handling stale functions

[getzdan]

When changing a source file, sometimes you change the signature of functions. Revise defines the new functions, but the old functions still pollute the run-time. Many times, the source still includes calls to the old function signature (because nobody remembers to change all calls), so they silently run. Having just encountered such a potential pitfall, I'm putting it out here.

In any case, if functions from a Module / file could be identified in the run-time, then all functions from a "revised" file about to be run, can be redefined to indicate them being stale. And then the redefinitions would overwrite them again.

This problem doesn't necessarily have a simple solution, or one which should be under Revise.jl.

[timholy]

See JuliaLang/julia#20048. Without @uncallable, it should be possible for Revise to notice that a method has been deleted and then redefine it so that calling it is an error. Unfortunately, that won't help in cases where you're deleting a more specific method and replacing it with a more generic method.