Issue #1894 - Part 7: Update tests

Based on https://bugzilla.mozilla.org/show_bug.cgi?id=1566141

31 files changed, 1622 insertions, 0 deletions

diff --git a/js/src/tests/js1_8_5/reflect-parse/expression.js b/js/src/tests/js1_8_5/reflect-parse/expression.js
index 55d85a0293..6ee208915b 100644
--- a/js/src/tests/js1_8_5/reflect-parse/expression.js
+++ b/js/src/tests/js1_8_5/reflect-parse/expression.js
@@ -15,6 +15,31 @@ assertExpr("foo[bar]", memExpr(ident("foo"), ident("bar")));
 assertExpr("foo['bar']", memExpr(ident("foo"), lit("bar")));
 assertExpr("foo[42]", memExpr(ident("foo"), lit(42)));
 
+// optional member expressions
+assertExpr("foo?.bar", optExpr(optDotExpr(ident("foo"), ident("bar"))));
+assertExpr("foo?.bar.baz", optExpr(dotExpr(optDotExpr(ident("foo"), ident("bar")), ident("baz"))));
+assertExpr("foo.bar?.baz", optExpr(optDotExpr(dotExpr(ident("foo"), ident("bar")), ident("baz"))));
+assertExpr("foo?.bar?.baz", optExpr(optDotExpr(optDotExpr(ident("foo"), ident("bar")), ident("baz"))));
+assertExpr("foo?.[bar].baz", optExpr(dotExpr(optMemExpr(ident("foo"), ident("bar")), ident("baz"))));
+assertExpr("foo.bar?.[baz]", optExpr(optMemExpr(dotExpr(ident("foo"), ident("bar")), ident("baz"))));
+assertExpr("foo[bar]?.[baz]", optExpr(optMemExpr(memExpr(ident("foo"), ident("bar")), ident("baz"))));
+assertExpr("foo?.[bar][baz]", optExpr(memExpr(optMemExpr(ident("foo"), ident("bar")), ident("baz"))));
+assertExpr("foo?.['bar']?.['baz']", optExpr(optMemExpr(optMemExpr(ident("foo"), lit("bar")), lit("baz"))));
+assertExpr("foo?.[bar]?.baz", optExpr(optDotExpr(optMemExpr(ident("foo"), ident("bar")), ident("baz"))));
+
+// delete optional expressions
+assertExpr("\ndelete [] ?. [1]", delOptExpr(optMemExpr(arrExpr([]), lit(1))));
+assertExpr("delete foo?.bar", delOptExpr(optDotExpr(ident("foo"), ident("bar"))));
+assertExpr("delete foo?.bar.baz", delOptExpr(dotExpr(optDotExpr(ident("foo"), ident("bar")), ident("baz"))));
+assertExpr("delete foo.bar?.baz", delOptExpr(optDotExpr(dotExpr(ident("foo"), ident("bar")), ident("baz"))));
+assertExpr("delete foo?.bar?.baz", delOptExpr(optDotExpr(optDotExpr(ident("foo"), ident("bar")), ident("baz"))));
+assertExpr("delete foo?.[bar].baz", delOptExpr(dotExpr(optMemExpr(ident("foo"), ident("bar")), ident("baz"))));
+assertExpr("delete foo.bar?.[baz]", delOptExpr(optMemExpr(dotExpr(ident("foo"), ident("bar")), ident("baz"))));
+assertExpr("delete foo[bar]?.[baz]", delOptExpr(optMemExpr(memExpr(ident("foo"), ident("bar")), ident("baz"))));
+assertExpr("delete foo?.[bar][baz]", delOptExpr(memExpr(optMemExpr(ident("foo"), ident("bar")), ident("baz"))));
+assertExpr("delete foo?.['bar']?.['baz']", delOptExpr(optMemExpr(optMemExpr(ident("foo"), lit("bar")), lit("baz"))));
+assertExpr("delete foo?.[bar]?.baz", delOptExpr(optDotExpr(optMemExpr(ident("foo"), ident("bar")), ident("baz"))));
+
 // function expressions
 assertExpr("(function(){})", funExpr(null, [], blockStmt([])));
 assertExpr("(function f() {})", funExpr(ident("f"), [], blockStmt([])));
@@ -86,6 +111,7 @@ assertExpr("(x &= y)", aExpr("&=", ident("x"), ident("y")));
 // Conditional expressions
 assertExpr("(x || y)", logExpr("||", ident("x"), ident("y")));
 assertExpr("(x && y)", logExpr("&&", ident("x"), ident("y")));
+assertExpr("(x ?? y)", logExpr("??", ident("x"), ident("y")));
 assertExpr("(w || x || y || z)", logExpr("||", logExpr("||", logExpr("||", ident("w"), ident("x")), ident("y")), ident("z")))
 assertExpr("(x ? y : z)", condExpr(ident("x"), ident("y"), ident("z")));
 
@@ -103,6 +129,15 @@ assertExpr("(String())", callExpr(ident("String"), []));
 assertExpr("(String(42))", callExpr(ident("String"), [lit(42)]));
 assertExpr("(String(1,2,3))", callExpr(ident("String"), [lit(1),lit(2),lit(3)]));
 
+// Optional Call expressions
+assertExpr("(String?.())", optExpr(optCallExpr(ident("String"), [])));
+assertExpr("(String?.(42))", optExpr(optCallExpr(ident("String"), [lit(42)])));
+assertExpr("(String?.(1,2,3))", optExpr(optCallExpr(ident("String"), [lit(1),lit(2),lit(3)])));
+assertExpr("(String?.foo?.())", optExpr(optCallExpr(optDotExpr(ident("String"), ident("foo")), [])));
+assertExpr("(String.foo?.())", optExpr(optCallExpr(dotExpr(ident("String"), ident("foo")), [])));
+assertExpr("(String?.foo)()", callExpr(optExpr(optDotExpr(ident("String"), ident("foo"))), []));
+assertExpr("(String?.foo)?.()", optExpr(optCallExpr(optExpr(optDotExpr(ident("String"), ident("foo"))), [])));
+
 // Array expressions
 assertExpr("[]", arrExpr([]));
 assertExpr("[1]", arrExpr([lit(1)]));
diff --git a/js/src/tests/non262/expressions/nullish-coalescing.js b/js/src/tests/non262/expressions/nullish-coalescing.js
new file mode 100644
index 0000000000..0ee491680a
--- /dev/null
+++ b/js/src/tests/non262/expressions/nullish-coalescing.js
@@ -0,0 +1,112 @@
+var BUGNUMBER = 1566141;
+var summary = "Implement the Nullish Coalescing operator (??) proposal";
+
+print(BUGNUMBER + ": " + summary);
+
+// These tests are originally from webkit.
