From c3121a176c366807bbfd24af149707ee6b4ad641 Mon Sep 17 00:00:00 2001
From: Alek Ratzloff <alekratz@gmail.com>
Date: Wed, 7 Oct 2020 18:41:45 -0700
Subject: [PATCH] Add self_referring_obj macro for self-referential objects.

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>
---
 src/obj/fun.rs    | 51 ++++++++++++++++++-----------------------------
 src/obj/macros.rs | 16 +++++++++++++++
 2 files changed, 35 insertions(+), 32 deletions(-)

diff --git a/src/obj/fun.rs b/src/obj/fun.rs
index 6c88e6b..b717537 100644
--- a/src/obj/fun.rs
+++ b/src/obj/fun.rs
@@ -31,24 +31,18 @@ pub struct UserFun {
 
 impl UserFun {
     pub fn new_obj(code: Vec<Inst>, locals: FunLocals) -> UserFunRef {
-        let obj_ref = ObjRef::new(UserFun {
-            vtable: Default::default(), // this is a placeholder for the real vtable
-            attrs: Default::default(),
-            code: Arc::new(code),
-            locals,
-        });
-
-        // XXX replace the vtable before returning, since __call__ member points to the object
-        // itself
-        {
-            write_obj!(let obj = obj_ref);
-            obj.vtable = vtable! {
+        self_referring_obj! (
+            Self {
+                vtable: Default::default(), // this is a placeholder for the real vtable
+                attrs: Default::default(),
+                code: Arc::new(code),
+                locals,
+            },
+            vtable: |obj_ref: ObjRef| vtable! {
                 TY_MEMBER_NAME.sym => USER_FUN_TY.clone(),
                 CALL_MEMBER_NAME.sym => obj_ref.clone(),
-            };
-        }
-
-        obj_ref
+            }
+        )
     }
 
     pub fn code(&self) -> &Vec<Inst> {
@@ -209,24 +203,17 @@ pub struct NativeFun {
 
 impl NativeFun {
     pub fn new_obj(fun: NativeFunPtr) -> ObjRef<Self> {
-        let obj_ref = ObjRef::new(Self {
-            vtable: Default::default(),
-            attrs: Default::default(),
-            fun: GcSafeWrapper::new(fun),
-        });
-
-
-        // XXX replace the vtable before returning, since __call__ member points to the object
-        // itself
-        {
-            write_obj!(let obj = obj_ref);
-            obj.vtable = vtable! {
+        self_referring_obj! (
+            Self {
+                vtable: Default::default(),
+                attrs: Default::default(),
+                fun: GcSafeWrapper::new(fun),
+            },
+            vtable: |obj_ref: ObjRef| vtable! {
                 TY_MEMBER_NAME.sym => NATIVE_FUN_TY.clone(),
                 CALL_MEMBER_NAME.sym => obj_ref.clone(),
-            };
-        }
-
-        obj_ref
+            }
+        )
     }
 
     /// Gets the native function that can be invoked.
diff --git a/src/obj/macros.rs b/src/obj/macros.rs
index b3ccc1e..91fbbc2 100644
--- a/src/obj/macros.rs
+++ b/src/obj/macros.rs
@@ -122,3 +122,19 @@ macro_rules! handle_type {
         impl shredder::EmptyScan for $name {}
     };
 }
+
+#[macro_export]
+macro_rules! self_referring_obj {
+    ($init:expr $(, $name:ident : $value:expr)* $(,)?) => {{
+        let obj_ref = $crate::obj::ObjRef::new($init);
+
+        {
+            write_obj!(let obj = obj_ref);
+            $(
+                obj.$name = ($value)(obj_ref.clone());
+            )*
+        }
+
+        obj_ref
+    }};
+}