From d9b1ae296b8952fdee9f163ff0ef69dd4e8bdeb7 Mon Sep 17 00:00:00 2001
From: Jeong YunWon <jeong@youknowone.org>
Date: Sun, 20 Sep 2020 10:43:31 +0900
Subject: [PATCH] tp_del

---
 vm/src/macros.rs      |  7 +++++--
 vm/src/obj/objtype.rs |  7 +++++++
 vm/src/pyobjectrc.rs  |  5 +++--
 vm/src/slots.rs       | 21 +++++++++++++++++++++
 vm/src/stdlib/io.rs   |  9 +++++++--
 5 files changed, 43 insertions(+), 6 deletions(-)

diff --git a/vm/src/macros.rs b/vm/src/macros.rs
index 292dc674c..515ce12ad 100644
--- a/vm/src/macros.rs
+++ b/vm/src/macros.rs
@@ -47,11 +47,14 @@ macro_rules! py_class {
             py_class
         }
     };
-    (@extract_slots($ctx:expr, $slots:expr, (slot $slot_name:ident), $value:expr)) => {
-        $slots.$slot_name = Some(
+    (@extract_slots($ctx:expr, $slots:expr, (slot new), $value:expr)) => {
+        $slots.new = Some(
             $crate::function::IntoPyNativeFunc::into_func($value)
         );
     };
+    (@extract_slots($ctx:expr, $slots:expr, (slot $slot_name:ident), $value:expr)) => {
+        $slots.$slot_name.store(Some($value));
+    };
     (@extract_slots($ctx:expr, $class:expr, $name:expr, $value:expr)) => {};
     (@extract_attrs($ctx:expr, $slots:expr, (slot $slot_name:ident), $value:expr)) => {};
     (@extract_attrs($ctx:expr, $class:expr, $name:expr, $value:expr)) => {
diff --git a/vm/src/obj/objtype.rs b/vm/src/obj/objtype.rs
index 0bd01e89b..5607bfcd9 100644
--- a/vm/src/obj/objtype.rs
+++ b/vm/src/obj/objtype.rs
@@ -150,6 +150,13 @@ impl PyClassRef {
                 } as _;
                 self.slots.hash.store(Some(func));
             }
+            "__del__" => {
+                let func: slots::DelFunc = |zelf, vm| {
+                    let magic = get_class_magic(&zelf, "__del__");
+                    vm.invoke(&magic, vec![zelf.clone()]).map(|_| ())
+                } as _;
+                self.slots.del.store(Some(func));
+            }
             _ => (),
         }
     }
diff --git a/vm/src/pyobjectrc.rs b/vm/src/pyobjectrc.rs
index 0e58b50cf..432dd90b0 100644
--- a/vm/src/pyobjectrc.rs
+++ b/vm/src/pyobjectrc.rs
@@ -146,11 +146,12 @@ where
 
         // CPython-compatible drop implementation
         let zelf = Self::into_ref(self.clone());
-        if let Some(del_method) = zelf.inner.get_class_attr("__del__") {
+        if let Some(del_slot) = zelf.class().first_in_mro(|cls| cls.slots.del.load()) {
             crate::vm::thread::with_vm(&zelf, |vm| {
-                if let Err(e) = vm.invoke(&del_method, vec![zelf.clone()]) {
+                if let Err(e) = del_slot(&zelf, vm) {
                     // exception in del will be ignored but printed
                     print!("Exception ignored in: ",);
+                    let del_method = zelf.get_class_attr("__del__").unwrap();
                     let repr = vm.to_repr(&del_method);
                     match repr {
                         Ok(v) => println!("{}", v.to_string()),
diff --git a/vm/src/slots.rs b/vm/src/slots.rs
index 68eb46829..10ec75137 100644
--- a/vm/src/slots.rs
+++ b/vm/src/slots.rs
@@ -41,6 +41,7 @@ impl Default for PyTpFlags {
 }
 
 pub(crate) type GenericMethod = fn(PyObjectRef, PyFuncArgs, &VirtualMachine) -> PyResult;
+pub(crate) type DelFunc = fn(&PyObjectRef, &VirtualMachine) -> PyResult<()>;
 pub(crate) type DescrGetFunc =
     fn(PyObjectRef, Option<PyObjectRef>, Option<PyObjectRef>, &VirtualMachine) -> PyResult;
 pub(crate) type HashFunc = fn(&PyObjectRef, &VirtualMachine) -> PyResult<PyHash>;
@@ -50,6 +51,7 @@ pub struct PyClassSlots {
     pub flags: PyTpFlags,
     pub name: PyRwLock<Option<String>>, // tp_name, not class name
     pub new: Option<PyNativeFunc>,
+    pub del: AtomicCell<Option<DelFunc>>,
     pub call: AtomicCell<Option<GenericMethod>>,
     pub descr_get: AtomicCell<Option<DescrGetFunc>>,
     pub hash: AtomicCell<Option<HashFunc>>,
@@ -82,6 +84,25 @@ impl std::fmt::Debug for PyClassSlots {
     }
 }
 
+#[pyimpl]
+pub trait SlotDesctuctor: PyValue {
+    #[pyslot]
+    fn tp_del(zelf: &PyObjectRef, vm: &VirtualMachine) -> PyResult<()> {
+        if let Some(zelf) = zelf.downcast_ref() {
+            Self::del(zelf, vm)
+        } else {
+            Err(vm.new_type_error("unexpected payload for __del__".to_owned()))
+        }
+    }
+
+    #[pymethod(magic)]
+    fn __del__(zelf: PyRef<Self>, vm: &VirtualMachine) -> PyResult<()> {
+        Self::del(&zelf, vm)
+    }
+
+    fn del(zelf: &PyRef<Self>, vm: &VirtualMachine) -> PyResult<()>;
+}
+
 #[pyimpl]
 pub trait SlotCall: PyValue {
     #[pymethod(magic)]
diff --git a/vm/src/stdlib/io.rs b/vm/src/stdlib/io.rs
index 170f1bb35..121d6cefe 100644
--- a/vm/src/stdlib/io.rs
+++ b/vm/src/stdlib/io.rs
@@ -416,11 +416,15 @@ fn io_base_cm_enter(instance: PyObjectRef) -> PyObjectRef {
     instance
 }
 
-fn io_base_cm_del(instance: PyObjectRef, vm: &VirtualMachine) -> PyResult<()> {
-    vm.call_method(&instance, "close", vec![])?;
+fn io_base_cm_del_slot(instance: &PyObjectRef, vm: &VirtualMachine) -> PyResult<()> {
+    vm.call_method(instance, "close", vec![])?;
     Ok(())
 }
 
+fn io_base_cm_del(instance: PyObjectRef, vm: &VirtualMachine) -> PyResult<()> {
+    io_base_cm_del_slot(&instance, vm)
+}
+
 fn io_base_cm_exit(instance: PyObjectRef, _args: PyFuncArgs, vm: &VirtualMachine) -> PyResult<()> {
     vm.call_method(&instance, "close", vec![])?;
     Ok(())
@@ -1271,6 +1275,7 @@ pub fn make_module(vm: &VirtualMachine) -> PyObjectRef {
     let io_base = py_class!(ctx, "_IOBase", &ctx.types.object_type, {
         "__enter__" => ctx.new_method(io_base_cm_enter),
         "__del__" => ctx.new_method(io_base_cm_del),
+        (slot del) => io_base_cm_del_slot,
         "__exit__" => ctx.new_method(io_base_cm_exit),
         "seekable" => ctx.new_method(io_base_seekable),
         "readable" => ctx.new_method(io_base_readable),