Fix a hash instability.

Apparently, accessing __annotations__ on a function changes func_annotations from a tuple
to a dict. These things hash differently, and so if you called Entrypoint or NotCompiled on
a function you could modify its hash.

Author: braxtonmckee

typed_python/CompilerVisibleObjectVisitor.hpp

@@ -594,10 +594,10 @@ class CompilerVisibleObjectVisitor {
             }
 
             instanceVisit(f->func_name);
-            instanceVisit(f->func_code);
-            visitDictOrTuple(f->func_annotations);
-            visitTuple(f->func_defaults);
-            visitDictOrTuple(f->func_kwdefaults);
+            instanceVisit(PyFunction_GetCode((PyObject*)f));
+            visitDictOrTuple(PyFunction_GetAnnotations((PyObject*)f));
+            visitTuple(PyFunction_GetDefaults((PyObject*)f));
+            visitDictOrTuple(PyFunction_GetKwDefaults((PyObject*)f));
 
             hashVisit(ShaHash(1));
 

typed_python/type_identity_test.py

@@ -18,7 +18,7 @@
     UInt64, UInt32,
     ListOf, TupleOf, Tuple, NamedTuple, Dict, OneOf, Forward, identityHash,
     Entrypoint, Class, Member, Final, TypeFunction, SerializationContext,
-    Function
+    Function, NotCompiled
 )
 
 import typed_python
@@ -94,6 +94,24 @@ class C:
     resetCompilerVisibleObjectHashCache()
 
 
+def test_identity_of_function_with_annotation():
+    def f(x: int):
+        pass
+
+    @Entrypoint
+    def g(x: int):
+        return f(x)
+
+    identityHash(f)
+    identityHash(NotCompiled(f))
+
+    hashInstability = checkForHashInstability()
+
+    if hashInstability is not None:
+        print(hashInstability)
+        raise Exception("hash instability found")
+
+
 def test_class_and_held_class_in_group():
     class C(Class):
         pass