Quoting the docs,
Precompilation cache files store definitions of modules, types, methods, and constants. They may also store method specializations and the code generated for them, but this typically requires that the developer add explicit
precompiledirectives or execute workloads that force compilation during the package build.
However, if you update the module’s dependencies or change its source code, the module is automatically recompiled upon
usingorimport.
In short, whenever you using or import after editing the source code, you are doing a change as big as reevaluating a module. It’s quicker to make small changes like interactively replacing a method in a REPL session. Some changes can’t be made (editing a struct’s field structure), and small edits out of order can be different from rerunning a whole thing, but you can get a lot of work done through small interactive changes between the big overhauls. Revise.jl is useful for making source code edits automatically perform those small changes in a REPL session, so you don’t have to repeat it manually in the session.