Remove ToString from ISO string parsing

This commit stops converting non-string primitive inputs to strings when
parsing ISO strings or subsets of ISO strings like time zone offsets.

While numbers are sometimes allowed for these fields, the result is
often brittle, yielding "data driven exceptions" that we've tried to
avoid.

Numbers can also be ambiguous, e.g. is a Number passed for
`offset` mean hours like an ISO string, minutes like
Date.p.getTimezoneOffset, of msecs like Date.p.getTime().

Objects are still coerced to strings when appropriate, e.g.
when parsing a string for the `offset` field.

spec/abstractops.html

@@ -623,8 +623,8 @@ <h1>ToRelativeTemporalObject ( _options_ )</h1>
         1. If _offsetString_ is *undefined*, then
           1. Set _offsetBehaviour_ to ~wall~.
       1. Else,
-        1. Let _string_ be ? ToString(_value_).
-        1. Let _result_ be ? ParseTemporalRelativeToString(_string_).
+        1. If _value_ is not a String, throw a *TypeError* exception.
+        1. Let _result_ be ? ParseTemporalRelativeToString(_value_).
         1. Let _offsetString_ be _result_.[[TimeZone]].[[OffsetString]].
         1. Let _timeZoneName_ be _result_.[[TimeZone]].[[Name]].
         1. If _timeZoneName_ is *undefined*, then
@@ -1832,6 +1832,9 @@ <h1>
             1. Else if _Conversion_ is ~ToPositiveIntegerWithTruncation~, then
               1. Set _value_ to ? ToPositiveIntegerWithTruncation(_value_).
               1. Set _value_ to 𝔽(_value_).
+            1. Else if _Conversion_ is ~StringOnly~, then
+              1. If _value_ is an Object, set _value_ to ? ToString(_value_).
+              1. Else if _value_ is not a String, throw a *TypeError* exception.
             1. Else,
               1. Assert: _Conversion_ is ~ToString~.
               1. Set _value_ to ? ToString(_value_).
@@ -1909,7 +1912,7 @@ <h1>
           </tr>
           <tr>
             <td>*"offset"*</td>
-            <td>~ToString~</td>
+            <td>~StringOnly~</td>
             <td>*undefined*</td>
           </tr>
           <tr>

spec/calendar.html

@@ -517,6 +517,7 @@ <h1>
         </dd>
       </dl>
       <emu-alg>
+        1. Assert: No non-String, non-Object value, when coerced to a String, is a built-in calendar identifier.
         1. If _temporalCalendarLike_ is *undefined* and _default_ is present, then
           1. Assert: IsBuiltinCalendar(_default_) is *true*.
           1. Return _default_.
@@ -525,8 +526,8 @@ <h1>
             1. Return _temporalCalendarLike_.[[Calendar]].
           1. If ? ObjectImplementsTemporalCalendarProtocol(_temporalCalendarLike_) is *false*, throw a *TypeError* exception.
           1. Return _temporalCalendarLike_.
-        1. Let _identifier_ be ? ToString(_temporalCalendarLike_).
-        1. Set _identifier_ to ? ParseTemporalCalendarString(_identifier_).
+        1. If _temporalCalendarLike_ is not a String, throw a *TypeError* exception.
+        1. Let _identifier_ be ? ParseTemporalCalendarString(_temporalCalendarLike_).
         1. If IsBuiltinCalendar(_identifier_) is *false*, throw a *RangeError* exception.
         1. Return the ASCII-lowercase of _identifier_.
       </emu-alg>
@@ -1013,17 +1014,18 @@ <h1>The Temporal.Calendar Constructor</h1>
     </ul>
 
     <emu-clause id="sec-temporal.calendar">
-      <h1>Temporal.Calendar ( _id_ )</h1>
+      <h1>Temporal.Calendar ( _identifier_ )</h1>
       <p>
         The `Temporal.Calendar` function performs the following steps when called:
       </p>
       <emu-alg>
         1. If NewTarget is *undefined*, then
           1. Throw a *TypeError* exception.
-        1. Set _id_ to ? ToString(_id_).
-        1. If IsBuiltinCalendar(_id_) is *false*, then
+        1. If _identifier_ is an Object, set _identifier_ to ? ToString(_identifier_).
+        1. Else if _identifier_ is not a String, throw a *TypeError* exception.
+        1. If IsBuiltinCalendar(_identifier_) is *false*, then
           1. Throw a *RangeError* exception.
-        1. Return ? CreateTemporalCalendar(_id_, NewTarget).
+        1. Return ? CreateTemporalCalendar(_identifier_, NewTarget).
       </emu-alg>
     </emu-clause>
   </emu-clause>

