Phi._hash_core: Fix crashes caused by None in src_and_vvars. (#259)

ailment/expression.py

@@ -333,7 +333,7 @@ def __init__(
         self,
         idx,
         bits,
-        src_and_vvars: list[tuple[tuple[int, int], VirtualVariable | None]],
+        src_and_vvars: list[tuple[tuple[int, int | None], VirtualVariable | None]],
         **kwargs,
     ):
         super().__init__(idx, **kwargs)
@@ -390,7 +390,7 @@ def __repr__(self):
     __hash__ = TaggedObject.__hash__
 
     def _hash_core(self):
-        return stable_hash(("phi", self.bits, tuple(sorted(self.src_and_vvars))))
+        return stable_hash(("phi", self.bits, tuple(sorted(self.src_and_vvars, key=self._src_and_vvar_filter))))
 
     def copy(self) -> Phi:
         return Phi(
@@ -423,6 +423,16 @@ def replace(self, old_expr, new_expr):
             )
         return False, self
 
+    @staticmethod
+    def _src_and_vvar_filter(
+        src_and_vvar: tuple[tuple[int, int | None], VirtualVariable | None]
+    ) -> tuple[tuple[int, int], int]:
+        src, vvar = src_and_vvar
+        if src[1] is None:
+            src = src[0], -1
+        vvar_id = vvar.varid if vvar is not None else -1
+        return src, vvar_id
+
 
 class Op(Expression):
     __slots__ = ("op",)

tests/test_expression.py

@@ -0,0 +1,21 @@
+# pylint: disable=missing-class-docstring,no-self-use
+import unittest
+
+import ailment
+
+
+class TestExpression(unittest.TestCase):
+
+    def test_phi_hashing(self):
+        vvar_0 = ailment.expression.VirtualVariable(100, 0, 32, ailment.expression.VirtualVariableCategory.REGISTER, 16)
+        vvar_1 = ailment.expression.VirtualVariable(101, 1, 32, ailment.expression.VirtualVariableCategory.REGISTER, 16)
+        vvar_2 = ailment.expression.VirtualVariable(102, 2, 32, ailment.expression.VirtualVariableCategory.REGISTER, 16)
+        phi_expr = ailment.expression.Phi(
+            0, 32, [((0, None), vvar_0), ((0, 0), vvar_2), ((1, None), vvar_1), ((4, None), None)]
+        )
+        h = hash(phi_expr)  # should not crash
+        assert h is not None
+
+
+if __name__ == "__main__":
+    unittest.main()