wip operator: added thoughts & only using in sqrt

Author: ym-pett

narwhals/_sql/expr.py

@@ -249,7 +249,7 @@ def _rolling_window_func(
             end = 0
 
         def func(
-            df: SQLLazyFrameT, inputs: WindowInputs[NativeSQLExprT]
+            df: SQLLazyFrameT, inputs: WindowInputs[NativeExprT]
         ) -> Sequence[NativeExprT]:
             if func_name in {"sum", "mean"}:
                 func_: str = func_name

narwhals/_sql/typing.py

@@ -4,22 +4,6 @@
 
 from narwhals._compliant.expr import NativeExpr
 
-if TYPE_CHECKING:
-    from narwhals._sql.dataframe import SQLLazyFrame
-    from narwhals._sql.expr import SQLExpr
-    from narwhals.dtypes import Boolean
-    from typing_extensions import Self
-
-    # TODO: @mp, understand why these are here & if we need one for NativeSQLExprT
-    SQLExprAny = SQLExpr[Any, Any]
-    SQLLazyFrameAny = SQLLazyFrame[Any, Any, Any]
-
-SQLExprT = TypeVar("SQLExprT", bound="SQLExprAny")
-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") 
-
 class NativeSQLExpr(NativeExpr):
     # both Self because we're comparing an expression with an expression? 
     def __gt__(self, value: Self) -> Self: ...
@@ -41,3 +25,22 @@ def __add__(self, value: Self) -> Self: ...
     def __truediv__(self, value: Self) -> Self: ...
 
     def __mul__(self, value: Self) -> Self: ...
+
+if TYPE_CHECKING:
+    from narwhals._sql.dataframe import SQLLazyFrame
+    from narwhals._sql.expr import SQLExpr
+    from narwhals.dtypes import Boolean
+    from typing_extensions import Self
+
+    # TODO: @mp, understand why these are here & if we need one for NativeSQLExprT;
+    # seem to reflect number of different 'catgories' each of the parent class has
+    # tbc! since NativeExpr only has Protocol, I don't think we need this for NativeSQLExpr
+    SQLExprAny = SQLExpr[Any, Any]
+    SQLLazyFrameAny = SQLLazyFrame[Any, Any, Any]
+
+SQLExprT = TypeVar("SQLExprT", bound="SQLExprAny")
+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") 
+