dart2js computes some number operations with non-web semantics

[vsmenon]

The following:

void main() {
  final list = [];
  for (var i = 0; i < 1; i++) {
    list.add(((i * 2) / 2).runtimeType);
  } 
  
  final item = (((0 * 2) / 2).runtimeType);
  
  print(list.first);
  print(item);
}

prints double and int in dart2js (2.10.4 - current dartpad).

For the former, it generates:

C.JSDouble_methods.get$runtimeType(i * 2 / 2);

which appears to unconditionally return double (

sdk/sdk/lib/_internal/js_runtime/lib/js_number.dart

Line 700 in 368d9f3

Type get runtimeType => double;

).

For the latter, it generates:

C.JSInt_methods.get$runtimeType(0)

[vsmenon]

@rakudrama - would changing runtimeType in JSDouble to something like:

  Type get runtimeType => JS(...) ? int : double;

make sense here?