Merge pull request #3291 from DimitrisJim/unconstructible

Add Unconstructible trait

extra_tests/snippets/forbidden_instantiation.py

@@ -0,0 +1,18 @@
+from typing import Type
+from testutils import assert_raises
+
+def check_forbidden_instantiation(typ, reverse=False):
+    f = reversed if reverse else iter
+    with assert_raises(TypeError):
+        type(f(typ()))()
+
+dict_values, dict_items = lambda: {}.values(), lambda: {}.items()
+# types with custom forward iterators
+iter_types = [list, set, str, bytearray, bytes, dict, tuple, lambda: range(0), dict_items, dict_values]
+# types with custom backwards iterators
+reviter_types = [list, dict, lambda: range(0), dict_values, dict_items]
+
+for typ in iter_types:
+    check_forbidden_instantiation(typ)
+for typ in reviter_types:
+    check_forbidden_instantiation(typ, reverse=True)

vm/src/builtins/bytearray.rs

@@ -24,7 +24,7 @@ use crate::{
     sliceable::{PySliceableSequence, PySliceableSequenceMut, SequenceIndex},
     slots::{
         AsBuffer, AsMapping, Callable, Comparable, Hashable, Iterable, IteratorIterable,
-        PyComparisonOp, SlotIterator, Unhashable,
+        PyComparisonOp, SlotConstructor, SlotIterator, Unconstructible, Unhashable,
     },
     utils::Either,
     IdProtocol, PyClassDef, PyClassImpl, PyComparisonValue, PyContext, PyObjectRef, PyRef,
@@ -816,7 +816,7 @@ impl PyValue for PyByteArrayIterator {
     }
 }
 
-#[pyimpl(with(SlotIterator))]
+#[pyimpl(with(SlotConstructor, SlotIterator))]
 impl PyByteArrayIterator {
     #[pymethod(magic)]
     fn length_hint(&self) -> usize {
@@ -836,6 +836,8 @@ impl PyByteArrayIterator {
             .set_state(state, |obj, pos| pos.min(obj.len()), vm)
     }
 }
+impl Unconstructible for PyByteArrayIterator {}
+
 impl IteratorIterable for PyByteArrayIterator {}
 impl SlotIterator for PyByteArrayIterator {
     fn next(zelf: &PyRef<Self>, vm: &VirtualMachine) -> PyResult<PyIterReturn> {

vm/src/builtins/bytes.rs

@@ -12,7 +12,7 @@ use crate::{
     protocol::{BufferInternal, BufferOptions, PyBuffer, PyIterReturn, PyMappingMethods},
     slots::{
         AsBuffer, AsMapping, Callable, Comparable, Hashable, Iterable, IteratorIterable,
-        PyComparisonOp, SlotConstructor, SlotIterator,
+        PyComparisonOp, SlotConstructor, SlotIterator, Unconstructible,
     },
     utils::Either,
     IdProtocol, PyClassImpl, PyComparisonValue, PyContext, PyObjectRef, PyRef, PyResult, PyValue,
@@ -649,7 +649,7 @@ impl PyValue for PyBytesIterator {
     }
 }
 
-#[pyimpl(with(SlotIterator))]
+#[pyimpl(with(SlotConstructor, SlotIterator))]
 impl PyBytesIterator {
     #[pymethod(magic)]
     fn length_hint(&self) -> usize {
@@ -670,6 +670,8 @@ impl PyBytesIterator {
             .set_state(state, |obj, pos| pos.min(obj.len()), vm)
     }
 }
+impl Unconstructible for PyBytesIterator {}
+
 impl IteratorIterable for PyBytesIterator {}
 impl SlotIterator for PyBytesIterator {
     fn next(zelf: &PyRef<Self>, vm: &VirtualMachine) -> PyResult<PyIterReturn> {

vm/src/builtins/dict.rs

@@ -9,8 +9,8 @@ use crate::{
     function::{ArgIterable, FuncArgs, IntoPyObject, KwArgs, OptionalArg},
     protocol::{PyIterIter, PyIterReturn, PyMappingMethods},
     slots::{
-        AsMapping, Comparable, Hashable, Iterable, IteratorIterable, PyComparisonOp, SlotIterator,
-        Unhashable,
+        AsMapping, Comparable, Hashable, Iterable, IteratorIterable, PyComparisonOp,
+        SlotConstructor, SlotIterator, Unconstructible, Unhashable,
     },
     vm::{ReprGuard, VirtualMachine},
     IdProtocol, ItemProtocol,
@@ -762,7 +762,7 @@ macro_rules! dict_view {
             }
         }
 
