Iterating over all except the last element of a list<T> reports that the offset might not exist #14234

Bug report

When iterating over a list<T> using a for loop from 0 until count($list) - 1:

for ($i = 0; $i < count($parts) - 1; $i++)

to handle all but the last element, PHPStan reports:

Offset int<0, max> might not exist on non-empty-list<string>.

It works correctly when iterating over all elements. Apparently PHPStan does not understand that the range stays within the bounds when performing the subtraction.

Code snippet that reproduces the problem

https://phpstan.org/r/0fc0f7ee-7d69-4c45-8ae9-e7204ad89da3

Expected output

No error.

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