Literal string concat with scalars

[staabm]

simliar to #768 this PR improves the literal-string-type for string-concat cases with other scalar types

closes phpstan/phpstan#6033

[craigfrancis]

Sorry @staabm, I'd rather not include this, so we can keep it in line with the is_literal() implementation. Hopefully my notes on issue #6033 explains why (and yes, in the ideal world PHP would be able to track all developer defined values, including integers, but that's very unlikely to change).

I'd also note, there was also a long discussion about treating all integers as trusted (resulting in the suggestion of a function called is_trusted()), this caused a lot of confusion, and was probably the main reason why the original RFC failed (I intend to try again next year).

Feel free to email me off-list if you want to discuss anything on this subject (I'm fairly sure Ondřej doesen't want to receive loads of discussion emails).

[ondrejmirtes]

@craigfrancis has some good points here, so I'm not gonna merge this, thanks for understanding.

[craigfrancis]

Thank you Ondřej... and Markus, please get in touch via email if you want to discuss further, I want to make sure we have the best solution, and we have everything covered.