+// webkit specifics have been removed and a test for `document.all` has
+// been added.
+function shouldBe(actual, expected) {
+  if (actual !== expected)
+    throw new Error(`expected ${expected} but got ${actual}`);
+}
+
+function shouldNotThrow(script) {
+  eval(script);
+}
+
+function shouldThrowSyntaxError(script) {
+  let error;
+  try {
+    eval(script);
+  } catch (e) {
+    error = e;
+  }
+
+  if (!(error instanceof SyntaxError))
+    throw new Error('Expected SyntaxError!');
+}
+
+function testBasicCases() {
+  shouldBe(undefined ?? 3, 3);
+  shouldBe(null ?? 3, 3);
+  shouldBe(true ?? 3, true);
+  shouldBe(false ?? 3, false);
+  shouldBe(0 ?? 3, 0);
+  shouldBe(1 ?? 3, 1);
+  shouldBe('' ?? 3, '');
+  shouldBe('hi' ?? 3, 'hi');
+  shouldBe(({} ?? 3) instanceof Object, true);
+  shouldBe(({ x: 'hi' } ?? 3).x, 'hi');
+  shouldBe(([] ?? 3) instanceof Array, true);
+  shouldBe((['hi'] ?? 3)[0], 'hi');
+  // test document.all, which has odd behavior
+  //shouldBe(typeof(createIsHTMLDDA() ?? 3), "undefined");
+}
+
+for (let i = 0; i < 1e5; i++)
+  testBasicCases();
+
+shouldBe(1 | null ?? 3, 1);
+shouldBe(1 ^ null ?? 3, 1);
+shouldBe(1 & null ?? 3, 0);
+shouldBe(3 == null ?? 3, false);
+shouldBe(3 != null ?? 3, true);
+shouldBe(3 === null ?? 3, false);
+shouldBe(3 !== null ?? 3, true);
+shouldBe(1 < null ?? 3, false);
+shouldBe(1 > null ?? 3, true);
+shouldBe(1 <= null ?? 3, false);
+shouldBe(1 >= null ?? 3, true);
+shouldBe(1 << null ?? 3, 1);
+shouldBe(1 >> null ?? 3, 1);
+shouldBe(1 >>> null ?? 3, 1);
+shouldBe(1 + null ?? 3, 1);
+shouldBe(1 - null ?? 3, 1);
+shouldBe(1 * null ?? 3, 0);
+shouldBe(1 / null ?? 3, Infinity);
+shouldBe(isNaN(1 % null ?? 3), true);
+shouldBe(1 ** null ?? 3, 1);
+shouldBe((void 0) ?? 3, 3);
+
+const obj = {
+      count: 0,
+          get x() { this.count++; return 'x'; }
+};
+false ?? obj.x;
+shouldBe(obj.count, 0);
+null ?? obj.x;
+shouldBe(obj.count, 1);
+obj.x ?? obj.x;
+shouldBe(obj.count, 2);
+
+shouldThrowSyntaxError('0 || 1 ?? 2');
+shouldThrowSyntaxError('0 && 1 ?? 2');
+shouldThrowSyntaxError('0 ?? 1 || 2');
+shouldThrowSyntaxError('0 ?? 1 && 2');
+shouldNotThrow('(0 || 1) ?? 2');
+shouldNotThrow('0 || (1 ?? 2)');
+shouldNotThrow('(0 && 1) ?? 2');
+shouldNotThrow('0 && (1 ?? 2)');
+shouldNotThrow('(0 ?? 1) || 2');
+shouldNotThrow('0 ?? (1 || 2)');
+shouldNotThrow('(0 ?? 1) && 2');
+shouldNotThrow('0 ?? (1 && 2)');
+
+shouldNotThrow('0 || 1 && 2 | 3 ^ 4 & 5 == 6 != 7 === 8 !== 9 < 0 > 1 <= 2 >= 3 << 4 >> 5 >>> 6 + 7 - 8 * 9 / 0 % 1 ** 2');
+shouldThrowSyntaxError('0 || 1 && 2 | 3 ^ 4 & 5 == 6 != 7 === 8 !== 9 < 0 > 1 <= 2 >= 3 << 4 >> 5 >>> 6 + 7 - 8 * 9 / 0 % 1 ** 2 ?? 3');
+shouldThrowSyntaxError('3 ?? 2 ** 1 % 0 / 9 * 8 - 7 + 6 >>> 5 >> 4 << 3 >= 2 <= 1 > 0 < 9 !== 8 === 7 != 6 == 5 & 4 ^ 3 | 2 && 1 || 0');
+
+shouldBe(null?.x ?? 3, 3);
+shouldBe(({})?.x ?? 3, 3);
+shouldBe(({ x: 0 })?.x ?? 3, 0);
+shouldBe(null?.() ?? 3, 3);
+shouldBe((() => 0)?.() ?? 3, 0);
+shouldBe(({ x: 0 })?.[null?.a ?? 'x'] ?? 3, 0);
+shouldBe((() => 0)?.(null?.a ?? 'x') ?? 3, 0);
+
+if (typeof reportCompare === "function")
+  reportCompare(true, true);
+
+print("Tests complete");
+
diff --git a/js/src/tests/test262/language/expressions/coalesce/abrupt-is-a-short-circuit.js b/js/src/tests/test262/language/expressions/coalesce/abrupt-is-a-short-circuit.js
new file mode 100644
index 0000000000..fb04d2c0ac
--- /dev/null
+++ b/js/src/tests/test262/language/expressions/coalesce/abrupt-is-a-short-circuit.js
@@ -0,0 +1,60 @@
+// Copyright (C) 2019 Leo Balter. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+description: >
+    Abrupt completions are also a Short circuit and prevent evaluation of the right-side expressions
+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;
+function poison() {
+    throw new Test262Error('poison handled');
+}
+
+function morePoison() {
+    throw 'poison!!!!';
+}
+
+x = undefined;
+assert.throws(Test262Error, function() {
+    undefined ?? poison() ?? morePoison();
+}, 'undefined ?? poison() ?? morePoison();');
+
+x = undefined;
+assert.throws(Test262Error, function() {
+    null ?? poison() ?? morePoison();
+}, 'null ?? poison() ?? morePoison();');
+
+assert.throws(Test262Error, function() {
+    poison() ?? morePoison();
+}, 'poison() ?? morePoison();');
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/language/expressions/coalesce/browser.js b/js/src/tests/test262/language/expressions/coalesce/browser.js
