code:
import { minify, _default_options } from "../main.js";
import { parse } from "./parse.js";
import {
    AST_Assign,
    AST_Array,
    AST_Constant,
    AST_Node,
    AST_PropAccess,
    AST_RegExp,
    AST_Sequence,
    AST_Symbol,
    AST_Token,
    walk
} from "./ast.js";
import { OutputStream } from "./output.js";

export async function run_cli({ program, packageJson, fs, path }) {
    const skip_keys = new Set([ "cname", "parent_scope", "scope", "uses_eval", "uses_with" ]);
    var files = {};
    var options = {
        compress: false,
        mangle: false
    };
    const default_options = await _default_options();
    program.version(packageJson.name + " " + packageJson.version);
    program.parseArgv = program.parse;
    program.parse = undefined;

    if (process.argv.includes("ast")) program.helpInformation = describe_ast;
    else if (process.argv.includes("options")) program.helpInformation = function() {
        var text = [];
        for (var option in default_options) {
            text.push("--" + (option === "sourceMap" ? "source-map" : option) + " options:");
            text.push(format_object(default_options[option]));
            text.push("");
        }
        return text.join("\n");
    };

    program.option("-p, --parse <options>", "Specify parser options.", parse_js());
    program.option("-c, --compress [options]", "Enable compressor/specify compressor options.", parse_js());
    program.option("-m, --mangle [options]", "Mangle names/specify mangler options.", parse_js());
    program.option("--mangle-props [options]", "Mangle properties/specify mangler options.", parse_js());
    program.option("-f, --format [options]", "Format options.", parse_js());
    program.option("-b, --beautify [options]", "Alias for --format.", parse_js());
    program.option("-o, --output <file>", "Output file (default STDOUT).");
    program.option("--comments [filter]", "Preserve copyright comments in the output.");
    program.option("--config-file <file>", "Read minify() options from JSON file.");
    program.option("-d, --define <expr>[=value]", "Global definitions.", parse_js("define"));
    program.option("--ecma <version>", "Specify ECMAScript release: 5, 2015, 2016 or 2017...");
    program.option("-e, --enclose [arg[,...][:value[,...]]]", "Embed output in a big function with configurable arguments and values.");
    program.option("--ie8", "Support non-standard Internet Explorer 8.");
    program.option("--keep-classnames", "Do not mangle/drop class names.");
    program.option("--keep-fnames", "Do not mangle/drop function names. Useful for code relying on Function.prototype.name.");
    program.option("--module", "Input is an ES6 module");
    program.option("--name-cache <file>", "File to hold mangled name mappings.");
    program.option("--rename", "Force symbol expansion.");
    program.option("--no-rename", "Disable symbol expansion.");
    program.option("--safari10", "Support non-standard Safari 10.");
    program.option("--source-map [options]", "Enable source map/specify source map options.", parse_js());
    program.option("--timings", "Display operations run time on STDERR.");
    program.option("--toplevel", "Compress and/or mangle variables in toplevel scope.");
    program.option("--wrap <name>", "Embed everything as a function with “exports” corresponding to “name” globally.");
    program.arguments("[files...]").parseArgv(process.argv);
    if (program.configFile) {
        options = JSON.parse(read_file(program.configFile));
    }
    if (!program.output && program.sourceMap && program.sourceMap.url != "inline") {
        fatal("ERROR: cannot write source map to STDOUT");
    }

    [
        "compress",
        "enclose",
        "ie8",
        "mangle",
        "module",
        "safari10",
        "sourceMap",
        "toplevel",
        "wrap"
    ].forEach(function(name) {
        if (name in program) {
            options[name] = program[name];
        }
    });

    if ("ecma" in program) {
        if (program.ecma != (program.ecma | 0)) fatal("ERROR: ecma must be an integer");
        const ecma = program.ecma | 0;
        if (ecma > 5 && ecma < 2015)
            options.ecma = ecma + 2009;
        else
            options.ecma = ecma;
    }
    if (program.format || program.beautify) {
        const chosenOption = program.format || program.beautify;
        options.format = typeof chosenOption === "object" ? chosenOption : {};
    }
    if (program.comments) {
        if (typeof options.format != "object") options.format = {};
        options.format.comments = typeof program.comments == "string" ? (program.comments == "false" ? false : program.comments) : "some";
    }
    if (program.define) {
        if (typeof options.compress != "object") options.compress = {};
        if (typeof options.compress.global_defs != "object") options.compress.global_defs = {};
        for (var expr in program.define) {
            options.compress.global_defs[expr] = program.define[expr];
        }
    }
    if (program.keepClassnames) {
        options.keep_classnames = true;
    }
    if (program.keepFnames) {
        options.keep_fnames = true;
    }
    if (program.mangleProps) {
        if (program.mangleProps.domprops) {
            delete program.mangleProps.domprops;
        } else {
            if (typeof program.mangleProps != "object") program.mangleProps = {};
            if (!Array.isArray(program.mangleProps.reserved)) program.mangleProps.reserved = [];
        }
        if (typeof options.mangle != "object") options.mangle = {};
        options.mangle.properties = program.mangleProps;
    }
    if (program.nameCache) {
        options.nameCache = JSON.parse(read_file(program.nameCache, "{}"));
    }
    if (program.output == "ast") {
        options.format = {
            ast: true,
            code: false
        };
    }
    if (program.parse) {
        if (!program.parse.acorn && !program.parse.spidermonkey) {
            options.parse = program.parse;
        } else if (program.sourceMap && program.sourceMap.content == "inline") {
            fatal("ERROR: inline source map only works with built-in parser");
        }
    }
    if (~program.rawArgs.indexOf("--rename")) {
        options.rename = true;
    } else if (!program.rename) {
        options.rename = false;
    }

    let convert_path = name => name;
    if (typeof program.sourceMap == "object" && "base" in program.sourceMap) {
        convert_path = function() {
            var base = program.sourceMap.base;
            delete options.sourceMap.base;
            return function(name) {
                return path.relative(base, name);
            };
        }();
    }

    let filesList;
    if (options.files && options.files.length) {
        filesList = options.files;

        delete options.files;
    } else if (program.args.length) {
        filesList = program.args;
    }

    if (filesList) {
        simple_glob(filesList).forEach(function(name) {
            files[convert_path(name)] = read_file(name);
        });
    } else {
        await new Promise((resolve) => {
            var chunks = [];
            process.stdin.setEncoding("utf8");
            process.stdin.on("data", function(chunk) {
                chunks.push(chunk);
            }).on("end", function() {
                files = [ chunks.join("") ];
                resolve();
            });
            process.stdin.resume();
        });
    }

    await run_cli();

    function convert_ast(fn) {
        return AST_Node.from_mozilla_ast(Object.keys(files).reduce(fn, null));
    }

    async function run_cli() {
        var content = program.sourceMap && program.sourceMap.content;
        if (content && content !== "inline") {
            options.sourceMap.content = read_file(content, content);
        }
        if (program.timings) options.timings = true;

        try {
            if (program.parse) {
                if (program.parse.acorn) {
                    files = convert_ast(function(toplevel, name) {
                        return require("acorn").parse(files[name], {
                            ecmaVersion: 2018,
                            locations: true,
                            program: toplevel,
                            sourceFile: name,
                            sourceType: options.module || program.parse.module ? "module" : "script"
                        });
                    });
                } else if (program.parse.spidermonkey) {
                    files = convert_ast(function(toplevel, name) {
                        var obj = JSON.parse(files[name]);
                        if (!toplevel) return obj;
                        toplevel.body = toplevel.body.concat(obj.body);
                        return toplevel;
                    });
                }
            }
        } catch (ex) {
            fatal(ex);
        }

        let result;
        try {
            result = await minify(files, options, fs);
        } catch (ex) {
            if (ex.name == "SyntaxError") {
                print_error("Parse error at " + ex.filename + ":" + ex.line + "," + ex.col);
                var col = ex.col;
                var lines = files[ex.filename].split(/\r?\n/);
                var line = lines[ex.line - 1];
                if (!line && !col) {
                    line = lines[ex.line - 2];
                    col = line.length;
                }
                if (line) {
                    var limit = 70;
                    if (col > limit) {
                        line = line.slice(col - limit);
                        col = limit;
                    }
                    print_error(line.slice(0, 80));
                    print_error(line.slice(0, col).replace(/\S/g, " ") + "^");
                }
            }
            if (ex.defs) {
                print_error("Supported options:");
                print_error(format_object(ex.defs));
            }
            fatal(ex);
            return;
        }

