DelegatingList: Fails dartanalyzer --strong due to mistype of expand and map

[matanlurey]

DelegatingList types the methods while dart:core|Iterable does not.

[matanlurey]

[error] Base class introduces an invalid override. The type of _DelegatingIterableBase.expand (((E) → Iterable<dynamic>) → Iterable<dynamic>) is not a subtype of Iterable<E>.expand (<T>((E) → Iterable<T>) → Iterable<T>). (/home/ubuntu/workspace/lib/src/observable_list.dart, line 49, col 5)
[error] Base class introduces an invalid override. The type of _DelegatingIterableBase.map (((E) → dynamic) → Iterable<dynamic>) is not a subtype of Iterable<E>.map (<T>((E) → T) → Iterable<T>). (/home/ubuntu/workspace/lib/src/observable_list.dart, line 49, col 5)

[sethladd]

cc @kevmoo @leafpetersen

I wonder if we could add --strong to our buildbots to ensure the packages we produce work with strong mode.

[nex3]

I'm going to merge this with #23, which @ochafik is actively working on.

[matanlurey]

Thanks Natalie!