webpack/lib/Parser.js

/*
	MIT License http://www.opensource.org/licenses/mit-license.php
	Author Tobias Koppers @sokra
*/
"use strict";

// Syntax: https://developer.mozilla.org/en/SpiderMonkey/Parser_API

const acorn = require("acorn-dynamic-import").default;
const Tapable = require("tapable").Tapable;
const SyncBailHook = require("tapable").SyncBailHook;
const HookMap = require("tapable/lib/HookMap");
const vm = require("vm");
const BasicEvaluatedExpression = require("./BasicEvaluatedExpression");
const StackedSetMap = require("./util/StackedSetMap");
const TrackingSet = require("./util/TrackingSet");

const joinRanges = (startRange, endRange) => {
	if(!endRange) return startRange;
	if(!startRange) return endRange;
	return [startRange[0], endRange[1]];
};

const defaultParserOptions = {
	ranges: true,
	locations: true,
	ecmaVersion: 2018,
	sourceType: "module",
	onComment: null,
	plugins: {
		dynamicImport: true
	}
};

class Parser extends Tapable {
	constructor(options, sourceType = "auto") {
		super();
		this.hooks = {
			evaluateTypeof: new HookMap(() => new SyncBailHook(["expression"])),
			evaluate: new HookMap(() => new SyncBailHook(["expression"])),
			evaluateIdentifier: new HookMap(() => new SyncBailHook(["expression"])),
			evaluateDefinedIdentifier: new HookMap(() => new SyncBailHook(["expression"])),
			evaluateCallExpressionMember: new HookMap(() => new SyncBailHook(["expression", "param"])),
			statement: new SyncBailHook(["statement"]),
			statementIf: new SyncBailHook(["statement"]),
			label: new HookMap(() => new SyncBailHook(["statement"])),
			import: new SyncBailHook(["statement", "source"]),
			importSpecifier: new SyncBailHook(["statement", "source", "exportName", "identifierName"]),
			export: new SyncBailHook(["statement"]),
			exportImport: new SyncBailHook(["statement", "source"]),
			exportDeclaration: new SyncBailHook(["statement", "declaration"]),
			exportExpression: new SyncBailHook(["statement", "declaration"]),
			exportSpecifier: new SyncBailHook(["statement", "identifierName", "exportName", "index"]),
			exportImportSpecifier: new SyncBailHook(["statement", "source", "identifierName", "exportName", "index"]),
			varDeclaration: new HookMap(() => new SyncBailHook(["declaration"])),
			varDeclarationLet: new HookMap(() => new SyncBailHook(["declaration"])),
			varDeclarationConst: new HookMap(() => new SyncBailHook(["declaration"])),
			varDeclarationVar: new HookMap(() => new SyncBailHook(["declaration"])),
			canRename: new HookMap(() => new SyncBailHook(["initExpression"])),
			rename: new HookMap(() => new SyncBailHook(["initExpression"])),
			assigned: new HookMap(() => new SyncBailHook(["expression"])),
			assign: new HookMap(() => new SyncBailHook(["expression"])),
			typeof: new HookMap(() => new SyncBailHook(["expression"])),
			importCall: new SyncBailHook(["expression"]),
			call: new HookMap(() => new SyncBailHook(["expression"])),
			callAnyMember: new HookMap(() => new SyncBailHook(["expression"])),
			new: new HookMap(() => new SyncBailHook(["expression"])),
			expression: new HookMap(() => new SyncBailHook(["expression"])),
			expressionAnyMember: new HookMap(() => new SyncBailHook(["expression"])),
			expressionConditionalOperator: new SyncBailHook(["expression"]),
			program: new SyncBailHook(["ast", "comments"]),
		};
		const HOOK_MAP_COMPAT_CONFIG = {
			evaluateTypeof: /^evaluate typeof (.+)$/,
			evaluateIdentifier: /^evaluate Identifier (.+)$/,
			evaluateDefinedIdentifier: /^evaluate defined Identifier (.+)$/,
			evaluateCallExpressionMember: /^evaluate CallExpression .(.+)$/,
			evaluate: /^evaluate (.+)$/,
			label: /^label (.+)$/,
			varDeclarationLet: /^var-let (.+)$/,
			varDeclarationConst: /^var-const (.+)$/,
			varDeclarationVar: /^var-var (.+)$/,
			varDeclaration: /^var (.+)$/,
			canRename: /^can-rename (.+)$/,
			rename: /^rename (.+)$/,
			typeof: /^typeof (.+)$/,
			assigned: /^assigned (.+)$/,
			assign: /^assign (.+)$/,
			callAnyMember: /^call (.+)\.\*$/,
			call: /^call (.+)$/,
			new: /^new (.+)$/,
			expressionConditionalOperator: /^expression \?:$/,
			expressionAnyMember: /^expression (.+)\.\*$/,
			expression: /^expression (.+)$/,
		};
		this._pluginCompat.tap("Parser", options => {
			for(const name of Object.keys(HOOK_MAP_COMPAT_CONFIG)) {
				const regexp = HOOK_MAP_COMPAT_CONFIG[name];
				const match = regexp.exec(options.name);
				if(match) {
					if(match[1])
						this.hooks[name].tap(match[1], options.fn.name || "unnamed compat plugin", options.fn.bind(this));
					else
						this.hooks[name].tap(options.fn.name || "unnamed compat plugin", options.fn.bind(this));
					return true;
				}
			}
		});
		this.options = options;
		this.sourceType = sourceType;
		this.scope = undefined;
		this.state = undefined;
		this.comments = undefined;
		this.initializeEvaluating();
	}

