introduce ArgSize

vm/src/function/mod.rs

@@ -17,7 +17,7 @@ pub use builtin::{IntoPyNativeFunc, OwnedParam, PyNativeFunc, RefParam};
 pub use either::Either;
 pub use getset::PySetterValue;
 pub(super) use getset::{IntoPyGetterFunc, IntoPySetterFunc, PyGetterFunc, PySetterFunc};
-pub use number::{ArgIndex, ArgIntoBool, ArgIntoComplex, ArgIntoFloat};
+pub use number::{ArgIndex, ArgIntoBool, ArgIntoComplex, ArgIntoFloat, ArgSize};
 pub use protocol::{ArgCallable, ArgIterable, ArgMapping, ArgSequence};
 
 use crate::{builtins::PyStr, convert::TryFromBorrowedObject, PyObject, PyResult, VirtualMachine};

vm/src/function/number.rs

@@ -154,3 +154,31 @@ impl TryFromObject for ArgIndex {
         })
     }
 }
+
+#[derive(Debug)]
+#[repr(transparent)]
+pub struct ArgSize {
+    value: isize,
+}
+
+impl From<ArgSize> for isize {
+    fn from(arg: ArgSize) -> Self {
+        arg.value
+    }
+}
+
+impl Deref for ArgSize {
+    type Target = isize;
+
+    fn deref(&self) -> &Self::Target {
+        &self.value
+    }
+}
+
+impl TryFromObject for ArgSize {
+    fn try_from_object(vm: &VirtualMachine, obj: PyObjectRef) -> PyResult<Self> {
+        Ok(Self {
+            value: obj.try_index(vm)?.try_to_primitive(vm)?,
+        })
+    }
+}