

          bounds(node.message_loc)
          message = visit_token(node.message)

          bounds(node.location)
          on_const_path_field(receiver, message)
        else
          receiver = visit(node.receiver)

          bounds(node.call_operator_loc)
          call_operator = visit_token(node.call_operator)

          bounds(node.message_loc)
          message = visit_token(node.message)

          bounds(node.location)
          on_field(receiver, call_operator, message)
        end
      end

      # foo => bar => baz
      #        ^^^^^^^^^^
      def visit_capture_pattern_node(node)
        value = visit(node.value)
        target = visit(node.target)

        bounds(node.location)
        on_binary(value, :"=>", target)
      end

      # case foo; when bar; end
      # ^^^^^^^^^^^^^^^^^^^^^^^
      def visit_case_node(node)
        predicate = visit(node.predicate)
        clauses =
          node.conditions.reverse_each.inject(visit(node.else_clause)) do |current, condition|
            on_when(*visit(condition), current)
          end

        bounds(node.location)
        on_case(predicate, clauses)
      end

      # case foo; in bar; end
      # ^^^^^^^^^^^^^^^^^^^^^
      def visit_case_match_node(node)
        predicate = visit(node.predicate)
        clauses =
          node.conditions.reverse_each.inject(visit(node.else_clause)) do |current, condition|
            on_in(*visit(condition), current)
          end

        bounds(node.location)
        on_case(predicate, clauses)
      end

      # class Foo; end
      # ^^^^^^^^^^^^^^
      def visit_class_node(node)
        constant_path =
          if node.constant_path.is_a?(ConstantReadNode)
            bounds(node.constant_path.location)
            on_const_ref(on_const(node.constant_path.name.to_s))
          else
            visit(node.constant_path)
          end

        superclass = visit(node.superclass)
        bodystmt = visit_body_node(node.superclass&.location || node.constant_path.location, node.body, node.superclass.nil?)

        bounds(node.location)
        on_class(constant_path, superclass, bodystmt)
      end

      # @@foo
      # ^^^^^
      def visit_class_variable_read_node(node)
        bounds(node.location)
        on_var_ref(on_cvar(node.slice))
      end

      # @@foo = 1
      # ^^^^^^^^^
      #
      # @@foo, @@bar = 1
      # ^^^^^  ^^^^^
      def visit_class_variable_write_node(node)
        bounds(node.name_loc)
        target = on_var_field(on_cvar(node.name.to_s))
        value = visit_write_value(node.value)

        bounds(node.location)
        on_assign(target, value)
      end

      # @@foo += bar
      # ^^^^^^^^^^^^
      def visit_class_variable_operator_write_node(node)
        bounds(node.name_loc)
        target = on_var_field(on_cvar(node.name.to_s))

        bounds(node.binary_operator_loc)
        operator = on_op("#{node.binary_operator}=")
        value = visit_write_value(node.value)

        bounds(node.location)
        on_opassign(target, operator, value)
      end

      # @@foo &&= bar
      # ^^^^^^^^^^^^^
      def visit_class_variable_and_write_node(node)
        bounds(node.name_loc)
        target = on_var_field(on_cvar(node.name.to_s))

        bounds(node.operator_loc)
        operator = on_op("&&=")
        value = visit_write_value(node.value)

        bounds(node.location)
        on_opassign(target, operator, value)
      end

      # @@foo ||= bar
      # ^^^^^^^^^^^^^
      def visit_class_variable_or_write_node(node)
        bounds(node.name_loc)
        target = on_var_field(on_cvar(node.name.to_s))

        bounds(node.operator_loc)
        operator = on_op("||=")
        value = visit_write_value(node.value)

        bounds(node.location)
        on_opassign(target, operator, value)
      end

      # @@foo, = bar
      # ^^^^^
      def visit_class_variable_target_node(node)
        bounds(node.location)
        on_var_field(on_cvar(node.name.to_s))
      end

      # Foo
      # ^^^
      def visit_constant_read_node(node)
        bounds(node.location)
        on_var_ref(on_const(node.name.to_s))
      end

      # Foo = 1
      # ^^^^^^^
      #
      # Foo, Bar = 1
      # ^^^  ^^^
      def visit_constant_write_node(node)
        bounds(node.name_loc)
        target = on_var_field(on_const(node.name.to_s))
        value = visit_write_value(node.value)

        bounds(node.location)
        on_assign(target, value)
      end

      # Foo += bar
      # ^^^^^^^^^^^
      def visit_constant_operator_write_node(node)
        bounds(node.name_loc)
        target = on_var_field(on_const(node.name.to_s))

        bounds(node.binary_operator_loc)
        operator = on_op("#{node.binary_operator}=")
        value = visit_write_value(node.value)

        bounds(node.location)
        on_opassign(target, operator, value)
      end

      # Foo &&= bar
      # ^^^^^^^^^^^^
      def visit_constant_and_write_node(node)
        bounds(node.name_loc)
        target = on_var_field(on_const(node.name.to_s))

        bounds(node.operator_loc)
        operator = on_op("&&=")
        value = visit_write_value(node.value)

        bounds(node.location)
        on_opassign(target, operator, value)
      end

      # Foo ||= bar
      # ^^^^^^^^^^^^
      def visit_constant_or_write_node(node)
        bounds(node.name_loc)
        target = on_var_field(on_const(node.name.to_s))

        bounds(node.operator_loc)
        operator = on_op("||=")
        value = visit_write_value(node.value)

        bounds(node.location)
        on_opassign(target, operator, value)
      end

      # Foo, = bar
      # ^^^
      def visit_constant_target_node(node)
        bounds(node.location)
        on_var_field(on_const(node.name.to_s))
      end

      # Foo::Bar
      # ^^^^^^^^
      def visit_constant_path_node(node)
        if node.parent.nil?
          bounds(node.name_loc)
          child = on_const(node.name.to_s)

          bounds(node.location)
          on_top_const_ref(child)
        else
          parent = visit(node.parent)

          bounds(node.name_loc)
          child = on_const(node.name.to_s)

          bounds(node.location)
          on_const_path_ref(parent, child)
        end
      end

      # Foo::Bar = 1
      # ^^^^^^^^^^^^
      #
      # Foo::Foo, Bar::Bar = 1
      # ^^^^^^^^  ^^^^^^^^
      def visit_constant_path_write_node(node)
        target = visit_constant_path_write_node_target(node.target)
        value = visit_write_value(node.value)

        bounds(node.location)
        on_assign(target, value)
      end

      # Visit a constant path that is part of a write node.
      private def visit_constant_path_write_node_target(node)
        if node.parent.nil?
          bounds(node.name_loc)
          child = on_const(node.name.to_s)

          bounds(node.location)
          on_top_const_field(child)
        else
          parent = visit(node.parent)

          bounds(node.name_loc)
          child = on_const(node.name.to_s)

          bounds(node.location)
          on_const_path_field(parent, child)
        end
      end

