v6 is better, but I found a few more questions:
+select pg_get_viewdef('tcast_v1', true);
+ pg_get_viewdef
+--------------------------------------------------------------------------------------------
+ SELECT CAST( col1 AS date FORMAT 'YYYY-MM-DD'::text) AS to_date,
+
Is that space after "CAST(" intentional?
+ format = coerce_to_target_type(pstate, fmt,
+ exprType(fmt), TEXTOID,
+ exprTypmod(fmt),
+ ccontext, cformat,
+ exprLocation(fmt));
Is exprTypmod(fmt) correct, shouldn't it use -1?
This one also shows a not so userfriendly error:
postgres=# SELECT CAST('hello' AS name FORMAT 'test') ;
2026-03-30 22:12:53.651 UTC [750980] ERROR: function
pg_catalog.to_char(text, text) does not exist
2026-03-30 22:12:53.651 UTC [750980] DETAIL: No function of that name
accepts the given argument types.
2026-03-30 22:12:53.651 UTC [750980] HINT: You might need to add
explicit type casts.
2026-03-30 22:12:53.651 UTC [750980] STATEMENT: SELECT CAST('hello'
AS name FORMAT 'test') ;
ERROR: function pg_catalog.to_char(text, text) does not exist
DETAIL: No function of that name accepts the given argument types.
HINT: You might need to add explicit type casts.
And varchar/bpchar adds details about binary coercible casts:
SELECT CAST('hello' AS bpchar FORMAT 'test') ;
2026-03-30 22:14:12.081 UTC [750980] ERROR: cannot cast type text to
character while using a format template at character 8
2026-03-30 22:14:12.081 UTC [750980] DETAIL: binary coercible type
cast is not supported while using a format template
2026-03-30 22:14:12.081 UTC [750980] STATEMENT: SELECT CAST('hello'
AS bpchar FORMAT 'test') ;
ERROR: cannot cast type text to character while using a format template
LINE 1: SELECT CAST('hello' AS bpchar FORMAT 'test') ;