spec/duration.html

@@ -928,8 +928,8 @@ <h1>
       </dl>
       <emu-alg>
         1. If Type(_temporalDurationLike_) is not Object, then
-          1. Let _string_ be ? ToString(_temporalDurationLike_).
-          1. Return ? ParseTemporalDurationString(_string_).
+          1. If _temporalDurationLike_ is not a String, throw a *TypeError* exception.
+          1. Return ? ParseTemporalDurationString(_temporalDurationLike_).
         1. If _temporalDurationLike_ has an [[InitializedTemporalDuration]] internal slot, then
           1. Return ! CreateDurationRecord(_temporalDurationLike_.[[Years]], _temporalDurationLike_.[[Months]], _temporalDurationLike_.[[Weeks]], _temporalDurationLike_.[[Days]], _temporalDurationLike_.[[Hours]], _temporalDurationLike_.[[Minutes]], _temporalDurationLike_.[[Seconds]], _temporalDurationLike_.[[Milliseconds]], _temporalDurationLike_.[[Microseconds]], _temporalDurationLike_.[[Nanoseconds]]).
         1. Let _result_ be a new Duration Record with each field set to 0.

spec/instant.html

@@ -518,8 +518,8 @@ <h1>ToTemporalInstant ( _item_ )</h1>
             1. Return _item_.
           1. If _item_ has an [[InitializedTemporalZonedDateTime]] internal slot, then
             1. Return ! CreateTemporalInstant(_item_.[[Nanoseconds]]).
-        1. Let _string_ be ? ToString(_item_).
-        1. Let _epochNanoseconds_ be ? ParseTemporalInstant(_string_).
+        1. If _item_ is not a String, throw a *TypeError* exception.
+        1. Let _epochNanoseconds_ be ? ParseTemporalInstant(_item_).
         1. Return ! CreateTemporalInstant(ℤ(_epochNanoseconds_)).
       </emu-alg>
     </emu-clause>

spec/plaindate.html

@@ -756,8 +756,8 @@ <h1>ToTemporalDate ( _item_ [ , _options_ ] )</h1>
           1. Let _fields_ be ? PrepareTemporalFields(_item_, _fieldNames_, «»).
           1. Return ? CalendarDateFromFields(_calendar_, _fields_, _options_).
         1. Perform ? ToTemporalOverflow(_options_).
-        1. Let _string_ be ? ToString(_item_).
-        1. Let _result_ be ? ParseTemporalDateString(_string_).
+        1. If _item_ is not a String, throw a *TypeError* exception.
+        1. Let _result_ be ? ParseTemporalDateString(_item_).
         1. Assert: IsValidISODate(_result_.[[Year]], _result_.[[Month]], _result_.[[Day]]) is *true*.
         1. Let _calendar_ be _result_.[[Calendar]].
         1. If _calendar_ is *undefined*, set _calendar_ to *"iso8601"*.

spec/plaindatetime.html

@@ -916,8 +916,8 @@ <h1>ToTemporalDateTime ( _item_ [ , _options_ ] )</h1>
           1. Let _result_ be ? InterpretTemporalDateTimeFields(_calendar_, _fields_, _options_).
         1. Else,
           1. Perform ? ToTemporalOverflow(_options_).
-          1. Let _string_ be ? ToString(_item_).
-          1. Let _result_ be ? ParseTemporalDateTimeString(_string_).
+          1. If _item_ is not a String, throw a *TypeError* exception.
+          1. Let _result_ be ? ParseTemporalDateTimeString(_item_).
           1. Assert: IsValidISODate(_result_.[[Year]], _result_.[[Month]], _result_.[[Day]]) is *true*.
           1. Assert: IsValidTime(_result_.[[Hour]], _result_.[[Minute]], _result_.[[Second]], _result_.[[Millisecond]], _result_.[[Microsecond]], _result_.[[Nanosecond]]) is *true*.
           1. Let _calendar_ be _result_.[[Calendar]].

spec/plainmonthday.html

@@ -383,8 +383,8 @@ <h1>ToTemporalMonthDay ( _item_ [ , _options_ ] )</h1>
             1. Perform ! CreateDataPropertyOrThrow(_fields_, *"year"*, 𝔽(_referenceISOYear_)).
           1. Return ? CalendarMonthDayFromFields(_calendar_, _fields_, _options_).
         1. Perform ? ToTemporalOverflow(_options_).
-        1. Let _string_ be ? ToString(_item_).
-        1. Let _result_ be ? ParseTemporalMonthDayString(_string_).
+        1. If _item_ is not a String, throw a *TypeError* exception.
+        1. Let _result_ be ? ParseTemporalMonthDayString(_item_).
         1. Let _calendar_ be _result_.[[Calendar]].
         1. If _calendar_ is *undefined*, set _calendar_ to *"iso8601"*.
         1. If IsBuiltinCalendar(_calendar_) is *false*, throw a *RangeError* exception.