	initializeEvaluating() {
		this.hooks.evaluate.for("Literal").tap("Parser", expr => {
			switch(typeof expr.value) {
				case "number":
					return new BasicEvaluatedExpression().setNumber(expr.value).setRange(expr.range);
				case "string":
					return new BasicEvaluatedExpression().setString(expr.value).setRange(expr.range);
				case "boolean":
					return new BasicEvaluatedExpression().setBoolean(expr.value).setRange(expr.range);
			}
			if(expr.value === null)
				return new BasicEvaluatedExpression().setNull().setRange(expr.range);
			if(expr.value instanceof RegExp)
				return new BasicEvaluatedExpression().setRegExp(expr.value).setRange(expr.range);
		});
		this.hooks.evaluate.for("LogicalExpression").tap("Parser", expr => {
			let left;
			let leftAsBool;
			let right;
			if(expr.operator === "&&") {
				left = this.evaluateExpression(expr.left);
				leftAsBool = left && left.asBool();
				if(leftAsBool === false) return left.setRange(expr.range);
				if(leftAsBool !== true) return;
				right = this.evaluateExpression(expr.right);
				return right.setRange(expr.range);
			} else if(expr.operator === "||") {
				left = this.evaluateExpression(expr.left);
				leftAsBool = left && left.asBool();
				if(leftAsBool === true) return left.setRange(expr.range);
				if(leftAsBool !== false) return;
				right = this.evaluateExpression(expr.right);
				return right.setRange(expr.range);
			}
		});
		this.hooks.evaluate.for("BinaryExpression").tap("Parser", expr => {
			let left;
			let right;
			let res;
			if(expr.operator === "+") {
				left = this.evaluateExpression(expr.left);
				right = this.evaluateExpression(expr.right);
				if(!left || !right) return;
				res = new BasicEvaluatedExpression();
				if(left.isString()) {
					if(right.isString()) {
						res.setString(left.string + right.string);
					} else if(right.isNumber()) {
						res.setString(left.string + right.number);
					} else if(right.isWrapped() && right.prefix && right.prefix.isString()) {
						res.setWrapped(
							new BasicEvaluatedExpression()
							.setString(left.string + right.prefix.string)
							.setRange(joinRanges(left.range, right.prefix.range)),
							right.postfix);
					} else if(right.isWrapped()) {
						res.setWrapped(
							new BasicEvaluatedExpression()
							.setString(left.string)
							.setRange(left.range),
							right.postfix);
					} else {
						res.setWrapped(left, null);
					}
				} else if(left.isNumber()) {
					if(right.isString()) {
						res.setString(left.number + right.string);
					} else if(right.isNumber()) {
						res.setNumber(left.number + right.number);
					}
				} else if(left.isWrapped()) {
					if(left.postfix && left.postfix.isString() && right.isString()) {
						res.setWrapped(left.prefix,
							new BasicEvaluatedExpression()
							.setString(left.postfix.string + right.string)
							.setRange(joinRanges(left.postfix.range, right.range))
						);
					} else if(left.postfix && left.postfix.isString() && right.isNumber()) {
						res.setWrapped(left.prefix,
							new BasicEvaluatedExpression()
							.setString(left.postfix.string + right.number)
							.setRange(joinRanges(left.postfix.range, right.range))
						);
					} else if(right.isString()) {
						res.setWrapped(left.prefix, right);
					} else if(right.isNumber()) {
						res.setWrapped(left.prefix,
							new BasicEvaluatedExpression()
							.setString(right.number + "")
							.setRange(right.range));
					} else {
						res.setWrapped(left.prefix, new BasicEvaluatedExpression());
					}
				} else {
					if(right.isString()) {
						res.setWrapped(null, right);
					}
				}
				res.setRange(expr.range);
				return res;
			} else if(expr.operator === "-") {
				left = this.evaluateExpression(expr.left);
				right = this.evaluateExpression(expr.right);
				if(!left || !right) return;
				if(!left.isNumber() || !right.isNumber()) return;
				res = new BasicEvaluatedExpression();
				res.setNumber(left.number - right.number);
				res.setRange(expr.range);
				return res;
			} else if(expr.operator === "*") {
				left = this.evaluateExpression(expr.left);
				right = this.evaluateExpression(expr.right);
				if(!left || !right) return;
				if(!left.isNumber() || !right.isNumber()) return;
				res = new BasicEvaluatedExpression();
				res.setNumber(left.number * right.number);
				res.setRange(expr.range);
				return res;
			} else if(expr.operator === "/") {
				left = this.evaluateExpression(expr.left);
				right = this.evaluateExpression(expr.right);
				if(!left || !right) return;
				if(!left.isNumber() || !right.isNumber()) return;
				res = new BasicEvaluatedExpression();
				res.setNumber(left.number / right.number);
				res.setRange(expr.range);
				return res;
			} else if(expr.operator === "**") {
				left = this.evaluateExpression(expr.left);
				right = this.evaluateExpression(expr.right);
				if(!left || !right) return;
				if(!left.isNumber() || !right.isNumber()) return;
				res = new BasicEvaluatedExpression();
				res.setNumber(Math.pow(left.number, right.number));
				res.setRange(expr.range);
				return res;
			} else if(expr.operator === "==" || expr.operator === "===") {
				left = this.evaluateExpression(expr.left);
				right = this.evaluateExpression(expr.right);
				if(!left || !right) return;
				res = new BasicEvaluatedExpression();
				res.setRange(expr.range);
				if(left.isString() && right.isString()) {
					return res.setBoolean(left.string === right.string);
				} else if(left.isNumber() && right.isNumber()) {
					return res.setBoolean(left.number === right.number);
				} else if(left.isBoolean() && right.isBoolean()) {
					return res.setBoolean(left.bool === right.bool);
				}
			} else if(expr.operator === "!=" || expr.operator === "!==") {
				left = this.evaluateExpression(expr.left);
				right = this.evaluateExpression(expr.right);
				if(!left || !right) return;
				res = new BasicEvaluatedExpression();
				res.setRange(expr.range);
				if(left.isString() && right.isString()) {
					return res.setBoolean(left.string !== right.string);
				} else if(left.isNumber() && right.isNumber()) {
					return res.setBoolean(left.number !== right.number);
				} else if(left.isBoolean() && right.isBoolean()) {
					return res.setBoolean(left.bool !== right.bool);
				}
			} else if(expr.operator === "&") {
				left = this.evaluateExpression(expr.left);
				right = this.evaluateExpression(expr.right);
				if(!left || !right) return;
				if(!left.isNumber() || !right.isNumber()) return;
				res = new BasicEvaluatedExpression();
				res.setNumber(left.number & right.number);
				res.setRange(expr.range);
				return res;
			} else if(expr.operator === "|") {
				left = this.evaluateExpression(expr.left);
				right = this.evaluateExpression(expr.right);
				if(!left || !right) return;
				if(!left.isNumber() || !right.isNumber()) return;
				res = new BasicEvaluatedExpression();
				res.setNumber(left.number | right.number);
				res.setRange(expr.range);
				return res;
			} else if(expr.operator === "^") {
				left = this.evaluateExpression(expr.left);
				right = this.evaluateExpression(expr.right);
				if(!left || !right) return;
				if(!left.isNumber() || !right.isNumber()) return;
				res = new BasicEvaluatedExpression();
				res.setNumber(left.number ^ right.number);
				res.setRange(expr.range);
				return res;
			} else if(expr.operator === ">>>") {
				left = this.evaluateExpression(expr.left);
				right = this.evaluateExpression(expr.right);
				if(!left || !right) return;
				if(!left.isNumber() || !right.isNumber()) return;
				res = new BasicEvaluatedExpression();
				res.setNumber(left.number >>> right.number);
				res.setRange(expr.range);
				return res;
			} else if(expr.operator === ">>") {
				left = this.evaluateExpression(expr.left);
				right = this.evaluateExpression(expr.right);
				if(!left || !right) return;
				if(!left.isNumber() || !right.isNumber()) return;
				res = new BasicEvaluatedExpression();
				res.setNumber(left.number >> right.number);
				res.setRange(expr.range);
				return res;
			} else if(expr.operator === "<<") {
				left = this.evaluateExpression(expr.left);
				right = this.evaluateExpression(expr.right);
				if(!left || !right) return;
				if(!left.isNumber() || !right.isNumber()) return;
				res = new BasicEvaluatedExpression();
				res.setNumber(left.number << right.number);
				res.setRange(expr.range);
				return res;
			}
		});
		this.hooks.evaluate.for("UnaryExpression").tap("Parser", expr => {
			if(expr.operator === "typeof") {
				let res;
				let name;
				if(expr.argument.type === "Identifier") {
					name = this.scope.renames.get(expr.argument.name) || expr.argument.name;
					if(!this.scope.definitions.has(name)) {
						const hook = this.hooks.evaluateTypeof.get(name);
						if(hook !== undefined) {
							res = hook.call(expr);
							if(res !== undefined) return res;
						}
					}
				}
				if(expr.argument.type === "MemberExpression") {
					const exprName = this.getNameForExpression(expr.argument);
					if(exprName && exprName.free) {
						const hook = this.hooks.evaluateTypeof.get(exprName.name);
						if(hook !== undefined) {
							res = hook.call(expr);
							if(res !== undefined) return res;
						}
					}
				}
				if(expr.argument.type === "FunctionExpression") {
					return new BasicEvaluatedExpression().setString("function").setRange(expr.range);
				}
				const arg = this.evaluateExpression(expr.argument);
				if(arg.isString() || arg.isWrapped()) return new BasicEvaluatedExpression().setString("string").setRange(expr.range);
				else if(arg.isNumber()) return new BasicEvaluatedExpression().setString("number").setRange(expr.range);
				else if(arg.isBoolean()) return new BasicEvaluatedExpression().setString("boolean").setRange(expr.range);
				else if(arg.isArray() || arg.isConstArray() || arg.isRegExp()) return new BasicEvaluatedExpression().setString("object").setRange(expr.range);
			} else if(expr.operator === "!") {
				const argument = this.evaluateExpression(expr.argument);
				if(!argument) return;
				if(argument.isBoolean()) {
					return new BasicEvaluatedExpression().setBoolean(!argument.bool).setRange(expr.range);
				} else if(argument.isTruthy()) {
					return new BasicEvaluatedExpression().setBoolean(false).setRange(expr.range);
				} else if(argument.isFalsy()) {
					return new BasicEvaluatedExpression().setBoolean(true).setRange(expr.range);
				} else if(argument.isString()) {
					return new BasicEvaluatedExpression().setBoolean(!argument.string).setRange(expr.range);
				} else if(argument.isNumber()) {
					return new BasicEvaluatedExpression().setBoolean(!argument.number).setRange(expr.range);
				}
			} else if(expr.operator === "~") {
				const argument = this.evaluateExpression(expr.argument);
				if(!argument) return;
				if(!argument.isNumber()) return;
				const res = new BasicEvaluatedExpression();
				res.setNumber(~argument.number);
				res.setRange(expr.range);
				return res;
			}
		});
		this.hooks.evaluateTypeof.for("undefined").tap("Parser", expr => {
			return new BasicEvaluatedExpression().setString("undefined").setRange(expr.range);
		});
		this.hooks.evaluate.for("Identifier").tap("Parser", expr => {
			const name = this.scope.renames.get(expr.name) || expr.name;
			if(!this.scope.definitions.has(expr.name)) {
				const hook = this.hooks.evaluateIdentifier.get(name);
				if(hook !== undefined) {
					const result = hook.call(expr);
					if(result) return result;
				}
				return new BasicEvaluatedExpression().setIdentifier(name).setRange(expr.range);
			} else {
				const hook = this.hooks.evaluateDefinedIdentifier.get(name);
				if(hook !== undefined) {
					return hook.call(expr);
				}
			}
		});
		this.hooks.evaluate.for("ThisExpression").tap("Parser", expr => {
			const name = this.scope.renames.get("this");
			if(name) {
				const hook = this.hooks.evaluateIdentifier.get(name);
				if(hook !== undefined) {
					const result = hook.call(expr);
					if(result) return result;
				}
				return new BasicEvaluatedExpression().setIdentifier(name).setRange(expr.range);
			}
		});
		this.hooks.evaluate.for("MemberExpression").tap("Parser", expression => {
			let exprName = this.getNameForExpression(expression);
			if(exprName) {
				if(exprName.free) {
					const hook = this.hooks.evaluateIdentifier.get(exprName.name);
					if(hook !== undefined) {
						const result = hook.call(expression);
						if(result) return result;
					}
					return new BasicEvaluatedExpression().setIdentifier(exprName.name).setRange(expression.range);
				} else {
					const hook = this.hooks.evaluateDefinedIdentifier.get(exprName.name);
					if(hook !== undefined) {
						return hook.call(expression);
					}
				}
			}
		});
		this.hooks.evaluate.for("CallExpression").tap("Parser", expr => {
			if(expr.callee.type !== "MemberExpression") return;
			if(expr.callee.property.type !== (expr.callee.computed ? "Literal" : "Identifier")) return;
			const param = this.evaluateExpression(expr.callee.object);
			if(!param) return;
			const property = expr.callee.property.name || expr.callee.property.value;
			const hook = this.hooks.evaluateCallExpressionMember.get(property);
			if(hook !== undefined) {
				return hook.call(expr, param);
			}
		});
		this.hooks.evaluateCallExpressionMember.for("replace").tap("Parser", (expr, param) => {
			if(!param.isString()) return;
			if(expr.arguments.length !== 2) return;
			let arg1 = this.evaluateExpression(expr.arguments[0]);
			let arg2 = this.evaluateExpression(expr.arguments[1]);
			if(!arg1.isString() && !arg1.isRegExp()) return;
			arg1 = arg1.regExp || arg1.string;
			if(!arg2.isString()) return;
			arg2 = arg2.string;
			return new BasicEvaluatedExpression().setString(param.string.replace(arg1, arg2)).setRange(expr.range);
		});
		["substr", "substring"].forEach(fn => {
			this.hooks.evaluateCallExpressionMember.for(fn).tap("Parser", (expr, param) => {
				if(!param.isString()) return;
				let arg1;
				let result, str = param.string;
				switch(expr.arguments.length) {
					case 1:
						arg1 = this.evaluateExpression(expr.arguments[0]);
						if(!arg1.isNumber()) return;
						result = str[fn](arg1.number);
						break;
					case 2:
						{
							arg1 = this.evaluateExpression(expr.arguments[0]);
							const arg2 = this.evaluateExpression(expr.arguments[1]);
							if(!arg1.isNumber()) return;
							if(!arg2.isNumber()) return;
							result = str[fn](arg1.number, arg2.number);
							break;
						}
					default:
						return;
				}
				return new BasicEvaluatedExpression().setString(result).setRange(expr.range);
			});
		});

