test/language/expressions: Add nullish coalescing tests

Copies a few tests for nullish coalescing straight from the newest
test262 master branch so that we can test
https://codereview.qt-project.org/c/qt/qtdeclarative/+/283241 .

Change-Id: I312e96c1e2934d2933421371d58bfce670f244ae
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>

1 files changed, 53 insertions, 0 deletions

diff --git a/test/language/expressions/coalesce/chainable-if-parenthesis-covered-logical-and.js b/test/language/expressions/coalesce/chainable-if-parenthesis-covered-logical-and.js
new file mode 100644
index 000000000..178789553
--- /dev/null
+++ b/test/language/expressions/coalesce/chainable-if-parenthesis-covered-logical-and.js
@@ -0,0 +1,53 @@
+// Copyright (C) 2019 Leo Balter. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+description: >
+    CoalesceExpression is chainable with the LogicalANDExpression is any is covered.
+esid: sec-conditional-operator
+info: |
+    ConditionalExpression :
+        ShortCircuitExpression
+        ShortCircuitExpression ? AssignmentExpression : AssignmentExpression
+
+    ShortCircuitExpression :
+        LogicalORExpression
+        CoalesceExpression
+
+    CoalesceExpression :
+        CoalesceExpressionHead ?? BitwiseORExpression
+
+    CoalesceExpressionHead :
+        CoalesceExpression
+        BitwiseORExpression
+
+    Runtime Semantics: Evaluation
+
+    CoalesceExpression:CoalesceExpressionHead??BitwiseORExpression
+
+    1. Let lref be the result of evaluating CoalesceExpressionHead.
+    2. Let lval be ? GetValue(lref).
+    3. If lval is undefined or null,
+        a. Let rref be the result of evaluating BitwiseORExpression.
+        b. Return ? GetValue(rref).
+    4. Otherwise, return lval.
+features: [coalesce-expression]
+---*/
+
+var x;
+
+x = undefined;
+x = (null ?? 41) && 42;
+assert.sameValue(x, 42, '(null ?? 41) && 42');
+
+x = undefined;
+x = null ?? (41 && 42);
+assert.sameValue(x, 42, 'null ?? (41 && 42)`');
+
+x = undefined;
+x = (41 && 42) ?? null;
+assert.sameValue(x, 42, '(41 && 42) ?? null');
+
+x = undefined;
+x = 41 && (null ?? 42);
+assert.sameValue(x, 42, '41 && (null ?? 42)`');