Is there a strong indication to use add: anAssociation over at:put: here? The latter is more idiomatic and does not use the implementation detail that a dictionary is made up of associations.
A new version of Collections was added to project The Inbox:
http://source.squeak.org/inbox/Collections-ct.860.mcz
==================== Summary ====================
Name: Collections-ct.860
Author: ct
Time: 15 November 2019, 1:58:56.418005 pm
UUID: f6364e7f-08c8-694a-9060-21bc0a0c28d4
Ancestors: Collections-pre.857
Add convenience constructor for Dictionary
Dictionary fromKeys: 'wasd' values: '8426'
=============== Diff against Collections-pre.857 ===============
Item was added:
+ ----- Method: Dictionary class>>fromKeys:values: (in category 'instance creation') -----
+ fromKeys: keys values: values
+
+ | dictionary |
+ self assert: [keys size = values size].
+ dictionary := self new: keys size.
+ keys with: values do: [:key :value |
+ dictionary add: key -> value].
+ ^ dictionary!