Fix Time.from when parameter is another Time

- Fixes #735.
- Adds tests for `Time.from` when the source is `Time` or `DateTime`.
- Also corrects an inaccurate comment.

polyfill/lib/time.mjs

@@ -255,13 +255,14 @@ export class Time {
     let hour, minute, second, millisecond, microsecond, nanosecond;
     if (typeof item === 'object' && item) {
       if (ES.IsTemporalTime(item)) {
+        hour = GetSlot(item, HOUR);
         minute = GetSlot(item, MINUTE);
         second = GetSlot(item, SECOND);
         millisecond = GetSlot(item, MILLISECOND);
         microsecond = GetSlot(item, MICROSECOND);
         nanosecond = GetSlot(item, NANOSECOND);
       } else {
-        // Intentionally alphabetical
+        // Intentionally largest to smallest units
         ({ hour, minute, second, millisecond, microsecond, nanosecond } = ES.ToTemporalTimeRecord(item));
       }
     } else {

polyfill/test/time.mjs

@@ -12,10 +12,10 @@ import Pretty from '@pipobscure/demitasse-pretty';
 const { reporter } = Pretty;
 
 import { strict as assert } from 'assert';
-const { equal, notEqual, throws } = assert;
+const { equal, notEqual, throws, deepEqual } = assert;
 
 import * as Temporal from 'proposal-temporal';
-const { Time } = Temporal;
+const { Time, DateTime } = Temporal;
 
 describe('Time', () => {
   describe('Structure', () => {
@@ -367,6 +367,14 @@ describe('Time', () => {
         equal(`${Time.from('23:59:60', { disambiguation: 'reject' })}`, '23:59:59');
       });
       it('Time.from(number) is converted to string', () => equal(`${Time.from(1523)}`, `${Time.from('1523')}`));
+      it('Time.from(time) returns the same properties', () => {
+        const t = Time.from('2020-02-12T11:42+01:00[Europe/Amsterdam]');
+        deepEqual(Time.from(t).getFields(), t.getFields());
+      });
+      it('Time.from(dateTime) returns the same time properties', () => {
+        const dt = DateTime.from('2020-02-12T11:42+01:00[Europe/Amsterdam]');
+        deepEqual(Time.from(dt).getFields(), dt.toTime().getFields());
+      });
       it('Time.from(time) is not the same object', () => {
         const t = Time.from('2020-02-12T11:42+01:00[Europe/Amsterdam]');
         notEqual(Time.from(t), t);