RustPython · youknowone · Dec 11, 2025 · Dec 11, 2025 · Dec 11, 2025 · coderabbitai
diff --git a/crates/vm/src/builtins/bytes.rs b/crates/vm/src/builtins/bytes.rs
@@ -92,15 +92,64 @@ pub(crate) fn init(context: &Context) {
 }
 
 impl Constructor for PyBytes {
-    type Args = ByteInnerNewOptions;
+    type Args = Vec<u8>;
 
     fn slot_new(cls: PyTypeRef, args: FuncArgs, vm: &VirtualMachine) -> PyResult {
-        let options: Self::Args = args.bind(vm)?;
-        options.get_bytes(cls, vm).to_pyresult(vm)
+        let options: ByteInnerNewOptions = args.bind(vm)?;
+
+        // Optimizations for exact bytes type
+        if cls.is(vm.ctx.types.bytes_type) {
+            // Return empty bytes singleton
+            if options.source.is_missing()
+                && options.encoding.is_missing()
+                && options.errors.is_missing()
+            {
+                return Ok(vm.ctx.empty_bytes.clone().into());
+            }
+
+            // Return exact bytes as-is
+            if let OptionalArg::Present(ref obj) = options.source
+                && options.encoding.is_missing()
+                && options.errors.is_missing()
+                && let Ok(b) = obj.clone().downcast_exact::<PyBytes>(vm)
+            {
+                return Ok(b.into_pyref().into());
+            }
+        }
+
+        // Handle __bytes__ method - may return PyBytes directly
+        if let OptionalArg::Present(ref obj) = options.source
+            && options.encoding.is_missing()
+            && options.errors.is_missing()
+            && let Some(bytes_method) = vm.get_method(obj.clone(), identifier!(vm, __bytes__))
+        {
+            let bytes = bytes_method?.call((), vm)?;
+            // If exact bytes type and __bytes__ returns bytes, use it directly
+            if cls.is(vm.ctx.types.bytes_type)
+                && let Ok(b) = bytes.clone().downcast::<PyBytes>()
+            {
+                return Ok(b.into());
+            }
+            // Otherwise convert to Vec<u8>
+            let inner = PyBytesInner::try_from_borrowed_object(vm, &bytes)?;
+            let payload = Self::py_new(&cls, inner.elements, vm)?;
+            return payload.into_ref_with_type(vm, cls).map(Into::into);
+        }
+
+        // Fallback to get_bytearray_inner
+        let elements = options.get_bytearray_inner(vm)?.elements;
+
+        // Return empty bytes singleton for exact bytes types
+        if elements.is_empty() && cls.is(vm.ctx.types.bytes_type) {
+            return Ok(vm.ctx.empty_bytes.clone().into());
+        }
+
+        let payload = Self::py_new(&cls, elements, vm)?;
+        payload.into_ref_with_type(vm, cls).map(Into::into)
     }
 
-    fn py_new(_cls: &Py<PyType>, _args: Self::Args, _vm: &VirtualMachine) -> PyResult<Self> {
-        unreachable!("use slot_new")
+    fn py_new(_cls: &Py<PyType>, elements: Self::Args, _vm: &VirtualMachine) -> PyResult<Self> {
+        Ok(Self::from(elements))
     }
 }
 

diff --git a/crates/vm/src/builtins/set.rs b/crates/vm/src/builtins/set.rs
@@ -918,35 +918,43 @@ impl Representable for PySet {
 }
 
 impl Constructor for PyFrozenSet {
-    type Args = OptionalArg<PyObjectRef>;
+    type Args = Vec<PyObjectRef>;
 
