/**
* 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.
*/
var assert = require("assert");
var types = require("ast-types");
var m = require("private").makeAccessor();
var _ = require("lodash");
var isArray = types.builtInTypes.array;
var n = types.namedTypes;
function makePredicate(propertyName, knownTypes) {
function onlyChildren(node) {
n.Node.check(node);
// Assume no side effects until we find out otherwise.
var result = false;
function check(child) {
if (result) {
// Do nothing.
} else if (isArray.check(child)) {
child.some(check);
} else if (n.Node.check(child)) {
assert.strictEqual(result, false);
result = predicate(child);
}
return result;
}
types.eachField(node, function (name, child) {
check(child);
});
return result;
}
function predicate(node) {
n.Node.check(node);
var meta = m(node);
if (_.has(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 (_.has(opaqueTypes, node.type)) return meta[propertyName] = false;
if (_.has(knownTypes, node.type)) return meta[propertyName] = true;
return meta[propertyName] = onlyChildren(node);
}
predicate.onlyChildren = onlyChildren;
return predicate;
}
var opaqueTypes = {
FunctionExpression: true
};
// These types potentially have side effects regardless of what side
// effects their subexpressions have.
var 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.
var leapTypes = {
YieldExpression: true,
BreakStatement: true,
ContinueStatement: true,
ReturnStatement: true,
ThrowStatement: true
};
// All leap types are also side effect types.
for (var type in leapTypes) {
Eif (_.has(leapTypes, type)) {
sideEffectTypes[type] = leapTypes[type];
}
}
exports.hasSideEffects = makePredicate("hasSideEffects", sideEffectTypes);
exports.containsLeap = makePredicate("containsLeap", leapTypes);
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