Function constructor_expr 

pub fn constructor_expr<T>(cx: &mut Cx, value: &T) -> Result<Expr>
where
    T: Citizen + ObjectEncode,

Encodes a citizen value as its read-construct Expr extension form.

Maps the value’s ObjectEncoding to the matching Expr::Extension: a constructor encoding becomes a citizen/read-construct vector, tagged data becomes a tagged map, and an opaque encoding becomes a tagged stable id.