AC_PACKAGE_VERSION visibility slightly changed in autoconf-2.69c. Bug or feature?

[Sergei Trofimovich]

Initial bug is reported as autoconf failure on ghc-8.8.4:
    https://bugs.gentoo.org/750191
There autconf 2.69 works, 2.69c does not.

Here is the minimal example:

OK:

  $ cat configure.ac
  AC_INIT([The Glorious Glasgow Haskell Compilation System], [9.1.0], 
[glasgow-haskell-bugs@haskell.org], [ghc-AC_PACKAGE_VERSION])

  echo "$PACKAGE_VERSION"

  AC_OUTPUT
  $ autoconf-2.69
  $ ./configure
  9.1.0
  configure: creating ./config.status

BAD:

  $ autoconf-2.70_beta2
  configure.ac:1: error: possibly undefined macro: AC_PACKAGE_VERSION
      If this token and others are legitimate, please use m4_pattern_allow.
      See the Autoconf documentation.

https://www.gnu.org/software/autoconf/manual/autoconf-2.67/html_node/Initializing-configure.html
says AC_INIT should define the AC_PACKAGE_VERSION, but evaluation probably 
happens later.

Should autoconf restore the old behaviour or should ghc adapt?
If we are to adapt what would be the best way not to repeat the version?

Thank you!

-- 

  Sergei