Add a linter rule to prevent the __lambda_func function from being redeclared

Summary:
See http://phpsadness.com/sad/39. Declaring a function named `__lambda_func` prevents the `create_function` function from working. This is because `create_function` eval-declares the function `__lambda_func`, then modifies the symbol table so that the function is instead named `"\0lambda_".(++$i)`, and returns that name.

NOTE: Personally, I don't think that anyone should use `create_function`. However, despite this, I think it is reasonable that no function is named `__lambda_func` in case some external library relies on `create_function`.

Test Plan: Added test case.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: Korvin, epriestley

Differential Revision: https://secure.phabricator.com/D12870

src/lint/linter/ArcanistXHPASTLinter.php

@@ -67,6 +67,7 @@ final class ArcanistXHPASTLinter extends ArcanistBaseXHPASTLinter {
   const LINT_ALIAS_FUNCTION             = 65;
   const LINT_CAST_SPACING               = 66;
   const LINT_TOSTRING_EXCEPTION         = 67;
+  const LINT_LAMBDA_FUNC_FUNCTION       = 68;
 
   private $blacklistedFunctions = array();
   private $naminghook;
@@ -209,6 +210,8 @@ final class ArcanistXHPASTLinter extends ArcanistBaseXHPASTLinter {
         => pht('Cast Spacing'),
       self::LINT_TOSTRING_EXCEPTION
         => pht('Throwing Exception in %s Method', '__toString'),
+      self::LINT_LAMBDA_FUNC_FUNCTION
+        => pht('%s Function', '__lambda_func'),
     );
   }
 
@@ -329,7 +332,7 @@ final class ArcanistXHPASTLinter extends ArcanistBaseXHPASTLinter {
 
   public function getVersion() {
     // The version number should be incremented whenever a new rule is added.
-    return '29';
+    return '30';
   }
 
   protected function resolveFuture($path, Future $future) {
@@ -423,6 +426,7 @@ final class ArcanistXHPASTLinter extends ArcanistBaseXHPASTLinter {
       'lintAliasFunctions' => self::LINT_ALIAS_FUNCTION,
       'lintCastSpacing' => self::LINT_CAST_SPACING,
       'lintThrowExceptionInToStringMethod' => self::LINT_TOSTRING_EXCEPTION,
+      'lintLambdaFuncFunction' => self::LINT_LAMBDA_FUNC_FUNCTION,
     );
 
     foreach ($method_codes as $method => $codes) {
@@ -4156,6 +4160,38 @@ final class ArcanistXHPASTLinter extends ArcanistBaseXHPASTLinter {
     }
   }
 
+  private function lintLambdaFuncFunction(XHPASTNode $root) {
+    $function_declarations = $root
+      ->selectDescendantsOfType('n_FUNCTION_DECLARATION');
+
+    foreach ($function_declarations as $function_declaration) {
+      $function_name = $function_declaration->getChildByIndex(2);
+
+      if ($function_name->getTypeName() == 'n_EMPTY') {
+        // Anonymous closure.
+        continue;
+      }
+
+      if ($function_name->getConcreteString() != '__lambda_func') {
+        continue;
+      }
+
+      $this->raiseLintAtNode(
+        $function_declaration,
+        self::LINT_LAMBDA_FUNC_FUNCTION,
+        pht(
+          'Declaring a function named %s causes any call to %s to fail. '.
+          'This is because %s eval-declares the function %s, then '.
+          'modifies the symbol table so that the function is instead '.
+          'named %s, and returns that name.',
+          '__lambda_func',
+          'create_function',
+          'create_function',
+          '__lambda_func',
+          '"\0lambda_".(++$i)'));
+    }
+  }
+
 
   /**
    * Retrieve all calls to some specified function(s).

src/lint/linter/__tests__/xhpast/lamba-func-function.lint-test

@@ -0,0 +1,4 @@
+<?php
+function __lambda_func() {}
+~~~~~~~~~~
+error:2:1