Comment by igouy
Smalltalk stores:
memory snapshot "image"
AND "change log" text file
AND "sources" text file.
https://cuis-smalltalk.github.io/TheCuisBook/Code-Management...
If the "sources" file is missing the byte code will be decompiled to show class and method definitions, but the original names will be unknown.
It is only an implementation detail. It is a matter of change of a few methods only to store sources directly in methods. I tried that once.