When using auto assist to fill possible properties, filter the possible types

When filling in widget properties, and they are expecting an a specific type, such as an enum, it would be really nice and much faster if filtered the types and suggested those as the options. It’s pointless to have the entire type list on auto assistance. And to find the type it expects I have to climb into the super class every time.

Bonus points if you can add the dart docs to the right when hovering over the type options. This is another activity that consumes much time figuring which each option does.

Steps to Reproduce

1. Add the property name such as Wrap.direction property.
2. Look at the list it auto suggests. (control + space)

Possible List:

Axis.horizontal
Axis.vertical

Version info

[✓] Flutter (on Mac OS X 10.12.5 16F73, locale en-US, channel master)
    • Flutter at /Users/branflake2267/git/flutter
    • Framework revision 6f77b4a9a7 (4 hours ago), 2017-06-14 17:27:08 -0700
    • Engine revision 18fdfb86bb
    • Tools Dart version 1.24.0-dev.6.7

[✓] Android toolchain - develop for Android devices (Android SDK 26.0.0)
    • Android SDK at /Users/branflake2267/Library/Android/sdk
    • Platform android-26, build-tools 26.0.0
    • Java binary at: /Applications/Android Studio.app/Contents/jre/jdk/Contents/Home/bin/java
    • Java version OpenJDK Runtime Environment (build 1.8.0_112-release-b06)

[✓] iOS toolchain - develop for iOS devices (Xcode 8.3.3)
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • Xcode 8.3.3, Build version 8E3004b
    • ios-deploy 1.9.1
    • CocoaPods version 1.2.1

[✓] Android Studio (version 2.3)
    • Android Studio at /Applications/Android Studio.app/Contents
    • Gradle version 3.2
    • Java version OpenJDK Runtime Environment (build 1.8.0_112-release-b06)

[✓] IntelliJ IDEA Community Edition (version 2017.1.4)
    • Flutter plugin version 14.0
    • Dart plugin version 171.4694.29

[✓] IntelliJ IDEA Ultimate Edition (version 2017.1.4)
    • Flutter plugin version 14.0
    • Dart plugin version 171.4694.29

[✓] Connected devices
    • iPhone 7 • 458BC4FE-8205-4369-8718-193B9FC88C8B • ios • iOS 10.3 (simulator)

[scheglov]

https://dart-review.googlesource.com/c/sdk/+/52863 switches to prioritizing relevant types.

[branflake2267]

Nice job!