Fix default type for Numeric columns to Decimal (#132)

Author: martinstein

sqlalchemy-stubs/sql/sqltypes.pyi

@@ -78,7 +78,8 @@ class SmallInteger(Integer):
 class BigInteger(Integer):
     __visit_name__: str = ...
 
-class Numeric(_LookupExpressionAdapter, TypeEngine[float]):  # TODO: this can be also decimal.Decimal
+# TODO: This can also be float (however, decimal is the default)
+class Numeric(_LookupExpressionAdapter, TypeEngine[decimal.Decimal]):
     __visit_name__: str = ...
     precision: Optional[int] = ...
     scale: Optional[int] = ...
@@ -90,7 +91,7 @@ class Numeric(_LookupExpressionAdapter, TypeEngine[float]):  # TODO: this can be
     def literal_processor(self, dialect: Dialect) -> Callable[[Union[float, decimal.Decimal]], str]: ...
     @property
     def python_type(self) -> Union[Type[float], Type[decimal.Decimal]]: ...  # type: ignore  # return type incompatible
-    def bind_processor(self, dialect: Dialect) -> Optional[Callable[[Optional[str]], float]]: ...
+    def bind_processor(self, dialect: Dialect) -> Optional[Callable[[Optional[str]], decimal.Decimal]]: ...
     def result_processor(self, dialect: Dialect, coltype: Any) -> Optional[Callable[[Optional[Any]],
                                                                                     Optional[Union[float, decimal.Decimal]]]]: ...