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/js/src/tests/test262/language/expressions/coalesce/browser.js
diff --git a/js/src/tests/test262/language/expressions/coalesce/cannot-chain-head-with-logical-and.js b/js/src/tests/test262/language/expressions/coalesce/cannot-chain-head-with-logical-and.js
new file mode 100644
index 0000000000..7d59d2aee2
--- /dev/null
+++ b/js/src/tests/test262/language/expressions/coalesce/cannot-chain-head-with-logical-and.js
@@ -0,0 +1,30 @@
+// |reftest| error:SyntaxError
+// Copyright (C) 2019 Leo Balter. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+description: >
+    Cannot immediately contain, or be contained within, an && or || operation.
+esid: sec-conditional-operator
+info: |
+    ConditionalExpression :
+        ShortCircuitExpression
+        ShortCircuitExpression ? AssignmentExpression : AssignmentExpression
+
+    ShortCircuitExpression :
+        LogicalORExpression
+        CoalesceExpression
+
+    CoalesceExpression :
+        CoalesceExpressionHead ?? BitwiseORExpression
+
+    CoalesceExpressionHead :
+        CoalesceExpression
+        BitwiseORExpression
+features: [coalesce-expression]
+negative:
+    phase: early
+    type: SyntaxError
+---*/
+
+0 && 0 ?? true;
\ No newline at end of file
diff --git a/js/src/tests/test262/language/expressions/coalesce/cannot-chain-head-with-logical-or.js b/js/src/tests/test262/language/expressions/coalesce/cannot-chain-head-with-logical-or.js
new file mode 100644
index 0000000000..8086667f1b
--- /dev/null
+++ b/js/src/tests/test262/language/expressions/coalesce/cannot-chain-head-with-logical-or.js
@@ -0,0 +1,30 @@
+// |reftest| error:SyntaxError
+// Copyright (C) 2019 Leo Balter. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+description: >
+    Cannot immediately contain, or be contained within, an && or || operation.
+esid: sec-conditional-operator
+info: |
+    ConditionalExpression :
+        ShortCircuitExpression
+        ShortCircuitExpression ? AssignmentExpression : AssignmentExpression
+
+    ShortCircuitExpression :
+        LogicalORExpression
+        CoalesceExpression
+
+    CoalesceExpression :
+        CoalesceExpressionHead ?? BitwiseORExpression
+
+    CoalesceExpressionHead :
+        CoalesceExpression
+        BitwiseORExpression
+features: [coalesce-expression]
+negative:
+    phase: early
+    type: SyntaxError
+---*/
+
+0 || 0 ?? true;
\ No newline at end of file
diff --git a/js/src/tests/test262/language/expressions/coalesce/cannot-chain-tail-with-logical-and.js b/js/src/tests/test262/language/expressions/coalesce/cannot-chain-tail-with-logical-and.js
new file mode 100644
index 0000000000..a85faef116
--- /dev/null
+++ b/js/src/tests/test262/language/expressions/coalesce/cannot-chain-tail-with-logical-and.js
@@ -0,0 +1,31 @@
+// |reftest| error:SyntaxError
+// Copyright (C) 2019 Leo Balter. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+description: >
+    If the CoalesceExpressionHead is undefined or null, follow return the right-side value.
+    Otherwise, return the left-side value.
+esid: sec-conditional-operator
+info: |
+    ConditionalExpression :
+        ShortCircuitExpression
+        ShortCircuitExpression ? AssignmentExpression : AssignmentExpression
+
+    ShortCircuitExpression :
+        LogicalORExpression
+        CoalesceExpression
+
+    CoalesceExpression :
+        CoalesceExpressionHead ?? BitwiseORExpression
+
+    CoalesceExpressionHead :
+        CoalesceExpression
+        BitwiseORExpression
+features: [coalesce-expression]
+negative:
+    phase: early
+    type: SyntaxError
+---*/
+
+0 ?? 0 && true;
\ No newline at end of file
diff --git a/js/src/tests/test262/language/expressions/coalesce/cannot-chain-tail-with-logical-or.js b/js/src/tests/test262/language/expressions/coalesce/cannot-chain-tail-with-logical-or.js
new file mode 100644
index 0000000000..352a966215
--- /dev/null
+++ b/js/src/tests/test262/language/expressions/coalesce/cannot-chain-tail-with-logical-or.js
@@ -0,0 +1,31 @@
+// |reftest| error:SyntaxError
+// Copyright (C) 2019 Leo Balter. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+description: >
+    If the CoalesceExpressionHead is undefined or null, follow return the right-side value.
+    Otherwise, return the left-side value.