      # Foo::Bar += baz
      # ^^^^^^^^^^^^^^^
      def visit_constant_path_operator_write_node(node)
        target = visit_constant_path_write_node_target(node.target)
        value = visit(node.value)

        bounds(node.binary_operator_loc)
        operator = on_op("#{node.binary_operator}=")
        value = visit_write_value(node.value)

        bounds(node.location)
        on_opassign(target, operator, value)
      end

      # Foo::Bar &&= baz
      # ^^^^^^^^^^^^^^^^
      def visit_constant_path_and_write_node(node)
        target = visit_constant_path_write_node_target(node.target)
        value = visit(node.value)

        bounds(node.operator_loc)
        operator = on_op("&&=")
        value = visit_write_value(node.value)

        bounds(node.location)
        on_opassign(target, operator, value)
      end

      # Foo::Bar ||= baz
      # ^^^^^^^^^^^^^^^^
      def visit_constant_path_or_write_node(node)
        target = visit_constant_path_write_node_target(node.target)
        value = visit(node.value)

        bounds(node.operator_loc)
        operator = on_op("||=")
        value = visit_write_value(node.value)

        bounds(node.location)
        on_opassign(target, operator, value)
      end

      # Foo::Bar, = baz
      # ^^^^^^^^
      def visit_constant_path_target_node(node)
        visit_constant_path_write_node_target(node)
      end

      # def foo; end
      # ^^^^^^^^^^^^
      #
      # def self.foo; end
      # ^^^^^^^^^^^^^^^^^
      def visit_def_node(node)
        receiver = visit(node.receiver)
        operator =
          if !node.operator_loc.nil?
            bounds(node.operator_loc)
            visit_token(node.operator)
          end

        bounds(node.name_loc)
        name = visit_token(node.name_loc.slice)

        parameters =
          if node.parameters.nil?
            bounds(node.location)
            on_params(nil, nil, nil, nil, nil, nil, nil)
          else
            visit(node.parameters)
          end

        if !node.lparen_loc.nil?
          bounds(node.lparen_loc)
          parameters = on_paren(parameters)
        end

        bodystmt =
          if node.equal_loc.nil?
            visit_body_node(node.rparen_loc || node.end_keyword_loc, node.body)
          else
            body = visit(node.body.body.first)

            bounds(node.body.location)
            on_bodystmt(body, nil, nil, nil)
          end

        bounds(node.location)
        if receiver.nil?
          on_def(name, parameters, bodystmt)
        else
          on_defs(receiver, operator, name, parameters, bodystmt)
        end
      end

      # defined? a
      # ^^^^^^^^^^
      #
      # defined?(a)
      # ^^^^^^^^^^^
      def visit_defined_node(node)
        bounds(node.location)
        on_defined(visit(node.value))
      end

      # if foo then bar else baz end
      #                 ^^^^^^^^^^^^
      def visit_else_node(node)
        statements =
          if node.statements.nil?
            [nil]
          else
            body = node.statements.body
            body.unshift(nil) if void_stmt?(node.else_keyword_loc, node.statements.body[0].location, false)
            body
          end

        bounds(node.location)
        on_else(visit_statements_node_body(statements))
      end

      # "foo #{bar}"
      #      ^^^^^^
      def visit_embedded_statements_node(node)
        bounds(node.opening_loc)
        on_embexpr_beg(node.opening)

        statements =
          if node.statements.nil?
            bounds(node.location)
            on_stmts_add(on_stmts_new, on_void_stmt)
          else
            visit(node.statements)
          end

        bounds(node.closing_loc)
        on_embexpr_end(node.closing)

        bounds(node.location)
        on_string_embexpr(statements)
      end

      # "foo #@bar"
      #      ^^^^^
      def visit_embedded_variable_node(node)
        bounds(node.operator_loc)
        on_embvar(node.operator)

        variable = visit(node.variable)

        bounds(node.location)
        on_string_dvar(variable)
      end

      # Visit an EnsureNode node.
      def visit_ensure_node(node)
        statements =
          if node.statements.nil?
            [nil]
          else
            body = node.statements.body
            body.unshift(nil) if void_stmt?(node.ensure_keyword_loc, body[0].location, false)
            body
          end

        statements = visit_statements_node_body(statements)

        bounds(node.location)
        on_ensure(statements)
      end

      # false
      # ^^^^^
      def visit_false_node(node)
        bounds(node.location)
        on_var_ref(on_kw("false"))
      end

      # foo => [*, bar, *]
      #        ^^^^^^^^^^^
      def visit_find_pattern_node(node)
        constant = visit(node.constant)
        left =
          if node.left.expression.nil?
            bounds(node.left.location)
            on_var_field(nil)
          else
            visit(node.left.expression)
          end

        requireds = visit_all(node.requireds) if node.requireds.any?
        right =
          if node.right.expression.nil?
            bounds(node.right.location)
            on_var_field(nil)
          else
            visit(node.right.expression)
          end

        bounds(node.location)
        on_fndptn(constant, left, requireds, right)
      end

      # if foo .. bar; end
      #    ^^^^^^^^^^
      def visit_flip_flop_node(node)
        left = visit(node.left)
        right = visit(node.right)

        bounds(node.location)
        if node.exclude_end?
          on_dot3(left, right)
        else
          on_dot2(left, right)
        end
      end

      # 1.0
      # ^^^
      def visit_float_node(node)
        visit_number_node(node) { |text| on_float(text) }
      end

      # for foo in bar do end
      # ^^^^^^^^^^^^^^^^^^^^^
      def visit_for_node(node)
        index = visit(node.index)
        collection = visit(node.collection)
        statements =
          if node.statements.nil?
            bounds(node.location)
            on_stmts_add(on_stmts_new, on_void_stmt)
          else
            visit(node.statements)
          end

        bounds(node.location)
        on_for(index, collection, statements)
      end

      # def foo(...); bar(...); end
      #                   ^^^
      def visit_forwarding_arguments_node(node)
        bounds(node.location)
        on_args_forward
      end

      # def foo(...); end
      #         ^^^
      def visit_forwarding_parameter_node(node)
        bounds(node.location)
        on_args_forward
      end

      # super
      # ^^^^^
      #
      # super {}
      # ^^^^^^^^
      def visit_forwarding_super_node(node)
        if node.block.nil?
          bounds(node.location)
          on_zsuper
        else
          block = visit(node.block)

          bounds(node.location)
          on_method_add_block(on_zsuper, block)
        end
      end

      # $foo
      # ^^^^
      def visit_global_variable_read_node(node)
        bounds(node.location)
        on_var_ref(on_gvar(node.name.to_s))
      end

