in

x in t

Membership. Searches an Array by value, a Set or HashMap through :has, a string by substring, and a raw table by key. A { } literal with items is an error, because its items sit under the keys 1, 2, and on: 2 in { 5, 6 } would hold. Write [ 5, 6 ] to search the items. A keyed literal, kind in { rect = true }, reads right.

Emits contains(t, x) from the std.