Fix clippy warning and enforce no warning in the CI

[chevdor]

This PR fixes a (the single) clippy warning and enforces in the CI that warnings are unwanted.

This PR is small/short but should not be merged lightly as it would require a major version bump.

It is also not critical to have immediately so it would be a good candidate to pack with other PRs that would change the public interface.

[dvdplm]

@chevdor I took the liberty to merge in master.

[niklasad1]

LGTM modulo -D warnings in the CI

[emostov]

not be merged lightly as it would require a major version bump.

dq: is this a breaking change because we now return an error in a logic branch that previously would have not error'ed? Since the return type doesn't change on try_merge could it be considered just a patch?

[niklasad1]

dq: is this a breaking change because we now return an error in a logic branch that previously would have not error'ed? Since the return type doesn't change on try_merge could it be considered just a patch?

I would regard it as patch/bug fix but for now we don't care about about breaking changes because we are still at pre release version

[chevdor]

@emostov in theory yes, with the last change I made, a fn has been changed.
It was returning a Result and so potentially an Err in theory but nothing in the code was ever returning an Err. Now, in some conditions, it may.

But if you treated already the Result properly before (= assuming it could be an Err), you should not have a suprise.

[emostov]

Thanks @chevdor & @niklasad1 for the quick answer. From my PoV this looks good

[dvdplm]

@chevdor feel free to merge when CI clears, and ty! :)