Is bool::to_string() guaranteed to yield "true" and "false"?

[jofas]

Here is a previous topic discussing whether changes to output of Display should be considered breaking:

Are changes to fmt::Display considered breaking?

As the title says: if I change the way a struct is formatted via fmt::Display, is this considered a breaking change? This would seem to be a "Behavioral change" as defined in RFC 1105, but the rule-of-thumb stated in that section raises another question: to what extent should the format used by fmt::Display implementation be documented? The context is that I would like to change the fmt::Display format output for a library I have, but I am unsure which part of the version number I should bump. …

Quote from this topic:

@yaahc

Backing up what @H2CO3 said, the libs team explicitly reserves the right to change Debug output but as far as I know we make no such guarantees about Display, so my understanding is that we currently treat Display output as part of our stable API.