BUG #8401: weird input accepted for intervals and geometric types

The following bug has been logged on the website:

Bug reference: 8401
Logged by: Alexey Borzov
Email address: borz_off(at)cs(dot)msu(dot)su
PostgreSQL version: 9.3rc1
Operating system: irrelevant
Description:

For interval, multiple units:

postgres=# select '1 year day second'::interval;
interval
----------
1 year
(1 row)

Geometric, missing comma:

postgres=# select '(1,2)(3,4)'::box, '1,2 3,4'::box;
box | box
-------------+-------------
(3,4),(1,2) | (3,4),(1,2)
(1 row)

Geometric, one trailing comma:

postgres=# select '(1,2)(3,4),'::box;
box
-------------
(3,4),(1,2)
(1 row)

Geometric, more trailing commas:

postgres=# select '(1,2)(3,4)(5,6),,'::path;
path
---------------------
((1,2),(3,4),(5,6))
(1 row)

Geometric, unbalanced delimiters:

postgres=# select '(1,2),3)'::circle;
circle
-----------
<(1,2),3>
(1 row)

Geometric, mismatched delimiters:

postgres=# select '((1,2),3>'::circle;
circle
-----------
<(1,2),3>
(1 row)

Confirmed on 9.0.13 and 9.3rc1, dates waaaaaay back.