Merge pull request #60 from RustPython/none

There is only one none.

tests/snippets/none.py

@@ -0,0 +1,16 @@
+assert None is None
+
+y = None
+x = None
+assert x is y
+
+def none():
+    pass
+
+def none2():
+    return None
+
+assert none() is none()
+assert none() is x
+
+assert none() is none2()

vm/src/objtype.rs

@@ -7,7 +7,11 @@ use std::collections::HashMap;
 use super::pyobject::{PyObject, PyObjectKind, PyObjectRef};
 
 pub fn create_type() -> PyObjectRef {
-    let typ = PyObject::default().into_ref();
+    let typ = PyObject {
+        kind: PyObjectKind::None,
+        typ: None,
+    }.into_ref();
+
     let dict = PyObject::new(
         PyObjectKind::Dict {
             elements: HashMap::new(),

vm/src/pyobject.rs

@@ -42,6 +42,7 @@ impl fmt::Display for PyObjectRef {
 #[derive(Debug)]
 pub struct PyContext {
     pub type_type: PyObjectRef,
+    pub none: PyObjectRef,
     pub int_type: PyObjectRef,
     pub list_type: PyObjectRef,
     pub tuple_type: PyObjectRef,
@@ -70,6 +71,7 @@ impl PyContext {
             list_type: type_type.clone(),
             tuple_type: type_type.clone(),
             dict_type: type_type.clone(),
+            none: PyObject::new(PyObjectKind::None, type_type.clone()),
             function_type: objfunction::create_type(type_type.clone()),
             bound_method_type: objfunction::create_bound_method_type(type_type.clone()),
             type_type: type_type,
@@ -187,16 +189,6 @@ pub struct PyObject {
     // pub dict: HashMap<String, PyObjectRef>, // __dict__ member
 }
 
-impl Default for PyObject {
-    fn default() -> PyObject {
-        PyObject {
-            kind: PyObjectKind::None,
-            typ: None,
-            // dict: HashMap::new(),
-        }
-    }
-}
-
 pub trait IdProtocol {
     fn get_id(&self) -> usize;
 }

vm/src/vm.rs

@@ -65,8 +65,7 @@ impl VirtualMachine {
     }
 
     pub fn get_none(&self) -> PyObjectRef {
-        // TODO
-        self.ctx.new_bool(false)
+        self.ctx.none.clone()
     }
 
     pub fn new_bound_method(&self, function: PyObjectRef, object: PyObjectRef) -> PyObjectRef {
@@ -573,7 +572,7 @@ impl VirtualMachine {
                     &bytecode::Constant::Code { ref code } => {
                         PyObject::new(PyObjectKind::Code { code: code.clone() }, self.get_type())
                     }
-                    &bytecode::Constant::None => PyObject::new(PyObjectKind::None, self.get_type()),
+                    &bytecode::Constant::None => self.ctx.none.clone(),
                 };
                 self.push_value(obj);
                 None