FTBFS using vala-0.46.1

libunity failed to build from source in Fedora rawhide/f31

https://koji.fedoraproject.org/koji/taskinfo?taskID=36635189

For details on the mass rebuild see:

https://fedoraproject.org/wiki/Fedora_31_Mass_Rebuild
Please fix libunity at your earliest convenience and set the bug's status to
ASSIGNED when you start fixing it. If the bug remains in NEW state for 8 weeks,
libunity will be orphaned. Before branching of Fedora 32,
libunity will be retired, if it still fails to build.

For more details on the FTBFS policy, please visit:
https://fedoraproject.org/wiki/Fails_to_build_from_source

Created attachment 1597558
build.log

file build.log too big, will only attach last 32768 bytes

Created attachment 1597559
root.log

file root.log too big, will only attach last 32768 bytes

Created attachment 1597560
state.log

This bug appears to have been reported against 'rawhide' during the Fedora 31 development cycle.
Changing version to 31.

Failure appears to be vala-related:

make[2]: Entering directory '/builddir/build/BUILD/libunity-7.1.4/src'
/usr/bin/valac -C -H unity.h -d . --gir=Unity-7.0.gir --library unity --internal-vapi=unity-internal.vapi --internal-header=unity-internal.h --target-glib=2.32 --thread --use-header --vapidir ../vapi --vapidir ../protocol --vapidir . --pkg unity-protocol --pkg config --pkg unity-trace --pkg glib-2.0 --pkg gmodule-2.0 --pkg gobject-2.0 --pkg gio-2.0 --pkg gio-unix-2.0 --pkg dee-1.0 --pkg Dbusmenu-0.4 unity-appinfo-manager.vala unity-icon.vala unity-inspector.vala unity-io.vala unity-launcher.vala unity-category.vala unity-filters.vala unity-preferences-manager.vala unity-merge-strategy.vala unity-models.vala unity-search.vala unity-synchronizer.vala unity-previews.vala unity-result-activation.vala unity-scope-interface.vala unity-scope-dbus-connector.vala unity-scope-dbus-impl.vala unity-scope-channel.vala unity-deprecated-scope.vala unity-deprecated-scope-impl.vala unity-aggregator-scope.vala unity-aggregator-scope-private.vala unity-master-scope.vala unity-simple-scope.vala unity-scope-loader.vala unity-scope-tracker.vala unity-sound-menu.vala unity-sound-menu-mpris.vala unity-utils.vala
Command-line option `--thread` is deprecated and will be ignored
Compilation failed: 2 error(s), 0 warning(s)
BUILDSTDERR: unity-deprecated-scope.vala:64.3-64.28: error: Creation method of abstract class cannot be public.
BUILDSTDERR: public DeprecatedScopeBase (string dbus_path_, string id_)
BUILDSTDERR: ^^^^^^^^^^^^^^^^^^^^^^^^^^
BUILDSTDERR: unity-aggregator-scope.vala:54.3-54.24: error: Creation method of abstract class cannot be public.
BUILDSTDERR: public AggregatorScope (string dbus_path_, string id_, MergeMode merge_mode = AggregatorScope.MergeMode.OWNER_SCOPE, bool proxy_filter_hints = false)
BUILDSTDERR: ^^^^^^^^^^^^^^^^^^^^^^
BUILDSTDERR: make[2]: *** [Makefile:1389: libunity_la_vala.stamp] Error 1
make[2]: Leaving directory '/builddir/build/BUILD/libunity-7.1.4/src'
BUILDSTDERR: make[1]: *** [Makefile:571: all-recursive] Error 1

*** Bug 1718302 has been marked as a duplicate of this bug. ***

Reported upstream,

https://bugs.launchpad.net/ubuntu/+source/libunity/+bug/1844158

Dear Maintainer,

your package has not been built successfully in 31. Action is required from you.

If you can fix your package to build, perform a build in koji, and either create
an update in bodhi, or close this bug without creating an update, if updating is
not appropriate [1]. If you are working on a fix, set the status to ASSIGNED to
acknowledge this. Following the latest policy for such packages [2], your package
can be orphaned if this bug remains in NEW state more than 8 weeks.

A week before the mass branching of Fedora 32 according to the schedule [3],
any packages which still have open FTBFS bugs from Fedora 31 will be retired.

[1] https://fedoraproject.org/wiki/Updates_Policy
[2] https://docs.fedoraproject.org/en-US/fesco/Fails_to_build_from_source_Fails_to_install/
[3] https://fedoraproject.org/wiki/Releases/32/Schedule