1/* 2 * Copyright (C) 2023 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17/** 18 * Asserts that the given value is defined. 19 * 20 * @param value The value to assert. 21 * @param lazyErrorMessage A function that returns a message to be included in the error if the assertion fails. 22 * @throws {Error} If the value is not defined. 23 * @return The value, asserted to be defined. 24 */ 25export function assertDefined<A>( 26 value: A | null | undefined, 27 lazyErrorMessage?: () => string, 28): A { 29 if (value === undefined || value === null) { 30 throw new Error( 31 lazyErrorMessage 32 ? lazyErrorMessage() 33 : `Expected value, but found '${value}'`, 34 ); 35 } 36 return value; 37} 38 39/** 40 * Asserts that the given value is true. 41 * 42 * @param value The value to assert. 43 * @param lazyErrorMessage A function that returns a message to be included in the error if the assertion fails. 44 * @throws {Error} If the value is not true. 45 */ 46export function assertTrue(value: boolean, lazyErrorMessage?: () => string) { 47 if (!value) { 48 throw new Error( 49 lazyErrorMessage ? lazyErrorMessage() : 'Expected value to be true', 50 ); 51 } 52} 53 54/** 55 * Ensures at compile-time that a certain line is not reachable. 56 * E.g., make sure that a switch/case handles all possible input values. 57 * 58 * @param x The value to assert. 59 * @throws {Error} If the line is reachable. 60 * @return The value, asserted to be unreachable. 61 */ 62export function assertUnreachable(x: never): never { 63 throw new Error('This line should never execute'); 64} 65