2a09d1a4
 liuqimichale
添加宜春 天水 宣化
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/**
* Copyright (c) 2014, Facebook, Inc.
* All rights reserved.
*
* This source code is licensed under the BSD-style license found in the
* https://raw.github.com/facebook/regenerator/master/LICENSE file. An
* additional grant of patent rights can be found in the PATENTS file in
* the same directory.
*/
import assert from "assert";
let m = require("private").makeAccessor();
import * as t from "babel-types";
let hasOwn = Object.prototype.hasOwnProperty;
function makePredicate(propertyName, knownTypes) {
function onlyChildren(node) {
t.assertNode(node);
// Assume no side effects until we find out otherwise.
let result = false;
function check(child) {
if (result) {
// Do nothing.
} else if (Array.isArray(child)) {
child.some(check);
} else if (t.isNode(child)) {
assert.strictEqual(result, false);
result = predicate(child);
}
return result;
}
let keys = t.VISITOR_KEYS[node.type];
if (keys) {
for (let i = 0; i < keys.length; i++) {
let key = keys[i];
let child = node[key];
check(child);
}
}
return result;
}
function predicate(node) {
t.assertNode(node);
let meta = m(node);
if (hasOwn.call(meta, propertyName))
return meta[propertyName];
// Certain types are "opaque," which means they have no side
// effects or leaps and we don't care about their subexpressions.
if (hasOwn.call(opaqueTypes, node.type))
return meta[propertyName] = false;
if (hasOwn.call(knownTypes, node.type))
return meta[propertyName] = true;
return meta[propertyName] = onlyChildren(node);
}
predicate.onlyChildren = onlyChildren;
return predicate;
}
let opaqueTypes = {
FunctionExpression: true,
ArrowFunctionExpression: true
};
// These types potentially have side effects regardless of what side
// effects their subexpressions have.
let sideEffectTypes = {
CallExpression: true, // Anything could happen!
ForInStatement: true, // Modifies the key variable.
UnaryExpression: true, // Think delete.
BinaryExpression: true, // Might invoke .toString() or .valueOf().
AssignmentExpression: true, // Side-effecting by definition.
UpdateExpression: true, // Updates are essentially assignments.
NewExpression: true // Similar to CallExpression.
};
// These types are the direct cause of all leaps in control flow.
let leapTypes = {
YieldExpression: true,
BreakStatement: true,
ContinueStatement: true,
ReturnStatement: true,
ThrowStatement: true
};
// All leap types are also side effect types.
for (let type in leapTypes) {
if (hasOwn.call(leapTypes, type)) {
sideEffectTypes[type] = leapTypes[type];
}
}
exports.hasSideEffects = makePredicate("hasSideEffects", sideEffectTypes);
exports.containsLeap = makePredicate("containsLeap", leapTypes);
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