CLN: require td64 in TimedeltaBlock (#37018)

Author: jbrockmendel

pandas/core/internals/blocks.py

@@ -2376,7 +2376,11 @@ class TimeDeltaBlock(DatetimeLikeBlockMixin, IntBlock):
 
     def _maybe_coerce_values(self, values):
         if values.dtype != TD64NS_DTYPE:
-            # e.g. non-nano or int64
+            # non-nano we will convert to nano
+            if values.dtype.kind != "m":
+                # caller is responsible for ensuring timedelta64 dtype
+                raise TypeError(values.dtype)  # pragma: no cover
+
             values = TimedeltaArray._from_sequence(values)._data
         if isinstance(values, TimedeltaArray):
             values = values._data

pandas/core/missing.py

@@ -573,9 +573,9 @@ def interpolate_2d(
     if ndim == 1:
         result = result[0]
 
-    if orig_values.dtype.kind == "M":
-        # convert float back to datetime64
-        result = result.astype(orig_values.dtype)
+    if orig_values.dtype.kind in ["m", "M"]:
+        # convert float back to datetime64/timedelta64
+        result = result.view(orig_values.dtype)
 
     return result