Fix Display docs to accurately describe bounds behaviour

[MegaBluejay]

Resolves #281

Synopsis

The docs for the Display derive state that explicitly specified bounds replace the auto-inferred ones, when this is actually not the case.

There's also some outdated information about what's allowed in #[display(bound(...)] arguments, and incorrect example generated where clauses.

Solution

Update the docs

Checklist

• Documentation is updated (if required)
• Tests are added/updated (if required)
• CHANGELOG entry is added (if required)

[MegaBluejay]

@tyranron
#[display(bound(...))] already adds to the inferred bounds, rather than replacing them

This is shown in the docs example and this test, just not documented correctly.

This was the case at least as far back as v0.99.0, so I'm not sure what to do about the changelog, since there's no actual change being made

[tyranron]

@MegaBluejay please, trace back the commit/PR where this was changed, and mention it in the CHANGELOG.

[tyranron]

Ah, sorry, didn't understand you correctly. Then, please, add the CHANGELOG entry to the "Fixed" section, explaining the wrong docs were fixed.

Do you see a need in more tests to control this behavior?

[MegaBluejay]

Do you see a need in more tests to control this behavior?

I added a few for the case with no inferred Display bound, but overall LGTM

[tyranron]

@MegaBluejay good job! 🍻