wip operator: fixed NativeSQLExprT bound

Author: ym-pett

narwhals/_sql/expr.py

@@ -502,7 +502,7 @@ def round(self, decimals: int) -> Self:
     def sqrt(self) -> Self:
         def _sqrt(expr: NativeSQLExprT) -> NativeSQLExprT:
             return self._when(
-                expr < self._lit(0),  # type: ignore[operator]
+                expr < self._lit(0),  
                 self._lit(float("nan")),
                 self._function("sqrt", expr),
             )

narwhals/_sql/typing.py

@@ -45,5 +45,5 @@ def __mul__(self, value: Self) -> Self: ...
 SQLExprT_contra = TypeVar("SQLExprT_contra", bound="SQLExprAny", contravariant=True)
 SQLLazyFrameT = TypeVar("SQLLazyFrameT", bound="SQLLazyFrameAny")
 # TODO: @mp, should this be contravariant as to do with function arguments? think through!
-NativeSQLExprT = TypeVar("NativeSQLExprT", bound="NativeSQLExpr") 
+NativeSQLExprT = TypeVar("NativeSQLExprT", bound="NativeSQLExprAny")