FOR UPDATE OF list does not work with columns qualified with a relation alias. [CORE3723]

[firebird-automations]

Submitted by: @jasonwharton

The following query fails:

SELECT R.RDB$DESCRIPTION
, R.RDB$VIEW_SOURCE
, R.RDB$RELATION_NAME
FROM RDB$RELATIONS R
ORDER BY R.RDB$RELATION_NAME
FOR UPDATE OF R.RDB$DESCRIPTION

Here is the SQL trace from IBO when I attempted to open this query:

/*---
PREPARE STATEMENT
TR_HANDLE = 27
STMT_HANDLE = 26

SELECT R.RDB$DESCRIPTION
, R.RDB$VIEW_SOURCE
, R.RDB$RELATION_NAME
FROM RDB$RELATIONS R
ORDER BY R.RDB$RELATION_NAME ASC
FOR UPDATE OF R.RDB$DESCRIPTION

FIELDS = [ Version 1 SQLd 3 SQLn 30
RDB$RELATIONS.RDB$DESCRIPTION = <NIL>
RDB$RELATIONS.RDB$VIEW_SOURCE = <NIL>
RDB$RELATIONS.RDB$RELATION_NAME = <NIL> ]

ERRCODE = 335544569
----*/
/*---
INTERPRET BUFFER =

ERRCODE = 17
----*/
/*---
INTERPRET BUFFER = Dynamic SQL Error

ERRCODE = 21
----*/
/*---
INTERPRET BUFFER = SQL error code = -104

ERRCODE = 33
----*/
/*---
INTERPRET BUFFER = Token unknown - line 6, column 16

ERRCODE = 1
----*/
/*---
INTERPRET BUFFER = .

ERRCODE = -1
----*/