x/tools/gopls: handle completion after defer and go statements

[stamblerre]

A defer or go statement is expected to be followed by an *ast.CallExpr. If they are not, the parser treats them as *ast.BadExprs, causing completion to fail. We need to handle this particular case.

Repro:

package main

import "fmt"

func main() {
    defer fmt.<>
}

Triggering a completion here will result in lexical completions, rather than the expected selector completions for package "fmt".

[alindeman]

I decided to poke at this a bit, but couldn't reproduce it. Is this a short code snippet you have handy that triggers the issue?

[stamblerre]

Updated to add a repro. This may be a tough first issue, if this is something you're interested in tackling, just because it will require special handling after a file has been parsed but before it has been type-checked.

[alindeman]

@stamblerre Thanks. I'm mostly using anything tagged as lsp as a way to get familiar with the current codebase. I don't want to get in the way yet :) I'll follow along on the CL if you get to it first.

[gopherbot]

Change https://golang.org/cl/172974 mentions this issue: internal/lsp: handle completion after defer, go statements