Dependant types - parsing logic (can't think of a better subject - please change) #4695
Description
Bug report
As requested from #4694
Complicated logic not being recognised, leading to erroneous errors.
Code snippet that reproduces the problem
https://phpstan.org/r/3d974ed6-7d4b-4f91-8dcf-7187222d3004
<?php declare(strict_types = 1);
/**
* @return no-return
*/
function no_return(){
echo "Dying\n";
die(1);
}
/**
* @param int|null $u
* @param int|null $a
* @return array<int, int>
*/
function foo($u=null, $a=null){
if (is_null($u) && is_null($a)){
no_return();
return [0,0]; // line 18
}
if ($u){
$a = $u;
}else if ($a){
$u = $a;
}
return [$u, $a]; // line 25
}
print_r(foo(1)); // first only
print_r(foo(null,2)); // second only
print_r(foo(1,2)); // both
print_r(foo()); // none - will die() and not returnActual output
18 | Unreachable statement - code above always terminates.
-- | --
25 | Function foo() should return array<int, int> but returns array<int, int|null>.
Expected output
18 | Unreachable statement - code above always terminates.
Line 18 added to check that no-return being honoured.
However $a (the int|null) will never be null if it gets that far through the function.