+ return bless [$value, {@_}], $class;
+}
+
+# influences(): return a reference to a copy of the hash
+# { page => dependency type } describing the pages that indirectly influenced
+# this result, but would not cause a dependency through ikiwiki's core
+# dependency logic.
+#
+# See [[todo/dependency_types]] for extensive discussion of what this means.
+#
+# influences(page => deptype, ...): remove all influences, replace them
+# with the arguments, and return a reference to a copy of the new influences.
+
+sub influences {
+ my $this=shift;
+ $this->[1]={@_} if @_;
+ my %i=%{$this->[1]};
+ delete $i{""};
+ return \%i;
+}
+
+# True if this result has the same influences whichever page it matches,
+# For instance, whether bar matches backlink(foo) is influenced only by
+# the set of links in foo, so its only influence is { foo => DEPEND_LINKS },
+# which does not mention bar anywhere.
+#
+# False if this result would have different influences when matching
+# different pages. For instance, when testing whether link(foo) matches bar,
+# { bar => DEPEND_LINKS } is an influence on that result, because changing
+# bar's links could change the outcome; so its influences are not the same
+# as when testing whether link(foo) matches baz.
+#
+# Static influences are one of the things that make pagespec_match_list
+# more efficient than repeated calls to pagespec_match.
+
+sub influences_static {
+ return ! $_[0][1]->{""};
+}
+
+# Change the influences of $this to be the influences of "$this & $other"
+# or "$this | $other".
+#
+# If both $this and $other are either successful or have influences,
+# or this is an "or" operation, the result has all the influences from
+# either of the arguments. It has dynamic influences if either argument
+# has dynamic influences.
+#
+# If this is an "and" operation, and at least one argument is a
+# FailReason with no influences, the result has no influences, and they
+# are not dynamic. For instance, link(foo) matching bar is influenced
+# by bar, but enabled(ddate) has no influences. Suppose ddate is disabled;
+# then (link(foo) and enabled(ddate)) not matching bar is not influenced by
+# bar, because it would be false however often you edit bar.
+
+sub merge_influences {
+ my $this=shift;
+ my $other=shift;
+ my $anded=shift;
+
+ # This "if" is odd because it needs to avoid negating $this
+ # or $other, which would alter the objects in-place. Be careful.
+ if (! $anded || (($this || %{$this->[1]}) &&
+ ($other || %{$other->[1]}))) {
+ foreach my $influence (keys %{$other->[1]}) {
+ $this->[1]{$influence} |= $other->[1]{$influence};
+ }
+ }
+ else {
+ # influence blocker
+ $this->[1]={};
+ }
+}
+
+# Change $this so it is not considered to be influenced by $torm.
+
+sub remove_influence {
+ my $this=shift;
+ my $torm=shift;
+
+ delete $this->[1]{$torm};
+}
+
+package IkiWiki::ErrorReason;
+
+our @ISA = 'IkiWiki::FailReason';