if-related invariants not erased before handling else branch

[quasilyte]

Code Example

<?php

class C {
  /***/
  public function example() {}
}

function f($c) {
  if ($c instanceof C) {
  } else {
    $c->example();
  }
}

Actual Behavior

No warnings.

Expected Behavior

Calling to undefined method, since $c is not C-typed.

[quasilyte]

This is not only about instanceof but rather about all things recorder from if.

function f() {
  if (isset($x)) {
  } else {
    var_dump($x);
  }
}

This code gives no warning about undefined $x.

Looks like we handle elseif correctly, but if it's else if then we have the same issue:

function f() {
  // No warnings
  if (isset($x)) {
  } else if (isset($y)) {
    var_dump($x);
  } else {
    var_dump($y);
  }
}

[quasilyte]

Another observation:

if (isset($x) && $foo = 10) {}

var_dump($foo);

The code above does not generate any warnings because we treat everything in if condition as evaluated unconditionally.

It should probably report usage $foo as "might not be defined".

[i582]

Done by #1058