Allow Traits to use $this (#25)

* Tests: add trait test using $this

* Tests: throw exception if fixture does not exist

* Allow Traits to use `$this`

Author: sirbrillig

VariableAnalysis/Sniffs/CodeAnalysis/VariableAnalysisSniff.php

@@ -760,7 +760,7 @@ protected function checkForThisWithinClass(
     $token  = $tokens[$stackPtr];
 
     // Are we $this within a class?
-    if (($varName != 'this') || empty($token['conditions'])) {
+    if (($varName !== 'this') || empty($token['conditions'])) {
       return false;
     }
 
@@ -770,7 +770,7 @@ protected function checkForThisWithinClass(
       if ($tokens[$scopePtr]['code'] === T_CLOSURE) {
         return true;
       }
-      if ($scopeCode === T_CLASS) {
+      if ($scopeCode === T_CLASS || $scopeCode === T_TRAIT) {
         return true;
       }
     }

VariableAnalysis/Tests/BaseTestCase.php

@@ -15,6 +15,9 @@ public function prepareLocalFileForSniffs($sniffFiles, string $fixtureFile): Loc
     }
     $ruleset->registerSniffs($sniffFiles, [], []);
     $ruleset->populateTokenListeners();
+    if (! file_exists($fixtureFile)) {
+      throw new \Exception('Fixture file does not exist: ' . $fixtureFile);
+    }
     return new LocalFile($fixtureFile, $ruleset, $config);
   }
 

VariableAnalysis/Tests/CodeAnalysis/VariableAnalysisTest.php

@@ -373,4 +373,16 @@ public function testCompactWarnings() {
     ];
     $this->assertEquals($expectedWarnings, $lines);
   }
+
+  public function testTraitAllowsThis() {
+    $fixtureFile = $this->getFixture('TraitFixture.php');
+    $phpcsFile = $this->prepareLocalFileForSniffs($this->getSniffFiles(), $fixtureFile);
+    $phpcsFile->process();
+    $lines = $this->getWarningLineNumbersFromFile($phpcsFile);
+    $expectedWarnings = [];
+    $this->assertEquals($expectedWarnings, $lines);
+    $lines = $this->getErrorLineNumbersFromFile($phpcsFile);
+    $expectedErrors = [];
+    $this->assertEquals($expectedErrors, $lines);
+  }
 }

VariableAnalysis/Tests/CodeAnalysis/fixtures/TraitFixture.php

@@ -0,0 +1,8 @@
+<?php
+
+trait Hello {
+    public function sayHelloWorld() {
+        echo 'Hello'.$this->getWorld();
+    }
+    abstract public function getWorld();
+}