Add epoch_ns_for_utc to all Plain APIs (#700)

The spec changed, the old API isn't useful anymore:
tc39/proposal-temporal#3212

Author: Manishearth

src/builtins/core/plain_date.rs

@@ -17,6 +17,7 @@ use crate::{
     },
     parsers::IxdtfStringBuilder,
     provider::{NeverProvider, TimeZoneProvider},
+    unix_time::EpochNanoseconds,
     MonthCode, TemporalError, TemporalResult, TimeZone,
 };
 use alloc::string::String;
@@ -685,6 +686,18 @@ impl PlainDate {
             epoch_ns.offset,
         )
     }
+
+    /// Gets the EpochNanoseconds represented by this PlainDate
+    /// (using noon time, and UTC timezone)
+    ///
+    // Useful for implementing HandleDateTimeTemporalYearMonth
+    pub fn epoch_ns_for_utc(&self) -> EpochNanoseconds {
+        // 2. Let isoDateTime be CombineISODateAndTimeRecord(temporalYearMonth.[[ISODate]], NoonTimeRecord()).
+        let iso = IsoDateTime::new(self.iso, IsoTime::noon());
+        debug_assert!(iso.is_ok());
+        // 3. Let epochNs be ? GetUTCEpochNanoseconds(isoDateTime).
+        iso.unwrap_or_default().as_nanoseconds()
+    }
 }
 
 // ==== Trait impls ====

src/builtins/core/plain_date_time.rs

@@ -19,6 +19,7 @@ use crate::{
     parsers::IxdtfStringBuilder,
     primitive::FiniteF64,
     provider::{NeverProvider, TimeZoneProvider},
+    unix_time::EpochNanoseconds,
     MonthCode, TemporalError, TemporalResult, TimeZone,
 };
 use alloc::string::String;
@@ -907,6 +908,15 @@ impl PlainDateTime {
         ))
     }
 
+    /// Gets the EpochNanoseconds represented by this PlainDateTime
+    /// (using and UTC timezone)
+    ///
+    // Useful for implementing HandleDateTimeTemporalDateTime
+    pub fn epoch_ns_for_utc(&self) -> EpochNanoseconds {
+        // 3. Let epochNs be ? GetUTCEpochNanoseconds(isoDateTime).
+        self.iso.as_nanoseconds()
+    }
+
     /// Create a [`PlainDate`] from the current `PlainDateTime`.
     #[inline]
     pub fn to_plain_date(&self) -> PlainDate {

src/builtins/core/plain_month_day.rs

@@ -364,6 +364,18 @@ impl PlainMonthDay {
             .ns)
     }
 
+    /// Gets the EpochNanoseconds represented by this MonthDay
+    /// (using the reference year, noon time, and UTC timezone)
+    ///
+    // Useful for implementing HandleDateTimeTemporalYearMonth
+    pub fn epoch_ns_for_utc(&self) -> EpochNanoseconds {
+        // 2. Let isoDateTime be CombineISODateAndTimeRecord(temporalMonthDay.[[ISODate]], NoonTimeRecord()).
+        let iso = IsoDateTime::new(self.iso, IsoTime::noon());
+        debug_assert!(iso.is_ok());
+        // 3. Let epochNs be ? GetUTCEpochNanoseconds(isoDateTime).
+        iso.unwrap_or_default().as_nanoseconds()
+    }
+
     /// Creates a RFC9557 IXDTF string from the current `PlainMonthDay`.
     pub fn to_ixdtf_string(&self, display_calendar: DisplayCalendar) -> String {
         self.to_ixdtf_writeable(display_calendar)

src/builtins/core/plain_time.rs

@@ -7,11 +7,13 @@ use crate::{
     },
     error::ErrorMessage,
     iso::IsoTime,
+    iso::{IsoDate, IsoDateTime},
     options::{
         DifferenceOperation, DifferenceSettings, Overflow, ResolvedRoundingOptions,
         RoundingOptions, ToStringRoundingOptions, Unit, UnitGroup,
     },
     parsers::{parse_time, IxdtfStringBuilder},
+    unix_time::EpochNanoseconds,
     TemporalError, TemporalResult,
 };
 use alloc::string::String;
@@ -541,6 +543,19 @@ impl PlainTime {
         let builder = IxdtfStringBuilder::default().with_time(result, resolved.precision);
         Ok(builder)
     }
+
+    /// Gets the EpochNanoseconds represented by this PlainTime
+    /// (using the Unix epoch, and UTC timezone)
+    ///
+    // Useful for implementing HandleDateTimeTemporalTime
+    pub fn epoch_ns_for_utc(&self) -> EpochNanoseconds {
+        // 1. Let isoDate be CreateISODateRecord(1970, 1, 1).
+        // 2. Let isoDateTime be CombineISODateAndTimeRecord(isoDate, temporalTime.[[Time]]).
+        let iso = IsoDateTime::new(IsoDate::UNIX_EPOCH, self.iso);
+        debug_assert!(iso.is_ok());
+        // 3. Let epochNs be ? GetUTCEpochNanoseconds(isoDateTime).
+        iso.unwrap_or_default().as_nanoseconds()
+    }
 }
 
 impl From<PlainDateTime> for PlainTime {

src/builtins/core/plain_year_month.rs

@@ -598,9 +598,7 @@ impl PlainYearMonth {
     }
 
     /// Gets the epochMilliseconds represented by this YearMonth in the given timezone
-    /// (using the reference year, and noon time)
-    ///
-    // Useful for implementing HandleDateTimeTemporalYearMonth
+    /// (using the reference day, and noon time)
     pub fn epoch_ns_for_with_provider(
         &self,
         time_zone: TimeZone,
@@ -614,6 +612,18 @@ impl PlainYearMonth {
             .ns)
     }
 
+    /// Gets the EpochNanoseconds represented by this YearMonth
+    /// (using the reference day, noon time, and UTC timezone)
+    ///
+    // Useful for implementing HandleDateTimeTemporalYearMonth
+    pub fn epoch_ns_for_utc(&self) -> EpochNanoseconds {
+        // 2. Let isoDateTime be CombineISODateAndTimeRecord(temporalYearMonth.[[ISODate]], NoonTimeRecord()).
+        let iso = IsoDateTime::new(self.iso, IsoTime::noon());
+        debug_assert!(iso.is_ok());
+        // 3. Let epochNs be ? GetUTCEpochNanoseconds(isoDateTime).
+        iso.unwrap_or_default().as_nanoseconds()
+    }
+
     /// Returns a RFC9557 IXDTF string for the current `PlainYearMonth`
     #[inline]
     pub fn to_ixdtf_string(&self, display_calendar: DisplayCalendar) -> String {

src/iso.rs

@@ -264,6 +264,8 @@ pub struct IsoDate {
 }
 
 impl IsoDate {
+    pub(crate) const UNIX_EPOCH: Self = Self::new_unchecked(1970, 1, 1);
+
     /// Creates a new `IsoDate` without determining the validity.
     pub(crate) const fn new_unchecked(year: i32, month: u8, day: u8) -> Self {
         Self { year, month, day }