From 648d069dddd0a4a5d6736d3bd83302169d6ec6d4 Mon Sep 17 00:00:00 2001
From: Callum Forrester <callum.forrester@diamond.ac.uk>
Date: Mon, 16 Sep 2024 09:29:17 +0100
Subject: [PATCH] Reuse TypeVars

---
 src/scanspec/core.py  |  4 +++-
 src/scanspec/specs.py | 10 +++-------
 2 files changed, 6 insertions(+), 8 deletions(-)

diff --git a/src/scanspec/core.py b/src/scanspec/core.py
index 0cd5f2b4..b216b99a 100644
--- a/src/scanspec/core.py
+++ b/src/scanspec/core.py
@@ -21,6 +21,8 @@
 from pydantic_core.core_schema import tagged_union_schema
 
 __all__ = [
+    "Axis",
+    "OtherAxis",
     "if_instance_do",
     "AxesPoints",
     "Frames",
@@ -199,7 +201,7 @@ def if_instance_do(x: C, cls: type[C], func: Callable[[C], T]):
 
 
 #: A type variable for an `axis_` that can be specified for a scan
-Axis = TypeVar("Axis")
+Axis = TypeVar("Axis", covariant=True)
 
 #: Alternative axis variable to be used when two are required in the same type binding
 OtherAxis = TypeVar("OtherAxis")
diff --git a/src/scanspec/specs.py b/src/scanspec/specs.py
index 26253e56..5a7807e9 100644
--- a/src/scanspec/specs.py
+++ b/src/scanspec/specs.py
@@ -8,7 +8,7 @@
 from __future__ import annotations
 
 from collections.abc import Callable, Mapping
-from typing import Any, Generic, TypeVar, overload
+from typing import Any, Generic, overload
 
 import numpy as np
 import numpy.typing as npt
@@ -16,8 +16,10 @@
 from pydantic.dataclasses import dataclass
 
 from .core import (
+    Axis,
     Frames,
     Midpoints,
+    OtherAxis,
     Path,
     SnakedFrames,
     StrictConfig,
@@ -49,12 +51,6 @@
 #: Can be used as a special key to indicate how long each point should be
 DURATION = "DURATION"
 
-#: A type variable for an `axis_` that can be specified for a scan
-Axis = TypeVar("Axis", covariant=True)
-
-#: Alternative axis variable to be used when two are required in the same type binding
-OtherAxis = TypeVar("OtherAxis")
-
 
 @discriminated_union_of_subclasses
 class Spec(Generic[Axis]):