From db73deb3bdede559bb7639bf3d0a07a32a17c6d8 Mon Sep 17 00:00:00 2001
From: Maximilian Goldstein <max.goldstein@qt.io>
Date: Fri, 29 Nov 2019 18:08:07 +0100
Subject: 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>
---
 .../coalesce/abrupt-is-a-short-circuit.js          | 58 ++++++++++++++
 .../coalesce/cannot-chain-head-with-logical-and.js | 31 ++++++++
 .../coalesce/cannot-chain-head-with-logical-or.js  | 31 ++++++++
 .../coalesce/cannot-chain-tail-with-logical-and.js | 32 ++++++++
 .../coalesce/cannot-chain-tail-with-logical-or.js  | 32 ++++++++
 ...chainable-if-parenthesis-covered-logical-and.js | 53 +++++++++++++
 .../chainable-if-parenthesis-covered-logical-or.js | 61 +++++++++++++++
 .../coalesce/chainable-with-bitwise-and.js         | 49 ++++++++++++
 .../coalesce/chainable-with-bitwise-or.js          | 49 ++++++++++++
 .../coalesce/chainable-with-bitwise-xor.js         | 49 ++++++++++++
 test/language/expressions/coalesce/chainable.js    | 50 ++++++++++++
 test/language/expressions/coalesce/follows-null.js | 49 ++++++++++++
 .../expressions/coalesce/follows-undefined.js      | 49 ++++++++++++
 .../expressions/coalesce/short-circuit-number-0.js | 81 ++++++++++++++++++++
 .../coalesce/short-circuit-number-42.js            | 81 ++++++++++++++++++++
 .../coalesce/short-circuit-number-empty-string.js  | 82 ++++++++++++++++++++
 .../coalesce/short-circuit-number-false.js         | 81 ++++++++++++++++++++
 .../coalesce/short-circuit-number-object.js        | 89 ++++++++++++++++++++++
 .../coalesce/short-circuit-number-string.js        | 82 ++++++++++++++++++++
 .../coalesce/short-circuit-number-symbol.js        | 82 ++++++++++++++++++++
 .../coalesce/short-circuit-number-true.js          | 81 ++++++++++++++++++++
 .../coalesce/short-circuit-prevents-evaluation.js  | 56 ++++++++++++++
 test/language/expressions/coalesce/tco-pos-null.js | 26 +++++++
 .../expressions/coalesce/tco-pos-undefined.js      | 26 +++++++
 24 files changed, 1360 insertions(+)
 create mode 100644 test/language/expressions/coalesce/abrupt-is-a-short-circuit.js
 create mode 100644 test/language/expressions/coalesce/cannot-chain-head-with-logical-and.js
 create mode 100644 test/language/expressions/coalesce/cannot-chain-head-with-logical-or.js
 create mode 100644 test/language/expressions/coalesce/cannot-chain-tail-with-logical-and.js
 create mode 100644 test/language/expressions/coalesce/cannot-chain-tail-with-logical-or.js
 create mode 100644 test/language/expressions/coalesce/chainable-if-parenthesis-covered-logical-and.js
 create mode 100644 test/language/expressions/coalesce/chainable-if-parenthesis-covered-logical-or.js
 create mode 100644 test/language/expressions/coalesce/chainable-with-bitwise-and.js
 create mode 100644 test/language/expressions/coalesce/chainable-with-bitwise-or.js
 create mode 100644 test/language/expressions/coalesce/chainable-with-bitwise-xor.js
 create mode 100644 test/language/expressions/coalesce/chainable.js
 create mode 100644 test/language/expressions/coalesce/follows-null.js
 create mode 100644 test/language/expressions/coalesce/follows-undefined.js
 create mode 100644 test/language/expressions/coalesce/short-circuit-number-0.js
 create mode 100644 test/language/expressions/coalesce/short-circuit-number-42.js
 create mode 100644 test/language/expressions/coalesce/short-circuit-number-empty-string.js
 create mode 100644 test/language/expressions/coalesce/short-circuit-number-false.js
