- if ($my_tc->check($right)) {
- $right = $right->flatten;
-
- my ($only_left, $common, $only_right) = $inter->(
- $left->_mods_cache,
- $right->_mods_cache,
- );
-
- if (@$common) {
- my $x = $left->new
- ->mod(@$only_left)
- ->body($left->_body);
- my $y = $left->new
- ->mod(@$only_right)
- ->body($right->_body);
- ($x, $y) = ($y, $x) if $rev;
- return $left->new
- ->mod(@$common)
- ->body($x . $y);
+ if ($my_tc->check($left)) {
+
+ if ($my_tc->check($right)) {
+
+ my ($only_left, $common, $only_right) = $inter->(
+ $left->_mods_cache,
+ $right->_mods_cache,
+ );
+
+ my $has_different_layers;
+ for (@$only_left, @$only_right) {
+ if ($_->type eq 'layer') {
+ $has_different_layers = 1;
+ last;
+ }
+ }
+
+ if (!$has_different_layers and @$common) {
+ my $x = $left->new(
+ mods => $only_left,
+ body => $left->body,
+ );
+ my $y = $left->new(
+ mods => $only_right,
+ body => $right->body,
+ );
+ return $left->new(
+ mods => $common,
+ body => fold($x, $y, $rev),
+ );
+ } else {
+ @right = $right->instantiate;
+ }