+esid: sec-conditional-operator
+info: |
+    ConditionalExpression :
+        ShortCircuitExpression
+        ShortCircuitExpression ? AssignmentExpression : AssignmentExpression
+
+    ShortCircuitExpression :
+        LogicalORExpression
+        CoalesceExpression
+
+    CoalesceExpression :
+        CoalesceExpressionHead ?? BitwiseORExpression
+
+    CoalesceExpressionHead :
+        CoalesceExpression
+        BitwiseORExpression
+features: [coalesce-expression]
+negative:
+    phase: early
+    type: SyntaxError
+---*/
+
+0 ?? 0 || true;
\ No newline at end of file
diff --git a/js/src/tests/test262/language/expressions/coalesce/chainable-if-parenthesis-covered-logical-and.js b/js/src/tests/test262/language/expressions/coalesce/chainable-if-parenthesis-covered-logical-and.js
new file mode 100644
index 0000000000..edcf93b557
--- /dev/null
+++ b/js/src/tests/test262/language/expressions/coalesce/chainable-if-parenthesis-covered-logical-and.js
@@ -0,0 +1,55 @@
+// 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)`');
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/language/expressions/coalesce/chainable-if-parenthesis-covered-logical-or.js b/js/src/tests/test262/language/expressions/coalesce/chainable-if-parenthesis-covered-logical-or.js
new file mode 100644
index 0000000000..79e9a6dd9e
--- /dev/null
+++ b/js/src/tests/test262/language/expressions/coalesce/chainable-if-parenthesis-covered-logical-or.js
@@ -0,0 +1,63 @@
+// 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 LogicalORExpression 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 ?? 42) || 43;
+assert.sameValue(x, 42, '(null ?? 42) || 43');
+
+x = undefined;
+x = null ?? (42 || 43);
+assert.sameValue(x, 42, 'null ?? (42 || 43)`');
+
+x = undefined;
+x = (null || 42) ?? 43;
+assert.sameValue(x, 42, '(null || 42) ?? 43');
+
+x = undefined;
+x = null || (42 ?? 43);
+assert.sameValue(x, 42, 'null || (42 ?? 43)`');
+
+x = undefined;
+x = (42 || 43) ?? null;
+assert.sameValue(x, 42, '(42 || 43) ?? null');
+
+x = undefined;
+x = 42 || (null ?? 43);
+assert.sameValue(x, 42, '42 || (null ?? 43)');
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/language/expressions/coalesce/chainable-with-bitwise-and.js b/js/src/tests/test262/language/expressions/coalesce/chainable-with-bitwise-and.js
new file mode 100644
index 0000000000..dac7e04fc4
--- /dev/null
+++ b/js/src/tests/test262/language/expressions/coalesce/chainable-with-bitwise-and.js
@@ -0,0 +1,51 @@
+// 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 BitwiseANDExpression
+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 = null ?? 42 & 43;
+assert.sameValue(x, 42, 'null ?? 42 & 43');
+
+x = undefined ?? 42 & 43;
+assert.sameValue(x, 42, 'null ?? 42 & 43');
+
+x = false ?? 42 & 43;
+assert.sameValue(x, false, 'false ?? 42 & 43');
+
+x = true ?? 42 & 43;
+assert.sameValue(x, true, 'true ?? 42 & 43');
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/language/expressions/coalesce/chainable-with-bitwise-or.js b/js/src/tests/test262/language/expressions/coalesce/chainable-with-bitwise-or.js
new file mode 100644
index 0000000000..214d4fd9aa
--- /dev/null
+++ b/js/src/tests/test262/language/expressions/coalesce/chainable-with-bitwise-or.js
@@ -0,0 +1,51 @@
+// 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 BitwiseORExpression
+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 = null ?? 1 | 42;
+assert.sameValue(x, 43, 'null ?? 1 | 42');
+
+x = undefined ?? 1 | 42;
+assert.sameValue(x, 43, 'null ?? 1 | 42');
+
+x = false ?? 1 | 42;
+assert.sameValue(x, false, 'false ?? 1 | 42');
+
+x = true ?? 1 | 42;
+assert.sameValue(x, true, 'true ?? 1 | 42');
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/language/expressions/coalesce/chainable-with-bitwise-xor.js b/js/src/tests/test262/language/expressions/coalesce/chainable-with-bitwise-xor.js
new file mode 100644
index 0000000000..a3b6ad4ab0
--- /dev/null
+++ b/js/src/tests/test262/language/expressions/coalesce/chainable-with-bitwise-xor.js
@@ -0,0 +1,51 @@
+// 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 BitwiseXORExpression
+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 = null ?? 1 ^ 42;
+assert.sameValue(x, 43, 'null ?? 1 ^ 42');
+
+x = undefined ?? 1 ^ 42;
+assert.sameValue(x, 43, 'null ?? 1 ^ 42');
+
+x = false ?? 1 ^ 42;
+assert.sameValue(x, false, 'false ?? 1 ^ 42');
+
+x = true ?? 1 ^ 42;
+assert.sameValue(x, true, 'true ?? 1 ^ 42');
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/language/expressions/coalesce/chainable.js b/js/src/tests/test262/language/expressions/coalesce/chainable.js
new file mode 100644
index 0000000000..09ad90452a
--- /dev/null
+++ b/js/src/tests/test262/language/expressions/coalesce/chainable.js
@@ -0,0 +1,52 @@
+// Copyright (C) 2019 Leo Balter. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+description: >
+    If the CoalesceExpressionHead is undefined or null, follow return the right-side value.
+    Otherwise, return the left-side value.
+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 = null ?? undefined ?? 42;
+assert.sameValue(x, 42, 'null ?? undefined ?? 42');
+
+x = undefined ?? null ?? 42;
+assert.sameValue(x, 42, 'undefined ?? null ?? 42');
+
+x = null ?? null ?? 42;
+assert.sameValue(x, 42, 'null ?? null ?? 42');
+
+x = undefined ?? undefined ?? 42;
+assert.sameValue(x, 42, 'null ?? null ?? 42');
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/language/expressions/coalesce/follows-null.js b/js/src/tests/test262/language/expressions/coalesce/follows-null.js
new file mode 100644
index 0000000000..82a95419ef
--- /dev/null
+++ b/js/src/tests/test262/language/expressions/coalesce/follows-null.js
@@ -0,0 +1,51 @@
+// Copyright (C) 2019 Leo Balter. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+description: >
+    If the CoalesceExpressionHead is null, follow return the right-side eval.
