From 5d5ca83884d9f965a520cdcafc5b7da3aea2fb85 Mon Sep 17 00:00:00 2001
From: Philip Chimento <pchimento@igalia.com>
Date: Fri, 6 Nov 2020 16:48:20 -0800
Subject: [PATCH] Specify ZonedDateTime.toPlain{YearMonth,MonthDay}()

And make a small adjustment to the polyfill to match.

See: #569
---
 polyfill/lib/zoneddatetime.mjs |  8 ++++----
 spec/zoneddatetime.html        | 14 ++++++++++++--
 2 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/polyfill/lib/zoneddatetime.mjs b/polyfill/lib/zoneddatetime.mjs
index f7c84be2b0..6c3322445b 100644
--- a/polyfill/lib/zoneddatetime.mjs
+++ b/polyfill/lib/zoneddatetime.mjs
@@ -657,16 +657,16 @@ export class ZonedDateTime {
     if (!ES.IsTemporalZonedDateTime(this)) throw new TypeError('invalid receiver');
     const YearMonth = GetIntrinsic('%Temporal.PlainYearMonth%');
     const calendar = GetSlot(this, CALENDAR);
-    const fieldNames = ES.CalendarFields(calendar, ['day', 'month', 'year']);
-    const fields = ES.ToTemporalDateFields(this, fieldNames);
+    const fieldNames = ES.CalendarFields(calendar, ['month', 'year']);
+    const fields = ES.ToTemporalYearMonthFields(this, fieldNames);
     return calendar.yearMonthFromFields(fields, {}, YearMonth);
   }
   toPlainMonthDay() {
     if (!ES.IsTemporalZonedDateTime(this)) throw new TypeError('invalid receiver');
     const MonthDay = GetIntrinsic('%Temporal.PlainMonthDay%');
     const calendar = GetSlot(this, CALENDAR);
-    const fieldNames = ES.CalendarFields(calendar, ['day', 'month', 'year']);
-    const fields = ES.ToTemporalDateFields(this, fieldNames);
+    const fieldNames = ES.CalendarFields(calendar, ['day', 'month']);
+    const fields = ES.ToTemporalMonthDayFields(this, fieldNames);
     return calendar.monthDayFromFields(fields, {}, MonthDay);
   }
   getFields() {
diff --git a/spec/zoneddatetime.html b/spec/zoneddatetime.html
index 0ad03b05e1..7054568f90 100644
--- a/spec/zoneddatetime.html
+++ b/spec/zoneddatetime.html
@@ -908,7 +908,12 @@ <h1>Temporal.ZonedDateTime.prototype.toPlainYearMonth ( )</h1>
         1. Let _timeZone_ be _zonedDateTime_.[[TimeZone]].
         1. Let _instant_ be ? CreateTemporalInstant(_zonedDateTime_.[[Nanoseconds]]).
         1. Let _temporalDateTime_ be ? GetTemporalDateTimeFor(_timeZone_, _instant_).
-        1. Return ? <mark>create via `calendar.yearMonthFromFields()`</mark>.
+        1. Let _calendar_ be _zonedDateTime_.[[Calendar]].
+        1. Let _fieldNames_ be ? CalendarFields(_calendar_, « *"month"*, *"year"* »).
+        1. Let _fields_ be ? ToTemporalYearMonthFields(_temporalDateTime_, _fieldNames_).
+        1. Let _yearMonthFromFields_ be ? Get(_calendar_, *"yearMonthFromFields"*).
+        1. Let _options_ be ? OrdinaryObjectCreate(%Object.prototype%).
+        1. Return ? Call(_yearMonthFromFields_, _calendar_, « _fields_, _options_, %Temporal.PlainMonthDay% »).
       </emu-alg>
     </emu-clause>
 
@@ -923,7 +928,12 @@ <h1>Temporal.ZonedDateTime.prototype.toPlainMonthDay ( )</h1>
         1. Let _timeZone_ be _zonedDateTime_.[[TimeZone]].
         1. Let _instant_ be ? CreateTemporalInstant(_zonedDateTime_.[[Nanoseconds]]).
         1. Let _temporalDateTime_ be ? GetTemporalDateTimeFor(_timeZone_, _instant_).
-        1. Return ? <mark>create via `calendar.monthDayFromFields()`</mark>.
+        1. Let _calendar_ be _zonedDateTime_.[[Calendar]].
+        1. Let _fieldNames_ be ? CalendarFields(_calendar_, « *"day"*, *"month"* »).
+        1. Let _fields_ be ? ToTemporalMonthDayFields(_temporalDateTime_, _fieldNames_).
+        1. Let _monthDayFromFields_ be ? Get(_calendar_, *"monthDayFromFields"*).
+        1. Let _options_ be ? OrdinaryObjectCreate(%Object.prototype%).
+        1. Return ? Call(_monthDayFromFields_, _calendar_, « _fields_, _options_, %Temporal.PlainMonthDay% »).
       </emu-alg>
     </emu-clause>