      # $foo = 1
      # ^^^^^^^^
      #
      # $foo, $bar = 1
      # ^^^^  ^^^^
      def visit_global_variable_write_node(node)
        bounds(node.name_loc)
        target = on_var_field(on_gvar(node.name.to_s))
        value = visit_write_value(node.value)

        bounds(node.location)
        on_assign(target, value)
      end

      # $foo += bar
      # ^^^^^^^^^^^
      def visit_global_variable_operator_write_node(node)
        bounds(node.name_loc)
        target = on_var_field(on_gvar(node.name.to_s))

        bounds(node.binary_operator_loc)
        operator = on_op("#{node.binary_operator}=")
        value = visit_write_value(node.value)

        bounds(node.location)
        on_opassign(target, operator, value)
      end

      # $foo &&= bar
      # ^^^^^^^^^^^^
      def visit_global_variable_and_write_node(node)
        bounds(node.name_loc)
        target = on_var_field(on_gvar(node.name.to_s))

        bounds(node.operator_loc)
        operator = on_op("&&=")
        value = visit_write_value(node.value)

        bounds(node.location)
        on_opassign(target, operator, value)
      end

      # $foo ||= bar
      # ^^^^^^^^^^^^
      def visit_global_variable_or_write_node(node)
        bounds(node.name_loc)
        target = on_var_field(on_gvar(node.name.to_s))

        bounds(node.operator_loc)
        operator = on_op("||=")
        value = visit_write_value(node.value)

        bounds(node.location)
        on_opassign(target, operator, value)
      end

      # $foo, = bar
      # ^^^^
      def visit_global_variable_target_node(node)
        bounds(node.location)
        on_var_field(on_gvar(node.name.to_s))
      end

      # {}
      # ^^
      def visit_hash_node(node)
        elements =
          if node.elements.any?
            args = visit_all(node.elements)

            bounds(node.elements.first.location)
            on_assoclist_from_args(args)
          end

        bounds(node.location)
        on_hash(elements)
      end

      # foo => {}
      #        ^^
      def visit_hash_pattern_node(node)
        constant = visit(node.constant)
        elements =
          if node.elements.any? || !node.rest.nil?
            node.elements.map do |element|
              [
                if (key = element.key).opening_loc.nil?
                  visit(key)
                else
                  bounds(key.value_loc)
                  if (value = key.value).empty?
                    on_string_content
                  else
                    on_string_add(on_string_content, on_tstring_content(value))
                  end
                end,
                visit(element.value)
              ]
            end
          end

        rest =
          case node.rest
          when AssocSplatNode
            visit(node.rest.value)
          when NoKeywordsParameterNode
            bounds(node.rest.location)
            on_var_field(visit(node.rest))
          end

        bounds(node.location)
        on_hshptn(constant, elements, rest)
      end

      # if foo then bar end
      # ^^^^^^^^^^^^^^^^^^^
      #
      # bar if foo
      # ^^^^^^^^^^
      #
      # foo ? bar : baz
      # ^^^^^^^^^^^^^^^
      def visit_if_node(node)
        if node.then_keyword == "?"
          predicate = visit(node.predicate)
          truthy = visit(node.statements.body.first)
          falsy = visit(node.subsequent.statements.body.first)

          bounds(node.location)
          on_ifop(predicate, truthy, falsy)
        elsif node.statements.nil? || (node.predicate.location.start_offset < node.statements.location.start_offset)
          predicate = visit(node.predicate)
          statements =
            if node.statements.nil?
              bounds(node.location)
              on_stmts_add(on_stmts_new, on_void_stmt)
            else
              visit(node.statements)
            end
          subsequent = visit(node.subsequent)

          bounds(node.location)
          if node.if_keyword == "if"
            on_if(predicate, statements, subsequent)
          else
            on_elsif(predicate, statements, subsequent)
          end
        else
          statements = visit(node.statements.body.first)
          predicate = visit(node.predicate)

          bounds(node.location)
          on_if_mod(predicate, statements)
        end
      end

      # 1i
      # ^^
      def visit_imaginary_node(node)
        visit_number_node(node) { |text| on_imaginary(text) }
      end

      # { foo: }
      #   ^^^^
      def visit_implicit_node(node)
      end

      # foo { |bar,| }
      #           ^
      def visit_implicit_rest_node(node)
        bounds(node.location)
        on_excessed_comma
      end

      # case foo; in bar; end
      # ^^^^^^^^^^^^^^^^^^^^^
      def visit_in_node(node)
        # This is a special case where we're not going to call on_in directly
        # because we don't have access to the subsequent. Instead, we'll return
        # the component parts and let the parent node handle it.
        pattern = visit_pattern_node(node.pattern)
        statements =
          if node.statements.nil?
            bounds(node.location)
            on_stmts_add(on_stmts_new, on_void_stmt)
          else
            visit(node.statements)
          end

        [pattern, statements]
      end

      # foo[bar] += baz
      # ^^^^^^^^^^^^^^^
      def visit_index_operator_write_node(node)
        receiver = visit(node.receiver)
        arguments, _ = visit_call_node_arguments(node.arguments, node.block, trailing_comma?(node.arguments&.location || node.location, node.closing_loc))

        bounds(node.location)
        target = on_aref_field(receiver, arguments)

        bounds(node.binary_operator_loc)
        operator = on_op("#{node.binary_operator}=")
        value = visit_write_value(node.value)

        bounds(node.location)
        on_opassign(target, operator, value)
      end

      # foo[bar] &&= baz
      # ^^^^^^^^^^^^^^^^
      def visit_index_and_write_node(node)
        receiver = visit(node.receiver)
        arguments, _ = visit_call_node_arguments(node.arguments, node.block, trailing_comma?(node.arguments&.location || node.location, node.closing_loc))

        bounds(node.location)
        target = on_aref_field(receiver, arguments)

        bounds(node.operator_loc)
        operator = on_op("&&=")
        value = visit_write_value(node.value)

        bounds(node.location)
        on_opassign(target, operator, value)
      end

      # foo[bar] ||= baz
      # ^^^^^^^^^^^^^^^^
      def visit_index_or_write_node(node)
        receiver = visit(node.receiver)
        arguments, _ = visit_call_node_arguments(node.arguments, node.block, trailing_comma?(node.arguments&.location || node.location, node.closing_loc))

        bounds(node.location)
        target = on_aref_field(receiver, arguments)

        bounds(node.operator_loc)
        operator = on_op("||=")
        value = visit_write_value(node.value)

        bounds(node.location)
        on_opassign(target, operator, value)
      end

      # foo[bar], = 1
      # ^^^^^^^^
      def visit_index_target_node(node)
        receiver = visit(node.receiver)
        arguments, _ = visit_call_node_arguments(node.arguments, node.block, trailing_comma?(node.arguments&.location || node.location, node.closing_loc))

        bounds(node.location)
        on_aref_field(receiver, arguments)
      end

      # @foo
      # ^^^^
      def visit_instance_variable_read_node(node)
        bounds(node.location)
        on_var_ref(on_ivar(node.name.to_s))
      end

