error safe for casting date to other types per pg_cast

select castsource::regtype, casttarget::regtype, castfunc,
castcontext,castmethod, pp.prosrc, pp.proname from pg_cast pc join pg_proc pp on
pp.oid = pc.castfunc and pc.castfunc > 0
and castsource::regtype = 'date'::regtype
order by castsource::regtype;

castsource |         casttarget          | castfunc | castcontext | castmethod |      prosrc      |   proname
------------+-----------------------------+----------+-------------+------------+------------------+-------------
 date       | timestamp without time zone |     2024 | i           | f          | date_timestamp   | timestamp
 date       | timestamp with time zone    |     1174 | i           | f          | date_timestamptz | timestamptz
(2 rows)

discussion: https://postgr.es/m/CADkLM=fv1JfY4Ufa-jcwwNbjQixNViskQ8jZu3Tz_p656i_4hQ@mail.gmail.com

Author: jianhe-fun

src/backend/utils/adt/date.c

@@ -1350,7 +1350,16 @@ date_timestamp(PG_FUNCTION_ARGS)
 	DateADT		dateVal = PG_GETARG_DATEADT(0);
 	Timestamp	result;
 
-	result = date2timestamp(dateVal);
+	if (likely(!fcinfo->context))
+		result = date2timestamp(dateVal);
+	else
+	{
+		int			overflow;
+
+		result = date2timestamp_opt_overflow(dateVal, &overflow);
+		if (overflow != 0)
+			PG_RETURN_NULL();
+	}
 
 	PG_RETURN_TIMESTAMP(result);
 }
@@ -1435,7 +1444,16 @@ date_timestamptz(PG_FUNCTION_ARGS)
 	DateADT		dateVal = PG_GETARG_DATEADT(0);
 	TimestampTz result;
 
-	result = date2timestamptz(dateVal);
+	if (likely(!fcinfo->context))
+		result = date2timestamptz(dateVal);
+	else
+	{
+		int			overflow;
+		result = date2timestamptz_opt_overflow(dateVal, &overflow);
+
+		if (overflow != 0)
+			PG_RETURN_NULL();
+	}
 
 	PG_RETURN_TIMESTAMP(result);
 }