We have some false-positives for null-safety and this pull-request should help us. I improved type inferring by true/false context and merge null-safety with more general rule: safety call (but null-safety separated)

• Improve type-inferring for bool/null
• Improve type-inferring for another type and checkers like is_bool, is_int, is_null and etc
• Merge null-safety with more general safety-call rule

Very important note: i improved type inferring only for if/else conditions and context inside it. Throwing context up is the future task.

$x <== User|false
if ($x === false){
$y = is_object($x); <=== here will be User
 return;
}

some code....

$y = is_object($x); <== will be false; current type will be User|false