        if (program.output == "ast") {
            if (!options.compress && !options.mangle) {
                result.ast.figure_out_scope({});
            }
            console.log(JSON.stringify(result.ast, function(key, value) {
                if (value) switch (key) {
                  case "thedef":
                    return symdef(value);
                  case "enclosed":
                    return value.length ? value.map(symdef) : undefined;
                  case "variables":
                  case "globals":
                    return value.size ? collect_from_map(value, symdef) : undefined;
                }
                if (skip_keys.has(key)) return;
                if (value instanceof AST_Token) return;
                if (value instanceof Map) return;
                if (value instanceof AST_Node) {
                    var result = {
                        _class: "AST_" + value.TYPE
                    };
                    if (value.block_scope) {
                        result.variables = value.block_scope.variables;
                        result.enclosed = value.block_scope.enclosed;
                    }
                    value.CTOR.PROPS.forEach(function(prop) {
                        if (prop !== "block_scope") {
                            result[prop] = value[prop];
                        }
                    });
                    return result;
                }
                return value;
            }, 2));
        } else if (program.output == "spidermonkey") {
            try {
                const minified = await minify(
                    result.code,
                    {
                        compress: false,
                        mangle: false,
                        format: {
                            ast: true,
                            code: false
                        }
                    },
                    fs
                );
                console.log(JSON.stringify(minified.ast.to_mozilla_ast(), null, 2));
            } catch (ex) {
                fatal(ex);
                return;
            }
        } else if (program.output) {
            fs.writeFileSync(program.output, result.code);
            if (options.sourceMap && options.sourceMap.url !== "inline" && result.map) {
                fs.writeFileSync(program.output + ".map", result.map);
            }
        } else {
            console.log(result.code);
        }
        if (program.nameCache) {
            fs.writeFileSync(program.nameCache, JSON.stringify(options.nameCache));
        }
        if (result.timings) for (var phase in result.timings) {
            print_error("- " + phase + ": " + result.timings[phase].toFixed(3) + "s");
        }
    }

    function fatal(message) {
        if (message instanceof Error) message = message.stack.replace(/^\S*?Error:/, "ERROR:");
        print_error(message);
        process.exit(1);
    }

    // A file glob function that only supports "*" and "?" wildcards in the basename.
    // Example: "foo/bar/*baz??.*.js"
    // Argument `glob` may be a string or an array of strings.
    // Returns an array of strings. Garbage in, garbage out.
    function simple_glob(glob) {
        if (Array.isArray(glob)) {
            return [].concat.apply([], glob.map(simple_glob));
        }
        if (glob && glob.match(/[*?]/)) {
            var dir = path.dirname(glob);
            try {
                var entries = fs.readdirSync(dir);
            } catch (ex) {}
            if (entries) {
                var pattern = "^" + path.basename(glob)
                    .replace(/[.+^$[\]\\(){}]/g, "\\$&")
                    .replace(/\*/g, "[^/\\\\]*")
                    .replace(/\?/g, "[^/\\\\]") + "$";
                var mod = process.platform === "win32" ? "i" : "";
                var rx = new RegExp(pattern, mod);
                var results = entries.filter(function(name) {
                    return rx.test(name);
                }).map(function(name) {
                    return path.join(dir, name);
                });
                if (results.length) return results;
            }
        }
        return [ glob ];
    }

    function read_file(path, default_value) {
        try {
            return fs.readFileSync(path, "utf8");
        } catch (ex) {
            if ((ex.code == "ENOENT" || ex.code == "ENAMETOOLONG") && default_value != null) return default_value;
            fatal(ex);
        }
    }

    function parse_js(flag) {
        return function(value, options) {
            options = options || {};
            try {
                walk(parse(value, { expression: true }), node => {
                    if (node instanceof AST_Assign) {
                        var name = node.left.print_to_string();
                        var value = node.right;
                        if (flag) {
                            options[name] = value;
                        } else if (value instanceof AST_Array) {
                            options[name] = value.elements.map(to_string);
                        } else if (value instanceof AST_RegExp) {
                            value = value.value;
                            options[name] = new RegExp(value.source, value.flags);
                        } else {
                            options[name] = to_string(value);
                        }
                        return true;
                    }
                    if (node instanceof AST_Symbol || node instanceof AST_PropAccess) {
                        var name = node.print_to_string();
                        options[name] = true;
                        return true;
                    }
                    if (!(node instanceof AST_Sequence)) throw node;

                    function to_string(value) {
                        return value instanceof AST_Constant ? value.getValue() : value.print_to_string({
                            quote_keys: true
                        });
                    }
                });
            } catch(ex) {
                if (flag) {
                    fatal("Error parsing arguments for '" + flag + "': " + value);
                } else {
                    options[value] = null;
                }
            }
            return options;
        };
    }

    function symdef(def) {
        var ret = (1e6 + def.id) + " " + def.name;
        if (def.mangled_name) ret += " " + def.mangled_name;
        return ret;
    }

    function collect_from_map(map, callback) {
        var result = [];
        map.forEach(function (def) {
            result.push(callback(def));
        });
        return result;
    }

    function format_object(obj) {
        var lines = [];
        var padding = "";
        Object.keys(obj).map(function(name) {
            if (padding.length < name.length) padding = Array(name.length + 1).join(" ");
            return [ name, JSON.stringify(obj[name]) ];
        }).forEach(function(tokens) {
            lines.push("  " + tokens[0] + padding.slice(tokens[0].length - 2) + tokens[1]);
        });
        return lines.join("\n");
    }

    function print_error(msg) {
        process.stderr.write(msg);
        process.stderr.write("\n");
    }

    function describe_ast() {
        var out = OutputStream({ beautify: true });
        function doitem(ctor) {
            out.print("AST_" + ctor.TYPE);
            const props = ctor.SELF_PROPS.filter(prop => !/^\$/.test(prop));

            if (props.length > 0) {
                out.space();
                out.with_parens(function() {
                    props.forEach(function(prop, i) {
                        if (i) out.space();
                        out.print(prop);
                    });
                });
            }

            if (ctor.documentation) {
                out.space();
                out.print_string(ctor.documentation);
            }

            if (ctor.SUBCLASSES.length > 0) {
                out.space();
                out.with_block(function() {
                    ctor.SUBCLASSES.forEach(function(ctor) {
                        out.indent();
                        doitem(ctor);
                        out.newline();
                    });
                });
            }
        }
        doitem(AST_Node);
        return out + "\n";
    }
}

license: mit


code:
/***********************************************************************

  A JavaScript tokenizer / parser / beautifier / compressor.
  https://github.com/mishoo/UglifyJS2

  -------------------------------- (C) ---------------------------------

                           Author: Mihai Bazon
                         <mihai.bazon@gmail.com>
                       http://mihai.bazon.net/blog

  Distributed under the BSD license:

    Copyright 2012 (c) Mihai Bazon <mihai.bazon@gmail.com>

    Redistribution and use in source and binary forms, with or without
    modification, are permitted provided that the following conditions
    are met:

        * Redistributions of source code must retain the above
          copyright notice, this list of conditions and the following
          disclaimer.

        * Redistributions in binary form must reproduce the above
          copyright notice, this list of conditions and the following
          disclaimer in the documentation and/or other materials
          provided with the distribution.

    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER “AS IS” AND ANY
    EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
    IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
    PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER BE
    LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
    OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
    PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
    PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
    THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR
    TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
    THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
    SUCH DAMAGE.

 ***********************************************************************/

import {
    AST_Array,
    AST_Arrow,
    AST_BigInt,
    AST_BlockStatement,
    AST_Call,
    AST_Chain,
    AST_Class,
    AST_Const,
    AST_Constant,
    AST_DefClass,
    AST_Defun,
    AST_EmptyStatement,
    AST_Export,
    AST_False,
    AST_Function,
    AST_Import,
    AST_Infinity,
    AST_LabeledStatement,
    AST_Lambda,
    AST_Let,
    AST_LoopControl,
    AST_NaN,
    AST_Node,
    AST_Null,
    AST_Number,
    AST_Object,
    AST_ObjectKeyVal,
    AST_PropAccess,
    AST_RegExp,
    AST_Scope,
    AST_Sequence,
    AST_SimpleStatement,
    AST_Statement,
    AST_String,
    AST_SymbolRef,
    AST_True,
    AST_UnaryPrefix,
    AST_Undefined,

    TreeWalker,
    walk,
    walk_abort,
    walk_parent,
} from "../ast.js";
import { make_node, regexp_source_fix, string_template, makePredicate } from "../utils/index.js";
import { first_in_statement } from "../utils/first_in_statement.js";
import { has_flag, TOP } from "./compressor-flags.js";

export function merge_sequence(array, node) {
    if (node instanceof AST_Sequence) {
        array.push(...node.expressions);
    } else {
        array.push(node);
    }
    return array;
}

export function make_sequence(orig, expressions) {
    if (expressions.length == 1) return expressions[0];
    if (expressions.length == 0) throw new Error("trying to create a sequence with length zero!");
    return make_node(AST_Sequence, orig, {
        expressions: expressions.reduce(merge_sequence, [])
    });
}

export function make_node_from_constant(val, orig) {
    switch (typeof val) {
      case "string":
        return make_node(AST_String, orig, {
            value: val
        });
      case "number":
        if (isNaN(val)) return make_node(AST_NaN, orig);
        if (isFinite(val)) {
            return 1 / val < 0 ? make_node(AST_UnaryPrefix, orig, {
                operator: "-",
                expression: make_node(AST_Number, orig, { value: -val })
            }) : make_node(AST_Number, orig, { value: val });
        }
        return val < 0 ? make_node(AST_UnaryPrefix, orig, {
            operator: "-",
            expression: make_node(AST_Infinity, orig)
        }) : make_node(AST_Infinity, orig);
      case "bigint":
        return make_node(AST_BigInt, orig, { value: val.toString() });
      case "boolean":
        return make_node(val ? AST_True : AST_False, orig);
      case "undefined":
        return make_node(AST_Undefined, orig);
      default:
        if (val === null) {
            return make_node(AST_Null, orig, { value: null });
        }
        if (val instanceof RegExp) {
            return make_node(AST_RegExp, orig, {
                value: {
                    source: regexp_source_fix(val.source),
                    flags: val.flags
                }
            });
        }
        throw new Error(string_template("Can't handle constant of type: {type}", {
            type: typeof val
        }));
    }
}

export function best_of_expression(ast1, ast2) {
    return ast1.size() > ast2.size() ? ast2 : ast1;
}

export function best_of_statement(ast1, ast2) {
    return best_of_expression(
        make_node(AST_SimpleStatement, ast1, {
            body: ast1
        }),
        make_node(AST_SimpleStatement, ast2, {
            body: ast2
        })
    ).body;
}

