Add support for the key-of<...> type

[ste93cry]

Fixes phpstan/phpstan#6084. This is my attempt at implementing the key-of<...> type borrowed from Psalm. However, I'm not sure where I should place the tests as I see a lot of files, but none that looks the right one. Also, Psalm tells the user precise errors when an invalid value is used as generic argument of the key-of type, however the resolveGenericTypeNode() method cannot return a RuleError and so I wonder how I could return a custom error message for certain cases. Any advice on these two qustions would be highly appreciated

[ondrejmirtes]

When TypeNodeResolver returns ErrorType, it's picked up by existing rules, for example: https://phpstan.org/r/2ae98fc7-9829-42bc-8a25-51e4ef022dad ("contains unresolvable type")

The tests should be done in NodeScopeResolverTest.

Also please add support for value-of.

[ste93cry]

Also please add support for value-of.

Since it's a separated feature (although it works basically the same), wouldn't be better to implement key-of first and then contribute value-of in a separate PR?

When TypeNodeResolver returns ErrorType, it's picked up by existing rules

I took as reference the class-string type and I could not find a rule that prints an error if the type could not be resolved, and in fact PHPStan just tells me that it is unresolvable. I would like to go even further and personalize the error message for certain cases. Making these checks inside the rule means that I should account for all possible places where the type could be used (param, variable, etc), which doesn't look reasonable and maintenable...

[ondrejmirtes]

wouldn't be better to implement key-of first and then contribute value-of in a separate PR?

Since they're closely connected and the implementation is just three lines of code, I want them together.

would like to go even further and personalize the error message for certain cases

I don't see this being possible without major refactoring, it certainly shouldn't be a concern for this PR

[ste93cry]

Since they're closely connected and the implementation is just three lines of code, I want them together.

Ok, I've added the missing feature

I don't see this being possible without major refactoring, it certainly shouldn't be a concern for this PR

Absolute agree, if that's the case 😃

The tests should be done in NodeScopeResolverTest.

I've added them, are they enough? I would have expected also some tests to assert that when a wrong value is given an error is thrown, but in this file it looks like all tests just assert the type is the expected one 🤔

[ondrejmirtes]

I've added them, are they enough?

You can add tests for the rule that you expect to report an error.

[ste93cry]

Done. PR is ready for review, let me know if there is something that I still have to do or feel free to make the changes yourself if you want

[ondrejmirtes]

Thank you! Feel free to update the docs at https://github.com/phpstan/phpstan/edit/master/website/src/writing-php-code/phpdoc-types.md (https://phpstan.org/writing-php-code/phpdoc-types)