return from function doesn't work when used in tail of pipeline

[Martin Schwenke]

Configuration Information [Automatically generated, do not change]:
Machine: i486
OS: linux-gnu
Compiler: gcc
Compilation CFLAGS:  -DPROGRAM='bash' -DCONF_HOSTTYPE='i486' 
-DCONF_OSTYPE='linux-gnu' -DCONF_MACHTYPE='i486-pc-linux-gnu' 
-DCONF_VENDOR='pc' -DLOCALEDIR='/usr/share/locale' -DPACKAGE='bash' -DSHELL 
-DHAVE_CONFIG_H   -I.  -I../bash -I../bash/include -I../bash/lib   -g -O2 -Wall
uname output: Linux rover 2.6.32-23-generic #37-Ubuntu SMP Fri Jun 11 07:54:58 
UTC 2010 i686 GNU/Linux
Machine Type: i486-pc-linux-gnu

Bash Version: 4.1
Patch Level: 5
Release Status: release

Description:
        I don't believe that the following behaviour is sensible or
        matches the standard/documentation:

        $ f () {   { echo 1 ; echo 2 ; } | while read line ; do echo $line ; 
return 0 ; done ; echo foo ; return 1 ; }
        $ f
        1
        foo
        $ echo $?
        1

        I expect f to return 0 from within the loop because a function
        is executing.

        I know the return 0 is in a subprocess at the end of a
        pipeline... but that whole pipeline is running within a
        function.

        Naturally, the above is a contrived, minimal example.  In
        general I expect to be able to pipe the output of a command
        into a loop and have the loop read lines until some condition
        occurs, at which point my function returns.  This could
        obviously be done using a out=$(cmd) subprocess... except in
        the case where cmd can block before producing all of its
        output.  Hence, the above seems convenient.

Repeat-By:
        See above.

Fix:
        I'd expect a fix to be tricky... which probably explains the
        current behaviour.  ;-)

peace & happiness,
martin