From 86cd77754a1fbd49a6f1e9357736d6cff69dea1a Mon Sep 17 00:00:00 2001
From: Paul Dicker <pitdicker@gmail.com>
Date: Fri, 19 May 2023 18:48:46 +0200
Subject: [PATCH] Use `NaiveDateTime::and_local_timezone` in
 `TimeZone::from_local_datetime`

---
 src/naive/datetime/mod.rs |  8 ++++++++
 src/offset/mod.rs         | 29 +++++++++++++++++++++++++++--
 2 files changed, 35 insertions(+), 2 deletions(-)

diff --git a/src/naive/datetime/mod.rs b/src/naive/datetime/mod.rs
index 0ea6f24153..4cdeb60b3e 100644
--- a/src/naive/datetime/mod.rs
+++ b/src/naive/datetime/mod.rs
@@ -948,6 +948,14 @@ impl NaiveDateTime {
     /// ```
     #[must_use]
     pub fn and_local_timezone<Tz: TimeZone>(&self, tz: Tz) -> LocalResult<DateTime<Tz>> {
+        self.and_local_timezone_internal(&tz)
+    }
+
+    // FIXME: ideally tz should be taken by reference, but that would be a breaking change.
+    pub(crate) fn and_local_timezone_internal<Tz: TimeZone>(
+        &self,
+        tz: &Tz,
+    ) -> LocalResult<DateTime<Tz>> {
         let local_result_offset = tz.offset_from_local_datetime(self);
         local_time_min_offset(local_result_offset, self).unwrap_or(LocalResult::None)
     }
diff --git a/src/offset/mod.rs b/src/offset/mod.rs
index ea53915309..64479f5321 100644
--- a/src/offset/mod.rs
+++ b/src/offset/mod.rs
@@ -473,8 +473,7 @@ pub trait TimeZone: Sized + Clone {
     /// Converts the local `NaiveDateTime` to the timezone-aware `DateTime` if possible.
     #[allow(clippy::wrong_self_convention)]
     fn from_local_datetime(&self, local: &NaiveDateTime) -> LocalResult<DateTime<Self>> {
-        self.offset_from_local_datetime(local)
-            .map(|offset| DateTime::from_naive_utc_and_offset(*local - offset.fix(), offset))
+        local.and_local_timezone_internal(self)
     }
 
     /// Creates the offset for given UTC `NaiveDate`. This cannot fail.
@@ -504,6 +503,32 @@ pub trait TimeZone: Sized + Clone {
 mod tests {
     use super::*;
 
+    #[test]
+    fn test_fixed_offset_min_max_dates() {
+        for offset_hour in -23..=23 {
+            dbg!(offset_hour);
+            let offset = FixedOffset::east_opt(offset_hour * 60 * 60).unwrap();
+
+            let local_max = offset.from_utc_datetime(&NaiveDateTime::MAX);
+            assert_eq!(local_max.naive_utc(), NaiveDateTime::MAX);
+            let local_min = offset.from_utc_datetime(&NaiveDateTime::MIN);
+            assert_eq!(local_min.naive_utc(), NaiveDateTime::MIN);
+
+            let local_max = offset.from_local_datetime(&NaiveDateTime::MAX);
+            if offset_hour >= 0 {
+                assert_eq!(local_max.unwrap().naive_local(), NaiveDateTime::MAX);
+            } else {
+                assert_eq!(local_max, LocalResult::None);
+            }
+            let local_min = offset.from_local_datetime(&NaiveDateTime::MIN);
+            if offset_hour <= 0 {
+                assert_eq!(local_min.unwrap().naive_local(), NaiveDateTime::MIN);
+            } else {
+                assert_eq!(local_min, LocalResult::None);
+            }
+        }
+    }
+
     #[test]
     fn test_negative_millis() {
         let dt = Utc.timestamp_millis_opt(-1000).unwrap();