      # @foo = 1
      # ^^^^^^^^
      def visit_instance_variable_write_node(node)
        bounds(node.name_loc)
        target = on_var_field(on_ivar(node.name.to_s))
        value = visit_write_value(node.value)

        bounds(node.location)
        on_assign(target, value)
      end

      # @foo += bar
      # ^^^^^^^^^^^
      def visit_instance_variable_operator_write_node(node)
        bounds(node.name_loc)
        target = on_var_field(on_ivar(node.name.to_s))

        bounds(node.binary_operator_loc)
        operator = on_op("#{node.binary_operator}=")
        value = visit_write_value(node.value)

        bounds(node.location)
        on_opassign(target, operator, value)
      end

      # @foo &&= bar
      # ^^^^^^^^^^^^
      def visit_instance_variable_and_write_node(node)
        bounds(node.name_loc)
        target = on_var_field(on_ivar(node.name.to_s))

        bounds(node.operator_loc)
        operator = on_op("&&=")
        value = visit_write_value(node.value)

        bounds(node.location)
        on_opassign(target, operator, value)
      end

      # @foo ||= bar
      # ^^^^^^^^^^^^
      def visit_instance_variable_or_write_node(node)
        bounds(node.name_loc)
        target = on_var_field(on_ivar(node.name.to_s))

        bounds(node.operator_loc)
        operator = on_op("||=")
        value = visit_write_value(node.value)

        bounds(node.location)
        on_opassign(target, operator, value)
      end

      # @foo, = bar
      # ^^^^
      def visit_instance_variable_target_node(node)
        bounds(node.location)
        on_var_field(on_ivar(node.name.to_s))
      end

      # 1
      # ^
      def visit_integer_node(node)
        visit_number_node(node) { |text| on_int(text) }
      end

      # if /foo #{bar}/ then end
      #    ^^^^^^^^^^^^
      def visit_interpolated_match_last_line_node(node)
        bounds(node.opening_loc)
        on_regexp_beg(node.opening)

        bounds(node.parts.first.location)
        parts =
          node.parts.inject(on_regexp_new) do |content, part|
            on_regexp_add(content, visit_string_content(part))
          end

        bounds(node.closing_loc)
        closing = on_regexp_end(node.closing)

        bounds(node.location)
        on_regexp_literal(parts, closing)
      end

      # /foo #{bar}/
      # ^^^^^^^^^^^^
      def visit_interpolated_regular_expression_node(node)
        bounds(node.opening_loc)
        on_regexp_beg(node.opening)

        bounds(node.parts.first.location)
        parts =
          node.parts.inject(on_regexp_new) do |content, part|
            on_regexp_add(content, visit_string_content(part))
          end

        bounds(node.closing_loc)
        closing = on_regexp_end(node.closing)

        bounds(node.location)
        on_regexp_literal(parts, closing)
      end

      # "foo #{bar}"
      # ^^^^^^^^^^^^
      def visit_interpolated_string_node(node)
        if node.opening&.start_with?("<<~")
          heredoc = visit_heredoc_string_node(node)

          bounds(node.location)
          on_string_literal(heredoc)
        elsif !node.heredoc? && node.parts.length > 1 && node.parts.any? { |part| (part.is_a?(StringNode) || part.is_a?(InterpolatedStringNode)) && !part.opening_loc.nil? }
          first, *rest = node.parts
          rest.inject(visit(first)) do |content, part|
            concat = visit(part)

            bounds(part.location)
            on_string_concat(content, concat)
          end
        else
          bounds(node.parts.first.location)
          parts =
            node.parts.inject(on_string_content) do |content, part|
              on_string_add(content, visit_string_content(part))
            end

          bounds(node.location)
          on_string_literal(parts)
        end
      end

      # :"foo #{bar}"
      # ^^^^^^^^^^^^^
      def visit_interpolated_symbol_node(node)
        bounds(node.parts.first.location)
        parts =
          node.parts.inject(on_string_content) do |content, part|
            on_string_add(content, visit_string_content(part))
          end

        bounds(node.location)
        on_dyna_symbol(parts)
      end

      # `foo #{bar}`
      # ^^^^^^^^^^^^
      def visit_interpolated_x_string_node(node)
        if node.opening.start_with?("<<~")
          heredoc = visit_heredoc_x_string_node(node)

          bounds(node.location)
          on_xstring_literal(heredoc)
        else
          bounds(node.parts.first.location)
          parts =
            node.parts.inject(on_xstring_new) do |content, part|
              on_xstring_add(content, visit_string_content(part))
            end

          bounds(node.location)
          on_xstring_literal(parts)
        end
      end

      # Visit an individual part of a string-like node.
      private def visit_string_content(part)
        if part.is_a?(StringNode)
          bounds(part.content_loc)
          on_tstring_content(part.content)
        else
          visit(part)
        end
      end

      # -> { it }
      #      ^^
      def visit_it_local_variable_read_node(node)
        bounds(node.location)
        on_vcall(on_ident(node.slice))
      end

      # -> { it }
      # ^^^^^^^^^
      def visit_it_parameters_node(node)
      end

      # foo(bar: baz)
      #     ^^^^^^^^
      def visit_keyword_hash_node(node)
        elements = visit_all(node.elements)

        bounds(node.location)
        on_bare_assoc_hash(elements)
      end

      # def foo(**bar); end
      #         ^^^^^
      #
      # def foo(**); end
      #         ^^
      def visit_keyword_rest_parameter_node(node)
        if node.name_loc.nil?
          bounds(node.location)
          on_kwrest_param(nil)
        else
          bounds(node.name_loc)
          name = on_ident(node.name.to_s)

          bounds(node.location)
          on_kwrest_param(name)
        end
      end

      # -> {}
      def visit_lambda_node(node)
        bounds(node.operator_loc)
        on_tlambda(node.operator)

        parameters =
          if node.parameters.is_a?(BlockParametersNode)
            # Ripper does not track block-locals within lambdas, so we skip
            # directly to the parameters here.
            params =
              if node.parameters.parameters.nil?
                bounds(node.location)
                on_params(nil, nil, nil, nil, nil, nil, nil)
              else
                visit(node.parameters.parameters)
              end

            if node.parameters.opening_loc.nil?
              params
            else
              bounds(node.parameters.opening_loc)
              on_paren(params)
            end
          else
            bounds(node.location)
            on_params(nil, nil, nil, nil, nil, nil, nil)
          end

        braces = node.opening == "{"
        if braces
          bounds(node.opening_loc)
          on_tlambeg(node.opening)
        end

        body =
          case node.body
          when nil
            bounds(node.location)
            stmts = on_stmts_add(on_stmts_new, on_void_stmt)

            bounds(node.location)
            braces ? stmts : on_bodystmt(stmts, nil, nil, nil)
          when StatementsNode
            stmts = node.body.body
            stmts.unshift(nil) if void_stmt?(node.parameters&.location || node.opening_loc, node.body.location, false)
            stmts = visit_statements_node_body(stmts)

            bounds(node.body.location)
            braces ? stmts : on_bodystmt(stmts, nil, nil, nil)
          when BeginNode
            visit_body_node(node.opening_loc, node.body)
          else
            raise
          end

        bounds(node.location)
        on_lambda(parameters, body)
      end

      # foo
      # ^^^
      def visit_local_variable_read_node(node)
        bounds(node.location)
        on_var_ref(on_ident(node.slice))
      end

