RustPython · youknowone · Dec 16, 2025 · Jun 16, 2024 · Jun 16, 2024 · Jun 16, 2024
diff --git a/Lib/test/test_descr.py b/Lib/test/test_descr.py
@@ -1788,7 +1788,6 @@ class D(C):
         self.assertEqual(b.foo, 3)
         self.assertEqual(b.__class__, D)
 
-    @unittest.expectedFailure
     def test_bad_new(self):
         self.assertRaises(TypeError, object.__new__)
         self.assertRaises(TypeError, object.__new__, '')

diff --git a/crates/derive-impl/src/pyclass.rs b/crates/derive-impl/src/pyclass.rs
@@ -954,7 +954,10 @@ where
         } else if let Ok(f) = args.item.function_or_method() {
             (&f.sig().ident, f.span())
         } else {
-            return Err(self.new_syn_error(args.item.span(), "can only be on a method"));
+            return Err(self.new_syn_error(
+                args.item.span(),
+                "can only be on a method or const function pointer",
+            ));
         };
 
         let item_attr = args.attrs.remove(self.index());
@@ -1496,7 +1499,9 @@ impl SlotItemMeta {
             }
         } else {
             let ident_str = self.inner().item_name();
-            let name = if let Some(stripped) = ident_str.strip_prefix("slot_") {
+            // Convert to lowercase to handle both SLOT_NEW and slot_new
+            let ident_lower = ident_str.to_lowercase();
+            let name = if let Some(stripped) = ident_lower.strip_prefix("slot_") {
                 proc_macro2::Ident::new(stripped, inner.item_ident.span())
             } else {
                 inner.item_ident.clone()
@@ -1609,7 +1614,6 @@ fn extract_impl_attrs(attr: PunctuatedNestedMeta, item: &Ident) -> Result<Extrac
     }];
     let mut payload = None;
 
-    let mut has_constructor = false;
     for attr in attr {
         match attr {
             NestedMeta::Meta(Meta::List(MetaList { path, nested, .. })) => {
@@ -1634,9 +1638,6 @@ fn extract_impl_attrs(attr: PunctuatedNestedMeta, item: &Ident) -> Result<Extrac
                                     "Try `#[pyclass(with(Constructor, ...))]` instead of `#[pyclass(with(DefaultConstructor, ...))]`. DefaultConstructor implicitly implements Constructor."
                                 )
                             }
-                            if path.is_ident("Constructor") || path.is_ident("Unconstructible") {
-                                has_constructor = true;
-                            }
                             (
                                 quote!(<Self as #path>::__extend_py_class),
                                 quote!(<Self as #path>::__OWN_METHOD_DEFS),
@@ -1689,11 +1690,6 @@ fn extract_impl_attrs(attr: PunctuatedNestedMeta, item: &Ident) -> Result<Extrac
             attr => bail_span!(attr, "Unknown pyimpl attribute"),
         }
     }
-    // TODO: DISALLOW_INSTANTIATION check is required
-    let _ = has_constructor;
-    // if !withs.is_empty() && !has_constructor {
-    //     bail_span!(item, "#[pyclass(with(...))] does not have a Constructor. Either #[pyclass(with(Constructor, ...))] or #[pyclass(with(Unconstructible, ...))] is mandatory. Consider to add `impl DefaultConstructor for T {{}}` or `impl Unconstructible for T {{}}`.")
-    // }
 
     Ok(ExtractedImplAttrs {
         payload,

diff --git a/crates/stdlib/src/array.rs b/crates/stdlib/src/array.rs
@@ -1399,7 +1399,7 @@ mod array {
         internal: PyMutex<PositionIterInternal<PyArrayRef>>,
     }
 
-    #[pyclass(with(IterNext, Iterable), flags(HAS_DICT))]
+    #[pyclass(with(IterNext, Iterable), flags(HAS_DICT, DISALLOW_INSTANTIATION))]
     impl PyArrayIter {
         #[pymethod]
         fn __setstate__(&self, state: PyObjectRef, vm: &VirtualMachine) -> PyResult<()> {

diff --git a/crates/stdlib/src/csv.rs b/crates/stdlib/src/csv.rs
@@ -908,7 +908,7 @@ mod _csv {
         }
     }
 
-    #[pyclass(with(IterNext, Iterable))]
+    #[pyclass(with(IterNext, Iterable), flags(DISALLOW_INSTANTIATION))]
     impl Reader {
         #[pygetset]
         fn line_num(&self) -> u64 {
@@ -1059,7 +1059,7 @@ mod _csv {
         }
     }
 
