Rewrite methods when type checking is disabled?

[maedi]

When config.type_checking = false we currently prepend a guard method that "untypes" the user's code. So when calling and debugging methods, there is always a guard method to go through. For more info see Redefiner

Should we instead rewrite the user's methods in the same class that they were defined? (no prepend). This may improve performance (by much?) and simplify debugging (one less step) and stack traces (one less line), but it involves rewriting the user's code; evaluating type expressions to get the default value and literally rewriting the method's params. We would likely use eval() to do this so that we can mirror the line numbers of the untyped method with the line numbers of the original typed method.

[paul-c-hartman]

Are we opposed to rewriting stack traces, interfacing with debuggers, etc.? Here's some quick research based on that:

• Lines in stack traces can be removed for transparency, IRB does this, though as you can see it has a configuration option to turn it off (IRB.conf[:BACKTRACE_FILTER]).
• The debug gem has a built-in configuration option (look for RUBY_DEBUG_SKIP_PATH) and helper to skip frames from specified directories transparently to the user.
• The byebug gem has an internal list of files which the debugger ignores.
• I briefly looked at the pry and pry-byebug repositories and couldn't find any obvious way to make this work with them, though that doesn't mean there isn't one.

It would probably mean more maintenance work and it would definitely mean worse overall performance, but it seems like this poll is meant to choose between the lesser of two evils (or at least suboptimals).

At the very least, I think rewrites with eval should be configurable.