Add a linter rule for invalid default parameters

Summary: See http://www.phpwtf.org/default-arguments-and-type-hinting.

Test Plan: Added test case.

Reviewers: #blessed_reviewers, epriestley

Reviewed By: #blessed_reviewers, epriestley

Subscribers: Korvin, epriestley

Differential Revision: https://secure.phabricator.com/D12855

src/lint/linter/ArcanistXHPASTLinter.php

@@ -69,6 +69,7 @@ final class ArcanistXHPASTLinter extends ArcanistBaseXHPASTLinter {
   const LINT_TOSTRING_EXCEPTION         = 67;
   const LINT_LAMBDA_FUNC_FUNCTION       = 68;
   const LINT_INSTANCEOF_OPERATOR        = 69;
+  const LINT_INVALID_DEFAULT_PARAMETER  = 70;
 
   private $blacklistedFunctions = array();
   private $naminghook;
@@ -215,6 +216,8 @@ final class ArcanistXHPASTLinter extends ArcanistBaseXHPASTLinter {
         => pht('%s Function', '__lambda_func'),
       self::LINT_INSTANCEOF_OPERATOR
         => pht('%s Operator', 'instanceof'),
+      self::LINT_INVALID_DEFAULT_PARAMETER
+        => pht('Invalid Default Parameter'),
     );
   }
 
@@ -335,7 +338,7 @@ final class ArcanistXHPASTLinter extends ArcanistBaseXHPASTLinter {
 
   public function getVersion() {
     // The version number should be incremented whenever a new rule is added.
-    return '31';
+    return '32';
   }
 
   protected function resolveFuture($path, Future $future) {
@@ -431,6 +434,7 @@ final class ArcanistXHPASTLinter extends ArcanistBaseXHPASTLinter {
       'lintThrowExceptionInToStringMethod' => self::LINT_TOSTRING_EXCEPTION,
       'lintLambdaFuncFunction' => self::LINT_LAMBDA_FUNC_FUNCTION,
       'lintInstanceOfOperator' => self::LINT_INSTANCEOF_OPERATOR,
+      'lintInvalidDefaultParameters' => self::LINT_INVALID_DEFAULT_PARAMETER,
     );
 
     foreach ($method_codes as $method => $codes) {
@@ -4224,6 +4228,76 @@ final class ArcanistXHPASTLinter extends ArcanistBaseXHPASTLinter {
     }
   }
 
+  private function lintInvalidDefaultParameters(XHPASTNode $root) {
+    $parameters = $root->selectDescendantsOfType('n_DECLARATION_PARAMETER');
+
+    foreach ($parameters as $parameter) {
+      $type = $parameter->getChildByIndex(0);
+      $default = $parameter->getChildByIndex(2);
+
+      if ($type->getTypeName() == 'n_EMPTY') {
+        continue;
+      }
+
+      if ($default->getTypeName() == 'n_EMPTY') {
+        continue;
+      }
+
+      $default_is_null = $default->getTypeName() == 'n_SYMBOL_NAME' &&
+        strtolower($default->getConcreteString()) == 'null';
+
+      switch (strtolower($type->getConcreteString())) {
+        case 'array':
+          if ($default->getTypeName() == 'n_ARRAY_LITERAL') {
+            break;
+          }
+          if ($default_is_null) {
+            break;
+          }
+
+          $this->raiseLintAtNode(
+            $default,
+            self::LINT_INVALID_DEFAULT_PARAMETER,
+            pht(
+              'Default value for parameters with %s type hint '.
+              'can only be an %s or %s.',
+              'array',
+              'array',
+              'null'));
+          break;
+
+        case 'callable':
+          if ($default_is_null) {
+            break;
+          }
+
+          $this->raiseLintAtNode(
+            $default,
+            self::LINT_INVALID_DEFAULT_PARAMETER,
+            pht(
+              'Default value for parameters with %s type hint can only be %s.',
+              'callable',
+              'null'));
+          break;
+
+        default:
+          // Class/interface parameter.
+          if ($default_is_null) {
+            break;
+          }
+
+          $this->raiseLintAtNode(
+            $default,
+            self::LINT_INVALID_DEFAULT_PARAMETER,
+            pht(
+              'Default value for parameters with a class type hint '.
+              'can only be %s.',
+              'null'));
+          break;
+      }
+    }
+  }
+
 
   /**
    * Retrieve all calls to some specified function(s).

src/lint/linter/__tests__/xhpast/invalid-default-paramter.lint-test

@@ -0,0 +1,17 @@
+<?php
+function func_one(array $x) {}
+function func_two(array $x = null) {}
+function func_three(array $x = array()) {}
+function func_four(array $x = false) {}
+
+function func_five(callable $x) {}
+function func_six(callable $x = null) {}
+function func_seven(callable $x = false) {}
+
+function func_eight(stdClass $x) {}
+function func_nine(stdClass $x = null) {}
+function func_ten(stdClass $x = array()) {}
+~~~~~~~~~~
+error:5:31
+error:9:35
+error:13:33