Custom space size such such as [u8; 64] always uses heap, no matter the size about smallbox

[andylokandy]

Sorry for the delay! There are two restrictions on whether a value can be store in the stack: the first one is the size, and the other one is alignment; if a value requires larger alignment than the Space, it will be stored in heap regardless of its size.

[andylokandy]

Reference: #6

[DzmitryFil]

I see. I think this behavior should be documented, because as of now, byte size capacity is mentioned casually as one of the valid alternatives, when it's actually almost always pointless.

[andylokandy]

You're right, the document is not up to date...