/** Find which node is smaller, and return that */
export function best_of(compressor, ast1, ast2) {
    if (first_in_statement(compressor)) {
        return best_of_statement(ast1, ast2);
    } else {
        return best_of_expression(ast1, ast2);
    }
}

/** Simplify an object property's key, if possible */
export function get_simple_key(key) {
    if (key instanceof AST_Constant) {
        return key.getValue();
    }
    if (key instanceof AST_UnaryPrefix
        && key.operator == "void"
        && key.expression instanceof AST_Constant) {
        return;
    }
    return key;
}

export function read_property(obj, key) {
    key = get_simple_key(key);
    if (key instanceof AST_Node) return;

    var value;
    if (obj instanceof AST_Array) {
        var elements = obj.elements;
        if (key == "length") return make_node_from_constant(elements.length, obj);
        if (typeof key == "number" && key in elements) value = elements[key];
    } else if (obj instanceof AST_Object) {
        key = "" + key;
        var props = obj.properties;
        for (var i = props.length; --i >= 0;) {
            var prop = props[i];
            if (!(prop instanceof AST_ObjectKeyVal)) return;
            if (!value && props[i].key === key) value = props[i].value;
        }
    }

    return value instanceof AST_SymbolRef && value.fixed_value() || value;
}

export function has_break_or_continue(loop, parent) {
    var found = false;
    var tw = new TreeWalker(function(node) {
        if (found || node instanceof AST_Scope) return true;
        if (node instanceof AST_LoopControl && tw.loopcontrol_target(node) === loop) {
            return found = true;
        }
    });
    if (parent instanceof AST_LabeledStatement) tw.push(parent);
    tw.push(loop);
    loop.body.walk(tw);
    return found;
}

// we shouldn't compress (1,func)(something) to
// func(something) because that changes the meaning of
// the func (becomes lexical instead of global).
export function maintain_this_binding(parent, orig, val) {
    if (requires_sequence_to_maintain_binding(parent, orig, val)) {
        const zero = make_node(AST_Number, orig, { value: 0 });
        return make_sequence(orig, [ zero, val ]);
    } else {
        return val;
    }
}

/** Detect (1, x.noThis)(), (0, eval)(), which need sequences */
export function requires_sequence_to_maintain_binding(parent, orig, val) {
    return (
        parent instanceof AST_UnaryPrefix && parent.operator == "delete"
        || parent instanceof AST_Call && parent.expression === orig
            && (
                val instanceof AST_Chain
                || val instanceof AST_PropAccess
                || val instanceof AST_SymbolRef && val.name == "eval"
            )
    );
}

export function is_func_expr(node) {
    return node instanceof AST_Arrow || node instanceof AST_Function;
}

/**
 * Used to determine whether the node can benefit from negation.
 * Not the case with arrow functions (you need an extra set of parens). */
export function is_iife_call(node) {
    if (node.TYPE != "Call") return false;
    return node.expression instanceof AST_Function || is_iife_call(node.expression);
}

export function is_empty(thing) {
    if (thing === null) return true;
    if (thing instanceof AST_EmptyStatement) return true;
    if (thing instanceof AST_BlockStatement) return thing.body.length == 0;
    return false;
}

export const identifier_atom = makePredicate("Infinity NaN undefined");
export function is_identifier_atom(node) {
    return node instanceof AST_Infinity
        || node instanceof AST_NaN
        || node instanceof AST_Undefined;
}

/** Check if this is a SymbolRef node which has one def of a certain AST type */
export function is_ref_of(ref, type) {
    if (!(ref instanceof AST_SymbolRef)) return false;
    var orig = ref.definition().orig;
    for (var i = orig.length; --i >= 0;) {
        if (orig[i] instanceof type) return true;
    }
}

/**Can we turn { block contents... } into just the block contents ?
 * Not if one of these is inside.
 **/
export function can_be_evicted_from_block(node) {
    return !(
        node instanceof AST_DefClass ||
        node instanceof AST_Defun ||
        node instanceof AST_Let ||
        node instanceof AST_Const ||
        node instanceof AST_Export ||
        node instanceof AST_Import
    );
}

export function as_statement_array(thing) {
    if (thing === null) return [];
    if (thing instanceof AST_BlockStatement) return thing.body;
    if (thing instanceof AST_EmptyStatement) return [];
    if (thing instanceof AST_Statement) return [ thing ];
    throw new Error("Can't convert thing to statement array");
}

export function is_reachable(scope_node, defs) {
    const find_ref = node => {
        if (node instanceof AST_SymbolRef && defs.includes(node.definition())) {
            return walk_abort;
        }
    };

    return walk_parent(scope_node, (node, info) => {
        if (node instanceof AST_Scope && node !== scope_node) {
            var parent = info.parent();

            if (
                parent instanceof AST_Call
                && parent.expression === node
                // Async/Generators aren't guaranteed to sync evaluate all of
                // their body steps, so it's possible they close over the variable.
                && !(node.async || node.is_generator)
            ) {
                return;
            }

            if (walk(node, find_ref)) return walk_abort;

            return true;
        }
    });
}

/** Check if a ref refers to the name of a function/class it's defined within */
export function is_recursive_ref(compressor, def) {
    var node;
    for (var i = 0; node = compressor.parent(i); i++) {
        if (node instanceof AST_Lambda || node instanceof AST_Class) {
            var name = node.name;
            if (name && name.definition() === def) {
                return true;
            }
        }
    }
    return false;
}

// TODO this only works with AST_Defun, shouldn't it work for other ways of defining functions?
export function retain_top_func(fn, compressor) {
    return compressor.top_retain
        && fn instanceof AST_Defun
        && has_flag(fn, TOP)
        && fn.name
        && compressor.top_retain(fn.name.definition());
}


code:
/***********************************************************************

  A JavaScript tokenizer / parser / beautifier / compressor.
  https://github.com/mishoo/UglifyJS2

  -------------------------------- (C) ---------------------------------

                           Author: Mihai Bazon
                         <mihai.bazon@gmail.com>
                       http://mihai.bazon.net/blog

  Distributed under the BSD license:

    Copyright 2012 (c) Mihai Bazon <mihai.bazon@gmail.com>

    Redistribution and use in source and binary forms, with or without
    modification, are permitted provided that the following conditions
    are met:

        * Redistributions of source code must retain the above
          copyright notice, this list of conditions and the following
          disclaimer.

        * Redistributions in binary form must reproduce the above
          copyright notice, this list of conditions and the following
          disclaimer in the documentation and/or other materials
          provided with the distribution.

    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER “AS IS” AND ANY
    EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
    IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
    PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER BE
    LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
    OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
    PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
    PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
    THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR
    TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
    THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
    SUCH DAMAGE.

 ***********************************************************************/

// bitfield flags to be stored in node.flags.
// These are set and unset during compression, and store information in the node without requiring multiple fields.
export const UNUSED = 0b00000001;
export const TRUTHY = 0b00000010;
export const FALSY = 0b00000100;
export const UNDEFINED = 0b00001000;
export const INLINED = 0b00010000;

// Nodes to which values are ever written. Used when keep_assign is part of the unused option string.
export const WRITE_ONLY = 0b00100000;

// information specific to a single compression pass
export const SQUEEZED = 0b0000000100000000;
export const OPTIMIZED = 0b0000001000000000;
export const TOP = 0b0000010000000000;
export const CLEAR_BETWEEN_PASSES = SQUEEZED | OPTIMIZED | TOP;

export const has_flag = (node, flag) => node.flags & flag;
export const set_flag = (node, flag) => { node.flags |= flag; };
export const clear_flag = (node, flag) => { node.flags &= ~flag; };


code:
/***********************************************************************

  A JavaScript tokenizer / parser / beautifier / compressor.
  https://github.com/mishoo/UglifyJS2

  -------------------------------- (C) ---------------------------------

                           Author: Mihai Bazon
                         <mihai.bazon@gmail.com>
                       http://mihai.bazon.net/blog

  Distributed under the BSD license:

    Copyright 2012 (c) Mihai Bazon <mihai.bazon@gmail.com>

    Redistribution and use in source and binary forms, with or without
    modification, are permitted provided that the following conditions
    are met:

        * Redistributions of source code must retain the above
          copyright notice, this list of conditions and the following
          disclaimer.

