Add changelog, fix typo, move test

hypothesis-python/RELEASE.rst

@@ -0,0 +1,8 @@
+RELEASE_TYPE: patch
+
+This patch refactors some internals.  There is no user-visible change,
+but we hope to improve performance and unlock support for alternative
+backends such as :pypi:`symbolic execution with crosshair <crosshair-tool>`
+in future (:issue:`3086`).
+
+Thanks to Liam DeVoe for this fantastic contribution!

hypothesis-python/src/hypothesis/internal/intervalsets.py

@@ -27,7 +27,7 @@ def __init__(self, intervals):
             self.offsets.append(self.offsets[-1] + v - u + 1)
         self.size = self.offsets.pop()
         self._idx_of_zero = self.index_above(ord("0"))
-        self._idx_of_Z = min(self.index_above(ord("Z")), len(self.intervals) - 1)
+        self._idx_of_Z = min(self.index_above(ord("Z")), len(self) - 1)
 
     def __len__(self):
         return self.size

hypothesis-python/tests/cover/test_intervalset.py

@@ -109,3 +109,12 @@ def test_interval_intersection(x, y):
     print(f"{set(x)=} {set(y)=} {set(x)-(set(y)-set(x))=}")
     assert set(x & y) == set(x) & set(y)
     assert set(x.intersection(y)) == set(x).intersection(y)
+
+
+def test_char_in_shrink_order():
+    xs = IntervalSet([(0, 256)])
+    assert xs[xs._idx_of_zero] == ord("0")
+    assert xs[xs._idx_of_Z] == ord("Z")
+    rewritten = [ord(xs.char_in_shrink_order(i)) for i in range(256)]
+    assert rewritten != list(range(256))
+    assert sorted(rewritten) == sorted(range(256))