-    #[pyclass]
+    #[pyclass(flags(DISALLOW_INSTANTIATION))]
     impl Writer {
         #[pygetset(name = "dialect")]
         const fn get_dialect(&self, _vm: &VirtualMachine) -> PyDialect {

diff --git a/crates/stdlib/src/pystruct.rs b/crates/stdlib/src/pystruct.rs
@@ -16,7 +16,7 @@ pub(crate) mod _struct {
         function::{ArgBytesLike, ArgMemoryBuffer, PosArgs},
         match_class,
         protocol::PyIterReturn,
-        types::{Constructor, IterNext, Iterable, Representable, SelfIter, Unconstructible},
+        types::{Constructor, IterNext, Iterable, Representable, SelfIter},
     };
     use crossbeam_utils::atomic::AtomicCell;
 
@@ -189,15 +189,15 @@ pub(crate) mod _struct {
         }
     }
 
-    #[pyclass(with(Unconstructible, IterNext, Iterable))]
+    #[pyclass(with(IterNext, Iterable), flags(DISALLOW_INSTANTIATION))]
     impl UnpackIterator {
         #[pymethod]
         fn __length_hint__(&self) -> usize {
             self.buffer.len().saturating_sub(self.offset.load()) / self.format_spec.size
         }
     }
     impl SelfIter for UnpackIterator {}
-    impl Unconstructible for UnpackIterator {}
+
     impl IterNext for UnpackIterator {
         fn next(zelf: &Py<Self>, vm: &VirtualMachine) -> PyResult<PyIterReturn> {
             let size = zelf.format_spec.size;

diff --git a/crates/stdlib/src/sqlite.rs b/crates/stdlib/src/sqlite.rs
@@ -75,7 +75,7 @@ mod _sqlite {
         sliceable::{SaturatedSliceIter, SliceableSequenceOp},
         types::{
             AsMapping, AsNumber, AsSequence, Callable, Comparable, Constructor, Hashable,
-            Initializer, IterNext, Iterable, PyComparisonOp, SelfIter, Unconstructible,
+            Initializer, IterNext, Iterable, PyComparisonOp, SelfIter,
         },
         utils::ToCString,
     };
@@ -2197,8 +2197,6 @@ mod _sqlite {
         inner: PyMutex<Option<BlobInner>>,
     }
 
-    impl Unconstructible for Blob {}
-
     #[derive(Debug)]
     struct BlobInner {
         blob: SqliteBlob,
@@ -2211,7 +2209,7 @@ mod _sqlite {
         }
     }
 
-    #[pyclass(with(AsMapping, Unconstructible, AsNumber, AsSequence))]
+    #[pyclass(flags(DISALLOW_INSTANTIATION), with(AsMapping, AsNumber, AsSequence))]
     impl Blob {
         #[pymethod]
         fn close(&self) {
@@ -2592,9 +2590,7 @@ mod _sqlite {
         }
     }
 
-    impl Unconstructible for Statement {}
-
-    #[pyclass(with(Unconstructible))]
+    #[pyclass(flags(DISALLOW_INSTANTIATION))]
     impl Statement {
         fn new(
             connection: &Connection,

diff --git a/crates/stdlib/src/unicodedata.rs b/crates/stdlib/src/unicodedata.rs
@@ -105,7 +105,7 @@ mod unicodedata {
         }
     }
 
-    #[pyclass]
+    #[pyclass(flags(DISALLOW_INSTANTIATION))]
     impl Ucd {
         #[pymethod]
         fn category(&self, character: PyStrRef, vm: &VirtualMachine) -> PyResult<String> {

diff --git a/crates/stdlib/src/zlib.rs b/crates/stdlib/src/zlib.rs
@@ -225,7 +225,7 @@ mod zlib {
         inner: PyMutex<PyDecompressInner>,
     }
 
-    #[pyclass]
+    #[pyclass(flags(DISALLOW_INSTANTIATION))]
     impl PyDecompress {
         #[pygetset]
         fn eof(&self) -> bool {
@@ -383,7 +383,7 @@ mod zlib {
         inner: PyMutex<CompressState<CompressInner>>,
     }
 
