fixing hash(-1) == hash(-2) (attempt 2) (#413)

ok so just return the integer does not work because Python will hash
that result with a seed implicitly. Here we convert the integer to a
byte and float to a hex repr. This is not the most ideal fix due to the
fact that Python is using fixpoint/infinite precision numbers. But this
should be non-breaking. We will do another fix by switching all `int` to
`np.int64` and `float` to `np.float64` and define the hash as their
bytes later.

Author: Roger-luo

src/kirin/ir/attrs/py.py

@@ -36,8 +36,11 @@ def __init__(self, data: T, pytype: TypeAttribute | None = None):
 
     def __hash__(self):
         # Fix hash(-1) == hash(-2) collision
+        # assume maximum is 8 bytes == 64 bits
         if isinstance(self.data, int):
-            return self.data
+            return hash(self.data.to_bytes(signed=True, byteorder="big", length=8))
+        elif isinstance(self.data, float):
+            return hash(self.data.hex())
         return hash(self.data) + hash(self.type)
 
     def print_impl(self, printer: Printer) -> None:

test/ir/test_hash.py

@@ -0,0 +1,17 @@
+from kirin import ir
+
+
+def test_hash():
+    # Test hash collision for PyAttr with different values
+    # This is a regression test for issue #1234
+    # where hash(-1) == hash(-2) for PyAttr
+    # This is fixed by using the value as bytes
+    a = ir.PyAttr(-1)
+    b = ir.PyAttr(-2)
+    assert hash(a) != hash(b)
+    assert hash(a.data) == hash(b.data)
+
+    a = ir.PyAttr(-1.0)
+    b = ir.PyAttr(-2.0)
+    assert hash(a) != hash(b)
+    assert hash(a.data) == hash(b.data)