+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 = null ?? 42;
+assert.sameValue(x, 42, 'null ?? 42');
+
+x = null ?? undefined;
+assert.sameValue(x, undefined, 'null ?? undefined');
+
+x = null ?? null;
+assert.sameValue(x, null, 'null ?? null');
+
+x = null ?? false;
+assert.sameValue(x, false, 'null ?? false');
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/language/expressions/coalesce/follows-undefined.js b/js/src/tests/test262/language/expressions/coalesce/follows-undefined.js
new file mode 100644
index 0000000000..0728ed1ff2
--- /dev/null
+++ b/js/src/tests/test262/language/expressions/coalesce/follows-undefined.js
@@ -0,0 +1,51 @@
+// Copyright (C) 2019 Leo Balter. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+description: >
+    If the CoalesceExpressionHead is undefined, follow return the right-side eval.
+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 ?? 42;
+assert.sameValue(x, 42, 'undefined ?? 42');
+
+x = undefined ?? undefined;
+assert.sameValue(x, undefined, 'undefined ?? undefined');
+
+x = undefined ?? null;
+assert.sameValue(x, null, 'undefined ?? null');
+
+x = undefined ?? false;
+assert.sameValue(x, false, 'undefined ?? false');
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/language/expressions/coalesce/shell.js b/js/src/tests/test262/language/expressions/coalesce/shell.js
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/js/src/tests/test262/language/expressions/coalesce/shell.js
diff --git a/js/src/tests/test262/language/expressions/coalesce/short-circuit-number-0.js b/js/src/tests/test262/language/expressions/coalesce/short-circuit-number-0.js
new file mode 100644
index 0000000000..547f62a1cf
--- /dev/null
+++ b/js/src/tests/test262/language/expressions/coalesce/short-circuit-number-0.js
@@ -0,0 +1,83 @@
+// Copyright (C) 2019 Leo Balter. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+description: >
+    Short circuit if the CoalesceExpressionHead is not undefined or null (0)
+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 = 0 ?? 1;
+assert.sameValue(x, 0, '0 ?? 1');
+
+x = undefined;
+x = 0 ?? null;
+assert.sameValue(x, 0, '0 ?? null');
+
+x = undefined;
+x = 0 ?? undefined;
+assert.sameValue(x, 0, '0 ?? undefined');
+
+x = undefined;
+x = 0 ?? null ?? undefined;
+assert.sameValue(x, 0, '0 ?? null ?? undefined');
+
+x = undefined;
+x = 0 ?? undefined ?? null;
+assert.sameValue(x, 0, '0 ?? undefined ?? null');
+
+x = undefined;
+x = 0 ?? null ?? null;
+assert.sameValue(x, 0, '0 ?? null ?? null');
+
+x = undefined;
+x = 0 ?? undefined ?? undefined;
+assert.sameValue(x, 0, '0 ?? null ?? null');
+
+x = undefined;
+x = null ?? 0 ?? null;
+assert.sameValue(x, 0, 'null ?? 0 ?? null');
+
+x = undefined;
+x = null ?? 0 ?? undefined;
+assert.sameValue(x, 0, 'null ?? 0 ?? undefined');
+
+x = undefined;
+x = undefined ?? 0 ?? null;
+assert.sameValue(x, 0, 'undefined ?? 0 ?? null');
+
+x = undefined;
+x = undefined ?? 0 ?? undefined;
+assert.sameValue(x, 0, 'undefined ?? 0 ?? undefined');
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/language/expressions/coalesce/short-circuit-number-42.js b/js/src/tests/test262/language/expressions/coalesce/short-circuit-number-42.js
new file mode 100644
index 0000000000..b30d905f2f
--- /dev/null
+++ b/js/src/tests/test262/language/expressions/coalesce/short-circuit-number-42.js
@@ -0,0 +1,83 @@
+// Copyright (C) 2019 Leo Balter. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+description: >
+    Short circuit if the CoalesceExpressionHead is not undefined or null (42)
+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 = 42 ?? 1;
+assert.sameValue(x, 42, '42 ?? 1');
+
+x = undefined;
+x = 42 ?? null;
+assert.sameValue(x, 42, '42 ?? null');
+
+x = undefined;
+x = 42 ?? undefined;
+assert.sameValue(x, 42, '42 ?? undefined');
+
+x = undefined;
+x = 42 ?? null ?? undefined;
+assert.sameValue(x, 42, '42 ?? null ?? undefined');
+
+x = undefined;
+x = 42 ?? undefined ?? null;
+assert.sameValue(x, 42, '42 ?? undefined ?? null');
+
+x = undefined;
+x = 42 ?? null ?? null;
+assert.sameValue(x, 42, '42 ?? null ?? null');
+
+x = undefined;
+x = 42 ?? undefined ?? undefined;
+assert.sameValue(x, 42, '42 ?? null ?? null');
+
+x = undefined;
+x = null ?? 42 ?? null;
+assert.sameValue(x, 42, 'null ?? 42 ?? null');
+
+x = undefined;
+x = null ?? 42 ?? undefined;
+assert.sameValue(x, 42, 'null ?? 42 ?? undefined');
+
+x = undefined;
+x = undefined ?? 42 ?? null;
+assert.sameValue(x, 42, 'undefined ?? 42 ?? null');
+
+x = undefined;
+x = undefined ?? 42 ?? undefined;
+assert.sameValue(x, 42, 'undefined ?? 42 ?? undefined');
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/language/expressions/coalesce/short-circuit-number-empty-string.js b/js/src/tests/test262/language/expressions/coalesce/short-circuit-number-empty-string.js
new file mode 100644
index 0000000000..c513e2cbc7
--- /dev/null
+++ b/js/src/tests/test262/language/expressions/coalesce/short-circuit-number-empty-string.js
@@ -0,0 +1,84 @@
+// Copyright (C) 2019 Leo Balter. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+description: >
+    Short circuit if the CoalesceExpressionHead is not undefined or null (the empty string)
+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;
+var str = '';
+
+x = undefined;
+x = str ?? 1;
+assert.sameValue(x, str, 'str ?? 1');
+
+x = undefined;
+x = str ?? null;
+assert.sameValue(x, str, 'str ?? null');
+
+x = undefined;
+x = str ?? undefined;
