Fix "list type lost in for loop"

[staabm]

if the for loop is in the shape of for($i = 0; $i < count($items); $i++) { we can set $items[$i] as existing expression type.

closes phpstan/phpstan#12807

[staabm]

we could make this work for more involved loops, but I think this will work as a first step

--

other examples

• for ($i = count($items) - 1; $i >= 0; --$i) {
• for ($i = count($items) - 1; $i >= 0; $i--) {
• for ($i = count($items) - 1; $i > -1; $i--) {
• for ($i = count($disk)-1, $f = 0; $i >= 0; $i--) {
• for ($i = count($bytes)-2; $i>=0; $i--)
• for ($i = 0; $i < count($items); $i+=4) {

[phpstan-bot]

This pull request has been marked as ready for review.

[staabm]

I think we could do >=0

[ondrejmirtes]

Thank you!

[staabm]

any opinions on the other given examples? do you think this can work and should be implemented?

[ondrejmirtes]

Instead of writing many many conditions, I'd like if this could be expressed more by the type system. That would cover all situations. But I'm not sure yet how it could look.

[staabm]

ok thanks. no priority on it.