Seems UPGRADING is not merged...

UPGRADING

@@ -323,21 +323,21 @@ Relevant RFCs:
 Changes to error handling
 -------------------------
 
-* The new base class of the exception hierarchy is BaseException, from which
-  Exception extends. Typehints in exception handling code may need to be changed
-  to account for this.
+* There are now two exception classes: Exception and Error. Both classes
+  implement a new interface Throwable. Type hints in exception handling code
+  may need to be changed to account for this.
 
-* Some fatal errors and recoverable fatal errors now throw an EngineException
-  instead. As EngineException extends BaseException but not Exception, these
-  exceptions will not caught by existing try/catch blocks.
+* Some fatal errors and recoverable fatal errors now throw an Error instead.
+  As Error is a separate class from Exception, these exceptions will not be
+  caught by existing try/catch blocks.
 
   For the recoverable fatal errors which have been converted into an exception,
   it is no longer possible to silently ignore the error from an error handler.
-  In particular, it is no longer possible to ignore typehint failures.
+  In particular, it is no longer possible to ignore type hint failures.
 
-* Parser errors now generate a ParseException (extends BaseException). Error
+* Parser errors now generate a ParseError that extends Error. Error
   handling for eval()s on potentially invalid code should be changed to catch
-  ParseException in addition to the previous return value / error_get_last()
+  ParseError in addition to the previous return value / error_get_last()
   based handling.
 
 * Constructors of internal classes will now always throw an exception on
@@ -347,6 +347,7 @@ Changes to error handling
 
 Relevant RFCs:
 * https://wiki.php.net/rfc/engine_exceptions_for_php7
+* https://wiki.php.net/rfc/throwable-interface
 * https://wiki.php.net/rfc/internal_constructor_behaviour
 * https://wiki.php.net/rfc/reclassify_e_strict