111 lines
2.8 KiB
JavaScript
Executable file
111 lines
2.8 KiB
JavaScript
Executable file
/**
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* Copyright (c) 2014-present, Facebook, Inc.
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*
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* This source code is licensed under the MIT license found in the
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* LICENSE file in the root directory of this source tree.
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*/
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import assert from "assert";
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import { getTypes } from "./util.js";
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const mMap = new WeakMap();
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function m(node) {
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if (!mMap.has(node)) {
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mMap.set(node, {});
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}
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return mMap.get(node);
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}
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const hasOwn = Object.prototype.hasOwnProperty;
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function makePredicate(propertyName, knownTypes) {
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function onlyChildren(node) {
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const t = getTypes();
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t.assertNode(node);
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// Assume no side effects until we find out otherwise.
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let result = false;
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function check(child) {
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if (result) {
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// Do nothing.
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} else if (Array.isArray(child)) {
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child.some(check);
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} else if (t.isNode(child)) {
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assert.strictEqual(result, false);
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result = predicate(child);
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}
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return result;
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}
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let keys = t.VISITOR_KEYS[node.type];
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if (keys) {
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for (let i = 0; i < keys.length; i++) {
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let key = keys[i];
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let child = node[key];
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check(child);
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}
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}
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return result;
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}
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function predicate(node) {
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getTypes().assertNode(node);
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let meta = m(node);
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if (hasOwn.call(meta, propertyName))
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return meta[propertyName];
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// Certain types are "opaque," which means they have no side
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// effects or leaps and we don't care about their subexpressions.
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if (hasOwn.call(opaqueTypes, node.type))
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return meta[propertyName] = false;
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if (hasOwn.call(knownTypes, node.type))
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return meta[propertyName] = true;
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return meta[propertyName] = onlyChildren(node);
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}
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predicate.onlyChildren = onlyChildren;
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return predicate;
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}
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let opaqueTypes = {
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FunctionExpression: true,
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ArrowFunctionExpression: true
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};
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// These types potentially have side effects regardless of what side
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// effects their subexpressions have.
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let sideEffectTypes = {
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CallExpression: true, // Anything could happen!
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ForInStatement: true, // Modifies the key variable.
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UnaryExpression: true, // Think delete.
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BinaryExpression: true, // Might invoke .toString() or .valueOf().
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AssignmentExpression: true, // Side-effecting by definition.
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UpdateExpression: true, // Updates are essentially assignments.
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NewExpression: true // Similar to CallExpression.
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};
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// These types are the direct cause of all leaps in control flow.
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let leapTypes = {
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YieldExpression: true,
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BreakStatement: true,
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ContinueStatement: true,
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ReturnStatement: true,
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ThrowStatement: true
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};
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// All leap types are also side effect types.
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for (let type in leapTypes) {
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if (hasOwn.call(leapTypes, type)) {
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sideEffectTypes[type] = leapTypes[type];
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}
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}
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exports.hasSideEffects = makePredicate("hasSideEffects", sideEffectTypes);
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exports.containsLeap = makePredicate("containsLeap", leapTypes);
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