bug #4894 Fix an empty destructuring pattern triggering a PHP fatal error instead of a SyntaxError (fabpot)

This PR was merged into the 3.x branch.

Discussion
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Fix an empty destructuring pattern triggering a PHP fatal error instead of a SyntaxError

Commits
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a2b0233 Fix an empty destructuring pattern triggering a PHP fatal error instead of a SyntaxError

Author: fabpot

CHANGELOG

@@ -1,6 +1,7 @@
 # 3.29.0 (2026-XX-XX)
 
  * Add documentation comments to attach metadata to nodes (experimental)
+ * Fix an empty destructuring pattern triggering a PHP fatal error instead of a `SyntaxError`
  * Fix sequence destructuring of iterators throwing a `TypeError`
  * Add `TempestMarkdown` to use `tempest/markdown` as the `markdown_to_html` converter
  * Fix imported macros not resolving their own template-level macro imports

src/ExpressionParser/Infix/AssignmentExpressionParser.php

@@ -50,6 +50,9 @@ public function parse(Parser $parser, AbstractExpression $left, Token $token): A
         };
 
         if ($left instanceof ArrayExpression) {
+            if (!$left->getKeyValuePairs()) {
+                throw new SyntaxError('Cannot destructure to an empty list of variables.', $token->getLine(), $parser->getStream()->getSourceContext());
+            }
             foreach ($left->getKeyValuePairs() as $i => $pair) {
                 if ($pair['value'] instanceof ContextVariable && !$pair['value'] instanceof AssignContextVariable) {
                     $left->setNode(2 * $i + 1, new AssignContextVariable($pair['value']->getAttribute('name'), $pair['value']->getTemplateLine()));

tests/ExpressionParserTest.php

@@ -268,6 +268,25 @@ public function testSequenceDestructuringUsesAssignmentTargets(): void
         $this->assertSame('third', $pairs[2]['value']->getAttribute('name'));
     }
 
+    /**
+     * @dataProvider getEmptyDestructuringTests
+     */
+    #[DataProvider('getEmptyDestructuringTests')]
+    public function testEmptyDestructuringThrows(string $template): void
+    {
+        $env = new Environment(new ArrayLoader(), ['cache' => false, 'autoescape' => false]);
+
+        $this->expectException(SyntaxError::class);
+        $this->expectExceptionMessage('Cannot destructure to an empty list of variables');
+        $env->compileSource(new Source($template, 'index'));
+    }
+
+    public static function getEmptyDestructuringTests()
+    {
+        yield ['{% do [] = values %}'];
+        yield ['{% do {} = values %}'];
+    }
+
     public function testObjectDestructuringUsesAssignmentTargets(): void
     {
         $env = new Environment(new ArrayLoader(), ['cache' => false, 'autoescape' => false]);