+assert.sameValue(x, str, 'str ?? undefined');
+
+x = undefined;
+x = str ?? null ?? undefined;
+assert.sameValue(x, str, 'str ?? null ?? undefined');
+
+x = undefined;
+x = str ?? undefined ?? null;
+assert.sameValue(x, str, 'str ?? undefined ?? null');
+
+x = undefined;
+x = str ?? null ?? null;
+assert.sameValue(x, str, 'str ?? null ?? null');
+
+x = undefined;
+x = str ?? undefined ?? undefined;
+assert.sameValue(x, str, 'str ?? null ?? null');
+
+x = undefined;
+x = null ?? str ?? null;
+assert.sameValue(x, str, 'null ?? str ?? null');
+
+x = undefined;
+x = null ?? str ?? undefined;
+assert.sameValue(x, str, 'null ?? str ?? undefined');
+
+x = undefined;
+x = undefined ?? str ?? null;
+assert.sameValue(x, str, 'undefined ?? str ?? null');
+
+x = undefined;
+x = undefined ?? str ?? undefined;
+assert.sameValue(x, str, 'undefined ?? str ?? undefined');
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/language/expressions/coalesce/short-circuit-number-false.js b/js/src/tests/test262/language/expressions/coalesce/short-circuit-number-false.js
new file mode 100644
index 0000000000..d235729393
--- /dev/null
+++ b/js/src/tests/test262/language/expressions/coalesce/short-circuit-number-false.js
@@ -0,0 +1,83 @@
+// Copyright (C) 2019 Leo Balter. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+description: >
+    Short circuit if the CoalesceExpressionHead is not undefined or null (false)
+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 = false ?? 1;
+assert.sameValue(x, false, 'false ?? 1');
+
+x = undefined;
+x = false ?? null;
+assert.sameValue(x, false, 'false ?? null');
+
+x = undefined;
+x = false ?? undefined;
+assert.sameValue(x, false, 'false ?? undefined');
+
+x = undefined;
+x = false ?? null ?? undefined;
+assert.sameValue(x, false, 'false ?? null ?? undefined');
+
+x = undefined;
+x = false ?? undefined ?? null;
+assert.sameValue(x, false, 'false ?? undefined ?? null');
+
+x = undefined;
+x = false ?? null ?? null;
+assert.sameValue(x, false, 'false ?? null ?? null');
+
+x = undefined;
+x = false ?? undefined ?? undefined;
+assert.sameValue(x, false, 'false ?? null ?? null');
+
+x = undefined;
+x = null ?? false ?? null;
+assert.sameValue(x, false, 'null ?? false ?? null');
+
+x = undefined;
+x = null ?? false ?? undefined;
+assert.sameValue(x, false, 'null ?? false ?? undefined');
+
+x = undefined;
+x = undefined ?? false ?? null;
+assert.sameValue(x, false, 'undefined ?? false ?? null');
+
+x = undefined;
+x = undefined ?? false ?? undefined;
+assert.sameValue(x, false, 'undefined ?? false ?? undefined');
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/language/expressions/coalesce/short-circuit-number-object.js b/js/src/tests/test262/language/expressions/coalesce/short-circuit-number-object.js
new file mode 100644
index 0000000000..5f2eee11e7
--- /dev/null
+++ b/js/src/tests/test262/language/expressions/coalesce/short-circuit-number-object.js
@@ -0,0 +1,91 @@
+// Copyright (C) 2019 Leo Balter. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+description: >
+    Short circuit if the CoalesceExpressionHead is not undefined or null (object)
+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;
+var obj = {
+    toString() {
+        return null;
+    },
+    valueOf() {
+        return null;
+    }
+};
+
+x = undefined;
+x = obj ?? 1;
+assert.sameValue(x, obj, 'obj ?? 1');
+
+x = undefined;
+x = obj ?? null;
+assert.sameValue(x, obj, 'obj ?? null');
+
+x = undefined;
+x = obj ?? undefined;
+assert.sameValue(x, obj, 'obj ?? undefined');
+
+x = undefined;
+x = obj ?? null ?? undefined;
+assert.sameValue(x, obj, 'obj ?? null ?? undefined');
+
+x = undefined;
+x = obj ?? undefined ?? null;
+assert.sameValue(x, obj, 'obj ?? undefined ?? null');
+
+x = undefined;
+x = obj ?? null ?? null;
+assert.sameValue(x, obj, 'obj ?? null ?? null');
+
+x = undefined;
+x = obj ?? undefined ?? undefined;
+assert.sameValue(x, obj, 'obj ?? null ?? null');
+
+x = undefined;
+x = null ?? obj ?? null;
+assert.sameValue(x, obj, 'null ?? obj ?? null');
+
+x = undefined;
+x = null ?? obj ?? undefined;
+assert.sameValue(x, obj, 'null ?? obj ?? undefined');
+
+x = undefined;
+x = undefined ?? obj ?? null;
+assert.sameValue(x, obj, 'undefined ?? obj ?? null');
+
+x = undefined;
+x = undefined ?? obj ?? undefined;
+assert.sameValue(x, obj, 'undefined ?? obj ?? undefined');
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/language/expressions/coalesce/short-circuit-number-string.js b/js/src/tests/test262/language/expressions/coalesce/short-circuit-number-string.js
new file mode 100644
index 0000000000..9979a685cc
--- /dev/null
+++ b/js/src/tests/test262/language/expressions/coalesce/short-circuit-number-string.js
@@ -0,0 +1,84 @@
+// Copyright (C) 2019 Leo Balter. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+description: >
+    Short circuit if the CoalesceExpressionHead is not undefined or null (string)
+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;
+var str = 'undefined';
+
+x = undefined;
+x = str ?? 1;
+assert.sameValue(x, str, 'str ?? 1');
+
+x = undefined;
+x = str ?? null;
+assert.sameValue(x, str, 'str ?? null');
+
+x = undefined;
+x = str ?? undefined;
+assert.sameValue(x, str, 'str ?? undefined');
+
+x = undefined;
+x = str ?? null ?? undefined;
+assert.sameValue(x, str, 'str ?? null ?? undefined');
+
+x = undefined;
+x = str ?? undefined ?? null;
+assert.sameValue(x, str, 'str ?? undefined ?? null');
+
+x = undefined;
+x = str ?? null ?? null;
