Enhancement request: auto-complete the types in a method/constructor call

Hey guys, I sometimes have trouble coding, for not remembering every type by heart, and think the intellij plugin could help alot in this.
For example in a streambuilder, you define the stream, maybe an initialData, but then you get to the builder, which must be ```(Builcontext context, AsyncSnapshot snapshot) { }``` and you just get no completion to help you, I wish some kind of completion be available to help you, instead of having to write it all yourself every time.

Thanks.
Regards

The request concerns the IntelliJ plugin's completion support for method or constructor calls, using a Flutter StreamBuilder builder callback as the example. Start by locating the plugin's existing completion behavior for these calls; done means it can suggest the callback parameter types instead of requiring them to be written manually.

Written by the indexing model from the issue text.