        * Redistributions in binary form must reproduce the above
          copyright notice, this list of conditions and the following
          disclaimer in the documentation and/or other materials
          provided with the distribution.

    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER “AS IS” AND ANY
    EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
    IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
    PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER BE
    LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
    OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
    PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
    PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
    THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR
    TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
    THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
    SUCH DAMAGE.

 ***********************************************************************/

import {
    AST_Accessor,
    AST_Array,
    AST_Arrow,
    AST_Assign,
    AST_Binary,
    AST_Call,
    AST_Chain,
    AST_Class,
    AST_ClassStaticBlock,
    AST_ClassProperty,
    AST_ConciseMethod,
    AST_Conditional,
    AST_Constant,
    AST_DefClass,
    AST_Dot,
    AST_Expansion,
    AST_Function,
    AST_Node,
    AST_Number,
    AST_Object,
    AST_ObjectGetter,
    AST_ObjectKeyVal,
    AST_ObjectProperty,
    AST_ObjectSetter,
    AST_PropAccess,
    AST_Scope,
    AST_Sequence,
    AST_SimpleStatement,
    AST_Sub,
    AST_SymbolRef,
    AST_TemplateSegment,
    AST_TemplateString,
    AST_This,
    AST_Unary,
} from "../ast.js";
import { make_node, return_null, return_this } from "../utils/index.js";
import { first_in_statement } from "../utils/first_in_statement.js";

import { pure_prop_access_globals } from "./native-objects.js";
import { lazy_op, unary_side_effects, is_nullish_shortcircuited } from "./inference.js";
import { WRITE_ONLY, set_flag, clear_flag } from "./compressor-flags.js";
import { make_sequence, is_func_expr, is_iife_call } from "./common.js";

// AST_Node#drop_side_effect_free() gets called when we don't care about the value,
// only about side effects. We'll be defining this method for each node type in this module
//
// Examples:
// foo++ -> foo++
// 1 + func() -> func()
// 10 -> (nothing)
// knownPureFunc(foo++) -> foo++

function def_drop_side_effect_free(node, func) {
    node.DEFMETHOD("drop_side_effect_free", func);
}

// Drop side-effect-free elements from an array of expressions.
// Returns an array of expressions with side-effects or null
// if all elements were dropped. Note: original array may be
// returned if nothing changed.
function trim(nodes, compressor, first_in_statement) {
    var len = nodes.length;
    if (!len)  return null;

    var ret = [], changed = false;
    for (var i = 0; i < len; i++) {
        var node = nodes[i].drop_side_effect_free(compressor, first_in_statement);
        changed |= node !== nodes[i];
        if (node) {
            ret.push(node);
            first_in_statement = false;
        }
    }
    return changed ? ret.length ? ret : null : nodes;
}

def_drop_side_effect_free(AST_Node, return_this);
def_drop_side_effect_free(AST_Constant, return_null);
def_drop_side_effect_free(AST_This, return_null);

def_drop_side_effect_free(AST_Call, function (compressor, first_in_statement) {
    if (is_nullish_shortcircuited(this, compressor)) {
        return this.expression.drop_side_effect_free(compressor, first_in_statement);
    }

    if (!this.is_callee_pure(compressor)) {
        if (this.expression.is_call_pure(compressor)) {
            var exprs = this.args.slice();
            exprs.unshift(this.expression.expression);
            exprs = trim(exprs, compressor, first_in_statement);
            return exprs && make_sequence(this, exprs);
        }
        if (is_func_expr(this.expression)
            && (!this.expression.name || !this.expression.name.definition().references.length)) {
            var node = this.clone();
            node.expression.process_expression(false, compressor);
            return node;
        }
        return this;
    }

    var args = trim(this.args, compressor, first_in_statement);
    return args && make_sequence(this, args);
});

def_drop_side_effect_free(AST_Accessor, return_null);

def_drop_side_effect_free(AST_Function, return_null);

def_drop_side_effect_free(AST_Arrow, return_null);

def_drop_side_effect_free(AST_Class, function (compressor) {
    const with_effects = [];

    if (this.is_self_referential() && this.has_side_effects(compressor)) {
        return this;
    }

    const trimmed_extends = this.extends && this.extends.drop_side_effect_free(compressor);
    if (trimmed_extends) with_effects.push(trimmed_extends);

    for (const prop of this.properties) {
        if (prop instanceof AST_ClassStaticBlock) {
            if (prop.has_side_effects(compressor)) {
                return this; // Be cautious about these
            }
        } else {
            const trimmed_prop = prop.drop_side_effect_free(compressor);
            if (trimmed_prop) with_effects.push(trimmed_prop);
        }
    }

    if (!with_effects.length)
        return null;

    const exprs = make_sequence(this, with_effects);
    if (this instanceof AST_DefClass) {
        // We want a statement
        return make_node(AST_SimpleStatement, this, { body: exprs });
    } else {
        return exprs;
    }
});

def_drop_side_effect_free(AST_ClassProperty, function (compressor) {
    const key = this.computed_key() && this.key.drop_side_effect_free(compressor);

    const value = this.static && this.value
        && this.value.drop_side_effect_free(compressor);

    if (key && value)
        return make_sequence(this, [key, value]);
    return key || value || null;
});

def_drop_side_effect_free(AST_Binary, function (compressor, first_in_statement) {
    var right = this.right.drop_side_effect_free(compressor);
    if (!right)
        return this.left.drop_side_effect_free(compressor, first_in_statement);
    if (lazy_op.has(this.operator)) {
        if (right === this.right)
            return this;
        var node = this.clone();
        node.right = right;
        return node;
    } else {
        var left = this.left.drop_side_effect_free(compressor, first_in_statement);
        if (!left)
            return this.right.drop_side_effect_free(compressor, first_in_statement);
        return make_sequence(this, [left, right]);
    }
});

def_drop_side_effect_free(AST_Assign, function (compressor) {
    if (this.logical)
        return this;

    var left = this.left;
    if (left.has_side_effects(compressor)
        || compressor.has_directive("use strict")
        && left instanceof AST_PropAccess
        && left.expression.is_constant()) {
        return this;
    }
    set_flag(this, WRITE_ONLY);
    while (left instanceof AST_PropAccess) {
        left = left.expression;
    }
    if (left.is_constant_expression(compressor.find_parent(AST_Scope))) {
        return this.right.drop_side_effect_free(compressor);
    }
    return this;
});

def_drop_side_effect_free(AST_Conditional, function (compressor) {
    var consequent = this.consequent.drop_side_effect_free(compressor);
    var alternative = this.alternative.drop_side_effect_free(compressor);
    if (consequent === this.consequent && alternative === this.alternative)
        return this;
    if (!consequent)
        return alternative ? make_node(AST_Binary, this, {
            operator: "||",
            left: this.condition,
            right: alternative
        }) : this.condition.drop_side_effect_free(compressor);
    if (!alternative)
        return make_node(AST_Binary, this, {
            operator: "&&",
            left: this.condition,
            right: consequent
        });
    var node = this.clone();
    node.consequent = consequent;
    node.alternative = alternative;
    return node;
});

def_drop_side_effect_free(AST_Unary, function (compressor, first_in_statement) {
    if (unary_side_effects.has(this.operator)) {
        if (!this.expression.has_side_effects(compressor)) {
            set_flag(this, WRITE_ONLY);
        } else {
            clear_flag(this, WRITE_ONLY);
        }
        return this;
    }
    if (this.operator == "typeof" && this.expression instanceof AST_SymbolRef)
        return null;
    var expression = this.expression.drop_side_effect_free(compressor, first_in_statement);
    if (first_in_statement && expression && is_iife_call(expression)) {
        if (expression === this.expression && this.operator == "!")
            return this;
        return expression.negate(compressor, first_in_statement);
    }
    return expression;
});

def_drop_side_effect_free(AST_SymbolRef, function (compressor) {
    const safe_access = this.is_declared(compressor)
        || pure_prop_access_globals.has(this.name);
    return safe_access ? null : this;
});

def_drop_side_effect_free(AST_Object, function (compressor, first_in_statement) {
    var values = trim(this.properties, compressor, first_in_statement);
    return values && make_sequence(this, values);
});

def_drop_side_effect_free(AST_ObjectProperty, function (compressor, first_in_statement) {
    const computed_key = this instanceof AST_ObjectKeyVal && this.key instanceof AST_Node;
    const key = computed_key && this.key.drop_side_effect_free(compressor, first_in_statement);
    const value = this.value && this.value.drop_side_effect_free(compressor, first_in_statement);
    if (key && value) {
        return make_sequence(this, [key, value]);
    }
    return key || value;
});

def_drop_side_effect_free(AST_ConciseMethod, function () {
    return this.computed_key() ? this.key : null;
});

def_drop_side_effect_free(AST_ObjectGetter, function () {
    return this.computed_key() ? this.key : null;
});

