fix(compiler): 拒绝所有$$语法而非仅特定表达式

phpunit/code/variable-variable-arraydim.php

@@ -0,0 +1,8 @@
+<?php
+
+function variable_variable_with_array_dim(): void
+{
+    $foo = ['bar' => 'hello'];
+    ${$foo['bar']} = 'world';
+    echo $hello;
+}

phpunit/src/VariableVariableTest.php

@@ -0,0 +1,9 @@
+<?php
+
+class VariableVariableTest extends \BaseTest
+{
+    public function testVariableVariableWithArrayDimThrowsUnsupportedError(): void
+    {
+        $this->exec('The `$$` syntax is not supported', 'variable-variable-arraydim.php');
+    }
+}

src/CompilerBase.php

@@ -1273,7 +1273,7 @@ class CompilerBase implements PropertyAccessContext
 
     protected function parseVariable(Variable $expr): string
     {
-        if (is_object($expr->name) and $this->isVarExpr($expr->name)) {
+        if (is_object($expr->name)) {
             $this->fatalError($expr, 'The `$$` syntax is not supported');
         }
         if ($this->isSuperGlobal($expr->name)) {