fix casting

Author: TiffL

pandas/core/indexes/base.py

@@ -6209,12 +6209,6 @@ def _maybe_downcast_for_indexing(self, other: Index) -> tuple[Index, Index]:
                 # let's instead try with a straight Index
                 self = Index(self._values)
 
-        elif self.inferred_type == "string" and isinstance(other, ABCPeriodIndex):
-            try:
-                return self.astype(other.dtype), other
-            except (TypeError, ValueError):
-                return self, other
-
         if not is_object_dtype(self.dtype) and is_object_dtype(other.dtype):
             # Reverse op so we dont need to re-implement on the subclasses
             other, self = other._maybe_downcast_for_indexing(self)

pandas/core/indexes/period.py

@@ -515,8 +515,8 @@ def shift(self, periods: int = 1, freq=None) -> Self:
         return self + periods
 
     def _difference(self, other, sort=None) -> PeriodIndex:
-        if not isinstance(other, PeriodIndex):
-            self, other = self._maybe_downcast_for_indexing(other)
+        if isinstance(other, Index) and other.inferred_type == "string":
+            other = other.astype(self.dtype)
 
         return super()._difference(other, sort=sort)