 create mode 100644 test/language/expressions/coalesce/short-circuit-number-object.js
 create mode 100644 test/language/expressions/coalesce/short-circuit-number-string.js
 create mode 100644 test/language/expressions/coalesce/short-circuit-number-symbol.js
 create mode 100644 test/language/expressions/coalesce/short-circuit-number-true.js
 create mode 100644 test/language/expressions/coalesce/short-circuit-prevents-evaluation.js
 create mode 100644 test/language/expressions/coalesce/tco-pos-null.js
 create mode 100644 test/language/expressions/coalesce/tco-pos-undefined.js

diff --git a/test/language/expressions/coalesce/abrupt-is-a-short-circuit.js b/test/language/expressions/coalesce/abrupt-is-a-short-circuit.js
new file mode 100644
index 000000000..94dd03837
--- /dev/null
+++ b/test/language/expressions/coalesce/abrupt-is-a-short-circuit.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: >
+    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();');
diff --git a/test/language/expressions/coalesce/cannot-chain-head-with-logical-and.js b/test/language/expressions/coalesce/cannot-chain-head-with-logical-and.js
new file mode 100644
index 000000000..de17de9f9
--- /dev/null
+++ b/test/language/expressions/coalesce/cannot-chain-head-with-logical-and.js
@@ -0,0 +1,31 @@
+// 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: parse
+    type: SyntaxError
+---*/
+
+$DONOTEVALUATE();
+
+0 && 0 ?? true;
diff --git a/test/language/expressions/coalesce/cannot-chain-head-with-logical-or.js b/test/language/expressions/coalesce/cannot-chain-head-with-logical-or.js
new file mode 100644
index 000000000..de9ff3fff
--- /dev/null
+++ b/test/language/expressions/coalesce/cannot-chain-head-with-logical-or.js
@@ -0,0 +1,31 @@
+// Copyright (C) 2019 Leo Balter. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+description: >
+    Cannot immediately contain, or be contained within, an && or || operation.
+esid: sec-conditional-operator
+info: |
+    ConditionalExpression :
+        ShortCircuitExpression
+        ShortCircuitExpression ? AssignmentExpression : AssignmentExpression
+
+    ShortCircuitExpression :
+        LogicalORExpression
+        CoalesceExpression
+
+    CoalesceExpression :
+        CoalesceExpressionHead ?? BitwiseORExpression
+
+    CoalesceExpressionHead :
+        CoalesceExpression
+        BitwiseORExpression
+features: [coalesce-expression]
+negative:
+    phase: parse
+    type: SyntaxError
+---*/
+
+$DONOTEVALUATE();
+
+0 || 0 ?? true;
diff --git a/test/language/expressions/coalesce/cannot-chain-tail-with-logical-and.js b/test/language/expressions/coalesce/cannot-chain-tail-with-logical-and.js
new file mode 100644
index 000000000..a279608cc
--- /dev/null
+++ b/test/language/expressions/coalesce/cannot-chain-tail-with-logical-and.js
@@ -0,0 +1,32 @@
+// 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: parse
+    type: SyntaxError
+---*/
+
+$DONOTEVALUATE();
+
+0 ?? 0 && true;
diff --git a/test/language/expressions/coalesce/cannot-chain-tail-with-logical-or.js b/test/language/expressions/coalesce/cannot-chain-tail-with-logical-or.js
new file mode 100644
index 000000000..0849f7613
--- /dev/null
+++ b/test/language/expressions/coalesce/cannot-chain-tail-with-logical-or.js
@@ -0,0 +1,32 @@
+// Copyright (C) 2019 Leo Balter. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+description: >
+    If the CoalesceExpressionHead is undefined or null, follow return the right-side value.
+    Otherwise, return the left-side value.
