short-circuit-prevents-evaluation.js (1470B)
1 // Copyright (C) 2019 Leo Balter. All rights reserved. 2 // This code is governed by the BSD license found in the LICENSE file. 3 4 /*--- 5 description: > 6 Short circuit can prevent evaluation of the right-side expressions 7 esid: sec-conditional-operator 8 info: | 9 ConditionalExpression : 10 ShortCircuitExpression 11 ShortCircuitExpression ? AssignmentExpression : AssignmentExpression 12 13 ShortCircuitExpression : 14 LogicalORExpression 15 CoalesceExpression 16 17 CoalesceExpression : 18 CoalesceExpressionHead ?? BitwiseORExpression 19 20 CoalesceExpressionHead : 21 CoalesceExpression 22 BitwiseORExpression 23 24 Runtime Semantics: Evaluation 25 26 CoalesceExpression:CoalesceExpressionHead??BitwiseORExpression 27 28 1. Let lref be the result of evaluating CoalesceExpressionHead. 29 2. Let lval be ? GetValue(lref). 30 3. If lval is undefined or null, 31 a. Let rref be the result of evaluating BitwiseORExpression. 32 b. Return ? GetValue(rref). 33 4. Otherwise, return lval. 34 features: [coalesce-expression] 35 ---*/ 36 37 var x; 38 function poison() { 39 throw new Test262Error('should not evaluate poison'); 40 } 41 42 x = undefined; 43 x = undefined ?? 42 ?? undefined ?? poison(); 44 assert.sameValue(x, 42); 45 46 x = undefined; 47 x = 42 ?? undefined ?? poison(); 48 assert.sameValue(x, 42); 49 50 x = undefined; 51 x = undefined ?? 42 ?? poison(); 52 assert.sameValue(x, 42); 53 54 x = undefined; 55 x = 42 ?? poison(); 56 assert.sameValue(x, 42); 57 58 reportCompare(0, 0);