-    #[pyclass]
+    #[pyclass(flags(DISALLOW_INSTANTIATION))]
     impl PyCompress {
         #[pymethod]
         fn compress(&self, data: ArgBytesLike, vm: &VirtualMachine) -> PyResult<Vec<u8>> {

diff --git a/crates/vm/src/builtins/asyncgenerator.rs b/crates/vm/src/builtins/asyncgenerator.rs
@@ -8,7 +8,7 @@ use crate::{
     frame::FrameRef,
     function::OptionalArg,
     protocol::PyIterReturn,
-    types::{IterNext, Iterable, Representable, SelfIter, Unconstructible},
+    types::{IterNext, Iterable, Representable, SelfIter},
 };
 
 use crossbeam_utils::atomic::AtomicCell;
@@ -32,7 +32,7 @@ impl PyPayload for PyAsyncGen {
     }
 }
 
-#[pyclass(with(PyRef, Unconstructible, Representable))]
+#[pyclass(flags(DISALLOW_INSTANTIATION), with(PyRef, Representable))]
 impl PyAsyncGen {
     pub const fn as_coro(&self) -> &Coro {
         &self.inner
@@ -201,8 +201,6 @@ impl Representable for PyAsyncGen {
     }
 }
 
-impl Unconstructible for PyAsyncGen {}
-
 #[pyclass(module = false, name = "async_generator_wrapped_value")]
 #[derive(Debug)]
 pub(crate) struct PyAsyncGenWrappedValue(pub PyObjectRef);

diff --git a/crates/vm/src/builtins/builtin_func.rs b/crates/vm/src/builtins/builtin_func.rs
@@ -5,7 +5,7 @@ use crate::{
     common::wtf8::Wtf8,
     convert::TryFromObject,
     function::{FuncArgs, PyComparisonValue, PyMethodDef, PyMethodFlags, PyNativeFn},
-    types::{Callable, Comparable, PyComparisonOp, Representable, Unconstructible},
+    types::{Callable, Comparable, PyComparisonOp, Representable},
 };
 use std::fmt;
 
@@ -74,7 +74,7 @@ impl Callable for PyNativeFunction {
     }
 }
 
-#[pyclass(with(Callable, Unconstructible), flags(HAS_DICT))]
+#[pyclass(with(Callable), flags(HAS_DICT, DISALLOW_INSTANTIATION))]
 impl PyNativeFunction {
     #[pygetset]
     fn __module__(zelf: NativeFunctionOrMethod) -> Option<&'static PyStrInterned> {
@@ -145,8 +145,6 @@ impl Representable for PyNativeFunction {
     }
 }
 
-impl Unconstructible for PyNativeFunction {}
-
 // `PyCMethodObject` in CPython
 #[pyclass(name = "builtin_method", module = false, base = PyNativeFunction, ctx = "builtin_method_type")]
 pub struct PyNativeMethod {
@@ -155,8 +153,8 @@ pub struct PyNativeMethod {
 }
 
 #[pyclass(
-    with(Unconstructible, Callable, Comparable, Representable),
-    flags(HAS_DICT)
+    with(Callable, Comparable, Representable),
+    flags(HAS_DICT, DISALLOW_INSTANTIATION)
 )]
 impl PyNativeMethod {
     #[pygetset]
@@ -246,8 +244,6 @@ impl Representable for PyNativeMethod {
     }
 }
 
-impl Unconstructible for PyNativeMethod {}
-
 pub fn init(context: &Context) {
     PyNativeFunction::extend_class(context, context.types.builtin_function_or_method_type);
     PyNativeMethod::extend_class(context, context.types.builtin_method_type);

diff --git a/crates/vm/src/builtins/bytearray.rs b/crates/vm/src/builtins/bytearray.rs
@@ -33,7 +33,7 @@ use crate::{
     types::{
         AsBuffer, AsMapping, AsNumber, AsSequence, Callable, Comparable, Constructor,
         DefaultConstructor, Initializer, IterNext, Iterable, PyComparisonOp, Representable,
-        SelfIter, Unconstructible,
+        SelfIter,
     },
 };
 use bstr::ByteSlice;
@@ -865,7 +865,7 @@ impl PyPayload for PyByteArrayIterator {
     }
 }
 
-#[pyclass(with(Unconstructible, IterNext, Iterable))]
+#[pyclass(flags(DISALLOW_INSTANTIATION), with(IterNext, Iterable))]
 impl PyByteArrayIterator {
     #[pymethod]
     fn __length_hint__(&self) -> usize {
@@ -886,8 +886,6 @@ impl PyByteArrayIterator {
     }
 }
 
