test(compiler): cover expression variable names

phpunit/code/variable-variable-function-call.php

@@ -0,0 +1,12 @@
+<?php
+
+function variable_name(): string
+{
+    return 'hello';
+}
+
+function variable_variable_with_function_call(): void
+{
+    ${variable_name()} = 'world';
+    echo $hello;
+}

phpunit/src/VariableVariableTest.php

@@ -6,4 +6,9 @@ class VariableVariableTest extends \BaseTest
     {
         $this->exec('The `$$` syntax is not supported', 'variable-variable-arraydim.php');
     }
+
+    public function testVariableVariableWithFunctionCallThrowsUnsupportedError(): void
+    {
+        $this->exec('The `$$` syntax is not supported', 'variable-variable-function-call.php');
+    }
 }

src/CompilerBase.php

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