Fix AssignNameExpression to forbid using names that won't work

src/ExpressionParser.php

@@ -784,11 +784,7 @@ class ExpressionParser
             } else {
                 $stream->expect(Token::NAME_TYPE, null, 'Only variables can be assigned to');
             }
-            $value = $token->getValue();
-            if (\in_array(strtolower($value), ['true', 'false', 'none', 'null'])) {
-                throw new SyntaxError(\sprintf('You cannot assign a value to "%s".', $value), $token->getLine(), $stream->getSourceContext());
-            }
-            $targets[] = new AssignNameExpression($value, $token->getLine());
+            $targets[] = new AssignNameExpression($token->getValue(), $token->getLine());
 
             if (!$stream->nextIf(Token::PUNCTUATION_TYPE, ',')) {
                 break;

src/Node/Expression/AssignNameExpression.php

@@ -13,9 +13,20 @@
 namespace Twig\Node\Expression;
 
 use Twig\Compiler;
+use Twig\Error\SyntaxError;
 
 class AssignNameExpression extends NameExpression
 {
+    public function __construct(string $name, int $lineno)
+    {
+        // All names supported by ExpressionParser::parsePrimaryExpression() should be excluded
+        if (\in_array(strtolower($name), ['true', 'false', 'none', 'null'])) {
+            throw new SyntaxError(\sprintf('You cannot assign a value to "%s".', $name), $lineno);
+        }
+
+        parent::__construct($name, $lineno);
+    }
+
     public function compile(Compiler $compiler): void
     {
         $compiler

src/TokenParser/FromTokenParser.php

@@ -35,9 +35,10 @@ final class FromTokenParser extends AbstractTokenParser
         while (true) {
             $name = $stream->expect(Token::NAME_TYPE)->getValue();
 
-            $alias = $name;
             if ($stream->nextIf('as')) {
-                $alias = $stream->expect(Token::NAME_TYPE)->getValue();
+                $alias = new AssignNameExpression($stream->expect(Token::NAME_TYPE)->getValue(), $token->getLine());
+            } else {
+                $alias = new AssignNameExpression($name, $token->getLine());
             }
 
             $targets[$name] = $alias;
@@ -53,7 +54,7 @@ final class FromTokenParser extends AbstractTokenParser
         $node = new ImportNode($macro, $var, $token->getLine(), $this->parser->isMainScope());
 
         foreach ($targets as $name => $alias) {
-            $this->parser->addImportedSymbol('function', $alias, 'macro_'.$name, $var);
+            $this->parser->addImportedSymbol('function', $alias->getAttribute('name'), 'macro_'.$name, $var);
         }
 
         return $node;

tests/Fixtures/filters/arrow_reserved_names.test

@@ -0,0 +1,8 @@
+--TEST--
+"map" filter
+--TEMPLATE--
+{{ [1, 2]|map(true => true * 2)|join(', ') }}
+--DATA--
+return []
+--EXCEPTION--
+Twig\Error\SyntaxError: You cannot assign a value to "true" in "index.twig" at line 2.

tests/Fixtures/tags/for/reserved_names.test

@@ -0,0 +1,9 @@
+--TEST--
+"for" tag
+--TEMPLATE--
+{% for true in [1, 2] %}
+{% endfor %}
+--DATA--
+return []
+--EXCEPTION--
+Twig\Error\SyntaxError: You cannot assign a value to "true" in "index.twig" at line 2.

tests/Fixtures/tags/macro/from_reserved_names.test

@@ -0,0 +1,13 @@
+--TEST--
+"from" tag
+--TEMPLATE--
+{% from _self import input as true %}
+
+{{ true('username') }}
+
+{% macro input(name) -%}
+{% endmacro %}
+--DATA--
+return []
+--EXCEPTION--
+Twig\Error\SyntaxError: You cannot assign a value to "true" in "index.twig" at line 2.

tests/Fixtures/tags/macro/import_reserved_names.test

@@ -0,0 +1,8 @@
+--TEST--
+"import" tag
+--TEMPLATE--
+{% import _self as true %}
+--DATA--
+return []
+--EXCEPTION--
+Twig\Error\SyntaxError: You cannot assign a value to "true" in "index.twig" at line 2.

tests/Fixtures/tags/set/reserved_names.test

@@ -0,0 +1,8 @@
+--TEST--
+"set" tag
+--TEMPLATE--
+{% set true = 'foo' %}
+--DATA--
+return []
+--EXCEPTION--
+Twig\Error\SyntaxError: You cannot assign a value to "true" in "index.twig" at line 2.