double assignment is an error in automake 1.5?

[Assar Westerlund]

I would like to check if it's the case that this is supposed to be an
error or not.  Being able to set a variable multiple times is a rather
common thing to do in Makefiles, so I was kind of assuming that would
be carried over to automake.

/assar

Makefile.am:
----------------------------------------------------------------------
foo = 1
foo = 1
----------------------------------------------------------------------

configure.in:
----------------------------------------------------------------------
AM_INIT_AUTOMAKE(foo,0.0)
AC_OUTPUT(Makefile)
----------------------------------------------------------------------

running: 

$ automake --version
automake (GNU automake) 1.5
Written by Tom Tromey <address@hidden>.

Copyright 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001
Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

$ automake --foreign -a
automake: configure.in: installing `./install-sh'
automake: configure.in: installing `./mkinstalldirs'
automake: configure.in: installing `./missing'
Makefile.am:1: foo multiply defined in condition TRUE

  foo (User, where = 1) =
  {
    TRUE => 1
  }