Test conversion of object to string in Temporal.Instant context

An object may be given in any context where a Temporal.Instant is expected
(see ToTemporalInstant). There is no conversion from a property bag to an
Instant, unlike with other Temporal types. Instead the object is converted
to a string, and if its toString() method yields a valid ISO string, the
conversion succeeds. (An object with the default Object.prototype.toString
will not.)

test/built-ins/Temporal/Instant/compare/argument-object-tostring.js

@@ -0,0 +1,22 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.instant.compare
+description: Object is converted to a string, then to Temporal.Instant
+features: [Temporal]
+---*/
+
+const epoch = new Temporal.Instant(0n);
+
+const arg = {};
+assert.throws(RangeError, () => Temporal.Instant.compare(arg, epoch), "[object Object] is not a valid ISO string (first argument)");
+assert.throws(RangeError, () => Temporal.Instant.compare(epoch, arg), "[object Object] is not a valid ISO string (second argument)");
+
+arg.toString = function() {
+  return "1970-01-01T00:00Z";
+};
+const result1 = Temporal.Instant.compare(arg, epoch);
+assert.sameValue(result1, 0, "result of toString is interpreted as ISO string (first argument)");
+const result2 = Temporal.Instant.compare(epoch, arg);
+assert.sameValue(result2, 0, "result of toString is interpreted as ISO string (second argument)");

test/built-ins/Temporal/Instant/from/argument-object-tostring.js

@@ -0,0 +1,17 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.instant.from
+description: Object is converted to a string, then to Temporal.Instant
+features: [Temporal]
+---*/
+
+const arg = {};
+assert.throws(RangeError, () => Temporal.Instant.from(arg), "[object Object] is not a valid ISO string");
+
+arg.toString = function() {
+  return "1970-01-01T00:00Z";
+};
+const result = Temporal.Instant.from(arg);
+assert.sameValue(result.epochNanoseconds, 0n, "result of toString is interpreted as ISO string");

test/built-ins/Temporal/Instant/prototype/equals/argument-object-tostring.js

@@ -0,0 +1,19 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.instant.prototype.equals
+description: Object is converted to a string, then to Temporal.Instant
+features: [Temporal]
+---*/
+
+const instance = new Temporal.Instant(0n);
+
+const arg = {};
+assert.throws(RangeError, () => instance.equals(arg), "[object Object] is not a valid ISO string");
+
+arg.toString = function() {
+  return "1970-01-01T00:00Z";
+};
+const result = instance.equals(arg);
+assert.sameValue(result, true, "result of toString is interpreted as ISO string");

test/built-ins/Temporal/Instant/prototype/since/argument-object-tostring.js

@@ -0,0 +1,20 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.instant.prototype.since
+description: Object is converted to a string, then to Temporal.Instant
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const instance = new Temporal.Instant(0n);
+
+const arg = {};
+assert.throws(RangeError, () => instance.since(arg), "[object Object] is not a valid ISO string");
+
+arg.toString = function() {
+  return "1970-01-01T00:00Z";
+};
+const result = instance.since(arg);
+TemporalHelpers.assertDuration(result, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, "result of toString is interpreted as ISO string");

test/built-ins/Temporal/Instant/prototype/until/argument-object-tostring.js

@@ -0,0 +1,20 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.instant.prototype.until
+description: Object is converted to a string, then to Temporal.Instant
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const instance = new Temporal.Instant(0n);
+
+const arg = {};
+assert.throws(RangeError, () => instance.until(arg), "[object Object] is not a valid ISO string");
+
+arg.toString = function() {
+  return "1970-01-01T00:00Z";
+};
+const result = instance.until(arg);
+TemporalHelpers.assertDuration(result, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, "result of toString is interpreted as ISO string");

test/built-ins/Temporal/TimeZone/prototype/getPlainDateTimeFor/argument-object-tostring.js

@@ -0,0 +1,20 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.timezone.prototype.getplaindatetimefor
+description: Object is converted to a string, then to Temporal.Instant
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const instance = new Temporal.TimeZone("UTC");
+
+const arg = {};
+assert.throws(RangeError, () => instance.getPlainDateTimeFor(arg), "[object Object] is not a valid ISO string");
+
+arg.toString = function() {
+  return "1970-01-01T00:00Z";
+};
+const result = instance.getPlainDateTimeFor(arg);
+TemporalHelpers.assertPlainDateTime(result, 1970, 1, "M01", 1, 0, 0, 0, 0, 0, 0, "result of toString is interpreted as ISO string");