Hi, I want to be able to identify whether a line of code will return,
because I want to modify it to capture it's return value. If it returns,
this results in a syntax error:

$ echo 'def m() a = return end' | ruby -c
-:1: void value expression

$ echo $?
1


Here are some tests:
https://github.com/JoshCheek/seeing_is_believing/blob/54f4044e1c858777f8b0beb690b9dafa9d497106/spec/syntax_analyzer_spec.rb#L114-126

Here is what I tried (hooking into `on_kw "return"` callback in Ripper):
https://github.com/JoshCheek/seeing_is_believing/blob/54f4044e1c858777f8b0beb690b9dafa9d497106/lib/seeing_is_believing/syntax_analyzer.rb#L123-138