		/**
		 * @param {string} kind "cooked" | "raw"
		 * @param {any[]} quasis quasis
		 * @param {any[]} expressions expressions
		 * @return {BasicEvaluatedExpression[]} Simplified template
		 */
		const getSimplifiedTemplateResult = (kind, quasis, expressions) => {
			const parts = [];

			for(let i = 0; i < quasis.length; i++) {
				parts.push(new BasicEvaluatedExpression().setString(quasis[i].value[kind]).setRange(quasis[i].range));

				if(i > 0) {
					const prevExpr = parts[parts.length - 2],
						lastExpr = parts[parts.length - 1];
					const expr = this.evaluateExpression(expressions[i - 1]);
					if(!(expr.isString() || expr.isNumber())) continue;

					prevExpr.setString(prevExpr.string + (expr.isString() ? expr.string : expr.number) + lastExpr.string);
					prevExpr.setRange([prevExpr.range[0], lastExpr.range[1]]);
					parts.pop();
				}
			}
			return parts;
		};

		this.hooks.evaluate.for("TemplateLiteral").tap("Parser", node => {
			const parts = getSimplifiedTemplateResult.call(this, "cooked", node.quasis, node.expressions);
			if(parts.length === 1) {
				return parts[0].setRange(node.range);
			}
			return new BasicEvaluatedExpression().setTemplateString(parts).setRange(node.range);
		});
		this.hooks.evaluate.for("TaggedTemplateExpression").tap("Parser", node => {
			if(this.evaluateExpression(node.tag).identifier !== "String.raw") return;
			const parts = getSimplifiedTemplateResult.call(this, "raw", node.quasi.quasis, node.quasi.expressions);
			return new BasicEvaluatedExpression().setTemplateString(parts).setRange(node.range);
		});

		this.hooks.evaluateCallExpressionMember.for("concat").tap("Parser", (expr, param) => {
			if(!param.isString() && !param.isWrapped()) return;

			let stringSuffix = null;
			let hasUnknownParams = false;
			for(let i = expr.arguments.length - 1; i >= 0; i--) {
				const argExpr = this.evaluateExpression(expr.arguments[i]);
				if(!argExpr.isString() && !argExpr.isNumber()) {
					hasUnknownParams = true;
					break;
				}

				const value = argExpr.isString() ? argExpr.string : "" + argExpr.number;

				const newString = value + (stringSuffix ? stringSuffix.string : "");
				const newRange = [argExpr.range[0], (stringSuffix || argExpr).range[1]];
				stringSuffix = new BasicEvaluatedExpression().setString(newString).setRange(newRange);
			}

