Fix uses_dynamic_as_bottom errors

[srawlins]

uses_dynamic_as_bottom is a new error in Dart 2.0. dart-lang/sdk#29630

These hints can be seen by using dartanalyzer.

[sigmundch]

Thanks Sam!

[sigmundch]

I believe these cast will fail at runtime.

These maps are created from json parsing, which I believe creates maps as Map<dynamic, dynamic> and lists as List<dynamic>

I'm guessing that changing this to Map<dynamic, dynamic> is equivalent to what we have today, correct? If so, I believe we have a few options:

• option A: wrap the closure to avoid the fuzzy arrow (this has an implicit cast):

(elements['library'] as Map).values.map((l) => parseLibrary(l));

• option B: same, but with the cast more explicit

(elements['library'] as Map).values.map((l) => parseLibrary(l as Map));

• option C: make the functions take dynamic and cast the parameter at the callee:

parseLibrary(dynamic jsonArg) {
  Map json = jsonArg;
  ...
}

I prefer option A.

[srawlins]

Updated with your suggestions, thanks @sigmundch !