diff --git a/src/error/PhutilErrorHandler.php b/src/error/PhutilErrorHandler.php
index df05e65..d48fdb2 100644
--- a/src/error/PhutilErrorHandler.php
+++ b/src/error/PhutilErrorHandler.php
@@ -1,280 +1,305 @@
 <?php
 
 /*
  * Copyright 2012 Facebook, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *   http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
 
 /**
  * Improve PHP error logs and optionally route errors, exceptions and debugging
  * information to a central listener.
  *
  * This class takes over the PHP error and exception handlers when you call
  * ##PhutilErrorHandler::initialize()## and forwards all debugging information
  * to a listener you install with ##PhutilErrorHandler::setErrorListener()##.
  *
  * To use PhutilErrorHandler, which will enhance the messages printed to the
  * PHP error log, just initialize it:
  *
  *    PhutilErrorHandler::initialize();
  *
  * This will also enable @{function:phlog}, for printing development debugging
  * messages.
  *
  * To additionally install a custom listener which can print error information
  * to some other file or console, register a listener:
  *
  *    PhutilErrorHandler::setErrorListener($some_callback);
  *
  * For information on writing an error listener, see
  * @{function:phutil_error_listener_example}. Providing a listener is optional,
  * you will benefit from improved error logs even without one.
  *
  * Phabricator uses this class to drive the DarkConsole "Error Log" plugin.
  *
  * @task config Configuring Error Dispatch
  * @task internal Internals
  * @group error
  */
 final class PhutilErrorHandler {
 
   private static $errorListener = null;
   private static $initialized = false;
 
   const EXCEPTION   = 'exception';
   const ERROR       = 'error';
   const PHLOG       = 'phlog';
   const DEPRECATED  = 'deprecated';
 
 
 /* -(  Configuring Error Dispatch  )----------------------------------------- */
 
 
   /**
    * Registers this class as the PHP error and exception handler. This will
    * overwrite any previous handlers!
    *
    * @return void
    * @task config
    */
   public static function initialize() {
     self::$initialized = true;
     set_error_handler(array('PhutilErrorHandler', 'handleError'));
     set_exception_handler(array('PhutilErrorHandler', 'handleException'));
   }
 
   /**
    * Provide an optional listener callback which will receive all errors,
    * exceptions and debugging messages. It can then print them to a web console,
    * for example.
    *
    * See @{function:phutil_error_listener_example} for details about the
    * callback parameters and operation.
    *
    * @return void
    * @task config
    */
   public static function setErrorListener($listener) {
     self::$errorListener = $listener;
   }
 
 
 /* -(  Internals  )---------------------------------------------------------- */
 
 
   /**
    * Determine if PhutilErrorHandler has been initialized.
    *
    * @return bool True if initialized.
    * @task internal
    */
   public static function hasInitialized() {
     return self::$initialized;
   }
 
 
   /**
    * Handles PHP errors and dispatches them forward. This is a callback for
    * ##set_error_handler()##. You should not call this function directly; use
    * @{function:phlog} to print debugging messages or ##trigger_error()## to
    * trigger PHP errors.
    *
+   * This handler converts E_RECOVERABLE_ERROR messages from violated typehints
+   * into @{class:InvalidArgumentException}s.
+   *
+   * This handler converts other E_RECOVERABLE_ERRORs into
+   * @{class:RuntimeException}s.
+   *
+   * This handler converts E_NOTICE messages from uses of undefined variables
+   * into @{class:RuntimeException}s.
+   *
    * @param int Error code.
    * @param string Error message.
    * @param string File where the error occurred.
    * @param int Line on which the error occurred.
    * @param wild Error context information.
    * @return void
    * @task internal
    */
   public static function handleError($num, $str, $file, $line, $ctx) {
+
+    // Convert typehint failures into exceptions.
+    if (preg_match('/^Argument (\d+) passed to (\S+) must be/', $str)) {
+      throw new InvalidArgumentException($str);
+    }
+
+    // Convert other E_RECOVERABLE_ERRORs into generic runtime exceptions.
+    if ($num == E_RECOVERABLE_ERROR) {
+      throw new RuntimeException($str);
+    }
+
+    // Convert uses of undefined variables into exceptions.
+    if (preg_match('/^Undefined variable: /', $str)) {
+      throw new RuntimeException($str);
+    }
+
     $trace = debug_backtrace();
     array_shift($trace);
     self::dispatchErrorMessage(
       self::ERROR,
       $str,
       array(
         'file'       => $file,
         'line'       => $line,
         'context'    => $ctx,
         'error_code' => $num,
         'trace'      => $trace,
       ));
   }
 
