Make assignment of a reference variable be considered a use (#128)

* Add a test

* Mark reference variables are used when they are

* Fix coding standards

VariableAnalysis/Lib/VariableInfo.php

@@ -28,6 +28,11 @@ class VariableInfo {
    */
   public $passByReference = false;
 
+  /**
+   * @var bool
+   */
+  public $isReference = false;
+
   /**
    * Stack pointer of first declaration
    *

VariableAnalysis/Sniffs/CodeAnalysis/VariableAnalysisSniff.php

@@ -756,6 +756,19 @@ protected function checkForAssignment(File $phpcsFile, $stackPtr, $varName, $cur
     // Plain ol' assignment. Simpl(ish).
     $writtenPtr = Helpers::findWhereAssignExecuted($phpcsFile, $assignPtr);
     $this->markVariableAssignment($varName, $writtenPtr, $currScope);
+
+    // Are we are reference variable?
+    $tokens = $tokens = $phpcsFile->getTokens();
+    $referencePtr = $phpcsFile->findNext(T_WHITESPACE, $assignPtr + 1, null, true, null, true);
+    $varInfo = $this->getOrCreateVariableInfo($varName, $currScope);
+    if (($referencePtr !== false) && ($tokens[$referencePtr]['code'] === T_BITWISE_AND)) {
+      $varInfo->isReference = true;
+    } elseif ($varInfo->isReference) {
+      // If this is an assigment to a reference variable then that variable is
+      // used.
+      $this->markVariableRead($varName, $stackPtr, $currScope);
+    }
+
     return true;
   }
 

VariableAnalysis/Tests/CodeAnalysis/VariableAnalysisTest.php

@@ -936,4 +936,16 @@ public function testUnusedVarWithValueChange() {
     ];
     $this->assertEquals($expectedWarnings, $lines);
   }
+
+  public function testAssignmentByReference() {
+    $fixtureFile = $this->getFixture('AssignmentByReferenceFixture.php');
+    $phpcsFile = $this->prepareLocalFileForSniffs($fixtureFile);
+    $phpcsFile->process();
+    $lines = $this->getWarningLineNumbersFromFile($phpcsFile);
+    $expectedWarnings = [
+      26,
+      33,
+    ];
+    $this->assertEquals($expectedWarnings, $lines);
+  }
 }

VariableAnalysis/Tests/CodeAnalysis/fixtures/AssignmentByReferenceFixture.php

@@ -0,0 +1,45 @@
+<?php
+
+class A {
+    protected $prop = [];
+
+    public function __construct() {
+      $this->prop[] = 'foo';
+    }
+
+    public function &getProp() {
+      return $this->prop;
+    }
+}
+
+function usedAssignmentByReference() {
+  $a = new A();
+
+  $var = &$a->getProp();
+  $var = ['bar'];
+  return $a;
+}
+
+function unusedAssignmentByReference() {
+  $a = new A();
+
+  $var = &$a->getProp();
+  return $a;
+}
+
+function doubleUnusedAssignmentByReference() {
+  $a = new A();
+
+  $var = &$a->getProp();
+  $var = &$a->getProp();
+  return $a;
+}
+
+function doubleUnusedThenUsedAssignmentByReference() {
+  $a = new A();
+
+  // @todo the first one should be marked as unused.
+  $var = &$a->getProp();
+  $var = &$a->getProp();
+  return $var;
+}