Function defGetTypeName

src/backend/commands/define.c:254–276

* Extract a TypeName from a DefElem. * * Note: we do not accept a List arg here, because the parser will only * return a bare List when the name looks like an operator name. */

 * return a bare List when the name looks like an operator name.
 */
TypeName *
defGetTypeName(DefElem *def)
{
	if (def->arg == NULL)
		ereport(ERROR,
				(errcode(ERRCODE_SYNTAX_ERROR),
				 errmsg("%s requires a parameter",
						def->defname)));
	switch (nodeTag(def->arg))
	{
		case T_TypeName:
			return (TypeName *) def->arg;
		case T_String:
			/* Allow quoted typename for backwards compatibility */
			return makeTypeNameFromNameList(list_make1(def->arg));
		default:
			ereport(ERROR,
					(errcode(ERRCODE_SYNTAX_ERROR),
					 errmsg("argument of %s must be a type name",
							def->defname)));
	}
	return NULL;				/* keep compiler quiet */
}

/*
 * Extract a type length indicator (either absolute bytes, or