Fix check_type_allowed_as_proc_argument to show the type name

[straight-shoota]

All other call sites of check_type_can_be_stored mention the respective type in the message, only for proc arguments this was missing.

Specs fail because Class type restriction sometimes reports as Object. Not sure about the reason or if that's intended, but it looks unexpected to me.

->(x : Class) { } # Can't use Object as a Proc argument type

def foo(&block : Class ->)
end

foo {} # Can't use Class as a Proc argument type

def foo(x)
end

->foo(Class) # Can't use Object as a Proc argument type

[asterite]

Looks good! Though CI is failing

[straight-shoota]

Yes, I mentioned that in the OP. Any idea why Class reports as Object?

[asterite]

It's a bug, but I can't remember why it happens.

Also, the original intention of the code was to show the invalid type inside a union type, but I guess that was unused.

[HertzDevil]

Class's instance type is Object, and somewhere Class is treated like a metaclass. #10590 also observed this.

[straight-shoota]

Ah thanks, I had a vague idea that something about that had come up somewhere lately. I'll adapt the specs for now.