     fn slot_new(cls: PyTypeRef, args: FuncArgs, vm: &VirtualMachine) -> PyResult {
-        let iterable: Self::Args = args.bind(vm)?;
-        let elements = if let OptionalArg::Present(iterable) = iterable {
-            let iterable = if cls.is(vm.ctx.types.frozenset_type) {
-                match iterable.downcast_exact::<Self>(vm) {
-                    Ok(fs) => return Ok(fs.into_pyref().into()),
-                    Err(iterable) => iterable,
-                }
-            } else {
-                iterable
-            };
+        let iterable: OptionalArg<PyObjectRef> = args.bind(vm)?;
+
+        // Optimizations for exact frozenset type
+        if cls.is(vm.ctx.types.frozenset_type) {
+            // Return exact frozenset as-is
+            if let OptionalArg::Present(ref input) = iterable
+                && let Ok(fs) = input.clone().downcast_exact::<PyFrozenSet>(vm)
+            {
+                return Ok(fs.into_pyref().into());
+            }
+
+            // Return empty frozenset singleton
+            if iterable.is_missing() {
+                return Ok(vm.ctx.empty_frozenset.clone().into());
+            }
+        }
+
+        let elements: Vec<PyObjectRef> = if let OptionalArg::Present(iterable) = iterable {
             iterable.try_to_value(vm)?
         } else {
             vec![]
         };
 
-        // Return empty fs if iterable passed is empty and only for exact fs types.
+        // Return empty frozenset singleton for exact frozenset types (when iterable was empty)
         if elements.is_empty() && cls.is(vm.ctx.types.frozenset_type) {
-            Ok(vm.ctx.empty_frozenset.clone().into())
-        } else {
-            Self::from_iter(vm, elements)
-                .and_then(|o| o.into_ref_with_type(vm, cls).map(Into::into))
+            return Ok(vm.ctx.empty_frozenset.clone().into());
         }
+
+        let payload = Self::py_new(&cls, elements, vm)?;
+        payload.into_ref_with_type(vm, cls).map(Into::into)
     }
 
-    fn py_new(_cls: &Py<PyType>, _args: Self::Args, _vm: &VirtualMachine) -> PyResult<Self> {
-        unreachable!("use slot_new")
+    fn py_new(_cls: &Py<PyType>, elements: Self::Args, vm: &VirtualMachine) -> PyResult<Self> {
+        Self::from_iter(vm, elements)
     }
 }
 

diff --git a/crates/vm/src/builtins/str.rs b/crates/vm/src/builtins/str.rs
@@ -351,36 +351,39 @@ impl Constructor for PyStr {
     type Args = StrArgs;
 
     fn slot_new(cls: PyTypeRef, func_args: FuncArgs, vm: &VirtualMachine) -> PyResult {
+        // Optimization: return exact str as-is (only when no encoding/errors provided)
+        if cls.is(vm.ctx.types.str_type)
+            && func_args.args.len() == 1
+            && func_args.kwargs.is_empty()
+            && func_args.args[0].class().is(vm.ctx.types.str_type)
+        {
+            return Ok(func_args.args[0].clone());
+        }
+
         let args: Self::Args = func_args.bind(vm)?;
-        let string: PyRef<PyStr> = match args.object {
+        let payload = Self::py_new(&cls, args, vm)?;
+        payload.into_ref_with_type(vm, cls).map(Into::into)
+    }
+
+    fn py_new(_cls: &Py<PyType>, args: Self::Args, vm: &VirtualMachine) -> PyResult<Self> {
+        match args.object {
             OptionalArg::Present(input) => {
                 if let OptionalArg::Present(enc) = args.encoding {
-                    vm.state.codec_registry.decode_text(
+                    let s = vm.state.codec_registry.decode_text(
                         input,
                         enc.as_str(),
                         args.errors.into_option(),
                         vm,
-                    )?
+                    )?;
+                    Ok(Self::from(s.as_wtf8().to_owned()))
                 } else {
-                    input.str(vm)?
+                    let s = input.str(vm)?;
+                    Ok(Self::from(s.as_wtf8().to_owned()))
                 }
             }
-            OptionalArg::Missing => {
-                Self::from(String::new()).into_ref_with_type(vm, cls.clone())?
-            }
-        };
-        if string.class().is(&cls) {
-            Ok(string.into())
-        } else {
-            Self::from(string.as_wtf8())
-                .into_ref_with_type(vm, cls)
-                .map(Into::into)
+            OptionalArg::Missing => Ok(Self::from(String::new())),
         }
     }
-
-    fn py_new(_cls: &Py<PyType>, _args: Self::Args, _vm: &VirtualMachine) -> PyResult<Self> {
-        unreachable!("use slot_new")
-    }
 }
 