			if(hasUnknownParams) {
				const prefix = param.isString() ? param : param.prefix;
				return new BasicEvaluatedExpression().setWrapped(prefix, stringSuffix).setRange(expr.range);
			} else if(param.isWrapped()) {
				const postfix = stringSuffix || param.postfix;
				return new BasicEvaluatedExpression().setWrapped(param.prefix, postfix).setRange(expr.range);
			} else {
				const newString = param.string + (stringSuffix ? stringSuffix.string : "");
				return new BasicEvaluatedExpression().setString(newString).setRange(expr.range);
			}
		});
		this.hooks.evaluateCallExpressionMember.for("split").tap("Parser", (expr, param) => {
			if(!param.isString()) return;
			if(expr.arguments.length !== 1) return;
			let result;
			const arg = this.evaluateExpression(expr.arguments[0]);
			if(arg.isString()) {
				result = param.string.split(arg.string);
			} else if(arg.isRegExp()) {
				result = param.string.split(arg.regExp);
			} else return;
			return new BasicEvaluatedExpression().setArray(result).setRange(expr.range);
		});
		this.hooks.evaluate.for("ConditionalExpression").tap("Parser", expr => {
			const condition = this.evaluateExpression(expr.test);
			const conditionValue = condition.asBool();
			let res;
			if(conditionValue === undefined) {
				const consequent = this.evaluateExpression(expr.consequent);
				const alternate = this.evaluateExpression(expr.alternate);
				if(!consequent || !alternate) return;
				res = new BasicEvaluatedExpression();
				if(consequent.isConditional())
					res.setOptions(consequent.options);
				else
					res.setOptions([consequent]);
				if(alternate.isConditional())
					res.addOptions(alternate.options);
				else
					res.addOptions([alternate]);
			} else {
				res = this.evaluateExpression(conditionValue ? expr.consequent : expr.alternate);
			}
			res.setRange(expr.range);
			return res;
		});
		this.hooks.evaluate.for("ArrayExpression").tap("Parser", expr => {
			const items = expr.elements.map(element => {
				return element !== null && this.evaluateExpression(element);
			});
			if(!items.every(Boolean)) return;
			return new BasicEvaluatedExpression().setItems(items).setRange(expr.range);
		});
	}

	getRenameIdentifier(expr) {
		const result = this.evaluateExpression(expr);
		if(!result) return;
		if(result.isIdentifier()) return result.identifier;
		return;
	}

	walkClass(classy) {
		if(classy.superClass)
			this.walkExpression(classy.superClass);
		if(classy.body && classy.body.type === "ClassBody") {
			const wasTopLevel = this.scope.topLevelScope;
			this.scope.topLevelScope = false;
			for(const methodDefinition of classy.body.body) {
				if(methodDefinition.type === "MethodDefinition")
					this.walkMethodDefinition(methodDefinition);
			}
			this.scope.topLevelScope = wasTopLevel;
		}
	}

	walkMethodDefinition(methodDefinition) {
		if(methodDefinition.computed && methodDefinition.key)
			this.walkExpression(methodDefinition.key);
		if(methodDefinition.value)
			this.walkExpression(methodDefinition.value);
	}

	// Prewalking iterates the scope for variable declarations
	prewalkStatements(statements) {
		for(let index = 0, len = statements.length; index < len; index++) {
			const statement = statements[index];
			this.prewalkStatement(statement);
		}
	}

	// Walking iterates the statements and expressions and processes them
	walkStatements(statements) {
		for(let index = 0, len = statements.length; index < len; index++) {
			const statement = statements[index];
			this.walkStatement(statement);
		}
	}

	prewalkStatement(statement) {
		switch(statement.type) {
			case "BlockStatement":
				this.prewalkBlockStatement(statement);
				break;
			case "ClassDeclaration":
				this.prewalkClassDeclaration(statement);
				break;
			case "DoWhileStatement":
				this.prewalkDoWhileStatement(statement);
				break;
			case "ExportAllDeclaration":
				this.prewalkExportAllDeclaration(statement);
				break;
			case "ExportDefaultDeclaration":
				this.prewalkExportDefaultDeclaration(statement);
				break;
			case "ExportNamedDeclaration":
				this.prewalkExportNamedDeclaration(statement);
				break;
			case "ForInStatement":
				this.prewalkForInStatement(statement);
				break;
			case "ForOfStatement":
				this.prewalkForOfStatement(statement);
				break;
			case "ForStatement":
				this.prewalkForStatement(statement);
				break;
			case "FunctionDeclaration":
				this.prewalkFunctionDeclaration(statement);
				break;
			case "IfStatement":
				this.prewalkIfStatement(statement);
				break;
			case "ImportDeclaration":
				this.prewalkImportDeclaration(statement);
				break;
			case "LabeledStatement":
				this.prewalkLabeledStatement(statement);
				break;
			case "SwitchStatement":
				this.prewalkSwitchStatement(statement);
				break;
			case "TryStatement":
				this.prewalkTryStatement(statement);
				break;
			case "VariableDeclaration":
				this.prewalkVariableDeclaration(statement);
				break;
			case "WhileStatement":
				this.prewalkWhileStatement(statement);
				break;
			case "WithStatement":
				this.prewalkWithStatement(statement);
				break;
		}
	}

	walkStatement(statement) {
		if(this.hooks.statement.call(statement) !== undefined) return;
		switch(statement.type) {
			case "BlockStatement":
				this.walkBlockStatement(statement);
				break;
			case "ClassDeclaration":
				this.walkClassDeclaration(statement);
				break;
			case "DoWhileStatement":
				this.walkDoWhileStatement(statement);
				break;
			case "ExportDefaultDeclaration":
				this.walkExportDefaultDeclaration(statement);
				break;
			case "ExportNamedDeclaration":
				this.walkExportNamedDeclaration(statement);
				break;
			case "ExpressionStatement":
				this.walkExpressionStatement(statement);
				break;
			case "ForInStatement":
				this.walkForInStatement(statement);
				break;
			case "ForOfStatement":
				this.walkForOfStatement(statement);
				break;
			case "ForStatement":
				this.walkForStatement(statement);
				break;
			case "FunctionDeclaration":
				this.walkFunctionDeclaration(statement);
				break;
			case "IfStatement":
				this.walkIfStatement(statement);
				break;
			case "LabeledStatement":
				this.walkLabeledStatement(statement);
				break;
			case "ReturnStatement":
				this.walkReturnStatement(statement);
				break;
			case "SwitchStatement":
				this.walkSwitchStatement(statement);
				break;
			case "ThrowStatement":
				this.walkThrowStatement(statement);
				break;
			case "TryStatement":
				this.walkTryStatement(statement);
				break;
			case "VariableDeclaration":
				this.walkVariableDeclaration(statement);
				break;
			case "WhileStatement":
				this.walkWhileStatement(statement);
				break;
			case "WithStatement":
				this.walkWithStatement(statement);
				break;
		}
	}

	// Real Statements
	prewalkBlockStatement(statement) {
		this.prewalkStatements(statement.body);
	}

	walkBlockStatement(statement) {
		this.walkStatements(statement.body);
	}

	walkExpressionStatement(statement) {
		this.walkExpression(statement.expression);
	}

	prewalkIfStatement(statement) {
		this.prewalkStatement(statement.consequent);
		if(statement.alternate)
			this.prewalkStatement(statement.alternate);
	}

	walkIfStatement(statement) {
		const result = this.hooks.statementIf.call(statement);
		if(result === undefined) {
			this.walkExpression(statement.test);
			this.walkStatement(statement.consequent);
			if(statement.alternate)
				this.walkStatement(statement.alternate);
		} else {
			if(result)
				this.walkStatement(statement.consequent);
			else if(statement.alternate)
				this.walkStatement(statement.alternate);
		}
	}

	prewalkLabeledStatement(statement) {
		this.prewalkStatement(statement.body);
	}

	walkLabeledStatement(statement) {
		const hook = this.hooks.label.get(statement.label.name);
		if(hook !== undefined) {
			const result = hook.call(statement);
			if(result === true)
				return;
		}
		this.walkStatement(statement.body);
	}

