tree dd77bb5f8df62cb0c29a8c4a10f84997a20dc2ac
parent 5bf02b21f123b83264fa2cf2d4b7aab4759d2d3c
author Muir Manders <muir@mnd.rs> 1596778427 -0700
committer Rebecca Stambler <rstambler@golang.org> 1596936520 +0000

internal/lsp/source: improve completion in switch cases

Now we downrank candidates that have already been used in other switch
cases. For example:

    switch time.Now().Weekday() {
    case time.Monday:
    case time.<> // downrank time.Monday
    }

It wasn't quite as simple as tracking the seen types.Objects.
Consider this example:

    type foo struct {
      i int
    }

    var a, b foo

    switch 123 {
    case a.i:
    case <>
    }

At <> we don't want to downrank "b.i" even though "i" is represented
as the same types.Object for "a.i" and "b.i". To accommodate this, we
track having seen ["a", "i"] together. We will downrank "a.i", but not
"b.i".

I applied only a minor 0.9 downranking when the candidate has already
been used in another case clause. It is hard to know what the user is
planning. For instance, in the preceding example the user could intend
to write "a.i + 1", so we mustn't downrank "a.i" too much.

Change-Id: I62debc5be3d5d310deb69d11770cf5f8bd9add1d
Reviewed-on: https://go-review.googlesource.com/c/tools/+/247337
Run-TryBot: Muir Manders <muir@mnd.rs>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rebecca Stambler <rstambler@golang.org>