[web] Constant symbol from constructor can be private. about sdk

[eernstg]

This might be the case with DDC as well.

[lrhn]

It's even more weird. The symbols are not equal, but they are identical.

void main() {
  const s1 = #_foo;
  const s2 = Symbol("_foo");
  print(s1 == s2); // false
  print(identical(s1, s2)); // true
}

The two objects are identical. (Also when not checked as constants, not even knowing that identical is the function being called):

  var id = DateTime.now().millisecondsSinceEpoch > 0 ? identical : (a, b) => Math.random().nextBool();
  print("id: ${id(s1, s2)}"); // True.                             

This still prints true, so it is the runtime check saying so.

On the other hand, a constant evaluation behaves correctly:

const ceq = s1 == s2;
const cid = identical(s1, s2);
print(ceq); // false
print(cid); // false

which means the front-end constant evaluation behavior is correct, but Dart2js, and probably DDC, both behave inconsistently.
(It's not even reflexive! Equality, you had one job! Well three, but this is the first one!)

(Interestingly, the analyzer is also wrong:

void main() {
  const s1 = #_foo;
  const s2 = Symbol("_foo");
  const Chk.neq(s1, s2); // Analyer: Error
  const Chk.nid(s1, s2); // Analyer: Error
  const Chk.eq(s1, s2); // Analyer: OK
  const Chk.id(s1, s2); // Analyer: OK
}

class Chk {
  const Chk.eq(Object? v1, Object? v2) : assert((v1 == v2), "eq failed");
  const Chk.id(Object? v1, Object? v2) : assert(identical(v1, v2), "id failed");
  const Chk.neq(Object? v1, Object? v2) : assert(!(v1 == v2), "neq failed");
  const Chk.nid(Object? v1, Object? v2)
      : assert(!identical(v1, v2), "nid failed");
}

The failures should be on the eq/id invocations instead.

The VM's only failure seems to be #_foo.bar which it treats as "library private", even if all library names should be unaffected by privacy.)