-impl Unconstructible for PyByteArrayIterator {}
-
 impl SelfIter for PyByteArrayIterator {}
 impl IterNext for PyByteArrayIterator {
     fn next(zelf: &Py<Self>, vm: &VirtualMachine) -> PyResult<PyIterReturn> {

diff --git a/crates/vm/src/builtins/bytes.rs b/crates/vm/src/builtins/bytes.rs
@@ -25,7 +25,7 @@ use crate::{
     sliceable::{SequenceIndex, SliceableSequenceOp},
     types::{
         AsBuffer, AsMapping, AsNumber, AsSequence, Callable, Comparable, Constructor, Hashable,
-        IterNext, Iterable, PyComparisonOp, Representable, SelfIter, Unconstructible,
+        IterNext, Iterable, PyComparisonOp, Representable, SelfIter,
     },
 };
 use bstr::ByteSlice;
@@ -749,7 +749,7 @@ impl PyPayload for PyBytesIterator {
     }
 }
 
-#[pyclass(with(Unconstructible, IterNext, Iterable))]
+#[pyclass(flags(DISALLOW_INSTANTIATION), with(IterNext, Iterable))]
 impl PyBytesIterator {
     #[pymethod]
     fn __length_hint__(&self) -> usize {
@@ -770,7 +770,6 @@ impl PyBytesIterator {
             .set_state(state, |obj, pos| pos.min(obj.len()), vm)
     }
 }
-impl Unconstructible for PyBytesIterator {}
 
 impl SelfIter for PyBytesIterator {}
 impl IterNext for PyBytesIterator {

diff --git a/crates/vm/src/builtins/coroutine.rs b/crates/vm/src/builtins/coroutine.rs
@@ -6,7 +6,7 @@ use crate::{
     frame::FrameRef,
     function::OptionalArg,
     protocol::PyIterReturn,
-    types::{IterNext, Iterable, Representable, SelfIter, Unconstructible},
+    types::{IterNext, Iterable, Representable, SelfIter},
 };
 use crossbeam_utils::atomic::AtomicCell;
 
@@ -24,7 +24,7 @@ impl PyPayload for PyCoroutine {
     }
 }
 
-#[pyclass(with(Py, Unconstructible, IterNext, Representable))]
+#[pyclass(flags(DISALLOW_INSTANTIATION), with(Py, IterNext, Representable))]
 impl PyCoroutine {
     pub const fn as_coro(&self) -> &Coro {
         &self.inner
@@ -123,8 +123,6 @@ impl Py<PyCoroutine> {
     }
 }
 
-impl Unconstructible for PyCoroutine {}
-
 impl Representable for PyCoroutine {
     #[inline]
     fn repr_str(zelf: &Py<Self>, vm: &VirtualMachine) -> PyResult<String> {

diff --git a/crates/vm/src/builtins/descriptor.rs b/crates/vm/src/builtins/descriptor.rs
@@ -4,7 +4,7 @@ use crate::{
     builtins::{PyTypeRef, builtin_func::PyNativeMethod, type_},
     class::PyClassImpl,
     function::{FuncArgs, PyMethodDef, PyMethodFlags, PySetterValue},
-    types::{Callable, GetDescriptor, Representable, Unconstructible},
+    types::{Callable, GetDescriptor, Representable},
 };
 use rustpython_common::lock::PyRwLock;
 
@@ -105,8 +105,8 @@ impl PyMethodDescriptor {
 }
 
 #[pyclass(
-    with(GetDescriptor, Callable, Unconstructible, Representable),
-    flags(METHOD_DESCRIPTOR)
+    with(GetDescriptor, Callable, Representable),
+    flags(METHOD_DESCRIPTOR, DISALLOW_INSTANTIATION)
 )]
 impl PyMethodDescriptor {
     #[pygetset]
@@ -159,8 +159,6 @@ impl Representable for PyMethodDescriptor {
     }
 }
 
-impl Unconstructible for PyMethodDescriptor {}
-
 #[derive(Debug)]
 pub enum MemberKind {
     Bool = 14,
@@ -246,7 +244,10 @@ fn calculate_qualname(descr: &PyDescriptorOwned, vm: &VirtualMachine) -> PyResul
     }
 }
 
-#[pyclass(with(GetDescriptor, Unconstructible, Representable), flags(BASETYPE))]
+#[pyclass(
+    with(GetDescriptor, Representable),
+    flags(BASETYPE, DISALLOW_INSTANTIATION)
+)]
 impl PyMemberDescriptor {
     #[pygetset]
     fn __doc__(&self) -> Option<String> {
@@ -339,8 +340,6 @@ fn set_slot_at_object(
     Ok(())
 }
 
-impl Unconstructible for PyMemberDescriptor {}
-
 impl Representable for PyMemberDescriptor {
     #[inline]
     fn repr_str(zelf: &Py<Self>, _vm: &VirtualMachine) -> PyResult<String> {