Bug: Negative array dimensions permitted when using `:displaced-to` with `make-array`

[fosskers]

I discovered this today while unit testing a new library of mine.

This will throw:

(make-array -5 :element-type 'character)

citing:

The size specified for this array (-5) is negative.

However, this will happily succeed:

(make-array -5 :element-type 'character :displaced-to "hello")

This yields an empty string. Each other Lisp implementation I tried throws a condition here. Looking at the Java, we see that the dimension isn't checked for negativity when handling :displaced-to, but that it is for other normal cases.

Cheers.