Is HEAD broken in rescue/ or am I being silly?

I haven't been able to build HEAD since a couple of days.  The breakage
is now in src/rescue/ and it stops at:

/home/build/src/bin/sh/arith.y:146: error: `arith_val' undeclared (first use in this function)
/home/build/src/bin/sh/arith.y:153: error: union has no member named `l_value'
/home/build/src/bin/sh/arith.y:157: error: union has no member named `l_value'
/home/build/src/bin/sh/arith.y:159: error: union has no member named `l_value'
/home/build/src/bin/sh/arith.y:159: error: union has no member named `l_value'
/home/build/src/bin/sh/arith.y:163: error: syntax error before "value"
/home/build/src/bin/sh/arith.y:165: error: `value' undeclared (first use in this function)
/home/build/src/bin/sh/arith.y:165: error: union has no member named `l_value'
/home/build/src/bin/sh/arith.y:168: error: union has no member named `l_value'
/home/build/src/bin/sh/arith.y:172: error: syntax error before "value"
/home/build/src/bin/sh/arith.y:174: error: union has no member named `l_value'
/home/build/src/bin/sh/arith.y:177: error: union has no member named `l_value'
/home/build/src/bin/sh/arith.y:181: error: syntax error before "value"
/home/build/src/bin/sh/arith.y:183: error: union has no member named `l_value'
/home/build/src/bin/sh/arith.y:186: error: union has no member named `l_value'
/home/build/src/bin/sh/arith.y:190: error: syntax error before "value"
/home/build/src/bin/sh/arith.y:192: error: union has no member named `l_value'
/home/build/src/bin/sh/arith.y:195: error: union has no member named `l_value'
/home/build/src/bin/sh/arith.y:198: error: union has no member named `l_value'
/home/build/src/bin/sh/arith.y:202: error: syntax error before "value"
/home/build/src/bin/sh/arith.y:204: error: union has no member named `l_value'
/home/build/src/bin/sh/arith.y:207: error: union has no member named `l_value'
/home/build/src/bin/sh/arith.y:210: error: union has no member named `l_value'
/home/build/src/bin/sh/arith.y:214: error: syntax error before "value"
/home/build/src/bin/sh/arith.y:216: error: union has no member named `l_value'
/home/build/src/bin/sh/arith.y:219: error: union has no member named `l_value'
/home/build/src/bin/sh/arith.y:223: error: syntax error before "value"
/home/build/src/bin/sh/arith.y:225: error: union has no member named `l_value'
/home/build/src/bin/sh/arith.y:228: error: union has no member named `l_value'
/home/build/src/bin/sh/arith.y:232: error: syntax error before "value"
/home/build/src/bin/sh/arith.y:234: error: union has no member named `l_value'
/home/build/src/bin/sh/arith.y:237: error: union has no member named `l_value'
/home/build/src/bin/sh/arith.y:241: error: syntax error before "value"
/home/build/src/bin/sh/arith.y:243: error: union has no member named `l_value'
/home/build/src/bin/sh/arith.y:246: error: union has no member named `l_value'
/home/build/src/bin/sh/arith.y:250: error: syntax error before "value"
/home/build/src/bin/sh/arith.y:252: error: union has no member named `l_value'
/home/build/src/bin/sh/arith.y:255: error: union has no member named `l_value'

Is this a known issue, or am I doing something silly?

My /etc/make.conf file contains:

% # cat -n /etc/make.conf
%      1  CPUTYPE?=               i686
%      2  NO_CPU_CFLAGS=          true    # Don't add -march=<cpu> to CFLAGS automatically
%      3  NO_CPU_COPTFLAGS=       true    # Don't add -march=<cpu> to COPTFLAGS automatically
%      4  
%      5  CFLAGS?=                -O -pipe
%      6  COPTFLAGS?=             -O -pipe
%      7  
%      8  BOOTWAIT=               0
%      9  PRINTERDEVICE=          ascii
%     10  
%     11  DOC_LANG=               en_US.ISO8859-1 el_GR.ISO8859-7
%     12  
%     13  SENDMAIL_MC=            /etc/mail/kobe.mc
%     14  SENDMAIL_SUBMIT_MC=     /etc/mail/kobe.submit.mc
%     15  
%     16  SENDMAIL_CFLAGS=        -I/usr/local/include -DSASL=2
%     17  SENDMAIL_LDFLAGS=       -L/usr/local/lib
%     18  SENDMAIL_LDADD=         -lsasl2
%     19  
%     20  XFREE86_VERSION?=       4
%     21  
%     22  # When fetching distfiles, try to continue failed or interrupted transfers.
%     23  FETCH_CMD?=             /usr/bin/fetch -A -r -R
%     24  
%     25  DEBUG_FLAGS?=           -g
%     26  
%     27  # added by use.perl 2006-10-31 21:47:35
%     28  PERL_VER=5.8.8
%     29  PERL_VERSION=5.8.8
% #