no documentation for (compval).* field selection

I couldn't find any documentation for using .* to select all fields
(attributes) of a composite type value, e.g.,

CREATE TYPE comp_t AS (intval integer, textval varchar(32));
CREATE TABLE t4 (compval comp_t);
SELECT (compval).* FROM t4;

The only place this is used is in the hstore documentation.

Would it be appropriate to document this in section "4.2.4. Field
Selection", or is this a special case of some other construct that is
already documented?