Describe the bug
DartCode is over-eager to offer class autocompletions to attributes. See the screenshot: here it should ideally be offering me @override as the completion, rather than trying to auto-import random classes from dart:io :)

To Reproduce
Create a class, attempt to add an override (e.g. toString())

Expected behavior
Either offer me autocomplete for available attributes, or don't offer me autocomplete. The proffered choices will always create a syntax error.

Screenshots

Versions (please complete the following information):

• VS Code version: 1.54.1
• Dart extension version: 3.20.1
• Dart/Flutter SDK version: 2.0 stable

(preview LSP is on)