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// Copyright (c) 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
/**
* @fileoverview Assertion support.
*/
/**
* Verify |condition| is truthy and return |condition| if so.
* @template T
* @param {T} condition A condition to check for truthiness. Note that this
* may be used to test whether a value is defined or not, and we don't want
* to force a cast to Boolean.
* @param {string=} opt_message A message to show on failure.
* @return {T} A non-null |condition|.
* @closurePrimitive {asserts.truthy}
* @suppress {reportUnknownTypes} because T is not sufficiently constrained.
*/
/* #export */ function assert(condition, opt_message) {
if (!condition) {
let message = 'Assertion failed';
if (opt_message) {
message = message + ': ' + opt_message;
}
const error = new Error(message);
const global = function() {
const thisOrSelf = this || self;
/** @type {boolean} */
thisOrSelf.traceAssertionsForTesting;
return thisOrSelf;
}();
if (global.traceAssertionsForTesting) {
console.warn(error.stack);
}
throw error;
}
return condition;
}
/**
* Call this from places in the code that should never be reached.
*
* For example, handling all the values of enum with a switch() like this:
*
* function getValueFromEnum(enum) {
* switch (enum) {
* case ENUM_FIRST_OF_TWO:
* return first
* case ENUM_LAST_OF_TWO:
* return last;
* }
* assertNotReached();
* return document;
* }
*
* This code should only be hit in the case of serious programmer error or
* unexpected input.
*
* @param {string=} opt_message A message to show when this is hit.
* @closurePrimitive {asserts.fail}
*/
/* #export */ function assertNotReached(opt_message) {
assert(false, opt_message || 'Unreachable code hit');
}
/**
* @param {*} value The value to check.
* @param {function(new: T, ...)} type A user-defined constructor.
* @param {string=} opt_message A message to show when this is hit.
* @return {T}
* @template T
*/
/* #export */ function assertInstanceof(value, type, opt_message) {
// We don't use assert immediately here so that we avoid constructing an error
// message if we don't have to.
if (!(value instanceof type)) {
assertNotReached(
opt_message ||
'Value ' + value + ' is not a[n] ' + (type.name || typeof type));
}
return value;
}
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