Chrono: makes FromPyObject impl on DateTime generic

ToPyObject was already generic

newsfragments/3663.changed.md

@@ -0,0 +1 @@
+Implements `FromPyObject` on `chrono::DateTime<Tz>` for all `Tz` and not only `FixedOffset` and `Utc`

src/conversions/chrono.rs

@@ -200,34 +200,24 @@ impl<Tz: TimeZone> IntoPy<PyObject> for DateTime<Tz> {
     }
 }
 
-impl FromPyObject<'_> for DateTime<FixedOffset> {
-    fn extract(ob: &PyAny) -> PyResult<DateTime<FixedOffset>> {
+impl<Tz: TimeZone + for<'a> FromPyObject<'a>> FromPyObject<'_> for DateTime<Tz> {
+    fn extract(ob: &PyAny) -> PyResult<DateTime<Tz>> {
         let dt: &PyDateTime = ob.downcast()?;
-        let tz: FixedOffset = if let Some(tzinfo) = dt.get_tzinfo() {
+        let tz = if let Some(tzinfo) = dt.get_tzinfo() {
             tzinfo.extract()?
         } else {
             return Err(PyTypeError::new_err(
                 "expected a datetime with non-None tzinfo",
             ));
         };
         let dt = NaiveDateTime::new(py_date_to_naive_date(dt)?, py_time_to_naive_time(dt)?);
-        // `FixedOffset` cannot have ambiguities so we don't have to worry about DST folds and such
-        Ok(dt.and_local_timezone(tz).unwrap())
-    }
-}
-
-impl FromPyObject<'_> for DateTime<Utc> {
-    fn extract(ob: &PyAny) -> PyResult<DateTime<Utc>> {
-        let dt: &PyDateTime = ob.downcast()?;
-        let _: Utc = if let Some(tzinfo) = dt.get_tzinfo() {
-            tzinfo.extract()?
-        } else {
-            return Err(PyTypeError::new_err(
-                "expected a datetime with non-None tzinfo",
-            ));
-        };
-        let dt = NaiveDateTime::new(py_date_to_naive_date(dt)?, py_time_to_naive_time(dt)?);
-        Ok(dt.and_utc())
+        dt.and_local_timezone(tz).single().ok_or_else(|| {
+            PyValueError::new_err(format!(
+                "The datetime {} contains an incompatible or ambiguous timezone",
+                ob.repr()
+                    .unwrap_or_else(|_| PyUnicode::new(ob.py(), "repr failed"))
+            ))
+        })
     }
 }