usage of pure-functions/methods within a loop

[staabm]

loops are the obvious performance bottlenecks we see in applications every day.
sometimes loops are slower then necessary, because method/function-calls which do not depend on a variable, which changes with iterations is used within the loop, but could just be moved outside the loop.

pseudo-code:

$x = 3;
foreach($iterator as $value)  {
  $this->somePureMethod($x);
  // more loop body
}

since the method is pure, invoking it on every iteration is unnecessary and the code could be rewritten to

$x = 3;
this->somePureMethod($x);
foreach($iterator as $value)  {
  // loop body
}

should phpstan error when pure functions/methods are used within a loop, but do not depend on its iterations?

another benefit of moving code outside a loop, is more readable code

[ondrejmirtes]

It's currently hard to track this and not report code that's valid but in the future this should be possible.