commit 138c814f66f4c0aa3ec9a1ede8c3355eddff441d
author Muir Manders <muir@mnd.rs> Fri Feb 28 21:03:44 2020 -0800
committer Rebecca Stambler <rstambler@golang.org> Tue Mar 10 21:06:53 2020 +0000
tree 6b8a7e9ff9ec60fb42c227aa6bf67c3aa853c94a
parent 20ab64c0d93f083c2eb6362b7f17c7e094783a84

internal/lsp/source: offer completion "if err != nil { return err }"

Now we offer an error-check-and-return completion candidate when
appropriate:

    func myFunc() (int, error) {
      f, err := os.Open("foo")
      <>
    }

offers the candidate:

    if err != nil {
      return 0, <err>
    }

where <> denotes a placeholder so you can easily alter "err".

The completion will only be offered when:
1. The position is in a function that returns an error as final result
   value, and
2. The statement preceding position is an assignment whose final LHS
   value is an error.

The completion will contain zero values for the non-error return values
as necessary.

Using the above example, the completion will be offered after the user
has typed:

    i
    if
    if err

Basically the candidate will be offered after every keystroke as the
user types "if err".

I call this new type of completion a statement completion - perfect
for when you want to make a statement!

Change-Id: I0a330e1c1fa81a2757d3afc84c24e853f46f26b0
Reviewed-on: https://go-review.googlesource.com/c/tools/+/221613
Run-TryBot: Muir Manders <muir@mnd.rs>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rebecca Stambler <rstambler@golang.org>