	prewalkWithStatement(statement) {
		this.prewalkStatement(statement.body);
	}

	walkWithStatement(statement) {
		this.walkExpression(statement.object);
		this.walkStatement(statement.body);
	}

	prewalkSwitchStatement(statement) {
		this.prewalkSwitchCases(statement.cases);
	}

	walkSwitchStatement(statement) {
		this.walkExpression(statement.discriminant);
		this.walkSwitchCases(statement.cases);
	}

	walkTerminatingStatement(statement) {
		if(statement.argument)
			this.walkExpression(statement.argument);
	}

	walkReturnStatement(statement) {
		this.walkTerminatingStatement(statement);
	}

	walkThrowStatement(statement) {
		this.walkTerminatingStatement(statement);
	}

	prewalkTryStatement(statement) {
		this.prewalkStatement(statement.block);
	}

	walkTryStatement(statement) {
		if(this.scope.inTry) {
			this.walkStatement(statement.block);
		} else {
			this.scope.inTry = true;
			this.walkStatement(statement.block);
			this.scope.inTry = false;
		}
		if(statement.handler)
			this.walkCatchClause(statement.handler);
		if(statement.finalizer)
			this.walkStatement(statement.finalizer);
	}

	prewalkWhileStatement(statement) {
		this.prewalkStatement(statement.body);
	}

	walkWhileStatement(statement) {
		this.walkExpression(statement.test);
		this.walkStatement(statement.body);
	}

	prewalkDoWhileStatement(statement) {
		this.prewalkStatement(statement.body);
	}

	walkDoWhileStatement(statement) {
		this.walkStatement(statement.body);
		this.walkExpression(statement.test);
	}

	prewalkForStatement(statement) {
		if(statement.init) {
			if(statement.init.type === "VariableDeclaration")
				this.prewalkStatement(statement.init);
		}
		this.prewalkStatement(statement.body);
	}

	walkForStatement(statement) {
		if(statement.init) {
			if(statement.init.type === "VariableDeclaration")
				this.walkStatement(statement.init);
			else
				this.walkExpression(statement.init);
		}
		if(statement.test)
			this.walkExpression(statement.test);
		if(statement.update)
			this.walkExpression(statement.update);
		this.walkStatement(statement.body);
	}

	prewalkForInStatement(statement) {
		if(statement.left.type === "VariableDeclaration")
			this.prewalkVariableDeclaration(statement.left);
		this.prewalkStatement(statement.body);
	}

	walkForInStatement(statement) {
		if(statement.left.type === "VariableDeclaration")
			this.walkVariableDeclaration(statement.left);
		else
			this.walkPattern(statement.left);
		this.walkExpression(statement.right);
		this.walkStatement(statement.body);
	}

	prewalkForOfStatement(statement) {
		if(statement.left.type === "VariableDeclaration")
			this.prewalkVariableDeclaration(statement.left);
		this.prewalkStatement(statement.body);
	}

	walkForOfStatement(statement) {
		if(statement.left.type === "VariableDeclaration")
			this.walkVariableDeclaration(statement.left);
		else
			this.walkPattern(statement.left);
		this.walkExpression(statement.right);
		this.walkStatement(statement.body);
	}

	// Declarations
	prewalkFunctionDeclaration(statement) {
		if(statement.id) {
			this.scope.renames.set(statement.id.name, null);
			this.scope.definitions.add(statement.id.name);
		}
	}

	walkFunctionDeclaration(statement) {
		for(const param of statement.params)
			this.walkPattern(param);
		this.inScope(statement.params, () => {
			this.scope.topLevelScope = false;
			if(statement.body.type === "BlockStatement") {
				this.detectStrictMode(statement.body.body);
				this.prewalkStatement(statement.body);
				this.walkStatement(statement.body);
			} else {
				this.walkExpression(statement.body);
			}
		});
	}

	prewalkImportDeclaration(statement) {
		const source = statement.source.value;
		this.hooks.import.call(statement, source);
		for(const specifier of statement.specifiers) {
			const name = specifier.local.name;
			this.scope.renames.set(name, null);
			this.scope.definitions.add(name);
			switch(specifier.type) {
				case "ImportDefaultSpecifier":
					this.hooks.importSpecifier.call(statement, source, "default", name);
					break;
				case "ImportSpecifier":
					this.hooks.importSpecifier.call(statement, source, specifier.imported.name, name);
					break;
				case "ImportNamespaceSpecifier":
					this.hooks.importSpecifier.call(statement, source, null, name);
					break;
			}
		}
	}

	prewalkExportNamedDeclaration(statement) {
		let source;
		if(statement.source) {
			source = statement.source.value;
			this.hooks.exportImport.call(statement, source);
		} else {
			this.hooks.export.call(statement);
		}
		if(statement.declaration) {
			if(!this.hooks.exportDeclaration.call(statement, statement.declaration)) {
				const originalDefinitions = this.scope.definitions;
				const tracker = new TrackingSet(this.scope.definitions);
				this.scope.definitions = tracker;
				this.prewalkStatement(statement.declaration);
				const newDefs = Array.from(tracker.getAddedItems());
				this.scope.definitions = originalDefinitions;
				for(let index = newDefs.length - 1; index >= 0; index--) {
					const def = newDefs[index];
					this.hooks.exportSpecifier.call(statement, def, def, index);
				}
			}
		}
		if(statement.specifiers) {
			for(let specifierIndex = 0; specifierIndex < statement.specifiers.length; specifierIndex++) {
				const specifier = statement.specifiers[specifierIndex];
				switch(specifier.type) {
					case "ExportSpecifier":
						{
							const name = specifier.exported.name;
							if(source)
								this.hooks.exportImportSpecifier.call(statement, source, specifier.local.name, name, specifierIndex);
							else
								this.hooks.exportSpecifier.call(statement, specifier.local.name, name, specifierIndex);
							break;
						}
				}
			}
		}
	}

	walkExportNamedDeclaration(statement) {
		if(statement.declaration) {
			this.walkStatement(statement.declaration);
		}
	}

	prewalkExportDefaultDeclaration(statement) {
		if(statement.declaration.id) {
			const originalDefinitions = this.scope.definitions;
			const tracker = new TrackingSet(this.scope.definitions);
			this.scope.definitions = tracker;
			this.prewalkStatement(statement.declaration);
			const newDefs = Array.from(tracker.getAddedItems());
			this.scope.definitions = originalDefinitions;
			for(let index = 0, len = newDefs.length; index < len; index++) {
				const def = newDefs[index];
				this.hooks.exportSpecifier.call(statement, def, "default");
			}
		}
	}

	walkExportDefaultDeclaration(statement) {
		this.hooks.export.call(statement);
		if(statement.declaration.id) {
			if(!this.hooks.exportDeclaration.call(statement, statement.declaration)) {
				this.walkStatement(statement.declaration);
			}
		} else {
			// Acorn parses `export default function() {}` as `FunctionDeclaration` and
			// `export default class {}` as `ClassDeclaration`, both with `id = null`.
			// These nodes must be treated as expressions.
			if(statement.declaration.type === "FunctionDeclaration") {
				this.walkFunctionDeclaration(statement.declaration);
			} else if(statement.declaration.type === "ClassDeclaration") {
				this.walkClassDeclaration(statement.declaration);
			} else {
				this.walkExpression(statement.declaration);
			}
			if(!this.hooks.exportExpression.call(statement, statement.declaration)) {
				this.hooks.exportSpecifier.call(statement, statement.declaration, "default");
			}
		}
	}

	prewalkExportAllDeclaration(statement) {
		const source = statement.source.value;
		this.hooks.exportImport.call(statement, source);
		this.hooks.exportImportSpecifier.call(statement, source, null, null, 0);
	}

