fix: Avoid dtypes imports

https://results.pre-commit.ci/run/github/760058710/1747601128.e2dXEDsSTO2XfoU3gLZrRg

Author: dangotbanned

narwhals/_plan/demo.py

@@ -17,8 +17,8 @@
 from narwhals._plan.literal import SeriesLiteral
 from narwhals._plan.strings import ConcatHorizontal
 from narwhals.dtypes import DType
-from narwhals.dtypes import Unknown
 from narwhals.exceptions import OrderDependentExprError
+from narwhals.utils import Version
 from narwhals.utils import flatten
 
 if t.TYPE_CHECKING:
@@ -56,7 +56,7 @@ def lit(
     if isinstance(value, DummySeries):
         return SeriesLiteral(value=value).to_literal().to_narwhals()
     if dtype is None or not isinstance(dtype, DType):
-        dtype = Unknown()
+        dtype = Version.MAIN.dtypes.Unknown()
     return ScalarLiteral(value=value, dtype=dtype).to_literal().to_narwhals()
 
 

narwhals/_plan/dummy.py

@@ -13,7 +13,7 @@
 from narwhals._plan.options import SortOptions
 from narwhals._plan.window import Over
 from narwhals.dtypes import DType
-from narwhals.dtypes import Unknown
+from narwhals.utils import Version
 from narwhals.utils import flatten
 
 if TYPE_CHECKING:
@@ -43,7 +43,7 @@ def alias(self, name: str) -> Self:
         return self._from_ir(expr.Alias(expr=self._ir, name=name))
 
     def cast(self, dtype: DType | type[DType]) -> Self:
-        dtype = dtype if isinstance(dtype, DType) else Unknown()
+        dtype = dtype if isinstance(dtype, DType) else Version.MAIN.dtypes.Unknown()
         return self._from_ir(expr.Cast(expr=self._ir, dtype=dtype))
 
     def count(self) -> Self:
@@ -215,9 +215,7 @@ class DummyCompliantSeries:
 
     @property
     def dtype(self) -> DType:
-        from narwhals.dtypes import Float64
-
-        return Float64()
+        return Version.MAIN.dtypes.Float64()
 
     @property
     def name(self) -> str: