Replace str built-in with str.__new__

tests/snippets/strings.py

@@ -8,3 +8,10 @@ assert "\n" == """
 """
 
 assert len(""" " \" """) == 5
+
+assert type("") is str
+
+assert str(1) == "1"
+assert str(2.1) == "2.1"
+assert str() == ""
+assert str("abc") == "abc"

vm/src/builtins.rs

@@ -307,25 +307,6 @@ fn builtin_setattr(vm: &mut VirtualMachine, args: PyFuncArgs) -> PyResult {
 // builtin_sorted
 // builtin_staticmethod
 
-// TODO: should with following format
-// class str(object='')
-// class str(object=b'', encoding='utf-8', errors='strict')
-fn builtin_str(vm: &mut VirtualMachine, args: PyFuncArgs) -> PyResult {
-    if args.args.len() != 1 {
-        panic!("str expects exactly one parameter");
-    };
-    let s = match args.args[0].borrow().kind {
-        PyObjectKind::Integer { value: _ } | PyObjectKind::String { value: _ } => {
-            args.args[0].borrow().str()
-        }
-        _ => {
-            return Err(vm
-                .context()
-                .new_str("TypeError: object of this type cannot be converted to str".to_string()))
-        }
-    };
-    Ok(vm.new_str(s))
-}
 // builtin_sum
 // builtin_super
 // builtin_vars

vm/src/objstr.rs

@@ -1,7 +1,29 @@
 use super::objsequence::PySliceableSequence;
-use super::pyobject::{PyObjectKind, PyObjectRef, PyResult};
+use super::pyobject::{
+    AttributeProtocol, PyContext, PyFuncArgs, PyObjectKind, PyObjectRef, PyResult,
+};
 use super::vm::VirtualMachine;
 
+pub fn init(context: &PyContext) {
+    let ref str_type = context.str_type;
+    str_type.set_attr("__new__", context.new_rustfunc(str_new));
+}
+
+// TODO: should with following format
+// class str(object='')
+// class str(object=b'', encoding='utf-8', errors='strict')
+fn str_new(vm: &mut VirtualMachine, args: PyFuncArgs) -> PyResult {
+    if args.args.len() == 1 {
+        return Ok(vm.new_str("".to_string()));
+    }
+
+    if args.args.len() > 2 {
+        panic!("str expects exactly one parameter");
+    };
+    let s = args.args[1].borrow().str();
+    Ok(vm.new_str(s))
+}
+
 impl PySliceableSequence for String {
     fn do_slice(&self, start: usize, stop: usize) -> Self {
         self[start..stop].to_string()

vm/src/pyobject.rs

@@ -5,6 +5,7 @@ use super::objfunction;
 use super::objint;
 use super::objlist;
 use super::objobject;
+use super::objstr;
 use super::objtype;
 use super::vm::VirtualMachine;
 use std::cell::RefCell;
@@ -139,6 +140,7 @@ impl PyContext {
         objdict::init(&context);
         objfunction::init(&context);
         objint::init(&context);
+        objstr::init(&context);
         exceptions::init(&context);
         // TODO: create exception hierarchy here?
         // exceptions::create_zoo(&context);
@@ -154,7 +156,7 @@ impl PyContext {
     }
 
     pub fn new_str(&self, s: String) -> PyObjectRef {
-        PyObject::new(PyObjectKind::String { value: s }, self.type_type.clone())
+        PyObject::new(PyObjectKind::String { value: s }, self.str_type.clone())
     }
 
     pub fn new_bool(&self, b: bool) -> PyObjectRef {