Type promotion could be even better if it analyzed more of the control flow

[Hixie]

This code runs fine (and is provably correct), but the analyzer complains error • The argument type 'dynamic' can't be assigned to the parameter type 'String' • test.dart:8:7 • argument_type_not_assignable:

void bar(String value) {
  print(value.runtimeType);
}

void foo(dynamic value) {
  if (value is! String)
    value = value.toString();
  bar(value);
}

void main() {
  foo(0);
}

[eernstg]

Type promotion has been discussed in many issues; I tried to summarize the discussion by adding a list of relevant issues (including this one) to #25565.

[srawlins]

I think this is being followed up on at dart-lang/language#80 and dart-lang/language#81

[leafpetersen]

This works now.