def_drop_side_effect_free(AST_ObjectSetter, function () {
    return this.computed_key() ? this.key : null;
});

def_drop_side_effect_free(AST_Array, function (compressor, first_in_statement) {
    var values = trim(this.elements, compressor, first_in_statement);
    return values && make_sequence(this, values);
});

def_drop_side_effect_free(AST_Dot, function (compressor, first_in_statement) {
    if (is_nullish_shortcircuited(this, compressor)) {
        return this.expression.drop_side_effect_free(compressor, first_in_statement);
    }
    if (!this.optional && this.expression.may_throw_on_access(compressor)) {
        return this;
    }

    return this.expression.drop_side_effect_free(compressor, first_in_statement);
});

def_drop_side_effect_free(AST_Sub, function (compressor, first_in_statement) {
    if (is_nullish_shortcircuited(this, compressor)) {
        return this.expression.drop_side_effect_free(compressor, first_in_statement);
    }
    if (!this.optional && this.expression.may_throw_on_access(compressor)) {
        return this;
    }

    var property = this.property.drop_side_effect_free(compressor);
    if (property && this.optional) return this;

    var expression = this.expression.drop_side_effect_free(compressor, first_in_statement);

    if (expression && property) return make_sequence(this, [expression, property]);
    return expression || property;
});

def_drop_side_effect_free(AST_Chain, function (compressor, first_in_statement) {
    return this.expression.drop_side_effect_free(compressor, first_in_statement);
});

def_drop_side_effect_free(AST_Sequence, function (compressor) {
    var last = this.tail_node();
    var expr = last.drop_side_effect_free(compressor);
    if (expr === last)
        return this;
    var expressions = this.expressions.slice(0, -1);
    if (expr)
        expressions.push(expr);
    if (!expressions.length) {
        return make_node(AST_Number, this, { value: 0 });
    }
    return make_sequence(this, expressions);
});

def_drop_side_effect_free(AST_Expansion, function (compressor, first_in_statement) {
    return this.expression.drop_side_effect_free(compressor, first_in_statement);
});

def_drop_side_effect_free(AST_TemplateSegment, return_null);

def_drop_side_effect_free(AST_TemplateString, function (compressor) {
    var values = trim(this.segments, compressor, first_in_statement);
    return values && make_sequence(this, values);
});


code:
/***********************************************************************

  A JavaScript tokenizer / parser / beautifier / compressor.
  https://github.com/mishoo/UglifyJS2

  -------------------------------- (C) ---------------------------------

                           Author: Mihai Bazon
                         <mihai.bazon@gmail.com>
                       http://mihai.bazon.net/blog

  Distributed under the BSD license:

    Copyright 2012 (c) Mihai Bazon <mihai.bazon@gmail.com>

    Redistribution and use in source and binary forms, with or without
    modification, are permitted provided that the following conditions
    are met:

        * Redistributions of source code must retain the above
          copyright notice, this list of conditions and the following
          disclaimer.

        * Redistributions in binary form must reproduce the above
          copyright notice, this list of conditions and the following
          disclaimer in the documentation and/or other materials
          provided with the distribution.

    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER “AS IS” AND ANY
    EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
    IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
    PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER BE
    LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
    OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
    PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
    PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
    THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR
    TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
    THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
    SUCH DAMAGE.

 ***********************************************************************/

import {
    AST_Accessor,
    AST_Assign,
    AST_BlockStatement,
    AST_Class,
    AST_ClassExpression,
    AST_ClassStaticBlock,
    AST_DefaultAssign,
    AST_DefClass,
    AST_Definitions,
    AST_Defun,
    AST_Destructuring,
    AST_EmptyStatement,
    AST_Expansion,
    AST_Export,
    AST_For,
    AST_ForIn,
    AST_Function,
    AST_LabeledStatement,
    AST_Lambda,
    AST_Number,
    AST_Scope,
    AST_Sequence,
    AST_SimpleStatement,
    AST_SymbolBlockDeclaration,
    AST_SymbolCatch,
    AST_SymbolDeclaration,
    AST_SymbolFunarg,
    AST_SymbolRef,
    AST_SymbolVar,
    AST_Toplevel,
    AST_Unary,
    AST_Var,

    TreeTransformer,
    TreeWalker,
    walk,
} from "../ast.js";
import {
    keep_name,
    make_node,
    map_add,
    MAP,
    remove,
    return_false,
} from "../utils/index.js";
import { SymbolDef } from "../scope.js";

import {
    WRITE_ONLY,
    UNUSED,

    has_flag,
    set_flag,
} from "./compressor-flags.js";
import {
    make_sequence,
    maintain_this_binding,
    is_empty,
    is_ref_of,
    can_be_evicted_from_block,
    requires_sequence_to_maintain_binding,
} from "./common.js";

const r_keep_assign = /keep_assign/;

/** Drop unused variables from this scope */
AST_Scope.DEFMETHOD("drop_unused", function(compressor) {
    if (!compressor.option("unused")) return;
    if (compressor.has_directive("use asm")) return;
    if (!this.variables) return; // not really a scope (eg: AST_Class)

    var self = this;
    if (self.pinned()) return;
    var drop_funcs = !(self instanceof AST_Toplevel) || compressor.toplevel.funcs;
    var drop_vars = !(self instanceof AST_Toplevel) || compressor.toplevel.vars;
    const assign_as_unused = r_keep_assign.test(compressor.option("unused")) ? return_false : function(node) {
        if (node instanceof AST_Assign
            && !node.logical
            && (has_flag(node, WRITE_ONLY) || node.operator == "=")
        ) {
            return node.left;
        }
        if (node instanceof AST_Unary && has_flag(node, WRITE_ONLY)) {
            return node.expression;
        }
    };
    var in_use_ids = new Map();
    var fixed_ids = new Map();
    if (self instanceof AST_Toplevel && compressor.top_retain) {
        self.variables.forEach(function(def) {
            if (compressor.top_retain(def)) {
                in_use_ids.set(def.id, def);
            }
        });
    }
    var var_defs_by_id = new Map();
    var initializations = new Map();
    var self_referential_classes = new Set();

    // pass 1: find out which symbols are directly used in
    // this scope (not in nested scopes).
    var scope = this;
    var tw = new TreeWalker(function(node, descend) {
        if (node instanceof AST_Lambda && node.uses_arguments && !tw.has_directive("use strict")) {
            node.argnames.forEach(function(argname) {
                if (!(argname instanceof AST_SymbolDeclaration)) return;
                var def = argname.definition();
                in_use_ids.set(def.id, def);
            });
        }
        if (node === self) return;
        if (node instanceof AST_Class && node.has_side_effects(compressor)) {
            if (node.is_self_referential()) self_referential_classes.add(node);
            node.visit_nondeferred_class_parts(tw);
        }
        if (node instanceof AST_Defun || node instanceof AST_DefClass) {
            var node_def = node.name.definition();
            const in_export = tw.parent() instanceof AST_Export;
            if (in_export || !drop_funcs && scope === self) {
                if (node_def.global) {
                    in_use_ids.set(node_def.id, node_def);
                }
            }