 impl PyStr {

diff --git a/crates/vm/src/builtins/tuple.rs b/crates/vm/src/builtins/tuple.rs
@@ -110,37 +110,45 @@ impl_from_into_pytuple!(A, B, C, D, E, F, G);
 pub type PyTupleRef = PyRef<PyTuple>;
 
 impl Constructor for PyTuple {
-    type Args = OptionalArg<PyObjectRef>;
+    type Args = Vec<PyObjectRef>;
 
     fn slot_new(cls: PyTypeRef, args: FuncArgs, vm: &VirtualMachine) -> PyResult {
-        let iterable: Self::Args = args.bind(vm)?;
+        let iterable: OptionalArg<PyObjectRef> = args.bind(vm)?;
+
+        // Optimizations for exact tuple type
+        if cls.is(vm.ctx.types.tuple_type) {
+            // Return exact tuple as-is
+            if let OptionalArg::Present(ref input) = iterable
+                && let Ok(tuple) = input.clone().downcast_exact::<PyTuple>(vm)
+            {
+                return Ok(tuple.into_pyref().into());
+            }
+
+            // Return empty tuple singleton
+            if iterable.is_missing() {
+                return Ok(vm.ctx.empty_tuple.clone().into());
+            }
+        }
+
         let elements = if let OptionalArg::Present(iterable) = iterable {
-            let iterable = if cls.is(vm.ctx.types.tuple_type) {
-                match iterable.downcast_exact::<Self>(vm) {
-                    Ok(tuple) => return Ok(tuple.into_pyref().into()),
-                    Err(iterable) => iterable,
-                }
-            } else {
-                iterable
-            };
             iterable.try_to_value(vm)?
         } else {
             vec![]
         };
-        // Return empty tuple only for exact tuple types if the iterable is empty.
+
+        // Return empty tuple singleton for exact tuple types (when iterable was empty)
         if elements.is_empty() && cls.is(vm.ctx.types.tuple_type) {
-            Ok(vm.ctx.empty_tuple.clone().into())
-        } else {
-            Self {
-                elements: elements.into_boxed_slice(),
-            }
-            .into_ref_with_type(vm, cls)
-            .map(Into::into)
+            return Ok(vm.ctx.empty_tuple.clone().into());
         }
+
+        let payload = Self::py_new(&cls, elements, vm)?;
+        payload.into_ref_with_type(vm, cls).map(Into::into)
     }
 
-    fn py_new(_cls: &Py<PyType>, _args: Self::Args, _vm: &VirtualMachine) -> PyResult<Self> {
-        unreachable!("use slot_new")
+    fn py_new(_cls: &Py<PyType>, elements: Self::Args, _vm: &VirtualMachine) -> PyResult<Self> {
+        Ok(Self {
+            elements: elements.into_boxed_slice(),
+        })
     }
 }
 

diff --git a/crates/vm/src/bytes_inner.rs b/crates/vm/src/bytes_inner.rs
@@ -1,16 +1,15 @@
 // spell-checker:ignore unchunked
 use crate::{
-    AsObject, PyObject, PyObjectRef, PyPayload, PyResult, TryFromBorrowedObject, VirtualMachine,
+    AsObject, PyObject, PyObjectRef, PyResult, TryFromBorrowedObject, VirtualMachine,
     anystr::{self, AnyStr, AnyStrContainer, AnyStrWrapper},
     builtins::{
         PyBaseExceptionRef, PyByteArray, PyBytes, PyBytesRef, PyInt, PyIntRef, PyStr, PyStrRef,
-        PyTypeRef, pystr,
+        pystr,
     },
     byte::bytes_from_object,
     cformat::cformat_bytes,
     common::hash,
     function::{ArgIterable, Either, OptionalArg, OptionalOption, PyComparisonValue},
-    identifier,
     literal::escape::Escape,
     protocol::PyBuffer,
     sequence::{SequenceExt, SequenceMutExt},
@@ -91,43 +90,6 @@ impl ByteInnerNewOptions {
         })
     }
 
