Format if expressions & loops

[marcusklaas]

Since a lot of code is inside these expressions, this should significantly increase coverage!

Blocked by rust-lang/rust#27065.

Single line if-else expressions are not implemented yet.

Closes https://github.com/nrc/rustfmt/issues/102.

[nrc]

I wonder if we should ever try to format the label on to the previous line? For example:

'a_long_label:
while a < b {
}

// rather than 
'a_long_label: while a <
                   b {
}

(assuming a and b are actually really long, or whatever).

I guess in practice labels are usually quite short, but it does prevent rightward drift a little bit.

Anyway, just a random thought, don't need to change anything with the PR.

[nrc]

This is awesome, thanks!

[marcusklaas]

Good thing you mentioned tests for ranges, because their bad spans still break this :-(

It seems we're blocked on rust-lang/rust#27162 now.

[marcusklaas]

How should we format if-else block inside functions? I'm tempted to format things as follows:

Some(if cond {
    ...
} else {
    ...
})

but that's not really consistent with how we format them within struct literals. OTOH,

Some(if cond {
         ...

     } else {

        ...

     })

just looks weird to me...

What to do? Maybe we could take a hint from the user here?

[nrc]

I would add options for this: block indent, block indent + tab, visual indent.

[nrc]

I'm not sure what the default should be, perhaps block + tab?

[marcusklaas]

I'll play around with a bit and see what looks good (enough), but that sounds sensible to me.

[marcusklaas]

The bad span for ranges should be fixed now, I hope nightly is updated in time!

This should also close https://github.com/nrc/rustfmt/issues/155.

[marcusklaas]

Guess not :-(

[marcusklaas]

This builds now!