object slice #77

o.{a:b, c} ⇔ {a: o.b, c: o.c}

This will:

• enable partial copy/import, e.g. import Array::{push, forEach}.
• mirror array slice (a[x, y] ⇔ [a[x], a[y]]) and object subdestructuring (p{a:b, c} = q ⇔ {a: p.b, c: p.c} = q), improving semantic consistency.

For applying ADI (o{a}; o?{b} ⇔ o.{a}; o?.{b}), the clone syntax (p = Point{x: 7, y: 8}) needs to change; probably to unary ^ (p = ^Point <<< x: 7, y: 8).