Add tests for Temporal.Instant.p*.subtract

(Philip, March 2022: I rebased Frank's original PR #3076, did some
reformatting, removed duplicate tests, and combined with some existing
tests.)

test/built-ins/Temporal/Instant/prototype/subtract/basic.js

@@ -0,0 +1,72 @@
+// Copyright (C) 2021 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.instant.prototype.subtract
+description: Basic functionality of Temporal.Instant.prototype.subtract()
+info: |
+  1. Let instant be the this value.
+  2. Perform ? RequireInternalSlot(instant, [[InitializedTemporalInstant]]).
+  3. Let duration be ? ToLimitedTemporalDuration(temporalDurationLike, « "years", "months", "weeks", "days" »).
+  4. Let ns be ? AddInstant(instant.[[EpochNanoseconds]], duration.[[Hours]], duration.[[Minutes]], duration.[[Seconds]], duration.[[Milliseconds]], duration.[[Microseconds]], duration.[[Nanoseconds]]).
+  5. Return ! CreateTemporalInstant(ns).
+features: [Temporal]
+---*/
+
+const i1 = new Temporal.Instant(50000n);
+
+let result = i1.subtract(new Temporal.Duration(0,0,0,0,0,0,0,3,2,1));
+assert.sameValue(
+  -2952001n,
+  result.epochNanoseconds,
+  "subtract positive sub-seconds"
+);
+
+result = i1.subtract(new Temporal.Duration(0,0,0,0,0,0,4,3,2,1));
+assert.sameValue(
+  BigInt(-4 * 1e9) - 2952001n,
+  result.epochNanoseconds,
+  "subtract positive seconds"
+);
+
+result = i1.subtract(new Temporal.Duration(0,0,0,0,0,5,4,3,2,1));
+assert.sameValue(
+  BigInt(5 * 60 + 4) * -1000000000n - 2952001n,
+  result.epochNanoseconds,
+  "subtract positive minutes"
+);
+
+result = i1.subtract(new Temporal.Duration(0,0,0,0,6,5,4,3,2,1));
+assert.sameValue(
+  BigInt(6 * 3600 + 5 * 60 + 4) * -1000000000n - 2952001n,
+  result.epochNanoseconds,
+  "subtract positive hours"
+);
+
+result = i1.subtract(new Temporal.Duration(0,0,0,0,0,0,0,-3,-2,-1));
+assert.sameValue(
+  3052001n,
+  result.epochNanoseconds,
+  "subtract negative sub-seconds"
+);
+
+result = i1.subtract(new Temporal.Duration(0,0,0,0,0,0,-4,-3,-2,-1));
+assert.sameValue(
+  BigInt(4 * 1e9) + 3052001n,
+  result.epochNanoseconds,
+  "subtract negative seconds"
+);
+
+result = i1.subtract(new Temporal.Duration(0,0,0,0,0,-5,-4,-3,-2,-1));
+assert.sameValue(
+  BigInt(5 * 60 + 4) * 1000000000n + 3052001n,
+  result.epochNanoseconds,
+  "subtract negative minutes"
+);
+
+result = i1.subtract(new Temporal.Duration(0,0,0,0,-6,-5,-4,-3,-2,-1));
+assert.sameValue(
+  BigInt(6 * 3600 + 5 * 60 + 4) * 1000000000n + 3052001n,
+  result.epochNanoseconds,
+  "subtract negative hours"
+);

test/built-ins/Temporal/Instant/prototype/subtract/disallowed-duration-units.js

@@ -0,0 +1,31 @@
+// Copyright (C) 2021 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.instant.prototype.subtract
+description: |
+  Temporal.Instant.prototype.subtract() throws RangeError when the duration has
+  non-zero years, months, weeks or days.
+info: |
+  1. Let instant be the this value.
+  3. Let duration be ? ToLimitedTemporalDuration(temporalDurationLike, « "years", "months", "weeks", "days" »).
+features: [Temporal]
+---*/
+
+let i1 = new Temporal.Instant(500000n);
+assert.throws(RangeError, () => i1.subtract(new Temporal.Duration(1)),
+    "should throw RangeError when the duration has non-zero years (positive)");
+assert.throws(RangeError, () => i1.subtract(new Temporal.Duration(0, 2)),
+    "should throw RangeError when the duration has non-zero months (positive)");
+assert.throws(RangeError, () => i1.subtract(new Temporal.Duration(0, 0, 3)),
+    "should throw RangeError when the duration has non-zero weeks (positive)");
+assert.throws(RangeError, () => i1.subtract(new Temporal.Duration(0, 0, 0, 4)),
+    "should throw RangeError when the duration has non-zero days (positive)");
+assert.throws(RangeError, () => i1.subtract(new Temporal.Duration(-1)),
+    "should throw RangeError when the duration has non-zero years (negative)");
+assert.throws(RangeError, () => i1.subtract(new Temporal.Duration(0, -2)),
+    "should throw RangeError when the duration has non-zero months (negative)");
+assert.throws(RangeError, () => i1.subtract(new Temporal.Duration(0, 0, -3)),
+    "should throw RangeError when the duration has non-zero weeks (negative)");
+assert.throws(RangeError, () => i1.subtract(new Temporal.Duration(0, 0, 0, -4)),
+    "should throw RangeError when the duration has non-zero days (negative)");

test/built-ins/Temporal/Instant/prototype/subtract/result-out-of-range.js

@@ -2,15 +2,29 @@
 // This code is governed by the BSD license found in the LICENSE file.
 
 /*---
-esid: sec-temporal.instant.prototype.add
+esid: sec-temporal.instant.prototype.subtract
 description: RangeError thrown if result is outside representable range
 features: [Temporal]
 ---*/
 
 const fields = ["hours", "minutes", "seconds", "milliseconds", "microseconds", "nanoseconds"];
 
-const instance = Temporal.Instant.fromEpochNanoseconds(-8640000_000_000_000_000_000n);
+const earliest = Temporal.Instant.fromEpochNanoseconds(-8640000_000_000_000_000_000n);
 
 fields.forEach((field) => {
-  assert.throws(RangeError, () => instance.subtract({ [field]: 1 }));
+  assert.throws(
+    RangeError,
+    () => earliest.subtract({ [field]: 1 }),
+    `subtracting ${field} with result out of range (negative)`
+  );
+});
+
+const latest = Temporal.Instant.fromEpochNanoseconds(8640000_000_000_000_000_000n);
+
+fields.forEach((field) => {
+  assert.throws(
+    RangeError,
+    () => latest.subtract({ [field]: -1 }),
+    `subtracting ${field} with result out of range (positive)`
+  );
 });