Make hashing fail for inexact arbs.

Author: Maegereg

src/flint/test/test_arb.py

@@ -126,21 +126,20 @@ def arb_pi(prec):
         (arb(10), arb(10), True),
         (arb(10), arb(11), False),
         (arb(10.0), arb(10), True),
-        (
-            arb(mid=10, rad=2),
-            arb(mid=10, rad=2),
-            True,
-        ),
-        (
-            arb(mid=10, rad=2),
-            arb(mid=10, rad=3),
-            False,
-        ),
-        (arb_pi(100), arb_pi(100), True),
-        (arb_pi(100), arb_pi(1000), False),
     ]:
         assert (hash(x) == hash(y)) == expected
 
+    for x in [
+        arb(mid=10, rad=2),
+        arb_pi(100),
+    ]:
+        try:
+            hash(x)
+        except ValueError:
+            pass
+        else:
+            assert False, f"Expected {x} to raise an error if hashed, but succeeded."
+
 
 
 # Tests for arithmetic functions in `flint.arb`.

src/flint/types/arb.pyx

@@ -529,7 +529,9 @@ cdef class arb(flint_scalar):
 
     def __hash__(self):
         """Hash."""
-        return hash((self.mid().man_exp(), self.rad().man_exp()))
+        if self.is_exact():
+            return hash((self.mid().man_exp(), self.rad().man_exp()))
+        raise ValueError(f"Cannot hash non-exact arb: {self}. See pull/341 for details.")
 
     def __contains__(self, other):
         other = any_as_arb(other)