-        #[pyimpl(with(SlotIterator))]
+        #[pyimpl(with(SlotConstructor, SlotIterator))]
         impl $iter_name {
             fn new(dict: PyDictRef) -> Self {
                 $iter_name {
@@ -776,6 +776,7 @@ macro_rules! dict_view {
                 self.internal.lock().length_hint(|_| self.size.entries_size)
             }
         }
+        impl Unconstructible for $iter_name {}
 
         impl IteratorIterable for $iter_name {}
         impl SlotIterator for $iter_name {
@@ -818,7 +819,7 @@ macro_rules! dict_view {
             }
         }
 
-        #[pyimpl(with(SlotIterator))]
+        #[pyimpl(with(SlotConstructor, SlotIterator))]
         impl $reverse_iter_name {
             fn new(dict: PyDictRef) -> Self {
                 let size = dict.size();
@@ -836,6 +837,7 @@ macro_rules! dict_view {
                     .rev_length_hint(|_| self.size.entries_size)
             }
         }
+        impl Unconstructible for $reverse_iter_name {}
 
         impl IteratorIterable for $reverse_iter_name {}
         impl SlotIterator for $reverse_iter_name {

vm/src/builtins/list.rs

@@ -8,8 +8,8 @@ use crate::{
     sequence::{self, SimpleSeq},
     sliceable::{PySliceableSequence, PySliceableSequenceMut, SequenceIndex},
     slots::{
-        AsMapping, Comparable, Hashable, Iterable, IteratorIterable, PyComparisonOp, SlotIterator,
-        Unhashable,
+        AsMapping, Comparable, Hashable, Iterable, IteratorIterable, PyComparisonOp,
+        SlotConstructor, SlotIterator, Unconstructible, Unhashable,
     },
     stdlib::sys,
     utils::Either,
@@ -517,7 +517,7 @@ impl PyValue for PyListIterator {
     }
 }
 
-#[pyimpl(with(SlotIterator))]
+#[pyimpl(with(SlotConstructor, SlotIterator))]
 impl PyListIterator {
     #[pymethod(magic)]
     fn length_hint(&self) -> usize {
@@ -538,6 +538,7 @@ impl PyListIterator {
             .builtins_iter_reduce(|x| x.clone().into(), vm)
     }
 }
+impl Unconstructible for PyListIterator {}
 
 impl IteratorIterable for PyListIterator {}
 impl SlotIterator for PyListIterator {
@@ -564,7 +565,7 @@ impl PyValue for PyListReverseIterator {
     }
 }
 
-#[pyimpl(with(SlotIterator))]
+#[pyimpl(with(SlotConstructor, SlotIterator))]
 impl PyListReverseIterator {
     #[pymethod(magic)]
     fn length_hint(&self) -> usize {
@@ -585,6 +586,7 @@ impl PyListReverseIterator {
             .builtins_reversed_reduce(|x| x.clone().into(), vm)
     }
 }
+impl Unconstructible for PyListReverseIterator {}
 
 impl IteratorIterable for PyListReverseIterator {}
 impl SlotIterator for PyListReverseIterator {

vm/src/builtins/pystr.rs

@@ -11,7 +11,7 @@ use crate::{
     sliceable::PySliceableSequence,
     slots::{
         Comparable, Hashable, Iterable, IteratorIterable, PyComparisonOp, SlotConstructor,
-        SlotIterator,
+        SlotIterator, Unconstructible,
     },
     stdlib::sys,
     utils::Either,
@@ -220,7 +220,7 @@ impl PyValue for PyStrIterator {
     }
 }
 
-#[pyimpl(with(SlotIterator))]
+#[pyimpl(with(SlotConstructor, SlotIterator))]
 impl PyStrIterator {
     #[pymethod(magic)]
     fn length_hint(&self) -> usize {
@@ -244,6 +244,7 @@ impl PyStrIterator {
             .builtins_iter_reduce(|x| x.clone().into(), vm)
     }
 }
+impl Unconstructible for PyStrIterator {}
 
 impl IteratorIterable for PyStrIterator {}
 impl SlotIterator for PyStrIterator {

vm/src/builtins/range.rs

@@ -5,7 +5,8 @@ use crate::{
     function::{FuncArgs, OptionalArg},
     protocol::{PyIterReturn, PyMappingMethods},
     slots::{
-        AsMapping, Comparable, Hashable, Iterable, IteratorIterable, PyComparisonOp, SlotIterator,
+        AsMapping, Comparable, Hashable, Iterable, IteratorIterable, PyComparisonOp,
+        SlotConstructor, SlotIterator, Unconstructible,
     },
     IdProtocol, IntoPyRef, PyClassImpl, PyContext, PyObjectRef, PyRef, PyResult, PyValue,
     TryFromObject, TypeProtocol, VirtualMachine,
@@ -511,7 +512,7 @@ impl PyValue for PyLongRangeIterator {
     }
 }
 
