From 3a8efec728fa254c83e1e0211a8ace9c2025aa4a Mon Sep 17 00:00:00 2001
From: Matthew Brown <github@muglug.com>
Date: Sat, 16 Sep 2017 13:16:21 -0400
Subject: [PATCH] Add error for pass by reference

---
 config.xsd                                    |  1 +
 .../Statements/Expression/CallChecker.php     | 27 ++++++++++++++++---
 src/Psalm/Issue/InvalidPassByReference.php    |  6 +++++
 tests/FunctionCallTest.php                    | 18 +++++++++++--
 4 files changed, 46 insertions(+), 6 deletions(-)
 create mode 100644 src/Psalm/Issue/InvalidPassByReference.php

diff --git a/config.xsd b/config.xsd
index 409697374..c68b05bb2 100644
--- a/config.xsd
+++ b/config.xsd
@@ -110,6 +110,7 @@
             <xs:element name="InvalidIterator" type="IssueHandlerType" minOccurs="0" />
             <xs:element name="InvalidMethodCall" type="IssueHandlerType" minOccurs="0" />
             <xs:element name="InvalidOperand" type="IssueHandlerType" minOccurs="0" />
+            <xs:element name="InvalidPassByReference" type="IssueHandlerType" minOccurs="0" />
             <xs:element name="InvalidPropertyAssignment" type="IssueHandlerType" minOccurs="0" />
             <xs:element name="InvalidPropertyFetch" type="IssueHandlerType" minOccurs="0" />
             <xs:element name="InvalidReturnType" type="IssueHandlerType" minOccurs="0" />
diff --git a/src/Psalm/Checker/Statements/Expression/CallChecker.php b/src/Psalm/Checker/Statements/Expression/CallChecker.php
index 3a285eb3b..181e919aa 100644
--- a/src/Psalm/Checker/Statements/Expression/CallChecker.php
+++ b/src/Psalm/Checker/Statements/Expression/CallChecker.php
@@ -23,6 +23,7 @@ use Psalm\Issue\ImplicitToStringCast;
 use Psalm\Issue\InvalidArgument;
 use Psalm\Issue\InvalidFunctionCall;
 use Psalm\Issue\InvalidMethodCall;
+use Psalm\Issue\InvalidPassByReference;
 use Psalm\Issue\InvalidScalarArgument;
 use Psalm\Issue\InvalidScope;
 use Psalm\Issue\MixedArgument;
@@ -1697,11 +1698,29 @@ class CallChecker
         }
 
         foreach ($args as $argument_offset => $arg) {
-            if (isset($arg->value->inferredType)) {
-                $function_param = count($function_params) > $argument_offset
-                    ? $function_params[$argument_offset]
-                    : ($last_param && $last_param->is_variadic ? $last_param : null);
+            $function_param = count($function_params) > $argument_offset
+                ? $function_params[$argument_offset]
+                : ($last_param && $last_param->is_variadic ? $last_param : null);
 
+            if ($function_param
+                && $function_param->by_ref
+                && !($arg->value instanceof PhpParser\Node\Expr\Variable)
+                && !($arg->value instanceof PhpParser\Node\Expr\PropertyFetch)
+            ) {
+                if (IssueBuffer::accepts(
+                    new InvalidPassByReference(
+                        'Parameter ' . ($argument_offset + 1) . ' of ' . $method_id . ' expects a variable',
+                        $code_location
+                    ),
+                    $statements_checker->getSuppressedIssues()
+                )) {
+                    return false;
+                }
+
+                break;
+            }
+
+            if (isset($arg->value->inferredType)) {
                 if ($function_param && $function_param->type) {
                     $param_type = clone $function_param->type;
 
diff --git a/src/Psalm/Issue/InvalidPassByReference.php b/src/Psalm/Issue/InvalidPassByReference.php
new file mode 100644
index 000000000..bd0ec490e
--- /dev/null
+++ b/src/Psalm/Issue/InvalidPassByReference.php
@@ -0,0 +1,6 @@
+<?php
+namespace Psalm\Issue;
+
+class InvalidPassByReference extends CodeError
+{
+}
diff --git a/tests/FunctionCallTest.php b/tests/FunctionCallTest.php
index e556199f5..27239362a 100644
--- a/tests/FunctionCallTest.php
+++ b/tests/FunctionCallTest.php
@@ -266,6 +266,21 @@ class FunctionCallTest extends TestCase
 
                   foo($a3);',
             ],
+            'goodByRef' => [
+                '<?php
+                    class A {
+                        /** @var string */
+                        public $foo = "hello";
+                    }
+
+                    $a = new A();
+                    $b = "goodbye";
+
+                    function fooFoo(string &$v) : void {}
+
+                    fooFoo($a->foo);
+                    fooFoo($b);',
+            ],
         ];
     }
 
@@ -359,8 +374,7 @@ class FunctionCallTest extends TestCase
                     function f($p = false) {}',
                 'error_message' => 'InvalidParamDefault',
             ],
-            // Skipped. Does not throw an error.
-            'SKIPPED-badByRef' => [
+            'badByRef' => [
                 '<?php
                     function fooFoo(string &$v) : void {}
                     fooFoo("a");',