      # foo = 1
      # ^^^^^^^
      def visit_local_variable_write_node(node)
        bounds(node.name_loc)
        target = on_var_field(on_ident(node.name_loc.slice))
        value = visit_write_value(node.value)

        bounds(node.location)
        on_assign(target, value)
      end

      # foo += bar
      # ^^^^^^^^^^
      def visit_local_variable_operator_write_node(node)
        bounds(node.name_loc)
        target = on_var_field(on_ident(node.name_loc.slice))

        bounds(node.binary_operator_loc)
        operator = on_op("#{node.binary_operator}=")
        value = visit_write_value(node.value)

        bounds(node.location)
        on_opassign(target, operator, value)
      end

      # foo &&= bar
      # ^^^^^^^^^^^
      def visit_local_variable_and_write_node(node)
        bounds(node.name_loc)
        target = on_var_field(on_ident(node.name_loc.slice))

        bounds(node.operator_loc)
        operator = on_op("&&=")
        value = visit_write_value(node.value)

        bounds(node.location)
        on_opassign(target, operator, value)
      end

      # foo ||= bar
      # ^^^^^^^^^^^
      def visit_local_variable_or_write_node(node)
        bounds(node.name_loc)
        target = on_var_field(on_ident(node.name_loc.slice))

        bounds(node.operator_loc)
        operator = on_op("||=")
        value = visit_write_value(node.value)

        bounds(node.location)
        on_opassign(target, operator, value)
      end

      # foo, = bar
      # ^^^
      def visit_local_variable_target_node(node)
        bounds(node.location)
        on_var_field(on_ident(node.name.to_s))
      end

      # if /foo/ then end
      #    ^^^^^
      def visit_match_last_line_node(node)
        bounds(node.opening_loc)
        on_regexp_beg(node.opening)

        bounds(node.content_loc)
        tstring_content = on_tstring_content(node.content)

        bounds(node.closing_loc)
        closing = on_regexp_end(node.closing)

        on_regexp_literal(on_regexp_add(on_regexp_new, tstring_content), closing)
      end

      # foo in bar
      # ^^^^^^^^^^
      def visit_match_predicate_node(node)
        value = visit(node.value)
        pattern = on_in(visit_pattern_node(node.pattern), nil, nil)

        on_case(value, pattern)
      end

      # foo => bar
      # ^^^^^^^^^^
      def visit_match_required_node(node)
        value = visit(node.value)
        pattern = on_in(visit_pattern_node(node.pattern), nil, nil)

        on_case(value, pattern)
      end

      # /(?<foo>foo)/ =~ bar
      # ^^^^^^^^^^^^^^^^^^^^
      def visit_match_write_node(node)
        visit(node.call)
      end

      # A node that is missing from the syntax tree. This is only used in the
      # case of a syntax error.
      def visit_missing_node(node)
        raise "Cannot visit missing nodes directly."
      end

      # module Foo; end
      # ^^^^^^^^^^^^^^^
      def visit_module_node(node)
        constant_path =
          if node.constant_path.is_a?(ConstantReadNode)
            bounds(node.constant_path.location)
            on_const_ref(on_const(node.constant_path.name.to_s))
          else
            visit(node.constant_path)
          end

        bodystmt = visit_body_node(node.constant_path.location, node.body, true)

        bounds(node.location)
        on_module(constant_path, bodystmt)
      end

      # (foo, bar), bar = qux
      # ^^^^^^^^^^
      def visit_multi_target_node(node)
        bounds(node.location)
        targets = visit_multi_target_node_targets(node.lefts, node.rest, node.rights, true)

        if node.lparen_loc.nil?
          targets
        else
          bounds(node.lparen_loc)
          on_mlhs_paren(targets)
        end
      end

      # Visit the targets of a multi-target node.
      private def visit_multi_target_node_targets(lefts, rest, rights, skippable)
        if skippable && lefts.length == 1 && lefts.first.is_a?(MultiTargetNode) && rest.nil? && rights.empty?
          return visit(lefts.first)
        end

        mlhs = on_mlhs_new

        lefts.each do |left|
          bounds(left.location)
          mlhs = on_mlhs_add(mlhs, visit(left))
        end

        case rest
        when nil
          # do nothing
        when ImplicitRestNode
          # these do not get put into the generated tree
          bounds(rest.location)
          on_excessed_comma
        else
          bounds(rest.location)
          mlhs = on_mlhs_add_star(mlhs, visit(rest))
        end

        if rights.any?
          bounds(rights.first.location)
          post = on_mlhs_new

          rights.each do |right|
            bounds(right.location)
            post = on_mlhs_add(post, visit(right))
          end

          mlhs = on_mlhs_add_post(mlhs, post)
        end

        mlhs
      end

      # foo, bar = baz
      # ^^^^^^^^^^^^^^
      def visit_multi_write_node(node)
        bounds(node.location)
        targets = visit_multi_target_node_targets(node.lefts, node.rest, node.rights, true)

        unless node.lparen_loc.nil?
          bounds(node.lparen_loc)
          targets = on_mlhs_paren(targets)
        end

        value = visit_write_value(node.value)

        bounds(node.location)
        on_massign(targets, value)
      end

      # next
      # ^^^^
      #
      # next foo
      # ^^^^^^^^
      def visit_next_node(node)
        if node.arguments.nil?
          bounds(node.location)
          on_next(on_args_new)
        else
          arguments = visit(node.arguments)

          bounds(node.location)
          on_next(arguments)
        end
      end

      # nil
      # ^^^
      def visit_nil_node(node)
        bounds(node.location)
        on_var_ref(on_kw("nil"))
      end

      # def foo(**nil); end
      #         ^^^^^
      def visit_no_keywords_parameter_node(node)
        bounds(node.location)
        on_nokw_param(nil)

        :nil
      end

      # -> { _1 + _2 }
      # ^^^^^^^^^^^^^^
      def visit_numbered_parameters_node(node)
      end

      # $1
      # ^^
      def visit_numbered_reference_read_node(node)
        bounds(node.location)
        on_backref(node.slice)
      end

      # def foo(bar: baz); end
      #         ^^^^^^^^
      def visit_optional_keyword_parameter_node(node)
        bounds(node.name_loc)
        name = on_label("#{node.name}:")
        value = visit(node.value)

        [name, value]
      end

      # def foo(bar = 1); end
      #         ^^^^^^^
      def visit_optional_parameter_node(node)
        bounds(node.name_loc)
        name = visit_token(node.name.to_s)
        value = visit(node.value)

        [name, value]
      end

      # a or b
      # ^^^^^^
      def visit_or_node(node)
        left = visit(node.left)
        right = visit(node.right)

        bounds(node.location)
        on_binary(left, node.operator.to_sym, right)
      end

