correct annotation in infer_kind

narwhals/_expression_parsing.py

@@ -30,6 +30,7 @@
     from narwhals.typing import CompliantSeries
     from narwhals.typing import CompliantSeriesT_co
     from narwhals.typing import IntoExpr
+    from narwhals.typing import _1DArray
 
     ArrowOrPandasLikeExpr = TypeVar(
         "ArrowOrPandasLikeExpr", bound=Union[ArrowExpr, PandasLikeExpr]
@@ -424,15 +425,17 @@ def all_exprs_are_aggs_or_literals(*args: IntoExpr, **kwargs: IntoExpr) -> bool:
     )
 
 
-def infer_expr_kind(into_expr: IntoExpr, *, strings_are_column_names: bool) -> ExprKind:
+def infer_kind(
+    obj: IntoExpr | _1DArray | object, *, strings_are_column_names: bool
+) -> ExprKind:
     from narwhals.expr import Expr
     from narwhals.series import Series
 
-    if isinstance(into_expr, Expr):
-        return into_expr._metadata["kind"]
-    if isinstance(into_expr, Series) or is_numpy_array(into_expr):
+    if isinstance(obj, Expr):
+        return obj._metadata["kind"]
+    if isinstance(obj, Series) or is_numpy_array(obj):
         return ExprKind.TRANSFORM
-    if isinstance(into_expr, str) and strings_are_column_names:
+    if isinstance(obj, str) and strings_are_column_names:
         return ExprKind.TRANSFORM
     return ExprKind.LITERAL
 
@@ -450,7 +453,7 @@ def apply_n_ary_operation(
         for comparand in comparands
     )
     kinds = [
-        infer_expr_kind(comparand, strings_are_column_names=strings_are_column_names)
+        infer_kind(comparand, strings_are_column_names=strings_are_column_names)
         for comparand in comparands
     ]
 

narwhals/dataframe.py

@@ -18,7 +18,7 @@
 from narwhals._expression_parsing import ExprKind
 from narwhals._expression_parsing import all_exprs_are_aggs_or_literals
 from narwhals._expression_parsing import check_expressions_transform
-from narwhals._expression_parsing import infer_expr_kind
+from narwhals._expression_parsing import infer_kind
 from narwhals.dependencies import get_polars
 from narwhals.dependencies import is_numpy_array
 from narwhals.dependencies import is_numpy_array_1d
@@ -89,11 +89,11 @@ def _flatten_and_extract(
         for expr in flatten(exprs):
             compliant_expr = self._extract_compliant(expr)
             out_exprs.append(compliant_expr)
-            out_kinds.append(infer_expr_kind(expr, strings_are_column_names=True))
+            out_kinds.append(infer_kind(expr, strings_are_column_names=True))
         for alias, expr in named_exprs.items():
             compliant_expr = self._extract_compliant(expr).alias(alias)
             out_exprs.append(compliant_expr)
-            out_kinds.append(infer_expr_kind(expr, strings_are_column_names=True))
+            out_kinds.append(infer_kind(expr, strings_are_column_names=True))
         return out_exprs, out_kinds
 
     @abstractmethod

narwhals/functions.py

@@ -19,7 +19,7 @@
 from narwhals._expression_parsing import check_expressions_transform
 from narwhals._expression_parsing import combine_metadata
 from narwhals._expression_parsing import extract_compliant
-from narwhals._expression_parsing import infer_expr_kind
+from narwhals._expression_parsing import infer_kind
 from narwhals.dataframe import DataFrame
 from narwhals.dataframe import LazyFrame
 from narwhals.dependencies import is_numpy_array
@@ -1438,7 +1438,7 @@ def then(self: Self, value: IntoExpr | Any) -> Then:
 
 class Then(Expr):
     def otherwise(self: Self, value: IntoExpr | Any) -> Expr:
-        kind = infer_expr_kind(value, strings_are_column_names=True)
+        kind = infer_kind(value, strings_are_column_names=True)
 
         def func(plx: CompliantNamespace[Any]) -> CompliantExpr[Any]:
             compliant_expr = self._to_compliant_expr(plx)