RustPython
diff --git a/‎Lib/concurrent/futures/__init__.py‎
Lines changed: 2 additions & 1 deletion b/‎Lib/concurrent/futures/__init__.py‎
Lines changed: 2 additions & 1 deletion
diff --git a/‎Lib/concurrent/futures/_base.py‎
Lines changed: 17 additions & 7 deletions b/‎Lib/concurrent/futures/_base.py‎
Lines changed: 17 additions & 7 deletions
@@ -23,6 +23,7 @@
     'ALL_COMPLETED',
     'CancelledError',
     'TimeoutError',
+    'InvalidStateError',
     'BrokenExecutor',
     'Future',
     'Executor',
@@ -50,4 +51,4 @@ def __getattr__(name):
         ThreadPoolExecutor = te
         return te
 
-    raise AttributeError(f"module {__name__} has no attribute {name}")
+    raise AttributeError(f"module {__name__!r} has no attribute {name!r}")
@@ -50,9 +50,7 @@ class CancelledError(Error):
     """The Future was cancelled."""
     pass
 
-class TimeoutError(Error):
-    """The operation exceeded the given deadline."""
-    pass
+TimeoutError = TimeoutError  # make local alias for the standard exception
 
 class InvalidStateError(Error):
     """The operation is not allowed in this state."""
@@ -284,7 +282,7 @@ def wait(fs, timeout=None, return_when=ALL_COMPLETED):
         A named 2-tuple of sets. The first set, named 'done', contains the
         futures that completed (is finished or cancelled) before the wait
         completed. The second set, named 'not_done', contains uncompleted
-        futures. Duplicate futures given to *fs* are removed and will be 
+        futures. Duplicate futures given to *fs* are removed and will be
         returned only once.
     """
     fs = set(fs)
@@ -312,6 +310,18 @@ def wait(fs, timeout=None, return_when=ALL_COMPLETED):
     done.update(waiter.finished_futures)
     return DoneAndNotDoneFutures(done, fs - done)
 
+
+def _result_or_cancel(fut, timeout=None):
+    try:
+        try:
+            return fut.result(timeout)
+        finally:
+            fut.cancel()
+    finally:
+        # Break a reference cycle with the exception in self._exception
+        del fut
+
+
 class Future(object):
     """Represents the result of an asynchronous computation."""
 
@@ -386,7 +396,7 @@ def done(self):
             return self._state in [CANCELLED, CANCELLED_AND_NOTIFIED, FINISHED]
 
     def __get_result(self):
-        if self._exception:
+        if self._exception is not None:
             try:
                 raise self._exception
             finally:
@@ -606,9 +616,9 @@ def result_iterator():
                 while fs:
                     # Careful not to keep a reference to the popped future
                     if timeout is None:
-                        yield fs.pop().result()
+                        yield _result_or_cancel(fs.pop())
                     else:
-                        yield fs.pop().result(end_time - time.monotonic())
+                        yield _result_or_cancel(fs.pop(), end_time - time.monotonic())
             finally:
                 for future in fs:
                     future.cancel()