      # def foo(bar, *baz); end
      #         ^^^^^^^^^
      def visit_parameters_node(node)
        requireds = node.requireds.map { |required| required.is_a?(MultiTargetNode) ? visit_destructured_parameter_node(required) : visit(required) } if node.requireds.any?
        optionals = visit_all(node.optionals) if node.optionals.any?
        rest = visit(node.rest)
        posts = node.posts.map { |post| post.is_a?(MultiTargetNode) ? visit_destructured_parameter_node(post) : visit(post) } if node.posts.any?
        keywords = visit_all(node.keywords) if node.keywords.any?
        keyword_rest = visit(node.keyword_rest)
        block = visit(node.block)

        bounds(node.location)
        on_params(requireds, optionals, rest, posts, keywords, keyword_rest, block)
      end

      # Visit a destructured positional parameter node.
      private def visit_destructured_parameter_node(node)
        bounds(node.location)
        targets = visit_multi_target_node_targets(node.lefts, node.rest, node.rights, false)

        bounds(node.lparen_loc)
        on_mlhs_paren(targets)
      end

      # ()
      # ^^
      #
      # (1)
      # ^^^
      def visit_parentheses_node(node)
        body =
          if node.body.nil?
            on_stmts_add(on_stmts_new, on_void_stmt)
          else
            visit(node.body)
          end

        bounds(node.location)
        on_paren(body)
      end

      # foo => ^(bar)
      #        ^^^^^^
      def visit_pinned_expression_node(node)
        expression = visit(node.expression)

        bounds(node.location)
        on_begin(expression)
      end

      # foo = 1 and bar => ^foo
      #                    ^^^^
      def visit_pinned_variable_node(node)
        visit(node.variable)
      end

      # END {}
      # ^^^^^^
      def visit_post_execution_node(node)
        statements =
          if node.statements.nil?
            bounds(node.location)
            on_stmts_add(on_stmts_new, on_void_stmt)
          else
            visit(node.statements)
          end

        bounds(node.location)
        on_END(statements)
      end

      # BEGIN {}
      # ^^^^^^^^
      def visit_pre_execution_node(node)
        statements =
          if node.statements.nil?
            bounds(node.location)
            on_stmts_add(on_stmts_new, on_void_stmt)
          else
            visit(node.statements)
          end

        bounds(node.location)
        on_BEGIN(statements)
      end

      # The top-level program node.
      def visit_program_node(node)
        body = node.statements.body
        body << nil if body.empty?
        statements = visit_statements_node_body(body)

        bounds(node.location)
        on_program(statements)
      end

      # 0..5
      # ^^^^
      def visit_range_node(node)
        left = visit(node.left)
        right = visit(node.right)

        bounds(node.location)
        if node.exclude_end?
          on_dot3(left, right)
        else
          on_dot2(left, right)
        end
      end

      # 1r
      # ^^
      def visit_rational_node(node)
        visit_number_node(node) { |text| on_rational(text) }
      end

      # redo
      # ^^^^
      def visit_redo_node(node)
        bounds(node.location)
        on_redo
      end

      # /foo/
      # ^^^^^
      def visit_regular_expression_node(node)
        bounds(node.opening_loc)
        on_regexp_beg(node.opening)

        if node.content.empty?
          bounds(node.closing_loc)
          closing = on_regexp_end(node.closing)

          on_regexp_literal(on_regexp_new, closing)
        else
          bounds(node.content_loc)
          tstring_content = on_tstring_content(node.content)

          bounds(node.closing_loc)
          closing = on_regexp_end(node.closing)

          on_regexp_literal(on_regexp_add(on_regexp_new, tstring_content), closing)
        end
      end

      # def foo(bar:); end
      #         ^^^^
      def visit_required_keyword_parameter_node(node)
        bounds(node.name_loc)
        [on_label("#{node.name}:"), false]
      end

      # def foo(bar); end
      #         ^^^
      def visit_required_parameter_node(node)
        bounds(node.location)
        on_ident(node.name.to_s)
      end

      # foo rescue bar
      # ^^^^^^^^^^^^^^
      def visit_rescue_modifier_node(node)
        expression = visit_write_value(node.expression)
        rescue_expression = visit(node.rescue_expression)

        bounds(node.location)
        on_rescue_mod(expression, rescue_expression)
      end

      # begin; rescue; end
      #        ^^^^^^^
      def visit_rescue_node(node)
        exceptions =
          case node.exceptions.length
          when 0
            nil
          when 1
            if (exception = node.exceptions.first).is_a?(SplatNode)
              bounds(exception.location)
              on_mrhs_add_star(on_mrhs_new, visit(exception))
            else
              [visit(node.exceptions.first)]
            end
          else
            bounds(node.location)
            length = node.exceptions.length

            node.exceptions.each_with_index.inject(on_args_new) do |mrhs, (exception, index)|
              arg = visit(exception)

              bounds(exception.location)
              mrhs = on_mrhs_new_from_args(mrhs) if index == length - 1

              if exception.is_a?(SplatNode)
                if index == length - 1
                  on_mrhs_add_star(mrhs, arg)
                else
                  on_args_add_star(mrhs, arg)
                end
              else
                if index == length - 1
                  on_mrhs_add(mrhs, arg)
                else
                  on_args_add(mrhs, arg)
                end
              end
            end
          end

        reference = visit(node.reference)
        statements =
          if node.statements.nil?
            bounds(node.location)
            on_stmts_add(on_stmts_new, on_void_stmt)
          else
            visit(node.statements)
          end

        subsequent = visit(node.subsequent)

        bounds(node.location)
        on_rescue(exceptions, reference, statements, subsequent)
      end

      # def foo(*bar); end
      #         ^^^^
      #
      # def foo(*); end
      #         ^
      def visit_rest_parameter_node(node)
        if node.name_loc.nil?
          bounds(node.location)
          on_rest_param(nil)
        else
          bounds(node.name_loc)
          on_rest_param(visit_token(node.name.to_s))
        end
      end

      # retry
      # ^^^^^
      def visit_retry_node(node)
        bounds(node.location)
        on_retry
      end

      # return
      # ^^^^^^
      #
      # return 1
      # ^^^^^^^^
      def visit_return_node(node)
        if node.arguments.nil?
          bounds(node.location)
          on_return0
        else
          arguments = visit(node.arguments)

          bounds(node.location)
          on_return(arguments)
        end
      end

      # self
      # ^^^^
      def visit_self_node(node)
        bounds(node.location)
        on_var_ref(on_kw("self"))
      end

      # A shareable constant.
      def visit_shareable_constant_node(node)
        visit(node.write)
      end

      # class << self; end
      # ^^^^^^^^^^^^^^^^^^
      def visit_singleton_class_node(node)
        expression = visit(node.expression)
        bodystmt = visit_body_node(node.body&.location || node.end_keyword_loc, node.body)

        bounds(node.location)
        on_sclass(expression, bodystmt)
      end

      # __ENCODING__
      # ^^^^^^^^^^^^
      def visit_source_encoding_node(node)
        bounds(node.location)
        on_var_ref(on_kw("__ENCODING__"))
      end

      # __FILE__
      # ^^^^^^^^
      def visit_source_file_node(node)
        bounds(node.location)
        on_var_ref(on_kw("__FILE__"))
      end

      # __LINE__
      # ^^^^^^^^
      def visit_source_line_node(node)
        bounds(node.location)
        on_var_ref(on_kw("__LINE__"))
      end

