From a7227b449936b4018b4c2e801003c3153d79059c Mon Sep 17 00:00:00 2001
From: Renata Hodovan <reni@inf.u-szeged.hu>
Date: Thu, 8 Dec 2016 10:36:12 +0100
Subject: [PATCH] Fix AttributeError when trying to write an immutable variable
 in Python.

The `removeOne` function of IntervalSet tries to directly
rewrite the start field of an immutable range variable when
splitting an existing interval. This causes AttributeError which
is fixed by the patch.
---
 runtime/Python2/src/antlr4/IntervalSet.py | 2 +-
 runtime/Python3/src/antlr4/IntervalSet.py | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/runtime/Python2/src/antlr4/IntervalSet.py b/runtime/Python2/src/antlr4/IntervalSet.py
index c4c93749e..bef5d4807 100644
--- a/runtime/Python2/src/antlr4/IntervalSet.py
+++ b/runtime/Python2/src/antlr4/IntervalSet.py
@@ -158,7 +158,7 @@ class IntervalSet(object):
                 # split existing range
                 elif v<i.stop-1:
                     x = Interval(i.start, v)
-                    i.start = v + 1
+                    self.intervals[k] = range(v + 1, i.stop)
                     self.intervals.insert(k, x)
                     return
                 k += 1
diff --git a/runtime/Python3/src/antlr4/IntervalSet.py b/runtime/Python3/src/antlr4/IntervalSet.py
index 980509821..4fb689c32 100644
--- a/runtime/Python3/src/antlr4/IntervalSet.py
+++ b/runtime/Python3/src/antlr4/IntervalSet.py
@@ -138,7 +138,7 @@ class IntervalSet(object):
                 # split existing range
                 elif v<i.stop-1:
                     x = range(i.start, v)
-                    i.start = v + 1
+                    self.intervals[k] = range(v + 1, i.stop)
                     self.intervals.insert(k, x)
                     return
                 k += 1