Eliot Miranda uploaded a new version of Collections to project The Trunk:
http://source.squeak.org/trunk/Collections-eem.920.mcz

==================== Summary ====================

Name: Collections-eem.920
Author: eem
Time: 2 December 2020, 9:49:01.130251 pm
UUID: 3767683c-33f6-4874-9e6c-83719db04fe3
Ancestors: Collections-mt.919

Add Symbol>>isMessageSelector, implemented in terms of Scanner class>>isMessageSelector:

=============== Diff against Collections-mt.919 ===============

Item was added:
+ ----- Method: Symbol>>isMessageSelector (in category 'testing') -----
+ isMessageSelector
+ 	"Answer if the receiver is a valid message selector.  This method is not perfect.
+ 	 The compiler does allow all caps to be selectors but these are not included.
+ 	 If AllowUnderscoreSelectors is true then _ is a valid selector but this will be excluded
+ 	 also.  But it is IMO more useful to exclude class names and hence exclude some rarely
+ 	 used selectors than to erroneously identify class names as message selectors."
+ 
+ 	^Scanner isMessageSelector: self!