Marcel Taeumel uploaded a new version of Collections to project The Trunk:
http://source.squeak.org/trunk/Collections-mt.935.mcz

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

Name: Collections-mt.935
Author: mt
Time: 13 April 2021, 5:05:38.802381 pm
UUID: 17800d3d-5975-7144-9608-deb8f5fccc2c
Ancestors: Collections-nice.934

Document thread-safety in symbol table(s) as class comment. Thanks to Levente (ul)!

=============== Diff against Collections-nice.934 ===============

Item was changed:
  String subclass: #Symbol
  	instanceVariableNames: ''
  	classVariableNames: 'NewSymbols SymbolTable'
  	poolDictionaries: ''
  	category: 'Collections-Strings'!
  
+ !Symbol commentStamp: 'mt 4/13/2021 17:04' prior: 0!
+ I represent Strings that are created uniquely. Thus, someString asSymbol == someString asSymbol.
+ 
+ ATTENTION!! To ensure consistency and thread safety without using a mutex, the two WeakSets which make up the symbol table are treated as if they were immutable. Removing from them without creating a copy just breaks that contract.!
- !Symbol commentStamp: '<historical>' prior: 0!
- I represent Strings that are created uniquely. Thus, someString asSymbol == someString asSymbol.!