typecheck.py: use isinstance for typing.Reversible

Technologicat · claude · Technologicat · commit 443a9c14d1b0 · 2026-03-12T11:41:30.000+02:00
The hasattr(__reversed__) check was a workaround for Python 3.5
where typing.Reversible was a protocol that rejected isinstance.
Works fine on 3.10+.

Co-Authored-By: Claude Opus 4.6 &lt;noreply@anthropic.com&gt;
diff --git a/unpythonic/typecheck.py b/unpythonic/typecheck.py
@@ -113,7 +113,7 @@ def isNewType(T):
             return isinstance(value, U)
 
     if T is typing.Reversible:  # can't non-destructively check element type
-        return hasattr(value, "__reversed__")
+        return isinstance(value, typing.Reversible)
 
     # "Protocols cannot be used with isinstance()", so:
     for U in (typing.SupportsInt,
