go/doc: confusing types displayed for mixed exported/unexported consts

[josharian]

Given:

const (
    a, _, c = T, iota, int
    D, E, f

    J, k = iota, T
    L, M
)

godoc outputs:

const (
    _ = T, iota, int
    D, E

    J = iota, T
    L, M
)

It is not clear from the output what the type of D, E, L, or M is.

I came across this while working on a follow-up to #5397. This is an edge case, and I've not seen it in the real world. It is not clear what the correct thing to do here is; probably we should just ignore it.

[griesemer]

One could probably come up with some heuristics to make this work, but it's not clear it's worth the effort.

The correct approach would be to use go/types to compute the correct export information, combine that with the comments present in the source, and produce a synthetic AST from that.

I would ignore this.

[agnivade]

Using go version devel +7a14f55 Sun Apr 29 16:14:16 2018, this is what it prints now

const (
    D, E, _

    J, _ = iota, T
    L, M
)

Not much improvement for D, E. But I think L and M are kinda clear now.

[griesemer]

@agnivade It's probably a mistake to not show the expressions in the first line - it would be nice if they were moved along. As is, these constants (D, E, _) look pretty lost.