Named arguments in async functions stopped working with consts of the same name

[enyo]

If the const name and the named parameter name are the same, then dart 1.20.1 fails with expression is not a valid compile-time constant.

const String lineLength = '120';

foo({lineLength: lineLength}) async {
  print(lineLength);
}

main() => foo();

• Removing async on vm works
• renaming one of lineLength: lineLength to something else works (so it only happens when they share the same name)