Flag for error on implicit dynamic

[munificent]

We've discussed this a few times, but I figured I should file a tracking issue (if there isn't one already). I would like to be able to run the analyzer in strong mode with an option to tell me if the type inference engine ever can't pick a static type and ends up picking dynamic instead.

For example, I would expect to get an error here:

someFunction(a) => a.mysteryProperty;

But not here:

someFunction(dynamic a) => a.mysteryProperty;

[jmesserly]

Nice!

another variant, more for codegen, is "no dynamic invokes" ... this would allow us to omit some helper code. Possibly useful if you're trying to export a Dart library to JS and you want really small code size.

(of course, as far as code size is concerned, we have bigger fish to fry in the SDK libs)

[vsmenon]

Would you guys want an error here:

var list = [1, 2, 4];

?
In this case, the implicit dynamic is within the List type - List<dynamic> - that is both the inferred static type of list as well as its reified runtime type. I believe TypeScript's no-implicit-any complains.

[vsmenon]

I filed a related bug for no reified dynamics: #365
I suspect that would also eliminate dynamic invokes, but probably the hard way to get there.

[munificent]

Yes, I'd want an error there too.

[jmesserly]

this is moved to the SDK now dart-lang/sdk#24712, dart-lang/sdk#25573