	prewalkVariableDeclaration(statement) {
		const hookMap = statement.kind === "const" ? this.hooks.varDeclarationConst :
			statement.kind === "let" ? this.hooks.varDeclarationLet :
			this.hooks.varDeclarationVar;
		for(const declarator of statement.declarations) {
			switch(declarator.type) {
				case "VariableDeclarator":
					{
						this.enterPattern(declarator.id, (name, decl) => {
							let hook = hookMap.get(name);
							if(hook === undefined || !hook.call(decl)) {
								hook = this.hooks.varDeclaration.get(name);
								if(hook === undefined || !hook.call(decl)) {
									this.scope.renames.set(name, null);
									this.scope.definitions.add(name);
								}
							}
						});
						break;
					}
			}
		}
	}

	walkVariableDeclaration(statement) {
		for(const declarator of statement.declarations) {
			switch(declarator.type) {
				case "VariableDeclarator":
					{
						const renameIdentifier = declarator.init && this.getRenameIdentifier(declarator.init);
						if(renameIdentifier && declarator.id.type === "Identifier") {
							const hook = this.hooks.canRename.get(renameIdentifier);
							if(hook !== undefined && hook.call(declarator.init)) {
								// renaming with "var a = b;"
								const hook = this.hooks.rename.get(renameIdentifier);
								if(hook === undefined || !hook.call(declarator.init)) {
									this.scope.renames.set(declarator.id.name, this.scope.renames.get(renameIdentifier) || renameIdentifier);
									this.scope.definitions.delete(declarator.id.name);
								}
								break;
							}
						}
						this.walkPattern(declarator.id);
						if(declarator.init)
							this.walkExpression(declarator.init);
						break;
					}
			}
		}
	}

	prewalkClassDeclaration(statement) {
		if(statement.id) {
			this.scope.renames.set(statement.id.name, null);
			this.scope.definitions.add(statement.id.name);
		}
	}

	walkClassDeclaration(statement) {
		this.walkClass(statement);
	}

	prewalkSwitchCases(switchCases) {
		for(let index = 0, len = switchCases.length; index < len; index++) {
			const switchCase = switchCases[index];
			this.prewalkStatements(switchCase.consequent);
		}
	}

	walkSwitchCases(switchCases) {
		for(let index = 0, len = switchCases.length; index < len; index++) {
			const switchCase = switchCases[index];

			if(switchCase.test) {
				this.walkExpression(switchCase.test);
			}
			this.walkStatements(switchCase.consequent);
		}
	}

	walkCatchClause(catchClause) {
		this.inScope([catchClause.param], () => {
			this.prewalkStatement(catchClause.body);
			this.walkStatement(catchClause.body);
		});
	}

	walkPattern(pattern) {
		switch(pattern.type) {
			case "ArrayPattern":
				this.walkArrayPattern(pattern);
				break;
			case "AssignmentPattern":
				this.walkAssignmentPattern(pattern);
				break;
			case "MemberExpression":
				this.walkMemberExpression(pattern);
				break;
			case "ObjectPattern":
				this.walkObjectPattern(pattern);
				break;
			case "RestElement":
				this.walkRestElement(pattern);
				break;
		}
	}

	walkAssignmentPattern(pattern) {
		this.walkExpression(pattern.right);
		this.walkPattern(pattern.left);
	}

	walkObjectPattern(pattern) {
		for(let i = 0, len = pattern.properties.length; i < len; i++) {
			const prop = pattern.properties[i];
			if(prop) {
				if(prop.computed)
					this.walkExpression(prop.key);
				if(prop.value)
					this.walkPattern(prop.value);
			}
		}
	}

	walkArrayPattern(pattern) {
		for(let i = 0, len = pattern.elements.length; i < len; i++) {
			const element = pattern.elements[i];
			if(element)
				this.walkPattern(element);
		}
	}

	walkRestElement(pattern) {
		this.walkPattern(pattern.argument);
	}

	walkExpressions(expressions) {
		for(let expressionsIndex = 0, len = expressions.length; expressionsIndex < len; expressionsIndex++) {
			const expression = expressions[expressionsIndex];
			if(expression)
				this.walkExpression(expression);
		}
	}

	walkExpression(expression) {
		switch(expression.type) {
			case "ArrayExpression":
				this.walkArrayExpression(expression);
				break;
			case "ArrowFunctionExpression":
				this.walkArrowFunctionExpression(expression);
				break;
			case "AssignmentExpression":
				this.walkAssignmentExpression(expression);
				break;
			case "AwaitExpression":
				this.walkAwaitExpression(expression);
				break;
			case "BinaryExpression":
				this.walkBinaryExpression(expression);
				break;
			case "CallExpression":
				this.walkCallExpression(expression);
				break;
			case "ClassExpression":
				this.walkClassExpression(expression);
				break;
			case "ConditionalExpression":
				this.walkConditionalExpression(expression);
				break;
			case "FunctionExpression":
				this.walkFunctionExpression(expression);
				break;
			case "Identifier":
				this.walkIdentifier(expression);
				break;
			case "LogicalExpression":
				this.walkLogicalExpression(expression);
				break;
			case "MemberExpression":
				this.walkMemberExpression(expression);
				break;
			case "NewExpression":
				this.walkNewExpression(expression);
				break;
			case "ObjectExpression":
				this.walkObjectExpression(expression);
				break;
			case "SequenceExpression":
				this.walkSequenceExpression(expression);
				break;
			case "SpreadElement":
				this.walkSpreadElement(expression);
				break;
			case "TaggedTemplateExpression":
				this.walkTaggedTemplateExpression(expression);
				break;
			case "TemplateLiteral":
				this.walkTemplateLiteral(expression);
				break;
			case "ThisExpression":
				this.walkThisExpression(expression);
				break;
			case "UnaryExpression":
				this.walkUnaryExpression(expression);
				break;
			case "UpdateExpression":
				this.walkUpdateExpression(expression);
				break;
			case "YieldExpression":
				this.walkYieldExpression(expression);
				break;
		}
	}

	walkAwaitExpression(expression) {
		this.walkExpression(expression.argument);
	}

	walkArrayExpression(expression) {
		if(expression.elements)
			this.walkExpressions(expression.elements);
	}

	walkSpreadElement(expression) {
		if(expression.argument)
			this.walkExpression(expression.argument);
	}

	walkObjectExpression(expression) {
		for(let propIndex = 0, len = expression.properties.length; propIndex < len; propIndex++) {
			const prop = expression.properties[propIndex];
			if(prop.type === "SpreadElement") {
				this.walkExpression(prop.argument);
				continue;
			}
			if(prop.computed)
				this.walkExpression(prop.key);
			if(prop.shorthand)
				this.scope.inShorthand = true;
			this.walkExpression(prop.value);
			if(prop.shorthand)
				this.scope.inShorthand = false;
		}
	}

	walkFunctionExpression(expression) {
		for(const param of expression.params)
			this.walkPattern(param);
		this.inScope(expression.params, () => {
			this.scope.topLevelScope = false;
			if(expression.body.type === "BlockStatement") {
				this.detectStrictMode(expression.body.body);
				this.prewalkStatement(expression.body);
				this.walkStatement(expression.body);
			} else {
				this.walkExpression(expression.body);
			}
		});
	}

	walkArrowFunctionExpression(expression) {
		for(const param of expression.params)
			this.walkPattern(param);
		this.inScope(expression.params, () => {
			if(expression.body.type === "BlockStatement") {
				this.detectStrictMode(expression.body.body);
				this.prewalkStatement(expression.body);
				this.walkStatement(expression.body);
			} else {
				this.walkExpression(expression.body);
			}
		});
	}

	walkSequenceExpression(expression) {
		if(expression.expressions)
			this.walkExpressions(expression.expressions);
	}

	walkUpdateExpression(expression) {
		this.walkExpression(expression.argument);
	}