+esid: sec-conditional-operator
+info: |
+    ConditionalExpression :
+        ShortCircuitExpression
+        ShortCircuitExpression ? AssignmentExpression : AssignmentExpression
+
+    ShortCircuitExpression :
+        LogicalORExpression
+        CoalesceExpression
+
+    CoalesceExpression :
+        CoalesceExpressionHead ?? BitwiseORExpression
+
+    CoalesceExpressionHead :
+        CoalesceExpression
+        BitwiseORExpression
+features: [coalesce-expression]
+negative:
+    phase: parse
+    type: SyntaxError
+---*/
+
+$DONOTEVALUATE();
+
+0 ?? 0 || true;
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)`');
diff --git a/test/language/expressions/coalesce/chainable-if-parenthesis-covered-logical-or.js b/test/language/expressions/coalesce/chainable-if-parenthesis-covered-logical-or.js
new file mode 100644
index 000000000..240613205
--- /dev/null
+++ b/test/language/expressions/coalesce/chainable-if-parenthesis-covered-logical-or.js
@@ -0,0 +1,61 @@
+// 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)');
diff --git a/test/language/expressions/coalesce/chainable-with-bitwise-and.js b/test/language/expressions/coalesce/chainable-with-bitwise-and.js
new file mode 100644
index 000000000..f88b4155d
--- /dev/null
+++ b/test/language/expressions/coalesce/chainable-with-bitwise-and.js
@@ -0,0 +1,49 @@
+// 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');
diff --git a/test/language/expressions/coalesce/chainable-with-bitwise-or.js b/test/language/expressions/coalesce/chainable-with-bitwise-or.js
new file mode 100644
index 000000000..e6441bca3
--- /dev/null
+++ b/test/language/expressions/coalesce/chainable-with-bitwise-or.js
@@ -0,0 +1,49 @@
+// 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');
diff --git a/test/language/expressions/coalesce/chainable-with-bitwise-xor.js b/test/language/expressions/coalesce/chainable-with-bitwise-xor.js
new file mode 100644
index 000000000..230c590a4
--- /dev/null
+++ b/test/language/expressions/coalesce/chainable-with-bitwise-xor.js
@@ -0,0 +1,49 @@
+// 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');
diff --git a/test/language/expressions/coalesce/chainable.js b/test/language/expressions/coalesce/chainable.js
new file mode 100644
index 000000000..948645f9a
--- /dev/null
+++ b/test/language/expressions/coalesce/chainable.js
@@ -0,0 +1,50 @@
+// 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');
diff --git a/test/language/expressions/coalesce/follows-null.js b/test/language/expressions/coalesce/follows-null.js
new file mode 100644
index 000000000..64068a5a5
--- /dev/null
+++ b/test/language/expressions/coalesce/follows-null.js
@@ -0,0 +1,49 @@
+// 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');
diff --git a/test/language/expressions/coalesce/follows-undefined.js b/test/language/expressions/coalesce/follows-undefined.js
new file mode 100644
index 000000000..050a91775
--- /dev/null
+++ b/test/language/expressions/coalesce/follows-undefined.js
@@ -0,0 +1,49 @@
+// 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');
diff --git a/test/language/expressions/coalesce/short-circuit-number-0.js b/test/language/expressions/coalesce/short-circuit-number-0.js
new file mode 100644
index 000000000..54ec3a54f
--- /dev/null
+++ b/test/language/expressions/coalesce/short-circuit-number-0.js
@@ -0,0 +1,81 @@
+// 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');
diff --git a/test/language/expressions/coalesce/short-circuit-number-42.js b/test/language/expressions/coalesce/short-circuit-number-42.js
new file mode 100644
index 000000000..b3c58b542
--- /dev/null
+++ b/test/language/expressions/coalesce/short-circuit-number-42.js
@@ -0,0 +1,81 @@
+// 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');
diff --git a/test/language/expressions/coalesce/short-circuit-number-empty-string.js b/test/language/expressions/coalesce/short-circuit-number-empty-string.js
