The following documentation comment has been logged on the website:
Page: https://www.postgresql.org/docs/11/sql-syntax-lexical.html
Description:
QUOTE:
The CAST() syntax conforms to SQL. The type 'string' syntax is a
generalization of the standard: SQL specifies this syntax only for a few
data types, but PostgreSQL allows it for all types. The syntax with :: is
historical PostgreSQL usage, as is the function-call syntax.
UNQUOTE
In fact, this is not 100% true. TIMESTAMP 'string' does not work this way.
It is mentioned in section 4.2.9 that TIMESTAMP( 'string') cannot be used,
but it does not mention TIMESTAMP 'string'.
I would really prefer if the respective information could be clear,
unequivocal, complete and included in other sections of the manual where it
is due, i.e. in sections 8.5 and 9.9 which deal with date & time types and
operators.