-#[pyimpl(with(SlotIterator))]
+#[pyimpl(with(SlotConstructor, SlotIterator))]
 impl PyLongRangeIterator {
     #[pyslot]
     fn slot_new(_cls: PyTypeRef, _args: FuncArgs, vm: &VirtualMachine) -> PyResult {
@@ -545,6 +546,7 @@ impl PyLongRangeIterator {
         )
     }
 }
+impl Unconstructible for PyLongRangeIterator {}
 
 impl IteratorIterable for PyLongRangeIterator {}
 impl SlotIterator for PyLongRangeIterator {
@@ -580,13 +582,8 @@ impl PyValue for PyRangeIterator {
     }
 }
 
-#[pyimpl(with(SlotIterator))]
+#[pyimpl(with(SlotConstructor, SlotIterator))]
 impl PyRangeIterator {
-    #[pyslot]
-    fn slot_new(_cls: PyTypeRef, _args: FuncArgs, vm: &VirtualMachine) -> PyResult {
-        Err(vm.new_type_error("cannot create 'range_iterator' instances".to_owned()))
-    }
-
     #[pymethod(magic)]
     fn length_hint(&self) -> usize {
         let index = self.index.load();
@@ -615,6 +612,7 @@ impl PyRangeIterator {
         )
     }
 }
+impl Unconstructible for PyRangeIterator {}
 
 impl IteratorIterable for PyRangeIterator {}
 impl SlotIterator for PyRangeIterator {

vm/src/builtins/set.rs

@@ -9,7 +9,7 @@ use crate::{
     protocol::PyIterReturn,
     slots::{
         Comparable, Hashable, Iterable, IteratorIterable, PyComparisonOp, SlotConstructor,
-        SlotIterator, Unhashable,
+        SlotIterator, Unconstructible, Unhashable,
     },
     vm::{ReprGuard, VirtualMachine},
     IdProtocol, PyClassImpl, PyComparisonValue, PyContext, PyObjectRef, PyRef, PyResult, PyValue,
@@ -884,7 +884,7 @@ impl PyValue for PySetIterator {
     }
 }
 
-#[pyimpl(with(SlotIterator))]
+#[pyimpl(with(SlotConstructor, SlotIterator))]
 impl PySetIterator {
     #[pymethod(magic)]
     fn length_hint(&self) -> usize {
@@ -907,6 +907,7 @@ impl PySetIterator {
         ))
     }
 }
+impl Unconstructible for PySetIterator {}
 
 impl IteratorIterable for PySetIterator {}
 impl SlotIterator for PySetIterator {

vm/src/builtins/tuple.rs

@@ -7,7 +7,7 @@ use crate::{
     sliceable::PySliceableSequence,
     slots::{
         AsMapping, Comparable, Hashable, Iterable, IteratorIterable, PyComparisonOp,
-        SlotConstructor, SlotIterator,
+        SlotConstructor, SlotIterator, Unconstructible,
     },
     stdlib::sys,
     utils::Either,
@@ -379,7 +379,7 @@ impl PyValue for PyTupleIterator {
     }
 }
 
-#[pyimpl(with(SlotIterator))]
+#[pyimpl(with(SlotConstructor, SlotIterator))]
 impl PyTupleIterator {
     #[pymethod(magic)]
     fn length_hint(&self) -> usize {
@@ -400,6 +400,7 @@ impl PyTupleIterator {
             .builtins_iter_reduce(|x| x.clone().into(), vm)
     }
 }
+impl Unconstructible for PyTupleIterator {}
 
 impl IteratorIterable for PyTupleIterator {}
 impl SlotIterator for PyTupleIterator {

vm/src/slots.rs

@@ -157,6 +157,20 @@ pub trait SlotConstructor: PyValue {
     fn py_new(cls: PyTypeRef, args: Self::Args, vm: &VirtualMachine) -> PyResult;
 }
 
+/// For types that cannot be instantiated through Python code.
+pub trait Unconstructible: PyValue {}
+
+impl<T> SlotConstructor for T
+where
+    T: Unconstructible,
+{
+    type Args = FuncArgs;
+
+    fn py_new(cls: PyTypeRef, _args: Self::Args, vm: &VirtualMachine) -> PyResult {
+        Err(vm.new_type_error(format!("cannot create {} instances", cls.slot_name())))
+    }
+}
+
 #[pyimpl]
 pub trait SlotDestructor: PyValue {
     #[inline] // for __del__