      # foo(*bar)
      #     ^^^^
      #
      # def foo((bar, *baz)); end
      #               ^^^^
      #
      # def foo(*); bar(*); end
      #                 ^
      def visit_splat_node(node)
        visit(node.expression)
      end

      # A list of statements.
      def visit_statements_node(node)
        bounds(node.location)
        visit_statements_node_body(node.body)
      end

      # Visit the list of statements of a statements node. We support nil
      # statements in the list. This would normally not be allowed by the
      # structure of the prism parse tree, but we manually add them here so that
      # we can mirror Ripper's void stmt.
      private def visit_statements_node_body(body)
        body.inject(on_stmts_new) do |stmts, stmt|
          on_stmts_add(stmts, stmt.nil? ? on_void_stmt : visit(stmt))
        end
      end

      # "foo"
      # ^^^^^
      def visit_string_node(node)
        if (content = node.content).empty?
          bounds(node.location)
          on_string_literal(on_string_content)
        elsif (opening = node.opening) == "?"
          bounds(node.location)
          on_CHAR("?#{node.content}")
        elsif opening.start_with?("<<~")
          heredoc = visit_heredoc_string_node(node.to_interpolated)

          bounds(node.location)
          on_string_literal(heredoc)
        else
          bounds(node.content_loc)
          tstring_content = on_tstring_content(content)

          bounds(node.location)
          on_string_literal(on_string_add(on_string_content, tstring_content))
        end
      end

      # Ripper gives back the escaped string content but strips out the common
      # leading whitespace. Prism gives back the unescaped string content and
      # a location for the escaped string content. Unfortunately these don't
      # work well together, so here we need to re-derive the common leading
      # whitespace.
      private def visit_heredoc_node_whitespace(parts)
        common_whitespace = nil
        dedent_next = true

        parts.each do |part|
          if part.is_a?(StringNode)
            if dedent_next && !(content = part.content).chomp.empty?
              common_whitespace = [
                common_whitespace || Float::INFINITY,
                content[/\A\s*/].each_char.inject(0) do |part_whitespace, char|
                  char == "\t" ? ((part_whitespace / 8 + 1) * 8) : (part_whitespace + 1)
                end
              ].min
            end

            dedent_next = true
          else
            dedent_next = false
          end
        end

        common_whitespace || 0
      end

      # Visit a string that is expressed using a <<~ heredoc.
      private def visit_heredoc_node(parts, base)
        common_whitespace = visit_heredoc_node_whitespace(parts)

        if common_whitespace == 0
          bounds(parts.first.location)

          string = []
          result = base

          parts.each do |part|
            if part.is_a?(StringNode)
              if string.empty?
                string = [part]
              else
                string << part
              end
            else
              unless string.empty?
                bounds(string[0].location)
                result = yield result, on_tstring_content(string.map(&:content).join)
                string = []
              end

              result = yield result, visit(part)
            end
          end

          unless string.empty?
            bounds(string[0].location)
            result = yield result, on_tstring_content(string.map(&:content).join)
          end

          result
        else
          bounds(parts.first.location)
          result =
            parts.inject(base) do |string_content, part|
              yield string_content, visit_string_content(part)
            end

          bounds(parts.first.location)
          on_heredoc_dedent(result, common_whitespace)
        end
      end

      # Visit a heredoc node that is representing a string.
      private def visit_heredoc_string_node(node)
        bounds(node.opening_loc)
        on_heredoc_beg(node.opening)

        bounds(node.location)
        result =
          visit_heredoc_node(node.parts, on_string_content) do |parts, part|
            on_string_add(parts, part)
          end

        bounds(node.closing_loc)
        on_heredoc_end(node.closing)

        result
      end

      # Visit a heredoc node that is representing an xstring.
      private def visit_heredoc_x_string_node(node)
        bounds(node.opening_loc)
        on_heredoc_beg(node.opening)

        bounds(node.location)
        result =
          visit_heredoc_node(node.parts, on_xstring_new) do |parts, part|
            on_xstring_add(parts, part)
          end

        bounds(node.closing_loc)
        on_heredoc_end(node.closing)

        result
      end

      # super(foo)
      # ^^^^^^^^^^
      def visit_super_node(node)
        arguments, block = visit_call_node_arguments(node.arguments, node.block, trailing_comma?(node.arguments&.location || node.location, node.rparen_loc || node.location))

        if !node.lparen_loc.nil?
          bounds(node.lparen_loc)
          arguments = on_arg_paren(arguments)
        end

        bounds(node.location)
        call = on_super(arguments)

        if block.nil?
          call
        else
          bounds(node.block.location)
          on_method_add_block(call, block)
        end
      end

      # :foo
      # ^^^^
      def visit_symbol_node(node)
        if (opening = node.opening)&.match?(/^%s|['"]:?$/)
          bounds(node.value_loc)
          content = on_string_content

          if !(value = node.value).empty?
            content = on_string_add(content, on_tstring_content(value))
          end

          on_dyna_symbol(content)
        elsif (closing = node.closing) == ":"
          bounds(node.location)
          on_label("#{node.value}:")
        elsif opening.nil? && node.closing_loc.nil?
          bounds(node.value_loc)
          on_symbol_literal(visit_token(node.value))
        else
          bounds(node.value_loc)
          on_symbol_literal(on_symbol(visit_token(node.value)))
        end
      end

      # true
      # ^^^^
      def visit_true_node(node)
        bounds(node.location)
        on_var_ref(on_kw("true"))
      end

      # undef foo
      # ^^^^^^^^^
      def visit_undef_node(node)
        names = visit_all(node.names)

        bounds(node.location)
        on_undef(names)
      end

      # unless foo; bar end
      # ^^^^^^^^^^^^^^^^^^^
      #
      # bar unless foo
      # ^^^^^^^^^^^^^^
      def visit_unless_node(node)
        if node.statements.nil? || (node.predicate.location.start_offset < node.statements.location.start_offset)
          predicate = visit(node.predicate)
          statements =
            if node.statements.nil?
              bounds(node.location)
              on_stmts_add(on_stmts_new, on_void_stmt)
            else
              visit(node.statements)
            end
          else_clause = visit(node.else_clause)

          bounds(node.location)
          on_unless(predicate, statements, else_clause)
        else
          statements = visit(node.statements.body.first)
          predicate = visit(node.predicate)

          bounds(node.location)
          on_unless_mod(predicate, statements)
        end
      end

      # until foo; bar end
      # ^^^^^^^^^^^^^^^^^
      #
      # bar until foo
      # ^^^^^^^^^^^^^
      def visit_until_node(node)
        if node.statements.nil? || (node.predicate.location.start_offset < node.statements.location.start_offset)
          predicate = visit(node.predicate)
          statements =
            if node.statements.nil?
              bounds(node.location)
              on_stmts_add(on_stmts_new, on_void_stmt)
            else
              visit(node.statements)
            end

          bounds(node.location)
          on_until(predicate, statements)
        else
          statements = visit(node.statements.body.first)
          predicate = visit(node.predicate)

          bounds(node.location)
          on_until_mod(predicate, statements)
        end
      end

