RustPython · youknowone · Jan 1, 2026 · Dec 31, 2025 · Dec 31, 2025 · Dec 31, 2025
diff --git a/crates/vm/src/builtins/bool.rs b/crates/vm/src/builtins/bool.rs
@@ -9,7 +9,6 @@ use crate::{
     types::{AsNumber, Constructor, Representable},
 };
 use core::fmt::{Debug, Formatter};
-use malachite_bigint::Sign;
 use num_traits::Zero;
 
 impl ToPyObject for bool {
@@ -42,46 +41,28 @@ impl PyObjectRef {
         if self.is(&vm.ctx.false_value) {
             return Ok(false);
         }
-        let rs_bool = if let Some(nb_bool) = self.class().slots.as_number.boolean.load() {
-            nb_bool(self.as_object().number(), vm)?
-        } else {
-            // TODO: Fully implement AsNumber and remove this block
-            match vm.get_method(self.clone(), identifier!(vm, __bool__)) {
-                Some(method_or_err) => {
-                    // If descriptor returns Error, propagate it further
-                    let method = method_or_err?;
-                    let bool_obj = method.call((), vm)?;
-                    if !bool_obj.fast_isinstance(vm.ctx.types.bool_type) {
-                        return Err(vm.new_type_error(format!(
-                            "__bool__ should return bool, returned type {}",
-                            bool_obj.class().name()
-                        )));
-                    }
-
-                    get_value(&bool_obj)
-                }
-                None => match vm.get_method(self, identifier!(vm, __len__)) {
-                    Some(method_or_err) => {
-                        let method = method_or_err?;
-                        let bool_obj = method.call((), vm)?;
-                        let int_obj = bool_obj.downcast_ref::<PyInt>().ok_or_else(|| {
-                            vm.new_type_error(format!(
-                                "'{}' object cannot be interpreted as an integer",
-                                bool_obj.class().name()
-                            ))
-                        })?;
-
-                        let len_val = int_obj.as_bigint();
-                        if len_val.sign() == Sign::Minus {
-                            return Err(vm.new_value_error("__len__() should return >= 0"));
-                        }
-                        !len_val.is_zero()
-                    }
-                    None => true,
-                },
-            }
-        };
-        Ok(rs_bool)
+
+        let slots = &self.class().slots;
+
+        // 1. Try nb_bool slot first
+        if let Some(nb_bool) = slots.as_number.boolean.load() {
+            return nb_bool(self.as_object().number(), vm);
+        }
+
+        // 2. Try mp_length slot (mapping protocol)
+        if let Some(mp_length) = slots.as_mapping.length.load() {
+            let len = mp_length(self.as_object().mapping_unchecked(), vm)?;
+            return Ok(len != 0);
+        }
+
+        // 3. Try sq_length slot (sequence protocol)
+        if let Some(sq_length) = slots.as_sequence.length.load() {
+            let len = sq_length(self.as_object().sequence_unchecked(), vm)?;
+            return Ok(len != 0);
+        }
+
+        // 4. Default: objects without __bool__ or __len__ are truthy
+        Ok(true)
     }
 }
 

diff --git a/crates/vm/src/builtins/bytearray.rs b/crates/vm/src/builtins/bytearray.rs
@@ -206,7 +206,6 @@ impl PyByteArray {
         self.inner().capacity()
     }
 
-    #[pymethod]
     fn __len__(&self) -> usize {
         self.borrow_buf().len()
     }

diff --git a/crates/vm/src/builtins/bytes.rs b/crates/vm/src/builtins/bytes.rs
@@ -205,7 +205,6 @@ impl PyRef<PyBytes> {
 )]
 impl PyBytes {
     #[inline]
-    #[pymethod]
     pub const fn __len__(&self) -> usize {
         self.inner.len()
     }

diff --git a/crates/vm/src/builtins/dict.rs b/crates/vm/src/builtins/dict.rs
@@ -212,7 +212,6 @@ impl PyDict {
         }
     }
 
-    #[pymethod]
     pub fn __len__(&self) -> usize {
         self.entries.len()
     }
@@ -764,7 +763,6 @@ trait DictView: PyPayload + PyClassDef + Iterable + Representable {
     fn dict(&self) -> &Py<PyDict>;
     fn item(vm: &VirtualMachine, key: PyObjectRef, value: PyObjectRef) -> PyObjectRef;
 
-    #[pymethod]
     fn __len__(&self) -> usize {
         self.dict().__len__()
     }

diff --git a/crates/vm/src/builtins/list.rs b/crates/vm/src/builtins/list.rs
@@ -182,7 +182,6 @@ impl PyList {
     }
 
     #[allow(clippy::len_without_is_empty)]
-    #[pymethod]
     pub fn __len__(&self) -> usize {
         self.borrow_vec().len()
     }

diff --git a/crates/vm/src/builtins/mappingproxy.rs b/crates/vm/src/builtins/mappingproxy.rs
@@ -173,7 +173,6 @@ impl PyMappingProxy {
         PyGenericAlias::from_args(cls, args, vm)
     }
 
-    #[pymethod]
     fn __len__(&self, vm: &VirtualMachine) -> PyResult<usize> {
         let obj = self.to_object(vm)?;
         obj.length(vm)
@@ -235,6 +234,7 @@ impl AsMapping for PyMappingProxy {
 impl AsSequence for PyMappingProxy {
     fn as_sequence() -> &'static PySequenceMethods {
         static AS_SEQUENCE: LazyLock<PySequenceMethods> = LazyLock::new(|| PySequenceMethods {
+            length: atomic_func!(|seq, vm| PyMappingProxy::sequence_downcast(seq).__len__(vm)),
             contains: atomic_func!(
                 |seq, target, vm| PyMappingProxy::sequence_downcast(seq)._contains(target, vm)
             ),

diff --git a/crates/vm/src/builtins/memory.rs b/crates/vm/src/builtins/memory.rs
@@ -690,7 +690,6 @@ impl PyMemoryView {
         Err(vm.new_type_error("cannot delete memory"))
     }
 
-    #[pymethod]
     fn __len__(&self, vm: &VirtualMachine) -> PyResult<usize> {
         self.try_not_released(vm)?;
         if self.desc.ndim() == 0 {