spec/plaintime.html

@@ -580,8 +580,8 @@ <h1>ToTemporalTime ( _item_ [ , _overflow_ ] )</h1>
           1. Let _result_ be ? ToTemporalTimeRecord(_item_).
           1. Set _result_ to ? RegulateTime(_result_.[[Hour]], _result_.[[Minute]], _result_.[[Second]], _result_.[[Millisecond]], _result_.[[Microsecond]], _result_.[[Nanosecond]], _overflow_).
         1. Else,
-          1. Let _string_ be ? ToString(_item_).
-          1. Let _result_ be ? ParseTemporalTimeString(_string_).
+          1. If _item_ is not a String, throw a *TypeError* exception.
+          1. Let _result_ be ? ParseTemporalTimeString(_item_).
           1. Assert: IsValidTime(_result_.[[Hour]], _result_.[[Minute]], _result_.[[Second]], _result_.[[Millisecond]], _result_.[[Microsecond]], _result_.[[Nanosecond]]) is *true*.
         1. Return ! CreateTemporalTime(_result_.[[Hour]], _result_.[[Minute]], _result_.[[Second]], _result_.[[Millisecond]], _result_.[[Microsecond]], _result_.[[Nanosecond]]).
       </emu-alg>

spec/plainyearmonth.html

@@ -497,8 +497,8 @@ <h1>ToTemporalYearMonth ( _item_ [ , _options_ ] )</h1>
           1. Let _fields_ be ? PrepareTemporalFields(_item_, _fieldNames_, «»).
           1. Return ? CalendarYearMonthFromFields(_calendar_, _fields_, _options_).
         1. Perform ? ToTemporalOverflow(_options_).
-        1. Let _string_ be ? ToString(_item_).
-        1. Let _result_ be ? ParseTemporalYearMonthString(_string_).
+        1. If _item_ is not a String, throw a *TypeError* exception.
+        1. Let _result_ be ? ParseTemporalYearMonthString(_item_).
         1. Let _calendar_ be _result_.[[Calendar]].
         1. If _calendar_ is *undefined*, set _calendar_ to *"iso8601"*.
         1. If IsBuiltinCalendar(_calendar_) is *false*, throw a *RangeError* exception.

spec/timezone.html

@@ -124,7 +124,8 @@ <h1>Temporal.TimeZone ( _identifier_ )</h1>
       <emu-alg>
         1. If NewTarget is *undefined*, then
           1. Throw a *TypeError* exception.
-        1. Set _identifier_ to ? ToString(_identifier_).
+        1. If _identifier_ is an Object, set _identifier_ to ? ToString(_identifier_).
+        1. Else if _identifier_ is not a String, throw a *TypeError* exception.
         1. If IsTimeZoneOffsetString(_identifier_) is *false*, then
           1. If IsAvailableTimeZoneName(_identifier_) is *false*, then
             1. Throw a *RangeError* exception.
@@ -612,13 +613,14 @@ <h1>
         <dd>It attempts to derive a value from _temporalTimeZoneLike_ that is suitable for storing in a Temporal.ZonedDateTime's [[TimeZone]] internal slot, and returns that value if found or throws an exception if not.</dd>
       </dl>
       <emu-alg>
+        1. Assert: No non-String, non-Object value, when coerced to a String, is an available time zone identifier.
         1. If Type(_temporalTimeZoneLike_) is Object, then
           1. If _temporalTimeZoneLike_ has an [[InitializedTemporalZonedDateTime]] internal slot, then
             1. Return _temporalTimeZoneLike_.[[TimeZone]].
           1. If ? ObjectImplementsTemporalTimeZoneProtocol(_temporalTimeZoneLike_) is *false*, throw a *TypeError* exception.
           1. Return _temporalTimeZoneLike_.
-        1. Let _identifier_ be ? ToString(_temporalTimeZoneLike_).
-        1. Let _parseResult_ be ? ParseTemporalTimeZoneString(_identifier_).
+        1. If _temporalTimeZoneLike_ is not a String, throw a *TypeError* exception.
+        1. Let _parseResult_ be ? ParseTemporalTimeZoneString(_temporalTimeZoneLike_).
         1. If _parseResult_.[[Name]] is not *undefined*, then
           1. Let _name_ be _parseResult_.[[Name]].
           1. If IsTimeZoneOffsetString(_name_) is *true*, return CanonicalizeTimeZoneOffsetString(_name_).

spec/zoneddatetime.html

@@ -1169,8 +1169,8 @@ <h1>
           1. Let _offsetOption_ be ? ToTemporalOffset(_options_, *"reject"*).
           1. Let _result_ be ? InterpretTemporalDateTimeFields(_calendar_, _fields_, _options_).
         1. Else,
-          1. Let _string_ be ? ToString(_item_).
-          1. Let _result_ be ? ParseTemporalZonedDateTimeString(_string_).
+          1. If _item_ is not a String, throw a *TypeError* exception.
+          1. Let _result_ be ? ParseTemporalZonedDateTimeString(_item_).
           1. Let _timeZoneName_ be _result_.[[TimeZone]].[[Name]].
           1. Assert: _timeZoneName_ is not *undefined*.
           1. Let _timeZone_ be ? ToTemporalTimeZoneSlotValue(_timeZoneName_).