Fix builtin hash()

vm/src/builtins.rs

@@ -303,8 +303,7 @@ fn builtin_hasattr(obj: PyObjectRef, attr: PyStringRef, vm: &VirtualMachine) ->
 
 fn builtin_hash(vm: &VirtualMachine, args: PyFuncArgs) -> PyResult {
     arg_check!(vm, args, required = [(obj, None)]);
-
-    vm.call_method(obj, "__hash__", vec![])
+    vm._hash(obj).and_then(|v| Ok(vm.new_int(v)))
 }
 
 // builtin_help

vm/src/vm.rs

@@ -23,6 +23,7 @@ use crate::obj::objcode::PyCodeRef;
 use crate::obj::objdict::PyDictRef;
 use crate::obj::objfunction::{PyFunction, PyMethod};
 use crate::obj::objgenerator::PyGenerator;
+use crate::obj::objint;
 use crate::obj::objiter;
 use crate::obj::objsequence;
 use crate::obj::objstr::{PyString, PyStringRef};
@@ -36,6 +37,7 @@ use crate::pyobject::{
 use crate::stdlib;
 use crate::sysmodule;
 use num_bigint::BigInt;
+use num_traits::ToPrimitive;
 
 // use objects::objects;
 
@@ -912,6 +914,19 @@ impl VirtualMachine {
         })
     }
 
+    pub fn _hash(&self, obj: &PyObjectRef) -> PyResult<usize> {
+        const PRIME: usize = 0x1fff_ffff_ffff_ffff;
+        let hash_obj = self.call_method(obj, "__hash__", vec![])?;
+        if objtype::isinstance(&hash_obj, &self.ctx.int_type()) {
+            let hash_int = objint::get_value(&hash_obj);
+            Ok(hash_int
+                .to_usize()
+                .unwrap_or_else(|| (hash_int % PRIME).to_usize().unwrap()))
+        } else {
+            Err(self.new_type_error("__hash__ method should return an integer".to_string()))
+        }
+    }
+
     // https://docs.python.org/3/reference/expressions.html#membership-test-operations
     fn _membership_iter_search(&self, haystack: PyObjectRef, needle: PyObjectRef) -> PyResult {
         let iter = objiter::get_iter(self, &haystack)?;