new file mode 100644
index 000000000..0868fc800
--- /dev/null
+++ b/test/language/expressions/coalesce/short-circuit-number-empty-string.js
@@ -0,0 +1,82 @@
+// 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');
diff --git a/test/language/expressions/coalesce/short-circuit-number-false.js b/test/language/expressions/coalesce/short-circuit-number-false.js
new file mode 100644
index 000000000..d11733f9e
--- /dev/null
+++ b/test/language/expressions/coalesce/short-circuit-number-false.js
@@ -0,0 +1,81 @@
+// 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');
diff --git a/test/language/expressions/coalesce/short-circuit-number-object.js b/test/language/expressions/coalesce/short-circuit-number-object.js
new file mode 100644
index 000000000..dce37d765
--- /dev/null
+++ b/test/language/expressions/coalesce/short-circuit-number-object.js
@@ -0,0 +1,89 @@
+// 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');
diff --git a/test/language/expressions/coalesce/short-circuit-number-string.js b/test/language/expressions/coalesce/short-circuit-number-string.js
new file mode 100644
index 000000000..38c60eafe
--- /dev/null
+++ b/test/language/expressions/coalesce/short-circuit-number-string.js
@@ -0,0 +1,82 @@
+// 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');
diff --git a/test/language/expressions/coalesce/short-circuit-number-symbol.js b/test/language/expressions/coalesce/short-circuit-number-symbol.js
new file mode 100644
index 000000000..fccfded68
--- /dev/null
+++ b/test/language/expressions/coalesce/short-circuit-number-symbol.js
@@ -0,0 +1,82 @@
+// 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');
diff --git a/test/language/expressions/coalesce/short-circuit-number-true.js b/test/language/expressions/coalesce/short-circuit-number-true.js
new file mode 100644
index 000000000..778f8087f
--- /dev/null
+++ b/test/language/expressions/coalesce/short-circuit-number-true.js
@@ -0,0 +1,81 @@
+// 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');
diff --git a/test/language/expressions/coalesce/short-circuit-prevents-evaluation.js b/test/language/expressions/coalesce/short-circuit-prevents-evaluation.js
new file mode 100644
index 000000000..b064f5a2a
--- /dev/null
+++ b/test/language/expressions/coalesce/short-circuit-prevents-evaluation.js
@@ -0,0 +1,56 @@
+// 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);
diff --git a/test/language/expressions/coalesce/tco-pos-null.js b/test/language/expressions/coalesce/tco-pos-null.js
new file mode 100644
index 000000000..93c24453a
--- /dev/null
+++ b/test/language/expressions/coalesce/tco-pos-null.js
@@ -0,0 +1,26 @@
+// 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);
+}($MAX_ITERATIONS));
+assert.sameValue(callCount, 1);
diff --git a/test/language/expressions/coalesce/tco-pos-undefined.js b/test/language/expressions/coalesce/tco-pos-undefined.js
new file mode 100644
index 000000000..0065123eb
--- /dev/null
+++ b/test/language/expressions/coalesce/tco-pos-undefined.js
@@ -0,0 +1,26 @@
+// Copyright (C) 2019 Leo Balter. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+description: Expression is a candidate for tail-call optimization.
+esid: sec-static-semantics-hascallintailposition
+info: |
+  Expression Rules
+
+  CoalesceExpression : CoalesceExpressionHead ?? BitwiseORExpression
+
+  1. Return HasCallInTailPosition of BitwiseORExpression with argument call.
+flags: [onlyStrict]
+features: [tail-call-optimization, coalesce-expression]
+includes: [tcoHelper.js]
+---*/
+
+var callCount = 0;
+(function f(n) {
+  if (n === 0) {
+    callCount += 1
+    return;
+  }
+  return undefined ?? f(n - 1);
+}($MAX_ITERATIONS));
+assert.sameValue(callCount, 1);
-- 
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