Specify pointer-sized integers a bit more

[tbu-]

E. g. specify that the largest possible array of u8-sized elements has a length that fits into an int, additionally require that i8 <= int, so that abnormal overflow conditions don't need to be checked, such as in #16701.

[thestinger]

It's already specified enough that those are guarantees. It's not possible to have a larger array because there's a guarantee of it being contiguous and addressable via pointer arithmetic. I don't think the documentation needs to spell out some of the consequences of it being pointer-size.

[tbu-]

The Rust type int is a two's complement signed integer type with target-machine-dependent size. Its size, in bits, is equal to the size of the rust type uint on the same target machine.

– Rust Reference Manual (2014-09-17)

This is the only thing I see that specifies int. I see no guarantee that int is the same as any other integer type, so I don't see where it follows that int is at least 8 bit long. I also see no guarantee why an array can't have the size as size that doesn't fit into an int, for example int::MAX as uint + 1 as that's completely addressable using pointer arithmetic using uint, yet is too big for int.

[steveklabnik]

I don't think the documentation needs to spell out some of the consequences of it being pointer-size.

Agreed.