	walkUnaryExpression(expression) {
		if(expression.operator === "typeof") {
			const exprName = this.getNameForExpression(expression.argument);
			if(exprName && exprName.free) {
				const hook = this.hooks.typeof.get(exprName.name);
				if(hook !== undefined) {
					const result = hook.call(expression);
					if(result === true)
						return;
				}
			}
		}
		this.walkExpression(expression.argument);
	}

	walkLeftRightExpression(expression) {
		this.walkExpression(expression.left);
		this.walkExpression(expression.right);
	}

	walkBinaryExpression(expression) {
		this.walkLeftRightExpression(expression);
	}

	walkLogicalExpression(expression) {
		this.walkLeftRightExpression(expression);
	}

	walkAssignmentExpression(expression) {
		const renameIdentifier = this.getRenameIdentifier(expression.right);
		if(expression.left.type === "Identifier" && renameIdentifier) {
			const hook = this.hooks.canRename.get(renameIdentifier);
			if(hook !== undefined && hook.call(expression.right)) {
				// renaming "a = b;"
				const hook = this.hooks.rename.get(renameIdentifier);
				if(hook === undefined || !hook.call(expression.right)) {
					this.scope.renames.set(expression.left.name, renameIdentifier);
					this.scope.definitions.delete(expression.left.name);
				}
				return;
			}
		}
		if(expression.left.type === "Identifier") {
			const assignedHook = this.hooks.assigned.get(expression.left.name);
			if(assignedHook === undefined || !assignedHook.call(expression)) {
				this.walkExpression(expression.right);
			}
			this.scope.renames.set(expression.left.name, null);
			const assignHook = this.hooks.assign.get(expression.left.name);
			if(assignHook === undefined || !assignHook.call(expression)) {
				this.walkExpression(expression.left);
			}
			return;
		}
		this.walkExpression(expression.right);
		this.walkPattern(expression.left);
		this.enterPattern(expression.left, (name, decl) => {
			this.scope.renames.set(name, null);
		});
	}

	walkConditionalExpression(expression) {
		const result = this.hooks.expressionConditionalOperator.call(expression);
		if(result === undefined) {
			this.walkExpression(expression.test);
			this.walkExpression(expression.consequent);
			if(expression.alternate)
				this.walkExpression(expression.alternate);
		} else {
			if(result)
				this.walkExpression(expression.consequent);
			else if(expression.alternate)
				this.walkExpression(expression.alternate);
		}
	}

	walkNewExpression(expression) {
		const callee = this.evaluateExpression(expression.callee);
		if(callee.isIdentifier()) {
			const hook = this.hooks.new.get(callee.identifier);
			if(hook !== undefined) {
				const result = hook.call(expression);
				if(result === true) {
					return;
				}
			}
		}

		this.walkExpression(expression.callee);
		if(expression.arguments)
			this.walkExpressions(expression.arguments);
	}

	walkYieldExpression(expression) {
		if(expression.argument)
			this.walkExpression(expression.argument);
	}

	walkTemplateLiteral(expression) {
		if(expression.expressions)
			this.walkExpressions(expression.expressions);
	}

	walkTaggedTemplateExpression(expression) {
		if(expression.tag)
			this.walkExpression(expression.tag);
		if(expression.quasi && expression.quasi.expressions)
			this.walkExpressions(expression.quasi.expressions);
	}

	walkClassExpression(expression) {
		this.walkClass(expression);
	}

	walkCallExpression(expression) {
		let result;

		const walkIIFE = (functionExpression, options, currentThis) => {
			const renameArgOrThis = argOrThis => {
				const renameIdentifier = this.getRenameIdentifier(argOrThis);
				if(renameIdentifier) {
					const hook = this.hooks.canRename.get(renameIdentifier);
					if(hook !== undefined && hook.call(argOrThis)) {
						const hook = this.hooks.rename.get(renameIdentifier);
						if(hook === undefined || !hook.call(argOrThis))
							return renameIdentifier;
					}
				}
				this.walkExpression(argOrThis);
			};
			const params = functionExpression.params;
			const renameThis = currentThis ? renameArgOrThis.call(this, currentThis) : null;
			const args = options.map(renameArgOrThis);
			this.inScope(params.filter((identifier, idx) => !args[idx]), () => {
				if(renameThis) {
					this.scope.renames.set("this", renameThis);
				}
				for(let i = 0; i < args.length; i++) {
					const param = args[i];
					if(!param) continue;
					if(!params[i] || params[i].type !== "Identifier") continue;
					this.scope.renames.set(params[i].name, param);
				}
				if(functionExpression.body.type === "BlockStatement") {
					this.prewalkStatement(functionExpression.body);
					this.walkStatement(functionExpression.body);
				} else
					this.walkExpression(functionExpression.body);
			});
		};
		if(expression.callee.type === "MemberExpression" &&
			expression.callee.object.type === "FunctionExpression" &&
			!expression.callee.computed &&
			(expression.callee.property.name === "call" || expression.callee.property.name === "bind") &&
			expression.arguments &&
			expression.arguments.length > 0
		) {
			// (function(...) { }.call/bind(?, ...))
			walkIIFE.call(this, expression.callee.object, expression.arguments.slice(1), expression.arguments[0]);
		} else if(expression.callee.type === "FunctionExpression" && expression.arguments) {
			// (function(...) { }(...))
			walkIIFE.call(this, expression.callee, expression.arguments);
		} else if(expression.callee.type === "Import") {
			result = this.hooks.importCall.call(expression);
			if(result === true)
				return;

			if(expression.arguments)
				this.walkExpressions(expression.arguments);
		} else {

			const callee = this.evaluateExpression(expression.callee);
			if(callee.isIdentifier()) {
				const callHook = this.hooks.call.get(callee.identifier);
				if(callHook !== undefined) {
					result = callHook.call(expression);
					if(result === true)
						return;
				}
				let identifier = callee.identifier.replace(/\.[^.]+$/, "");
				if(identifier !== callee.identifier) {
					const callAnyHook = this.hooks.callAnyMember.get(identifier);
					if(callAnyHook !== undefined) {
						result = callAnyHook.call(expression);
						if(result === true)
							return;
					}
				}
			}

			if(expression.callee)
				this.walkExpression(expression.callee);
			if(expression.arguments)
				this.walkExpressions(expression.arguments);
		}
	}

	walkMemberExpression(expression) {
		const exprName = this.getNameForExpression(expression);
		if(exprName && exprName.free) {
			const expressionHook = this.hooks.expression.get(exprName.name);
			if(expressionHook !== undefined) {
				const result = expressionHook.call(expression);
				if(result === true)
					return;
			}
			const expressionAnyMemberHook = this.hooks.expressionAnyMember.get(exprName.nameGeneral);
			if(expressionAnyMemberHook !== undefined) {
				const result = expressionAnyMemberHook.call(expression);
				if(result === true)
					return;
			}
		}
		this.walkExpression(expression.object);
		if(expression.computed === true)
			this.walkExpression(expression.property);
	}

	walkThisExpression(expression) {
		const expressionHook = this.hooks.expression.get("this");
		if(expressionHook !== undefined) {
			expressionHook.call(expression);
		}
	}

	walkIdentifier(expression) {
		if(!this.scope.definitions.has(expression.name)) {
			const hook = this.hooks.expression.get(this.scope.renames.get(expression.name) || expression.name);
			if(hook !== undefined) {
				const result = hook.call(expression);
				if(result === true)
					return;
			}
		}
	}

	inScope(params, fn) {
		const oldScope = this.scope;
		this.scope = {
			topLevelScope: oldScope.topLevelScope,
			inTry: false,
			inShorthand: false,
			isStrict: oldScope.isStrict,
			definitions: oldScope.definitions.createChild(),
			renames: oldScope.renames.createChild()
		};

		this.scope.renames.set("this", null);

