FP: string++ | "Only numeric types are allowed in post-increment, string given."

[voku]

Bug report

I am uncertain if this is a "normal" use-case, but I see sometimes code like this: $a = 'a'; $a++;

https://3v4l.org/JEv7V

... especially in some excel related code, this is working as expected.

Code snippet that reproduces the problem

https://phpstan.org/r/379c2ebf-cde5-4d10-aab2-17c9080a984a

Expected output

no error for ConstantStringType [a-zA-Z]{0,1}

Did PHPStan help you today? Did it make you happy in any way?

Currently, I am trying to enable the strict rules for a legacy project, and it's cool that we can enable one rules after another. Thanks for these features. :1st_place_medal:

[rajyan]

https://3v4l.org/FGt21 https://3v4l.org/QHiFj Just for additional information, $a = 'a'; $a++; doesn't always mean $a === 'b' and behaves different in some encodings. I don't have a opinion whether it is "normal" or not, but it is a documented behavior (and at least valid) https://www.php.net/manual/en/language.operators.increment.php

ConstantStringType [a-zA-Z]{0,1}

I think it should be [a-zA-Z0-9]* looking at the documentation.

[ondrejmirtes]

I agree string++ should not be reported. But (int|string)++ still should be.

[VincentLanglet]

'a9'++ is computed to 'b0' which is a string but '9' is computed to '10` which is an int.

Currently it's always considered to be a string https://phpstan.org/r/62872dfa-096d-4b43-ad3b-6d7a8610f1ee

Should we first modify this behavior @ondrejmirtes ?

The issue is that if we change the result to int|string or (int|string), then doing

$string++;
$string++;

We will report the second line as an error since you said

I agree string++ should not be reported. But (int|string)++ still should be.

[VincentLanglet]

I opened a PR to at least avoid the false positive https://github.com/phpstan/phpstan-strict-rules/pull/200

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