Insert explicit type arguments where types could not be inferred.

[srawlins]

This change is a no-op.

The Dart compiler front-end (“CFE”) and static analyzer (“analyzer”) intend to fix a bug in which “could not infer” errors are not reported for top-level elements. (The same error is already reported in local elements.) Typically in such code, the developer has incorrectly expected inference to flow a certain way and infer a type which satisfies a bound, and the CFE and analyzer don’t report any error, so they submit their code. Here is a minified example:

class C<P extends num> {
  factory C(Iterable<P> p) => C._();
  C._();
}

var c = C([]);

A developer expects (reasonably) that inference would land on C<num> and List<num> for the types of c and the List literal. However, details in the inference algorithms actually mean that inference cannot determine the implicit type of C, which needs to be a compile-time error.