How to disallow casting mixed to string

[still-dreaming-1]

This might be an issue, but I wanted to start it as a discussion first because it seems so fundamental it must have been thought about already. Also, I think I remember reading about this somewhere but now I can't find anything about it.

Is there a setting or some way to not allow casting mixed to string?

Currently in the project I'm working on, if a type is known to be mixed by Psalm, it will allow me to cast it to string. I can see how this is very convenient and many programmers may want to do this, but technically it is invalid and so it seems like Psalm should consider it a PossiblyInvalidCast or something like that. The reason I say this is, php does not consider all casts to a string as being valid. For example, if you cast an array to a string you will get an "Array to string conversion" warning and they are always converted to the string "Array". Also you will get a php error if you try to cast an object to string if its class does not have a __toString() method. There may be other types this applies to as well, I'm not sure. Casting something to a string is not the same as asserting that it is a string or that it is castable to a string. There could still be a programming mistake where the type is actually an array and should not be casted to a string, so Psalm should help us catch this.

[weirdan]

Surely looks like a missing feature to me.

[orklah]

We have a RiskyCast for some known weirdness (like casting an array to int) but it is not triggered on mixed or scalar. We could perfectly extends the usage, perhaps behind a config

[still-dreaming-1]

I could see there being a config for it because it would be too strict for some people.