            map_add(initializations, node_def.id, node);
            return true; // don't go in nested scopes
        }
        // In the root scope, we drop things. In inner scopes, we just check for uses.
        const in_root_scope = scope === self;
        if (node instanceof AST_SymbolFunarg && in_root_scope) {
            map_add(var_defs_by_id, node.definition().id, node);
        }
        if (node instanceof AST_Definitions && in_root_scope) {
            const in_export = tw.parent() instanceof AST_Export;
            node.definitions.forEach(function(def) {
                if (def.name instanceof AST_SymbolVar) {
                    map_add(var_defs_by_id, def.name.definition().id, def);
                }
                if (in_export || !drop_vars) {
                    walk(def.name, node => {
                        if (node instanceof AST_SymbolDeclaration) {
                            const def = node.definition();
                            if (def.global) {
                                in_use_ids.set(def.id, def);
                            }
                        }
                    });
                }
                if (def.name instanceof AST_Destructuring) {
                    def.walk(tw);
                }
                if (def.name instanceof AST_SymbolDeclaration && def.value) {
                    var node_def = def.name.definition();
                    map_add(initializations, node_def.id, def.value);
                    if (!node_def.chained && def.name.fixed_value() === def.value) {
                        fixed_ids.set(node_def.id, def);
                    }
                    if (def.value.has_side_effects(compressor)) {
                        def.value.walk(tw);
                    }
                }
            });
            return true;
        }
        return scan_ref_scoped(node, descend);
    });
    self.walk(tw);
    // pass 2: for every used symbol we need to walk its
    // initialization code to figure out if it uses other
    // symbols (that may not be in_use).
    tw = new TreeWalker(scan_ref_scoped);
    in_use_ids.forEach(function (def) {
        var init = initializations.get(def.id);
        if (init) init.forEach(function(init) {
            init.walk(tw);
        });
    });
    self_referential_classes.forEach(function (cls) {
        cls.walk(tw);
    });
    // pass 3: we should drop declarations not in_use
    var tt = new TreeTransformer(
        function before(node, descend, in_list) {
            var parent = tt.parent();
            if (drop_vars) {
                const sym = assign_as_unused(node);
                if (sym instanceof AST_SymbolRef) {
                    var def = sym.definition();
                    var in_use = in_use_ids.has(def.id);
                    if (node instanceof AST_Assign) {
                        if (!in_use || fixed_ids.has(def.id) && fixed_ids.get(def.id) !== node) {
                            const assignee = node.right.transform(tt);
                            if (!in_use && !assignee.has_side_effects(compressor) && !is_used_in_expression(tt)) {
                                return in_list ? MAP.skip : make_node(AST_Number, node, { value: 0 });
                            }
                            return maintain_this_binding(parent, node, assignee);
                        }
                    } else if (!in_use) {
                        return in_list ? MAP.skip : make_node(AST_Number, node, { value: 0 });
                    }
                }
            }
            if (scope !== self) return;
            var def;
            if (node.name
                && (node instanceof AST_ClassExpression
                    && !keep_name(compressor.option("keep_classnames"), (def = node.name.definition()).name)
                || node instanceof AST_Function
                    && !keep_name(compressor.option("keep_fnames"), (def = node.name.definition()).name))) {
                // any declarations with same name will overshadow
                // name of this anonymous function and can therefore
                // never be used anywhere
                if (!in_use_ids.has(def.id) || def.orig.length > 1) node.name = null;
            }
            if (node instanceof AST_Lambda && !(node instanceof AST_Accessor)) {
                var trim = !compressor.option("keep_fargs");
                for (var a = node.argnames, i = a.length; --i >= 0;) {
                    var sym = a[i];
                    if (sym instanceof AST_Expansion) {
                        sym = sym.expression;
                    }
                    if (sym instanceof AST_DefaultAssign) {
                        sym = sym.left;
                    }
                    // Do not drop destructuring arguments.
                    // They constitute a type assertion of sorts
                    if (
                        !(sym instanceof AST_Destructuring)
                        && !in_use_ids.has(sym.definition().id)
                    ) {
                        set_flag(sym, UNUSED);
                        if (trim) {
                            a.pop();
                        }
                    } else {
                        trim = false;
                    }
                }
            }
            if (node instanceof AST_DefClass && node !== self) {
                const def = node.name.definition();
                descend(node, this);
                const keep_class = def.global && !drop_funcs || in_use_ids.has(def.id);
                if (!keep_class) {
                    const kept = node.drop_side_effect_free(compressor);
                    if (kept == null) {
                        def.eliminated++;
                        return in_list ? MAP.skip : make_node(AST_EmptyStatement, node);
                    }
                    return kept;
                }
                return node;
            }
            if (node instanceof AST_Defun && node !== self) {
                const def = node.name.definition();
                const keep = def.global && !drop_funcs || in_use_ids.has(def.id);
                if (!keep) {
                    def.eliminated++;
                    return in_list ? MAP.skip : make_node(AST_EmptyStatement, node);
                }
            }
            if (node instanceof AST_Definitions && !(parent instanceof AST_ForIn && parent.init === node)) {
                var drop_block = !(parent instanceof AST_Toplevel) && !(node instanceof AST_Var);
                // place uninitialized names at the start
                var body = [], head = [], tail = [];
                // for unused names whose initialization has
                // side effects, we can cascade the init. code
                // into the next one, or next statement.
                var side_effects = [];
                node.definitions.forEach(function(def) {
                    if (def.value) def.value = def.value.transform(tt);
                    var is_destructure = def.name instanceof AST_Destructuring;
                    var sym = is_destructure
                        ? new SymbolDef(null, { name: "<destructure>" }) /* fake SymbolDef */
                        : def.name.definition();
                    if (drop_block && sym.global) return tail.push(def);
                    if (!(drop_vars || drop_block)
                        || is_destructure
                            && (def.name.names.length
                                || def.name.is_array
                                || compressor.option("pure_getters") != true)
                        || in_use_ids.has(sym.id)
                    ) {
                        if (def.value && fixed_ids.has(sym.id) && fixed_ids.get(sym.id) !== def) {
                            def.value = def.value.drop_side_effect_free(compressor);
                        }
                        if (def.name instanceof AST_SymbolVar) {
                            var var_defs = var_defs_by_id.get(sym.id);
                            if (var_defs.length > 1 && (!def.value || sym.orig.indexOf(def.name) > sym.eliminated)) {
                                if (def.value) {
                                    var ref = make_node(AST_SymbolRef, def.name, def.name);
                                    sym.references.push(ref);
                                    var assign = make_node(AST_Assign, def, {
                                        operator: "=",
                                        logical: false,
                                        left: ref,
                                        right: def.value
                                    });
                                    if (fixed_ids.get(sym.id) === def) {
                                        fixed_ids.set(sym.id, assign);
                                    }
                                    side_effects.push(assign.transform(tt));
                                }
                                remove(var_defs, def);
                                sym.eliminated++;
                                return;
                            }
                        }
                        if (def.value) {
                            if (side_effects.length > 0) {
                                if (tail.length > 0) {
                                    side_effects.push(def.value);
                                    def.value = make_sequence(def.value, side_effects);
                                } else {
                                    body.push(make_node(AST_SimpleStatement, node, {
                                        body: make_sequence(node, side_effects)
                                    }));
                                }
                                side_effects = [];
                            }
                            tail.push(def);
                        } else {
                            head.push(def);
                        }
                    } else if (sym.orig[0] instanceof AST_SymbolCatch) {
                        var value = def.value && def.value.drop_side_effect_free(compressor);
                        if (value) side_effects.push(value);
                        def.value = null;
                        head.push(def);
                    } else {
                        var value = def.value && def.value.drop_side_effect_free(compressor);
                        if (value) {
                            side_effects.push(value);
                        }
                        sym.eliminated++;
                    }
                });
                if (head.length > 0 || tail.length > 0) {
                    node.definitions = head.concat(tail);
                    body.push(node);
                }
                if (side_effects.length > 0) {
                    body.push(make_node(AST_SimpleStatement, node, {
                        body: make_sequence(node, side_effects)
                    }));
                }
                switch (body.length) {
                  case 0:
                    return in_list ? MAP.skip : make_node(AST_EmptyStatement, node);
                  case 1:
                    return body[0];
                  default:
                    return in_list ? MAP.splice(body) : make_node(AST_BlockStatement, node, { body });
                }
            }
            // certain combination of unused name + side effect leads to:
            //    https://github.com/mishoo/UglifyJS2/issues/44
            //    https://github.com/mishoo/UglifyJS2/issues/1830
            //    https://github.com/mishoo/UglifyJS2/issues/1838
            // that's an invalid AST.
            // We fix it at this stage by moving the `var` outside the `for`.
            if (node instanceof AST_For) {
                descend(node, this);
                var block;
                if (node.init instanceof AST_BlockStatement) {
                    block = node.init;
                    node.init = block.body.pop();
                    block.body.push(node);
                }
                if (node.init instanceof AST_SimpleStatement) {
                    node.init = node.init.body;
                } else if (is_empty(node.init)) {
                    node.init = null;
                }
                return !block ? node : in_list ? MAP.splice(block.body) : block;
            }
            if (node instanceof AST_LabeledStatement
                && node.body instanceof AST_For
            ) {
                descend(node, this);
                if (node.body instanceof AST_BlockStatement) {
                    var block = node.body;
                    node.body = block.body.pop();
                    block.body.push(node);
                    return in_list ? MAP.splice(block.body) : block;
                }
                return node;
            }
            if (node instanceof AST_BlockStatement) {
                descend(node, this);
                if (in_list && node.body.every(can_be_evicted_from_block)) {
                    return MAP.splice(node.body);
                }
                return node;
            }
            if (node instanceof AST_Scope && !(node instanceof AST_ClassStaticBlock)) {
                const save_scope = scope;
                scope = node;
                descend(node, this);
                scope = save_scope;
                return node;
            }
        },
        function after(node, in_list) {
            if (node instanceof AST_Sequence) {
                switch (node.expressions.length) {
                    case 0: return in_list ? MAP.skip : make_node(AST_Number, node, { value: 0 });
                    case 1: return node.expressions[0];
                }
            }
        }
    );

    self.transform(tt);

    function scan_ref_scoped(node, descend) {
        var node_def;
        const sym = assign_as_unused(node);
        if (sym instanceof AST_SymbolRef
            && !is_ref_of(node.left, AST_SymbolBlockDeclaration)
            && self.variables.get(sym.name) === (node_def = sym.definition())
        ) {
            if (node instanceof AST_Assign) {
                node.right.walk(tw);
                if (!node_def.chained && node.left.fixed_value() === node.right) {
                    fixed_ids.set(node_def.id, node);
                }
            }
            return true;
        }
        if (node instanceof AST_SymbolRef) {
            node_def = node.definition();
            if (!in_use_ids.has(node_def.id)) {
                in_use_ids.set(node_def.id, node_def);
                if (node_def.orig[0] instanceof AST_SymbolCatch) {
                    const redef = node_def.scope.is_block_scope()
                        && node_def.scope.get_defun_scope().variables.get(node_def.name);
                    if (redef) in_use_ids.set(redef.id, redef);
                }
            }
            return true;
        }
        if (node instanceof AST_Class) {
            descend();
            return true;
        }
        if (node instanceof AST_Scope && !(node instanceof AST_ClassStaticBlock)) {
            var save_scope = scope;
            scope = node;
            descend();
            scope = save_scope;
            return true;
        }
    }
});