+assert.sameValue(x, str, 'str ?? null ?? null');
+
+x = undefined;
+x = str ?? undefined ?? undefined;
+assert.sameValue(x, str, 'str ?? null ?? null');
+
+x = undefined;
+x = null ?? str ?? null;
+assert.sameValue(x, str, 'null ?? str ?? null');
+
+x = undefined;
+x = null ?? str ?? undefined;
+assert.sameValue(x, str, 'null ?? str ?? undefined');
+
+x = undefined;
+x = undefined ?? str ?? null;
+assert.sameValue(x, str, 'undefined ?? str ?? null');
+
+x = undefined;
+x = undefined ?? str ?? undefined;
+assert.sameValue(x, str, 'undefined ?? str ?? undefined');
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/language/expressions/coalesce/short-circuit-number-symbol.js b/js/src/tests/test262/language/expressions/coalesce/short-circuit-number-symbol.js
new file mode 100644
index 0000000000..827c6e8535
--- /dev/null
+++ b/js/src/tests/test262/language/expressions/coalesce/short-circuit-number-symbol.js
@@ -0,0 +1,84 @@
+// Copyright (C) 2019 Leo Balter. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+description: >
+    Short circuit if the CoalesceExpressionHead is not undefined or null (Symbol)
+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;
+var s = Symbol();
+
+x = undefined;
+x = s ?? 1;
+assert.sameValue(x, s, 's ?? null');
+
+x = undefined;
+x = s ?? null;
+assert.sameValue(x, s, 's ?? null');
+
+x = undefined;
+x = s ?? undefined;
+assert.sameValue(x, s, 's ?? undefined');
+
+x = undefined;
+x = s ?? null ?? undefined;
+assert.sameValue(x, s, 's ?? null ?? undefined');
+
+x = undefined;
+x = s ?? undefined ?? null;
+assert.sameValue(x, s, 's ?? undefined ?? null');
+
+x = undefined;
+x = s ?? null ?? null;
+assert.sameValue(x, s, 's ?? null ?? null');
+
+x = undefined;
+x = s ?? undefined ?? undefined;
+assert.sameValue(x, s, 's ?? null ?? null');
+
+x = undefined;
+x = null ?? s ?? null;
+assert.sameValue(x, s, 'null ?? s ?? null');
+
+x = undefined;
+x = null ?? s ?? undefined;
+assert.sameValue(x, s, 'null ?? s ?? undefined');
+
+x = undefined;
+x = undefined ?? s ?? null;
+assert.sameValue(x, s, 'undefined ?? s ?? null');
+
+x = undefined;
+x = undefined ?? s ?? undefined;
+assert.sameValue(x, s, 'undefined ?? s ?? undefined');
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/language/expressions/coalesce/short-circuit-number-true.js b/js/src/tests/test262/language/expressions/coalesce/short-circuit-number-true.js
new file mode 100644
index 0000000000..9b24181ab3
--- /dev/null
+++ b/js/src/tests/test262/language/expressions/coalesce/short-circuit-number-true.js
@@ -0,0 +1,83 @@
+// Copyright (C) 2019 Leo Balter. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+description: >
+    Short circuit if the CoalesceExpressionHead is not undefined or null (true)
+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 = true ?? 1;
+assert.sameValue(x, true, 'true ?? null');
+
+x = undefined;
+x = true ?? null;
+assert.sameValue(x, true, 'true ?? null');
+
+x = undefined;
+x = true ?? undefined;
+assert.sameValue(x, true, 'true ?? undefined');
+
+x = undefined;
+x = true ?? null ?? undefined;
+assert.sameValue(x, true, 'true ?? null ?? undefined');
+
+x = undefined;
+x = true ?? undefined ?? null;
+assert.sameValue(x, true, 'true ?? undefined ?? null');
+
+x = undefined;
+x = true ?? null ?? null;
+assert.sameValue(x, true, 'true ?? null ?? null');
+
+x = undefined;
+x = true ?? undefined ?? undefined;
+assert.sameValue(x, true, 'true ?? null ?? null');
+
+x = undefined;
+x = null ?? true ?? null;
+assert.sameValue(x, true, 'null ?? true ?? null');
+
+x = undefined;
+x = null ?? true ?? undefined;
+assert.sameValue(x, true, 'null ?? true ?? undefined');
+
+x = undefined;
+x = undefined ?? true ?? null;
+assert.sameValue(x, true, 'undefined ?? true ?? null');
+
+x = undefined;
+x = undefined ?? true ?? undefined;
+assert.sameValue(x, true, 'undefined ?? true ?? undefined');
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/language/expressions/coalesce/short-circuit-prevents-evaluation.js b/js/src/tests/test262/language/expressions/coalesce/short-circuit-prevents-evaluation.js
new file mode 100644
index 0000000000..14cbd109e4
--- /dev/null
+++ b/js/src/tests/test262/language/expressions/coalesce/short-circuit-prevents-evaluation.js
@@ -0,0 +1,58 @@
+// Copyright (C) 2019 Leo Balter. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+description: >
+    Short circuit can prevent evaluation of the right-side expressions
+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;
+function poison() {
+    throw new Test262Error('should not evaluate poison');
+}
+
+x = undefined;
+x = undefined ?? 42 ?? undefined ?? poison();
+assert.sameValue(x, 42);
+
+x = undefined;
+x = 42 ?? undefined ?? poison();
+assert.sameValue(x, 42);
+
+x = undefined;
+x = undefined ?? 42 ?? poison();
+assert.sameValue(x, 42);
+
+x = undefined;
+x = 42 ?? poison();
+assert.sameValue(x, 42);
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/language/expressions/coalesce/tco-pos-null-strict.js b/js/src/tests/test262/language/expressions/coalesce/tco-pos-null-strict.js
new file mode 100644
index 0000000000..9030e2227c
--- /dev/null
+++ b/js/src/tests/test262/language/expressions/coalesce/tco-pos-null-strict.js
@@ -0,0 +1,30 @@
+// |reftest| skip -- tail-call-optimization is not supported
+'use strict';
+// Copyright (C) 2019 Leo Balter. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+description: Expression is a candidate for tail-call optimization.
