I re-read section 41.11.2. on Plan Caching:
"The PL/pgSQL interpreter parses the function's source text and
produces an internal binary instruction tree the first time the
function is called (within each session). The instruction tree fully
translates the PL/pgSQL statement structure,
The type of a plpgsql variable is by definition its structure; established in a statement, so this is actually covered by that paragraph. But I would be for adding a bit more specific terminology here.
David J.