/**
 * Check if a node may be used by the expression it's in
 * void (0, 1, {node}, 2) -> false
 * console.log(0, {node}) -> true
 */
function is_used_in_expression(tw) {
    for (let p = -1, node, parent; node = tw.parent(p), parent = tw.parent(p + 1); p++) {
        if (parent instanceof AST_Sequence) {
            const nth_expression = parent.expressions.indexOf(node);
            if (nth_expression !== parent.expressions.length - 1) {
                // Detect (0, x.noThis)() constructs
                const grandparent = tw.parent(p + 2);
                if (
                    parent.expressions.length > 2
                    || parent.expressions.length === 1
                    || !requires_sequence_to_maintain_binding(grandparent, parent, parent.expressions[1])
                ) {
                    return false;
                }
                return true;
            } else {
                continue;
            }
        }
        if (parent instanceof AST_Unary) {
            const op = parent.operator;
            if (op === "void") {
                return false;
            }
            if (op === "typeof" || op === "+" || op === "-" || op === "!" || op === "~") {
                continue;
            }
        }
        return true;
    }

    return true;
}


code:
/***********************************************************************

  A JavaScript tokenizer / parser / beautifier / compressor.
  https://github.com/mishoo/UglifyJS2

  -------------------------------- (C) ---------------------------------

                           Author: Mihai Bazon
                         <mihai.bazon@gmail.com>
                       http://mihai.bazon.net/blog

  Distributed under the BSD license:

    Copyright 2012 (c) Mihai Bazon <mihai.bazon@gmail.com>

    Redistribution and use in source and binary forms, with or without
    modification, are permitted provided that the following conditions
    are met:

        * Redistributions of source code must retain the above
          copyright notice, this list of conditions and the following
          disclaimer.

        * Redistributions in binary form must reproduce the above
          copyright notice, this list of conditions and the following
          disclaimer in the documentation and/or other materials
          provided with the distribution.

    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER “AS IS” AND ANY
    EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
    IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
    PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER BE
    LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
    OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
    PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
    PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
    THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR
    TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
    THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
    SUCH DAMAGE.

 ***********************************************************************/

import {
    HOP,
    makePredicate,
    return_this,
    string_template,
    regexp_source_fix,
    regexp_is_safe,
} from "../utils/index.js";
import {
    AST_Array,
    AST_BigInt,
    AST_Binary,
    AST_Call,
    AST_Chain,
    AST_Class,
    AST_Conditional,
    AST_Constant,
    AST_Dot,
    AST_Expansion,
    AST_Function,
    AST_Lambda,
    AST_New,
    AST_Node,
    AST_Object,
    AST_PropAccess,
    AST_RegExp,
    AST_Statement,
    AST_Symbol,
    AST_SymbolRef,
    AST_TemplateString,
    AST_UnaryPrefix,
    AST_With,
} from "../ast.js";
import { is_undeclared_ref} from "./inference.js";
import { is_pure_native_value, is_pure_native_fn, is_pure_native_method } from "./native-objects.js";

// methods to evaluate a constant expression

function def_eval(node, func) {
    node.DEFMETHOD("_eval", func);
}

// Used to propagate a nullish short-circuit signal upwards through the chain.
export const nullish = Symbol("This AST_Chain is nullish");

// If the node has been successfully reduced to a constant,
// then its value is returned; otherwise the element itself
// is returned.
// They can be distinguished as constant value is never a
// descendant of AST_Node.
AST_Node.DEFMETHOD("evaluate", function (compressor) {
    if (!compressor.option("evaluate"))
        return this;
    var val = this._eval(compressor, 1);
    if (!val || val instanceof RegExp)
        return val;
    if (typeof val == "function" || typeof val == "object" || val == nullish)
        return this;

    // Evaluated strings can be larger than the original expression
    if (typeof val === "string") {
        const unevaluated_size = this.size(compressor);
        if (val.length + 2 > unevaluated_size) return this;
    }

    return val;
});

var unaryPrefix = makePredicate("! ~ - + void");
AST_Node.DEFMETHOD("is_constant", function () {
    // Accomodate when compress option evaluate=false
    // as well as the common constant expressions !0 and -1
    if (this instanceof AST_Constant) {
        return !(this instanceof AST_RegExp);
    } else {
        return this instanceof AST_UnaryPrefix
            && this.expression instanceof AST_Constant
            && unaryPrefix.has(this.operator);
    }
});

def_eval(AST_Statement, function () {
    throw new Error(string_template("Cannot evaluate a statement [{file}:{line},{col}]", this.start));
});

def_eval(AST_Lambda, return_this);
def_eval(AST_Class, return_this);
def_eval(AST_Node, return_this);
def_eval(AST_Constant, function () {
    return this.getValue();
});

const supports_bigint = typeof BigInt === "function";
def_eval(AST_BigInt, function () {
    if (supports_bigint) {
        return BigInt(this.value);
    } else {
        return this;
    }
});

def_eval(AST_RegExp, function (compressor) {
    let evaluated = compressor.evaluated_regexps.get(this.value);
    if (evaluated === undefined && regexp_is_safe(this.value.source)) {
        try {
            const { source, flags } = this.value;
            evaluated = new RegExp(source, flags);
        } catch (e) {
            evaluated = null;
        }
        compressor.evaluated_regexps.set(this.value, evaluated);
    }
    return evaluated || this;
});

def_eval(AST_TemplateString, function () {
    if (this.segments.length !== 1) return this;
    return this.segments[0].value;
});

def_eval(AST_Function, function (compressor) {
    if (compressor.option("unsafe")) {
        var fn = function () { };
        fn.node = this;
        fn.toString = () => this.print_to_string();
        return fn;
    }
    return this;
});

def_eval(AST_Array, function (compressor, depth) {
    if (compressor.option("unsafe")) {
        var elements = [];
        for (var i = 0, len = this.elements.length; i < len; i++) {
            var element = this.elements[i];
            var value = element._eval(compressor, depth);
            if (element === value)
                return this;
            elements.push(value);
        }
        return elements;
    }
    return this;
});

def_eval(AST_Object, function (compressor, depth) {
    if (compressor.option("unsafe")) {
        var val = {};
        for (var i = 0, len = this.properties.length; i < len; i++) {
            var prop = this.properties[i];
            if (prop instanceof AST_Expansion)
                return this;
            var key = prop.key;
            if (key instanceof AST_Symbol) {
                key = key.name;
            } else if (key instanceof AST_Node) {
                key = key._eval(compressor, depth);
                if (key === prop.key)
                    return this;
            }
            if (typeof Object.prototype[key] === "function") {
                return this;
            }
            if (prop.value instanceof AST_Function)
                continue;
            val[key] = prop.value._eval(compressor, depth);
            if (val[key] === prop.value)
                return this;
        }
        return val;
    }
    return this;
});

var non_converting_unary = makePredicate("! typeof void");
def_eval(AST_UnaryPrefix, function (compressor, depth) {
    var e = this.expression;
    // Function would be evaluated to an array and so typeof would
    // incorrectly return 'object'. Hence making is a special case.
    if (compressor.option("typeofs")
        && this.operator == "typeof"
        && (e instanceof AST_Lambda
            || e instanceof AST_SymbolRef
            && e.fixed_value() instanceof AST_Lambda)) {
        return typeof function () { };
    }
    if (!non_converting_unary.has(this.operator))
        depth++;
    e = e._eval(compressor, depth);
    if (e === this.expression)
        return this;
    switch (this.operator) {
        case "!": return !e;
        case "typeof":
            // typeof <RegExp> returns "object" or "function" on different platforms
            // so cannot evaluate reliably
            if (e instanceof RegExp)
                return this;
            return typeof e;
        case "void": return void e;
        case "~": return ~e;
        case "-": return -e;
        case "+": return +e;
    }
    return this;
});

var non_converting_binary = makePredicate("&& || ?? === !==");
const identity_comparison = makePredicate("== != === !==");
const has_identity = value => typeof value === "object"
    || typeof value === "function"
    || typeof value === "symbol";

def_eval(AST_Binary, function (compressor, depth) {
    if (!non_converting_binary.has(this.operator))
        depth++;

    var left = this.left._eval(compressor, depth);
    if (left === this.left)
        return this;
    var right = this.right._eval(compressor, depth);
    if (right === this.right)
        return this;

    if (left != null
        && right != null
        && identity_comparison.has(this.operator)
        && has_identity(left)
        && has_identity(right)
        && typeof left === typeof right) {
        // Do not compare by reference
        return this;
    }