+esid: sec-static-semantics-hascallintailposition
+info: |
+  Expression Rules
+
+  CoalesceExpression : CoalesceExpressionHead ?? BitwiseORExpression
+
+  1. Return HasCallInTailPosition of BitwiseORExpression with argument call.
+flags: [onlyStrict]
+features: [tail-call-optimization, coalesce-expression]
+includes: [tcoHelper.js]
+---*/
+
+var callCount = 0;
+(function f(n) {
+  if (n === 0) {
+    callCount += 1
+    return;
+  }
+  return null ?? f(n - 1);
+}($MAX_ITERATIONS));
+assert.sameValue(callCount, 1);
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/language/expressions/coalesce/tco-pos-undefined-strict.js b/js/src/tests/test262/language/expressions/coalesce/tco-pos-undefined-strict.js
new file mode 100644
index 0000000000..70f6ff59ec
--- /dev/null
+++ b/js/src/tests/test262/language/expressions/coalesce/tco-pos-undefined-strict.js
@@ -0,0 +1,30 @@
+// |reftest| skip -- tail-call-optimization is not supported
+'use strict';
+// Copyright (C) 2019 Leo Balter. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+description: Expression is a candidate for tail-call optimization.
+esid: sec-static-semantics-hascallintailposition
+info: |
+  Expression Rules
+
+  CoalesceExpression : CoalesceExpressionHead ?? BitwiseORExpression
+
+  1. Return HasCallInTailPosition of BitwiseORExpression with argument call.
+flags: [onlyStrict]
+features: [tail-call-optimization, coalesce-expression]
+includes: [tcoHelper.js]
+---*/
+
+var callCount = 0;
+(function f(n) {
+  if (n === 0) {
+    callCount += 1
+    return;
+  }
+  return undefined ?? f(n - 1);
+}($MAX_ITERATIONS));
+assert.sameValue(callCount, 1);
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/language/expressions/conditional/browser.js b/js/src/tests/test262/language/expressions/conditional/browser.js
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/js/src/tests/test262/language/expressions/conditional/browser.js
diff --git a/js/src/tests/test262/language/expressions/conditional/coalesce-expr-ternary.js b/js/src/tests/test262/language/expressions/conditional/coalesce-expr-ternary.js
new file mode 100644
index 0000000000..543f22127a
--- /dev/null
+++ b/js/src/tests/test262/language/expressions/conditional/coalesce-expr-ternary.js
@@ -0,0 +1,75 @@
+// Copyright (C) 2019 Leo Balter. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+description: >
+    ShortCircuitExpression in the Conditional Expression (? :)
+esid: sec-conditional-operator
+info: |
+    ShortCircuitExpression :
+        LogicalORExpression
+        CoalesceExpression
+
+    CoalesceExpression :
+        CoalesceExpressionHead ?? BitwiseORExpression
+
+    CoalesceExpressionHead :
+        CoalesceExpression
+        BitwiseORExpression
+
+    ConditionalExpression :
+        ShortCircuitExpression
+        ShortCircuitExpression ? AssignmentExpression : AssignmentExpression
+features: [coalesce-expression]
+---*/
+
+var x;
+
+x = undefined ?? true ? 0 : 42;
+assert.sameValue(x, 0, 'undefined ?? true ? 0 : 42');
+
+x = undefined;
+x = null ?? true ? 0 : 42;
+assert.sameValue(x, 0, 'null ?? true ? 0 : 42');
+
+x = undefined;
+x = undefined ?? false ? 0 : 42;
+assert.sameValue(x, 42, 'undefined ?? false ? 0 : 42');
+
+x = undefined;
+x = null ?? false ? 0 : 42;
+assert.sameValue(x, 42, 'null ?? false ? 0 : 42');
+
+x = undefined;
+x = false ?? true ? 0 : 42;
+assert.sameValue(x, 42, 'false ?? true ? 0 : 42');
+
+x = undefined;
+x = 0 ?? true ? 0 : 42;
+assert.sameValue(x, 42, '0 ?? true ? 0 : 42');
+
+x = undefined;
+x = 1 ?? false ? 0 : 42;
+assert.sameValue(x, 0, '1 ?? false ? 0 : 42');
+
+x = undefined;
+x = true ?? false ? 0 : 42;
+assert.sameValue(x, 0, 'true ?? false ? 0 : 42');
+
+x = undefined;
+x = true ?? true ? 0 : 42;
+assert.sameValue(x, 0, 'true ?? true ? 0 : 42');
+
+x = undefined;
+x = '' ?? true ? 0 : 42;
+assert.sameValue(x, 42, '"" ?? true ? 0 : 42');
+
+x = undefined;
+x = Symbol() ?? false ? 0 : 42;
+assert.sameValue(x, 0, 'Symbol() ?? false ? 0 : 42');
+
+x = undefined;
+x = {} ?? false ? 0 : 42;
+assert.sameValue(x, 0, 'object ?? false ? 0 : 42');
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/language/expressions/conditional/shell.js b/js/src/tests/test262/language/expressions/conditional/shell.js
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/js/src/tests/test262/language/expressions/conditional/shell.js