		for(let paramIndex = 0, len = params.length; paramIndex < len; paramIndex++) {
			const param = params[paramIndex];

			if(typeof param !== "string") {
				this.enterPattern(param, param => {
					this.scope.renames.set(param, null);
					this.scope.definitions.add(param);
				});
			} else if(param) {
				this.scope.renames.set(param, null);
				this.scope.definitions.add(param);
			}
		}

		fn();
		this.scope = oldScope;
	}

	detectStrictMode(statements) {
		const isStrict = statements.length >= 1 &&
			statements[0].type === "ExpressionStatement" &&
			statements[0].expression.type === "Literal" &&
			statements[0].expression.value === "use strict";
		if(isStrict) {
			this.scope.isStrict = true;
		}
	}

	enterPattern(pattern, onIdent) {
		if(!pattern) return;
		switch(pattern.type) {
			case "ArrayPattern":
				this.enterArrayPattern(pattern, onIdent);
				break;
			case "AssignmentPattern":
				this.enterAssignmentPattern(pattern, onIdent);
				break;
			case "Identifier":
				this.enterIdentifier(pattern, onIdent);
				break;
			case "ObjectPattern":
				this.enterObjectPattern(pattern, onIdent);
				break;
			case "RestElement":
				this.enterRestElement(pattern, onIdent);
				break;
		}
	}

	enterIdentifier(pattern, onIdent) {
		onIdent(pattern.name, pattern);
	}

	enterObjectPattern(pattern, onIdent) {
		for(let propIndex = 0, len = pattern.properties.length; propIndex < len; propIndex++) {
			const prop = pattern.properties[propIndex];
			this.enterPattern(prop.value, onIdent);
		}
	}

	enterArrayPattern(pattern, onIdent) {
		for(let elementIndex = 0, len = pattern.elements.length; elementIndex < len; elementIndex++) {
			const element = pattern.elements[elementIndex];
			this.enterPattern(element, onIdent);
		}
	}

	enterRestElement(pattern, onIdent) {
		this.enterPattern(pattern.argument, onIdent);
	}

	enterAssignmentPattern(pattern, onIdent) {
		this.enterPattern(pattern.left, onIdent);
	}

	evaluateExpression(expression) {
		try {
			const hook = this.hooks.evaluate.get(expression.type);
			if(hook !== undefined) {
				const result = hook.call(expression);
				if(result !== undefined)
					return result;
			}
		} catch(e) {
			console.warn(e);
			// ignore error
		}
		return new BasicEvaluatedExpression().setRange(expression.range);
	}

	parseString(expression) {
		switch(expression.type) {
			case "BinaryExpression":
				if(expression.operator === "+")
					return this.parseString(expression.left) + this.parseString(expression.right);
				break;
			case "Literal":
				return expression.value + "";
		}
		throw new Error(expression.type + " is not supported as parameter for require");
	}

	parseCalculatedString(expression) {
		switch(expression.type) {
			case "BinaryExpression":
				if(expression.operator === "+") {
					const left = this.parseCalculatedString(expression.left);
					const right = this.parseCalculatedString(expression.right);
					if(left.code) {
						return {
							range: left.range,
							value: left.value,
							code: true
						};
					} else if(right.code) {
						return {
							range: [left.range[0], right.range ? right.range[1] : left.range[1]],
							value: left.value + right.value,
							code: true
						};
					} else {
						return {
							range: [left.range[0], right.range[1]],
							value: left.value + right.value
						};
					}
				}
				break;
			case "ConditionalExpression":
				{
					const consequent = this.parseCalculatedString(expression.consequent);
					const alternate = this.parseCalculatedString(expression.alternate);
					const items = [];
					if(consequent.conditional)
						items.push(...consequent.conditional);
					else if(!consequent.code)
						items.push(consequent);
					else break;
					if(alternate.conditional)
						items.push(...alternate.conditional);
					else if(!alternate.code)
						items.push(alternate);
					else break;
					return {
						value: "",
						code: true,
						conditional: items
					};
				}
			case "Literal":
				return {
					range: expression.range,
					value: expression.value + ""
				};
		}
		return {
			value: "",
			code: true
		};
	}

	parse(source, initialState) {
		let ast;
		let comments;
		if(typeof source === "object" && source !== null) {
			ast = source;
			comments = source.comments;
		} else {
			comments = [];
			ast = Parser.parse(source, {
				sourceType: this.sourceType,
				onComment: comments
			});
		}

		const oldScope = this.scope;
		const oldState = this.state;
		const oldComments = this.comments;
		this.scope = {
			topLevelScope: true,
			inTry: false,
			inShorthand: false,
			isStrict: false,
			definitions: new StackedSetMap(),
			renames: new StackedSetMap()
		};
		const state = this.state = initialState || {};
		this.comments = comments;
		if(this.hooks.program.call(ast, comments) === undefined) {
			this.detectStrictMode(ast.body);
			this.prewalkStatements(ast.body);
			this.walkStatements(ast.body);
		}
		this.scope = oldScope;
		this.state = oldState;
		this.comments = oldComments;
		return state;
	}

	evaluate(source) {
		const ast = Parser.parse("(" + source + ")", {
			sourceType: this.sourceType,
			locations: false,
		});
		if(ast.body.length !== 1 || ast.body[0].type !== "ExpressionStatement")
			throw new Error("evaluate: Source is not a expression");
		return this.evaluateExpression(ast.body[0].expression);
	}

	getComments(range) {
		return this.comments.filter(comment => comment.range[0] >= range[0] && comment.range[1] <= range[1]);
	}

	getCommentOptions(range) {
		const comments = this.getComments(range);
		if(comments.length === 0) return null;
		const options = comments.map(comment => {
			try {
				let val = vm.runInNewContext(`(function(){return {${comment.value}};})()`);
				return val;
			} catch(e) {
				return {};
			}
		});
		return options.reduce((o, i) => Object.assign(o, i), {});
	}

	getNameForExpression(expression) {
		let expr = expression;
		const exprName = [];
		while(expr.type === "MemberExpression" && expr.property.type === (expr.computed ? "Literal" : "Identifier")) {
			exprName.push(expr.computed ? expr.property.value : expr.property.name);
			expr = expr.object;
		}
		let free;
		if(expr.type === "Identifier") {
			free = !this.scope.definitions.has(expr.name);
			exprName.push(this.scope.renames.get(expr.name) || expr.name);
		} else if(expr.type === "ThisExpression" && this.scope.renames.get("this")) {
			free = true;
			exprName.push(this.scope.renames.get("this"));
		} else if(expr.type === "ThisExpression") {
			free = false;
			exprName.push("this");
		} else {
			return null;
		}
		let prefix = "";
		for(let i = exprName.length - 1; i >= 2; i--)
			prefix += exprName[i] + ".";
		if(exprName.length > 1)
			prefix += exprName[1];
		const name = prefix ? prefix + "." + exprName[0] : exprName[0];
		const nameGeneral = prefix;
		return {
			name,
			nameGeneral,
			free
		};
	}

	static parse(code, options) {
		const type = options ? options.sourceType : "module";
		const parserOptions = Object.assign(Object.create(null), defaultParserOptions, options);

		if(type === "auto") {
			parserOptions.sourceType = "module";
		}

		let ast;
		let error;
		let threw = false;
		try {
			ast = acorn.parse(code, parserOptions);
		} catch(e) {
			error = e;
			threw = true;
		}

		if(threw && type === "auto") {
			parserOptions.sourceType = "script";
			if(Array.isArray(parserOptions.onComment)) {
				parserOptions.onComment.length = 0;
			}
			try {
				ast = acorn.parse(code, parserOptions);
				threw = false;
			} catch(e) {}
		}

		if(threw) {
			throw error;
		}

		return ast;
	}
}

module.exports = Parser;