      # case foo; when bar; end
      #           ^^^^^^^^^^^^^
      def visit_when_node(node)
        # This is a special case where we're not going to call on_when directly
        # because we don't have access to the subsequent. Instead, we'll return
        # the component parts and let the parent node handle it.
        conditions = visit_arguments(node.conditions)
        statements =
          if node.statements.nil?
            bounds(node.location)
            on_stmts_add(on_stmts_new, on_void_stmt)
          else
            visit(node.statements)
          end

        [conditions, statements]
      end

      # while foo; bar end
      # ^^^^^^^^^^^^^^^^^^
      #
      # bar while foo
      # ^^^^^^^^^^^^^
      def visit_while_node(node)
        if node.statements.nil? || (node.predicate.location.start_offset < node.statements.location.start_offset)
          predicate = visit(node.predicate)
          statements =
            if node.statements.nil?
              bounds(node.location)
              on_stmts_add(on_stmts_new, on_void_stmt)
            else
              visit(node.statements)
            end

          bounds(node.location)
          on_while(predicate, statements)
        else
          statements = visit(node.statements.body.first)
          predicate = visit(node.predicate)

          bounds(node.location)
          on_while_mod(predicate, statements)
        end
      end

      # `foo`
      # ^^^^^
      def visit_x_string_node(node)
        if node.unescaped.empty?
          bounds(node.location)
          on_xstring_literal(on_xstring_new)
        elsif node.opening.start_with?("<<~")
          heredoc = visit_heredoc_x_string_node(node.to_interpolated)

          bounds(node.location)
          on_xstring_literal(heredoc)
        else
          bounds(node.content_loc)
          content = on_tstring_content(node.content)

          bounds(node.location)
          on_xstring_literal(on_xstring_add(on_xstring_new, content))
        end
      end

      # yield
      # ^^^^^
      #
      # yield 1
      # ^^^^^^^
      def visit_yield_node(node)
        if node.arguments.nil? && node.lparen_loc.nil?
          bounds(node.location)
          on_yield0
        else
          arguments =
            if node.arguments.nil?
              bounds(node.location)
              on_args_new
            else
              visit(node.arguments)
            end

          unless node.lparen_loc.nil?
            bounds(node.lparen_loc)
            arguments = on_paren(arguments)
          end

          bounds(node.location)
          on_yield(arguments)
        end
      end

      private

      # Lazily initialize the parse result.
      def result
        @result ||= Prism.parse(source, partial_script: true)
      end

      ##########################################################################
      # Helpers
      ##########################################################################

      # Returns true if there is a comma between the two locations.
      def trailing_comma?(left, right)
        source.byteslice(left.end_offset...right.start_offset).include?(",")
      end

      # Returns true if there is a semicolon between the two locations.
      def void_stmt?(left, right, allow_newline)
        pattern = allow_newline ? /[;\n]/ : /;/
        source.byteslice(left.end_offset...right.start_offset).match?(pattern)
      end

      # Visit the string content of a particular node. This method is used to
      # split into the various token types.
      def visit_token(token, allow_keywords = true)
        case token
        when "."
          on_period(token)
        when "`"
          on_backtick(token)
        when *(allow_keywords ? KEYWORDS : [])
          on_kw(token)
        when /^_/
          on_ident(token)
        when /^[[:upper:]]\w*$/
          on_const(token)
        when /^@@/
          on_cvar(token)
        when /^@/
          on_ivar(token)
        when /^\$/
          on_gvar(token)
        when /^[[:punct:]]/
          on_op(token)
        else
          on_ident(token)
        end
      end

      # Visit a node that represents a number. We need to explicitly handle the
      # unary - operator.
      def visit_number_node(node)
        slice = node.slice
        location = node.location

        if slice[0] == "-"
          bounds(location.copy(start_offset: location.start_offset + 1))
          value = yield slice[1..-1]

          bounds(node.location)
          on_unary(:-@, value)
        else
          bounds(location)
          yield slice
        end
      end

      # Visit a node that represents a write value. This is used to handle the
      # special case of an implicit array that is generated without brackets.
      def visit_write_value(node)
        if node.is_a?(ArrayNode) && node.opening_loc.nil?
          elements = node.elements
          length = elements.length

          bounds(elements.first.location)
          elements.each_with_index.inject((elements.first.is_a?(SplatNode) && length == 1) ? on_mrhs_new : on_args_new) do |args, (element, index)|
            arg = visit(element)
            bounds(element.location)

            if index == length - 1
              if element.is_a?(SplatNode)
                mrhs = index == 0 ? args : on_mrhs_new_from_args(args)
                on_mrhs_add_star(mrhs, arg)
              else
                on_mrhs_add(on_mrhs_new_from_args(args), arg)
              end
            else
              case element
              when BlockArgumentNode
                on_args_add_block(args, arg)
              when SplatNode
                on_args_add_star(args, arg)
              else
                on_args_add(args, arg)
              end
            end
          end
        else
          visit(node)
        end
      end

      # This method is responsible for updating lineno and column information
      # to reflect the current node.
      #
      # This method could be drastically improved with some caching on the start
      # of every line, but for now it's good enough.
      def bounds(location)
        @lineno = location.start_line
        @column = location.start_column
      end

      ##########################################################################
      # Ripper interface
      ##########################################################################

      # :stopdoc:
      def _dispatch_0; end
      def _dispatch_1(_); end
      def _dispatch_2(_, _); end
      def _dispatch_3(_, _, _); end
      def _dispatch_4(_, _, _, _); end
      def _dispatch_5(_, _, _, _, _); end
      def _dispatch_7(_, _, _, _, _, _, _); end
      # :startdoc:

      #
      # Parser Events
      #

      PARSER_EVENT_TABLE.each do |id, arity|
        alias_method "on_#{id}", "_dispatch_#{arity}"
      end

      # This method is called when weak warning is produced by the parser.
      # +fmt+ and +args+ is printf style.
      def warn(fmt, *args)
      end

      # This method is called when strong warning is produced by the parser.
      # +fmt+ and +args+ is printf style.
      def warning(fmt, *args)
      end

      # This method is called when the parser found syntax error.
      def compile_error(msg)
      end

      #
      # Scanner Events
      #

      SCANNER_EVENTS.each do |id|
        alias_method "on_#{id}", :_dispatch_1
      end

      # This method is provided by the Ripper C extension. It is called when a
      # string needs to be dedented because of a tilde heredoc. It is expected
      # that it will modify the string in place and return the number of bytes
      # that were removed.
      def dedent_string(string, width)
        whitespace = 0
        cursor = 0

        while cursor < string.length && string[cursor].match?(/\s/) && whitespace < width
          if string[cursor] == "\t"
            whitespace = ((whitespace / 8 + 1) * 8)
            break if whitespace > width
          else
            whitespace += 1
          end

          cursor += 1
        end

        string.replace(string[cursor..])
        cursor
      end
    end
  end
end