fix(compiler): 支持返回引用转发引用调用

src/CompilerBase.php

@@ -1801,12 +1801,67 @@ class CompilerBase implements PropertyAccessContext
         $this->fatalError($arg, 'Only string literals or `ClassName::class` constant are supported');
     }
 
+    /**
+     * Returns true when the expression is a function/method/static call that
+     * itself returns by reference, so its result can be forwarded directly
+     * from a `return by reference` context. In PHP, `function &f() { return g(); }`
+     * is valid as long as `g()` also returns by reference.
+     */
+    protected function isRefReturningCall(Node $expr): bool
+    {
+        if ($expr instanceof Expr\FuncCall && ($this->isNameExpr($expr->name) || $this->isFullNameExpr($expr->name))) {
+            $name = $this->parseIdentifier($expr->name);
+            $function = $this->findNativeFunction($name);
+            if ($function !== false) {
+                return $this->getFunction($function)->returnsByRef;
+            }
+            $reflection = \TypePhp\Resolver\Reflection::getFunction(ltrim($this->getNamespacedFuncName($name), '\\'));
+            return $reflection !== null && $reflection->isInternal() && $reflection->returnsReference();
+        }
+        if ($expr instanceof Expr\MethodCall && $this->isNamedMethod($expr->name) && $this->isVarExpr($expr->var)) {
+            $object = $this->parseIdentifier($expr->var);
+            $method = $this->parseIdentifier($expr->name);
+            $function = $this->findNativeMethod($expr, $object, $method);
+            if ($function !== false) {
+                return $this->getFunction($function)->returnsByRef;
+            }
+            return false;
+        }
+        if ($expr instanceof Expr\StaticCall && ($this->isNameExpr($expr->class) || $this->isFullNameExpr($expr->class)) && $this->isIdExpr($expr->name)) {
+            $class = $this->parseIdentifier($expr->class);
+            if ($class === 'self') {
+                $class = $this->getFullClassName();
+            } elseif ($class === 'parent') {
+                if (!$this->classDef || !$this->classDef->extends) {
+                    return false;
+                }
+                $class = $this->classDef->extends;
+            } elseif ($class !== 'static') {
+                $class = $this->getNamespacedClassName($class);
+            }
+            if ($class === 'static') {
+                return false;
+            }
+            $method = $this->parseIdentifier($expr->name);
+            $function = $this->getNativeMethod($expr, $class, $method);
+            if ($function !== false) {
+                return $this->getFunction($function)->returnsByRef;
+            }
+            return false;
+        }
+        return false;
+    }
+
     protected function parseReturn(Node\Stmt\Return_ $v): string
     {
         if ($this->functionDef->returnsByRef) {
             if ($v->expr === null) {
                 return 'return ' . Type::REF . '{};';
             }
+            // Forwarding a call that itself returns by reference is valid PHP.
+            if ($this->isRefReturningCall($v->expr)) {
+                return 'return ' . $this->parseExpr($v->expr) . ';';
+            }
             if (!$this->isVarExpr($v->expr)
                 && !$this->isPropertyFetch($v->expr)
                 && !$this->isStaticPropertyFetch($v->expr)

tests/compiler/ref/function-return-reference-chain.phpt

@@ -0,0 +1,34 @@
+--TEST--
+Function returning by reference can forward another by-reference call
+--FILE--
+<?php
+
+function main()
+{
+    $value1 = test1();
+    var_dump($value1);
+    $value2 = &test1();
+    var_dump($value2);
+    $value2 = 0;
+    $value3 = test1();
+    var_dump($value3);
+}
+
+function &test1()
+{
+    return test2();
+}
+
+function &test2()
+{
+    global $value;
+    $value++;
+    return $value;
+}
+
+// main();
+?>
+--EXPECT--
+int(1)
+int(2)
+int(1)

tests/compiler/ref/method-return-reference-chain.phpt

@@ -0,0 +1,33 @@
+--TEST--
+Method returning by reference can forward another by-reference method call
+--FILE--
+<?php
+class Test
+{
+    private $value = 1;
+
+    public function &getValue()
+    {
+        return $this->value;
+    }
+
+    public function &getRefValue()
+    {
+        return $this->getValue();
+    }
+}
+
+function main()
+{
+    $test = new Test;
+    var_dump($test->getRefValue());
+    $ref = &$test->getRefValue();
+    $ref = 2;
+    var_dump($test->getValue());
+}
+
+// main();
+?>
+--EXPECT--
+int(1)
+int(2)

tests/compiler/ref/static-return-reference-chain.phpt

@@ -0,0 +1,33 @@
+--TEST--
+Static method returning by reference can forward another by-reference static call
+--FILE--
+<?php
+class Counter
+{
+    private static $value = 0;
+
+    public static function &next()
+    {
+        self::$value++;
+        return self::$value;
+    }
+
+    public static function &current()
+    {
+        return self::next();
+    }
+}
+
+function main()
+{
+    var_dump(Counter::current());
+    $ref = &Counter::current();
+    $ref = 10;
+    var_dump(Counter::next());
+}
+
+// main();
+?>
+--EXPECT--
+int(1)
+int(11)