MAINT: stats._SimpleDomain: ensure that instances do not share symbols (scipy#22139)

* MAINT: stats._SimpleDomain: ensure that instances do not share symbols

Co-authored-by: Matt Haberland <[email protected]>

Author: mdhaber

scipy/stats/_distribution_infrastructure.py

@@ -267,11 +267,10 @@ class _SimpleDomain(_Domain):
 
     """
     def __init__(self, endpoints=(-inf, inf), inclusive=(False, False)):
+        self.symbols = super().symbols.copy()
         a, b = endpoints
         self.endpoints = np.asarray(a)[()], np.asarray(b)[()]
         self.inclusive = inclusive
-        # self.all_inclusive = (endpoints == (-inf, inf)
-        #                       and inclusive == (True, True))
 
     def define_parameters(self, *parameters):
         r""" Records any parameters used to define the endpoints of the domain.

scipy/stats/tests/test_continuous.py

@@ -117,6 +117,14 @@ def test_str2(self, a, b, inclusive_a, inclusive_b):
         ref = f"{left_bracket}{a}, {b}{right_bracket}"
         assert str(domain) == ref
 
+    def test_symbols_gh22137(self):
+        # `symbols` was accidentally shared between instances originally
+        # Check that this is no longer the case
+        domain1 = _RealDomain(endpoints=(0, 1))
+        domain2 = _RealDomain(endpoints=(0, 1))
+        assert domain1.symbols is not domain2.symbols
+
+
 def draw_distribution_from_family(family, data, rng, proportions, min_side=0):
     # If the distribution has parameters, choose a parameterization and
     # draw broadcastable shapes for the parameter arrays.