   /**
    * Handles PHP exceptions and dispatches them forward. This is a callback for
    * ##set_exception_handler()##. You should not call this function directly;
    * to print exceptions, pass the exception object to @{function:phlog}.
    *
    * @param Exception Uncaught exception object.
    * @return void
    * @task internal
    */
   public static function handleException(Exception $ex) {
     self::dispatchErrorMessage(
       self::EXCEPTION,
       $ex,
       array(
         'file'  => $ex->getFile(),
         'line'  => $ex->getLine(),
         'trace' => $ex->getTrace(),
         'catch_trace' => debug_backtrace(),
       ));
 
     // Normally, PHP exits with code 255 after an uncaught exception is thrown.
     // However, if we install an exception handler (as we have here), it exits
     // with code 0 instead. Script execution terminates after this function
     // exits in either case, so exit explicitly with the correct exit code.
     exit(255);
   }
 
   /**
    * Output a stacktrace to the PHP error log.
    *
    * @param trace A stacktrace, e.g. from debug_backtrace();
    * @return void
    * @task internal
    */
   public static function outputStacktrace($trace) {
     foreach ($trace as $key => $entry) {
       $line = '  #'.$key.' ';
       if (isset($entry['class'])) {
         $line .= $entry['class'].'::';
       }
       $line .= idx($entry, 'function', '');
 
       if (isset($entry['args'])) {
         $args = array();
         foreach ($entry['args'] as $arg) {
           $args[] = PhutilReadableSerializer::printShort($arg);
         }
         $line .= '('.implode(', ', $args).')';
       }
 
       if (isset($entry['file'])) {
         $line .= ' called at ['.$entry['file'].':'.$entry['line'].']';
       }
       error_log($line);
     }
   }
 
   /**
    * All different types of error messages come here before they are
    * dispatched to the listener; this method also prints them to the PHP error
    * log.
    *
    * @param const Event type constant.
    * @param wild Event value.
    * @param dict Event metadata.
    * @return void
    * @task internal
    */
   public static function dispatchErrorMessage($event, $value, $metadata) {
     $timestamp = strftime("%F %T");
 
     switch ($event) {
       case PhutilErrorHandler::ERROR:
         if (error_reporting() === 0) {
           // Respect the use of "@" to silence warnings: if this error was
           // emitted from a context where "@" was in effect, the
           // value returned by error_reporting() will be 0. This is the
           // recommended way to check for this, see set_error_handler() docs
           // on php.net.
           break;
         }
         $default_message = sprintf(
           '[%s] ERROR %d: %s at [%s:%d]',
           $timestamp,
           $metadata['error_code'],
           $value,
           $metadata['file'],
           $metadata['line']);
 
         $metadata['default_message'] = $default_message;
         error_log($default_message);
         self::outputStacktrace($metadata['trace']);
         break;
       case PhutilErrorHandler::EXCEPTION:
         $default_message = sprintf(
           '[%s] EXCEPTION: %s at [%s:%d]',
           $timestamp,
           '('.get_class($value).') '.$value->getMessage(),
           $value->getFile(),
           $value->getLine());
 
         $metadata['default_message'] = $default_message;
         error_log($default_message);
         self::outputStacktrace($value->getTrace());
         break;
       case PhutilErrorHandler::PHLOG:
         $default_message = sprintf(
           '[%s] PHLOG: %s at [%s:%d]',
           $timestamp,
           PhutilReadableSerializer::printShort($value),
           $metadata['file'],
           $metadata['line']);
 
         $metadata['default_message'] = $default_message;
         error_log($default_message);
         break;
       case PhutilErrorHandler::DEPRECATED:
         $default_message = sprintf(
           '[%s] DEPRECATED: %s is deprecated; %s',
           $timestamp,
           $value,
           $metadata['why']);
 
         $metadata['default_message'] = $default_message;
         error_log($default_message);
         break;
       default:
         error_log('Unknown event '.$event);
         break;
     }
 
     if (self::$errorListener) {
       static $handling_error;
       if ($handling_error) {
         error_log(
           "Error handler was reentered, some errors were not passed to the ".
           "listener.");
         return;
       }
       $handling_error = true;
       call_user_func(self::$errorListener, $event, $value, $metadata);
       $handling_error = false;
     }
   }
 }