    // Do not mix BigInt and Number; Don't use `>>>` on BigInt or `/ 0n`
    if (
        (typeof left === "bigint") !== (typeof right === "bigint")
        || typeof left === "bigint"
            && (this.operator === ">>>"
                || this.operator === "/" && Number(right) === 0)
    ) {
        return this;
    }

    var result;
    switch (this.operator) {
        case "&&": result = left && right; break;
        case "||": result = left || right; break;
        case "??": result = left != null ? left : right; break;
        case "|": result = left | right; break;
        case "&": result = left & right; break;
        case "^": result = left ^ right; break;
        case "+": result = left + right; break;
        case "*": result = left * right; break;
        case "**": result = left ** right; break;
        case "/": result = left / right; break;
        case "%": result = left % right; break;
        case "-": result = left - right; break;
        case "<<": result = left << right; break;
        case ">>": result = left >> right; break;
        case ">>>": result = left >>> right; break;
        case "==": result = left == right; break;
        case "===": result = left === right; break;
        case "!=": result = left != right; break;
        case "!==": result = left !== right; break;
        case "<": result = left < right; break;
        case "<=": result = left <= right; break;
        case ">": result = left > right; break;
        case ">=": result = left >= right; break;
        default:
            return this;
    }
    if (typeof result === "number" && isNaN(result) && compressor.find_parent(AST_With)) {
        // leave original expression as is
        return this;
    }
    return result;
});

def_eval(AST_Conditional, function (compressor, depth) {
    var condition = this.condition._eval(compressor, depth);
    if (condition === this.condition)
        return this;
    var node = condition ? this.consequent : this.alternative;
    var value = node._eval(compressor, depth);
    return value === node ? this : value;
});

// Set of AST_SymbolRef which are currently being evaluated.
// Avoids infinite recursion of ._eval()
const reentrant_ref_eval = new Set();
def_eval(AST_SymbolRef, function (compressor, depth) {
    if (reentrant_ref_eval.has(this))
        return this;

    var fixed = this.fixed_value();
    if (!fixed)
        return this;

    reentrant_ref_eval.add(this);
    const value = fixed._eval(compressor, depth);
    reentrant_ref_eval.delete(this);

    if (value === fixed)
        return this;

    if (value && typeof value == "object") {
        var escaped = this.definition().escaped;
        if (escaped && depth > escaped)
            return this;
    }
    return value;
});

const global_objs = { Array, Math, Number, Object, String };

const regexp_flags = new Set([
    "dotAll",
    "global",
    "ignoreCase",
    "multiline",
    "sticky",
    "unicode",
]);

def_eval(AST_PropAccess, function (compressor, depth) {
    let obj = this.expression._eval(compressor, depth + 1);
    if (obj === nullish || (this.optional && obj == null)) return nullish;

    // `.length` of strings and arrays is always safe
    if (this.property === "length") {
        if (typeof obj === "string") {
            return obj.length;
        }

        const is_spreadless_array =
            obj instanceof AST_Array
            && obj.elements.every(el => !(el instanceof AST_Expansion));

        if (
            is_spreadless_array
            && obj.elements.every(el => !el.has_side_effects(compressor))
        ) {
            return obj.elements.length;
        }
    }

    if (compressor.option("unsafe")) {
        var key = this.property;
        if (key instanceof AST_Node) {
            key = key._eval(compressor, depth);
            if (key === this.property)
                return this;
        }

        var exp = this.expression;
        if (is_undeclared_ref(exp)) {
            var aa;
            var first_arg = exp.name === "hasOwnProperty"
                && key === "call"
                && (aa = compressor.parent() && compressor.parent().args)
                && (aa && aa[0]
                    && aa[0].evaluate(compressor));

            first_arg = first_arg instanceof AST_Dot ? first_arg.expression : first_arg;

            if (first_arg == null || first_arg.thedef && first_arg.thedef.undeclared) {
                return this.clone();
            }
            if (!is_pure_native_value(exp.name, key))
                return this;
            obj = global_objs[exp.name];
        } else {
            if (obj instanceof RegExp) {
                if (key == "source") {
                    return regexp_source_fix(obj.source);
                } else if (key == "flags" || regexp_flags.has(key)) {
                    return obj[key];
                }
            }
            if (!obj || obj === exp || !HOP(obj, key))
                return this;

            if (typeof obj == "function")
                switch (key) {
                    case "name":
                        return obj.node.name ? obj.node.name.name : "";
                    case "length":
                        return obj.node.length_property();
                    default:
                        return this;
                }
        }
        return obj[key];
    }
    return this;
});

def_eval(AST_Chain, function (compressor, depth) {
    const evaluated = this.expression._eval(compressor, depth);
    return evaluated === nullish
        ? undefined
        : evaluated === this.expression
          ? this
          : evaluated;
});

def_eval(AST_Call, function (compressor, depth) {
    var exp = this.expression;

    const callee = exp._eval(compressor, depth);
    if (callee === nullish || (this.optional && callee == null)) return nullish;

    if (compressor.option("unsafe") && exp instanceof AST_PropAccess) {
        var key = exp.property;
        if (key instanceof AST_Node) {
            key = key._eval(compressor, depth);
            if (key === exp.property)
                return this;
        }
        var val;
        var e = exp.expression;
        if (is_undeclared_ref(e)) {
            var first_arg = e.name === "hasOwnProperty" &&
                key === "call" &&
                (this.args[0] && this.args[0].evaluate(compressor));

            first_arg = first_arg instanceof AST_Dot ? first_arg.expression : first_arg;

            if ((first_arg == null || first_arg.thedef && first_arg.thedef.undeclared)) {
                return this.clone();
            }
            if (!is_pure_native_fn(e.name, key)) return this;
            val = global_objs[e.name];
        } else {
            val = e._eval(compressor, depth + 1);
            if (val === e || !val)
                return this;
            if (!is_pure_native_method(val.constructor.name, key))
                return this;
        }
        var args = [];
        for (var i = 0, len = this.args.length; i < len; i++) {
            var arg = this.args[i];
            var value = arg._eval(compressor, depth);
            if (arg === value)
                return this;
            if (arg instanceof AST_Lambda)
                return this;
            args.push(value);
        }
        try {
            return val[key].apply(val, args);
        } catch (ex) {
            // We don't really care
        }
    }
    return this;
});

// Also a subclass of AST_Call
def_eval(AST_New, return_this);


code:
import {
    AST_Array,
    AST_Chain,
    AST_Constant,
    AST_Dot,
    AST_ImportMeta,
    AST_Node,
    AST_Object,
    AST_ObjectKeyVal,
    AST_PropAccess,
    AST_SymbolDeclaration,
    AST_SymbolRef,
    AST_Toplevel,
    TreeTransformer,
} from "../ast.js";
import { make_node, noop, HOP } from "../utils/index.js";
import { make_node_from_constant } from "./common.js";
import { is_lhs } from "./inference.js";

(function(def_find_defs) {
    function to_node(value, orig) {
        if (value instanceof AST_Node) {
            if (!(value instanceof AST_Constant)) {
                // Value may be a function, an array including functions and even a complex assign / block expression,
                // so it should never be shared in different places.
                // Otherwise wrong information may be used in the compression phase
                value = value.clone(true);
            }
            return make_node(value.CTOR, orig, value);
        }
        if (Array.isArray(value)) return make_node(AST_Array, orig, {
            elements: value.map(function(value) {
                return to_node(value, orig);
            })
        });
        if (value && typeof value == "object") {
            var props = [];
            for (var key in value) if (HOP(value, key)) {
                props.push(make_node(AST_ObjectKeyVal, orig, {
                    key: key,
                    value: to_node(value[key], orig)
                }));
            }
            return make_node(AST_Object, orig, {
                properties: props
            });
        }
        return make_node_from_constant(value, orig);
    }

    AST_Toplevel.DEFMETHOD("resolve_defines", function(compressor) {
        if (!compressor.option("global_defs")) return this;
        this.figure_out_scope({ ie8: compressor.option("ie8") });
        return this.transform(new TreeTransformer(function(node) {
            var def = node._find_defs(compressor, "");
            if (!def) return;
            var level = 0, child = node, parent;
            while (parent = this.parent(level++)) {
                if (!(parent instanceof AST_PropAccess)) break;
                if (parent.expression !== child) break;
                child = parent;
            }
            if (is_lhs(child, parent)) {
                return;
            }
            return def;
        }));
    });
    def_find_defs(AST_Node, noop);
    def_find_defs(AST_Chain, function(compressor, suffix) {
        return this.expression._find_defs(compressor, suffix);
    });
    def_find_defs(AST_Dot, function(compressor, suffix) {
        return this.expression._find_defs(compressor, "." + this.property + suffix);
    });
    def_find_defs(AST_SymbolDeclaration, function() {
        if (!this.global()) return;
    });
    def_find_defs(AST_SymbolRef, function(compressor, suffix) {
        if (!this.global()) return;
        var defines = compressor.option("global_defs");
        var name = this.name + suffix;
        if (HOP(defines, name)) return to_node(defines[name], this);
    });
    def_find_defs(AST_ImportMeta, function(compressor, suffix) {
        var defines = compressor.option("global_defs");
        var name = "import.meta" + suffix;
        if (HOP(defines, name)) return to_node(defines[name], this);
    });
})(function(node, func) {
    node.DEFMETHOD("_find_defs", func);
});