Default constraint names use the str() function. (#265)

In the case of the diameter constraint, it will return either "Radius" or "Diameter"
depending on the setting.

If you edit the name of the Diameter constarint, it replaces the default naming.

class_defines.py

@@ -2179,11 +2179,9 @@ def set_origin_props(e):
 
 
 class GenericConstraint:
+
     def _name_getter(self):
-        name = self.get("name")
-        if not name:
-            return type(self).__name__
-        return name
+        return self.get("name", str(self))
 
     def _name_setter(self, new_name):
         self["name"] = new_name
@@ -2827,7 +2825,10 @@ def use_radius_setter(self, setting):
             # Avoid triggering the property's update callback
             self["value"] = distance
 
-    label = "Diameter"
+    @property
+    def label(self):
+        return "Radius" if self.setting else "Diameter"
+
     value: FloatProperty(
         name="Size",
         subtype="DISTANCE",