Possible bug: AC_USE_SYSTEM_EXTENSIONS ignores "AS_IF" conditionals

[David A. Wheeler]

I *think* that AC_USE_SYSTEM_EXTENSIONS has a bug; it seems to ignore 
conditionals.

E.G., given this configure.ac:
====
AC_PREREQ([2.63])
AC_INIT([bug], [0.01])
AC_CONFIG_HEADERS([config.h])
AS_IF([test 0 = 1 ],
 [AC_USE_SYSTEM_EXTENSIONS])
AC_OUTPUT
====

The file "config.h" still enables extensions, even though the test is false.

I'm trying to conditionally use extensions like this:
 AS_IF([test "$enable_all_system_extensions" = "yes"],
  [AC_USE_SYSTEM_EXTENSIONS])

Am I going about this the wrong way?

Suggestions welcome.

--- David A. Wheeler