Fix usage of loop in a for else clause

src/Runtime/LoopContext.php

@@ -38,7 +38,7 @@ final class LoopContext
 
     public function getRevindex0(): int
     {
-        return $this->loop->getLength('revindex0') - $this->getIndex();
+        return max(0, $this->loop->getLength('revindex0') - $this->getIndex());
     }
 
     public function getRevindex(): int

src/Runtime/LoopIterator.php

@@ -74,8 +74,8 @@ final class LoopIterator implements \Iterator
     public function rewind(): void
     {
         $this->seq->rewind();
+        $this->previous = ['valid' => false, 'key' => null, 'value' => null];
         if ($this->seq->valid()) {
-            $this->previous = ['valid' => false, 'key' => null, 'value' => null];
             $this->current = ['valid' => $this->seq->valid(), 'key' => $this->seq->key(), 'value' => $this->seq->current()];
         } else {
             // EmptyIterator
@@ -123,7 +123,12 @@ final class LoopIterator implements \Iterator
     {
         if (!$this->next) {
             $this->seq->next();
-            $this->next = ['valid' => $this->seq->valid(), 'key' => $this->seq->key(), 'value' => $this->seq->current()];
+            if ($this->seq->valid()) {
+                $this->next = ['valid' => $this->seq->valid(), 'key' => $this->seq->key(), 'value' => $this->seq->current()];
+            } else {
+                // EmptyIterator
+                $this->next = ['valid' => false, 'key' => null, 'value' => null];
+            }
         }
 
         return $this->next;

tests/Fixtures/tags/for/loop_in_else.test

@@ -0,0 +1,62 @@
+--TEST--
+"for" tag loop behavior in an else clause
+--TEMPLATE--
+{% for item in [] %}
+{% else %}
+{{ loop.previous is null ? 'OK' : 'KO' }}
+{{ loop.next is null ? 'OK' : 'KO' }}
+{{ loop.first ? 'OK' : 'KO' }}
+{{ loop.last ? 'OK' : 'KO' }}
+{{ loop.index0 is same as 0 ? 'OK' : 'KO' }}
+{{ loop.revindex0 is same as 0 ? 'OK' : 'KO' }}
+{{ loop.length is same as 0 ? 'OK' : 'KO' }}
+{{ loop.depth is same as 1 ? 'OK' : 'KO' }}
+{% endfor %}
+
+{% for item in empty_it %}
+{% else %}
+{{ loop.previous is null ? 'OK' : 'KO' }}
+{{ loop.next is null ? 'OK' : 'KO' }}
+{{ loop.first ? 'OK' : 'KO' }}
+{{ loop.last ? 'OK' : 'KO' }}
+{{ loop.index0 is same as 0 ? 'OK' : 'KO' }}
+{{ loop.depth is same as 1 ? 'OK' : 'KO' }}
+{% endfor %}
+
+{% for item in yielding_it %}
+{% else %}
+{{ loop.previous is null ? 'OK' : 'KO' }}
+{{ loop.next is null ? 'OK' : 'KO' }}
+{{ loop.first ? 'OK' : 'KO' }}
+{{ loop.last ? 'OK' : 'KO' }}
+{{ loop.index0 is same as 0 ? 'OK' : 'KO' }}
+{{ loop.depth is same as 1 ? 'OK' : 'KO' }}
+{% endfor %}
+--DATA--
+return [
+    'empty_it' => new \EmptyIterator(),
+    'yielding_it' => (function (): \Generator { return; yield; })(),
+]
+--EXPECT--
+OK
+OK
+OK
+OK
+OK
+OK
+OK
+OK
+
+OK
+OK
+OK
+OK
+OK
+OK
+
+OK
+OK
+OK
+OK
+OK
+OK