Method auto-complete randomly doesn't work (jumps between three different behaviors)

[kangalio]

output-2021-02-04_21.37.48.mp4

As you can see in the video, when typing the first few characters of a method, three different things may happen, seemingly without no pattern:

1. rust-analyzer's nice method list pops up
2. VSCode's built-in autocomplete pops up
3. Nothing pops up

Through experimentation, I could identify what triggers each of the behaviors:

1. type all characters normally
2. type the first 2-3 characters rapidly
3. type the last 2-3 characters rapidly

This issue seems easy to reproduce, but here is a copy-and-pastable code just in case (I tested it in a blank project, it behaves the same)

fn trim_multiline(string: &str) -> &str {
    while string./*type "ends" here, in varying speeds*/
}

Versions:

• VSCode: 1.52.1
• rust-analyzer: v0.2.473
• OS: KDE Linux

If there is anything else I can provide to make the issue more clear, I'm happy to provide it

[SomeoneToIgnore]

Thank you for finding the time to record a video and experiment with it.

Most probably it's the same case as discussed in #7542
When zero completion input is done after . symbol, we might get slow when finding traits appropriate for importing.

I have a few ideas in the same issue on how to improve the situation, we also have an issue for benchmarks.

[memoryruins]

Before finding this, I posted a couple vscode settings in a similar issue #10187 (comment)

"editor.wordBasedSuggestions": false,
"editor.quickSuggestionsDelay": 200,

It has made r-a's suggestions pop up much more consistently for me.