[foobarbaz33]

I was coming here to say: "grep as IDE". It's dynamic language tooling 101.

Find defs and refs. Master a little bit of regex and you will reduce false positives.

Grep serves as a rudimentary autocomplete. find the definition, open in a buffer, observe fields. This is analogous to an autocomplete popup displayed inline. The buffer can now power your contextual completions, similar to an inline popup.