PYTHON-3679 Fix bson/decimal128.py:103: error: Unsupported operand types for + ("Literal['n']"

Author: ShaneHarvey

bson/decimal128.py

@@ -19,7 +19,7 @@
 
 import decimal
 import struct
-from typing import Any, Sequence, Tuple, Type, Union
+from typing import Any, Sequence, Tuple, Type, Union, cast
 
 _PACK_64 = struct.Struct("<Q").pack
 _UNPACK_64 = struct.Struct("<Q").unpack
@@ -100,7 +100,7 @@ def _decimal_to_128(value: _VALUE_OPTIONS) -> Tuple[int, int]:
         if significand & (1 << i):
             high |= 1 << (i - 64)
 
-    biased_exponent = exponent + _EXPONENT_BIAS
+    biased_exponent = cast(int, exponent) + _EXPONENT_BIAS
 
     if high >> 49 == 1:
         high = high & 0x7FFFFFFFFFFF