Add runtime checks for the statements which can be optimized to true or false

[sgrekhov]

We have some checks like

  Expect.isTrue(c is Object);

These statements are optimized by dart2js to Expect_isTrue(true);. Most probably, these statements are optimized in the similar way by AOT. We need to add some runtime checkings here to test not only compiler optimizations but the runtime as well.

To do that find all of the tests that have analyzer hints like hint - Unnecessary type check; the result is always 'true'. and add some runtime checks

[eernstg]

Probably (c is dynamic) is Object will do.

[sgrekhov]

@eernstg do you mean (c as dynamic) is Object?

[eernstg]

Yes, thanks!

[sgrekhov]

Thank you. But dart2js is too smart, it optimizes it to Expect_isTrue(true); as well :). I'd suggest something like

class C {}
class D extends C {}

main() {
  Expect.isTrue(D() is C);  // Optimized to Expect_isTrue(true);
  Expect.isTrue(((Object o) {return o;})(D()) is C); // Does runtime check in JS
}

[rakudrama]

The way to outwit dart2js is to make things sufficiently indirect, and have possible true and false results.

class C {}
class D extends C {}

void checkIsD(bool expected, Object? o) {
  Expect.equals(expected, o is D);
}

void checkIsC(bool expected, Object? o) {
  Expect.equals(expected, o is C);
}

void checkIs<T>(bool expected, Object? o) {
  Expect.equals(expected, o is T);
}

void directChecks() {  // Most of these tests are inlined and simplified
  checkIsD(true, D());
  checkIsD(false, C());
  checkIsD(false, Object());
  checkIsC(true, D());
  checkIsC(true, C());
  checkIsC(false, Object());
  checkIs<D>(true, D());
  checkIs<D>(false, C());
  checkIs<D>(false, Object());
  checkIs<C>(true, D());
  checkIs<C>(true, C());
  checkIs<C>(false, Object());
}

@pragma('dart2js:noInline')
void check(void Function(bool, Object?) checker, bool expected, Object? o) {
  checker(expected, o);
}

void indirectChecks() { // Indirect calls via non-inlined function prevent the compiler reducing the code to the answer
  check(checkIsD, true, D());
  check(checkIsD, false, C());
  check(checkIsD, false, Object());
  check(checkIsC, true, D());
  check(checkIsC, true, C());
  check(checkIsC, false, Object());
  check(checkIs<D>, true, D());
  check(checkIs<D>, false, C());
  check(checkIs<D>, false, Object());
  check(checkIs<C>, true, D());
  check(checkIs<C>, true, C());
  check(checkIs<C>, false, Object());
}