find_subcommand_mut doesn't seem to be usable in a loop

[jyn514]

here is a small clap program that does not compile: https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=b452d684735297330b56c4353ebbb98f

as far as i can tell, the problem is this: on each iteration of the loop, the lifetime returned by find_subcommand_mut shrinks in scope: it can't be live for previous iterations. but the compiler is trying to unify them all, and it gets mad that they don't match up.

i am kind of surprised that no one has run into this before; i guess everyone has a fixed number of times they call find_subcommand_mut, they're not doing programatically? the only code example i found searching was #1350 (comment), which indeed does not use a loop (it calls the function twice in a row instead).

is there some way to get this to work? my use case is that i want to add support for user-defined aliases by

1. programatically finding the deepest nested subcommand that matches the alias definition
2. running *subcmd = subcmd.visible_alias(alias_name)

2 works ok; the trouble i'm having is with 1.

[jyn514]

this error is fixed by polonius :( rust-lang/rust#125217

[jyn514]

here is the workaround: https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=2fee0a2398b2eff2a24a6219a80113dc