Make UNKNOWN into an actual pseudo-type.

Previously, type "unknown" was labeled as a base type in pg_type, which
perhaps had some sense to it because you were allowed to create tables with
unknown-type columns.  But now that we don't allow that, it makes more
sense to label it a pseudo-type.  This has the additional effects of
forbidding use of "unknown" as a domain base type, cast source or target
type, PL function argument or result type, or plpgsql local variable type;
all of which seem like good holes to plug.

Discussion: https://postgr.es/m/CAH2L28uwwbL9HUM-WR=hromW1Cvamkn7O-g8fPY2m=_7muJ0oA@mail.gmail.com

1 files changed, 3 insertions, 3 deletions

diff --git a/doc/src/sgml/ref/create_function.sgml b/doc/src/sgml/ref/create_function.sgml
index 8108a430951..e7057789d32 100644
--- a/doc/src/sgml/ref/create_function.sgml
+++ b/doc/src/sgml/ref/create_function.sgml
@@ -160,8 +160,8 @@ CREATE [ OR REPLACE ] FUNCTION
       </para>
       <para>
        Depending on the implementation language it might also be allowed
-       to specify <quote>pseudotypes</> such as <type>cstring</>.
-       Pseudotypes indicate that the actual argument type is either
+       to specify <quote>pseudo-types</> such as <type>cstring</>.
+       Pseudo-types indicate that the actual argument type is either
        incompletely specified, or outside the set of ordinary SQL data types.
       </para>
       <para>
@@ -199,7 +199,7 @@ CREATE [ OR REPLACE ] FUNCTION
        can be a base, composite, or domain type,
        or can reference the type of a table column.
        Depending on the implementation language it might also be allowed
-       to specify <quote>pseudotypes</> such as <type>cstring</>.
+       to specify <quote>pseudo-types</> such as <type>cstring</>.
        If the function is not supposed to return a value, specify
        <type>void</> as the return type.
       </para>