-    pub fn get_bytes(self, cls: PyTypeRef, vm: &VirtualMachine) -> PyResult<PyBytesRef> {
-        let inner = match (&self.source, &self.encoding, &self.errors) {
-            (OptionalArg::Present(obj), OptionalArg::Missing, OptionalArg::Missing) => {
-                let obj = obj.clone();
-                // construct an exact bytes from an exact bytes do not clone
-                let obj = if cls.is(vm.ctx.types.bytes_type) {
-                    match obj.downcast_exact::<PyBytes>(vm) {
-                        Ok(b) => return Ok(b.into_pyref()),
-                        Err(obj) => obj,
-                    }
-                } else {
-                    obj
-                };
-
-                if let Some(bytes_method) = vm.get_method(obj, identifier!(vm, __bytes__)) {
-                    // construct an exact bytes from __bytes__ slot.
-                    // if __bytes__ return a bytes, use the bytes object except we are the subclass of the bytes
-                    let bytes = bytes_method?.call((), vm)?;
-                    let bytes = if cls.is(vm.ctx.types.bytes_type) {
-                        match bytes.downcast::<PyBytes>() {
-                            Ok(b) => return Ok(b),
-                            Err(bytes) => bytes,
-                        }
-                    } else {
-                        bytes
-                    };
-                    Some(PyBytesInner::try_from_borrowed_object(vm, &bytes))
-                } else {
-                    None
-                }
-            }
-            _ => None,
-        }
-        .unwrap_or_else(|| self.get_bytearray_inner(vm))?;
-        PyBytes::from(inner).into_ref_with_type(vm, cls)
-    }
-
     pub fn get_bytearray_inner(self, vm: &VirtualMachine) -> PyResult<PyBytesInner> {
         match (self.source, self.encoding, self.errors) {
             (OptionalArg::Present(obj), OptionalArg::Missing, OptionalArg::Missing) => {

diff --git a/crates/vm/src/protocol/object.rs b/crates/vm/src/protocol/object.rs
@@ -4,17 +4,16 @@
 use crate::{
     AsObject, Py, PyObject, PyObjectRef, PyRef, PyResult, TryFromObject, VirtualMachine,
     builtins::{
-        PyAsyncGen, PyDict, PyDictRef, PyGenericAlias, PyInt, PyList, PyStr, PyTuple, PyTupleRef,
-        PyType, PyTypeRef, PyUtf8Str, pystr::AsPyStr,
+        PyAsyncGen, PyBytes, PyDict, PyDictRef, PyGenericAlias, PyInt, PyList, PyStr, PyTuple,
+        PyTupleRef, PyType, PyTypeRef, PyUtf8Str, pystr::AsPyStr,
     },
-    bytes_inner::ByteInnerNewOptions,
     common::{hash::PyHash, str::to_ascii},
     convert::{ToPyObject, ToPyResult},
     dict_inner::DictKey,
-    function::{Either, OptionalArg, PyArithmeticValue, PySetterValue},
+    function::{Either, FuncArgs, PyArithmeticValue, PySetterValue},
     object::PyPayload,
     protocol::{PyIter, PyMapping, PySequence},
-    types::PyComparisonOp,
+    types::{Constructor, PyComparisonOp},
 };
 
 // RustPython doesn't need these items
@@ -37,12 +36,8 @@ impl PyObjectRef {
         match self.downcast_exact::<PyInt>(vm) {
             Ok(int) => Err(vm.new_downcast_type_error(bytes_type, &int)),
             Err(obj) => {
-                let options = ByteInnerNewOptions {
-                    source: OptionalArg::Present(obj),
-                    encoding: OptionalArg::Missing,
-                    errors: OptionalArg::Missing,
-                };
-                options.get_bytes(bytes_type.to_owned(), vm).map(Into::into)
+                let args = FuncArgs::from(vec![obj]);
+                <PyBytes as Constructor>::slot_new(bytes_type.to_owned(), args, vm)
             }
         }
     }