General changes across the runtime crate in support of compile module

* Compile module is able to compile bytecode (or so it seems...)
* Runtime crate has had some new stuff added to it, mostly with objects
  and vtables. Still not 100% on the object method function call story,
  but I guess it'll be tackled when we get there.

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

runtime/src/obj/mod.rs

@@ -8,8 +8,9 @@ pub mod intern;
 pub mod names;
 pub mod str;
 pub mod sym;
+#[cfg(test)]
+mod test;
 pub mod ty;
-#[cfg(test)] mod test;
 
 pub mod prelude {
     pub use crate::obj::{attrs::*, fun::*, int::*, intern::*, str::*, sym::*, ty::*, Obj, ObjRef};
@@ -17,8 +18,8 @@ pub mod prelude {
 
 use shredder::{Gc, Scan};
 use std::{
-    ops::{Deref, DerefMut, CoerceUnsized},
     marker::Unsize,
+    ops::{CoerceUnsized, Deref, DerefMut},
     sync::RwLock,
 };
 
@@ -30,11 +31,18 @@ use sym::Sym;
 //
 
 pub trait Obj: Scan + std::fmt::Debug {
+    fn vtable(&self) -> &Vtable;
     fn attrs(&self) -> &Attrs;
     fn attrs_mut(&mut self) -> Option<&mut Attrs>;
 
-    fn get_attr(&self, sym: &Sym) -> Option<&ObjRef> {
-        self.attrs().get(&sym)
+    fn get_attr(&self, sym: &Sym) -> Option<ObjRef> {
+        self.attrs()
+            .get(&sym)
+            .cloned()
+            .or_else(|| {
+                let vtable = self.vtable().get();
+                vtable.get(&sym).cloned()
+            })
     }
 
     fn set_attr(&mut self, sym: Sym, value: ObjRef) -> Option<ObjRef> {
@@ -47,13 +55,21 @@ pub trait Obj: Scan + std::fmt::Debug {
 //
 
 #[derive(Debug, Scan)]
-pub struct ObjRef<T: Obj + ?Sized + Send + Sync = (dyn Obj + Send + Sync + 'static)> {
+pub struct ObjRef<T = (dyn Obj + Send + Sync + 'static)>
+where
+    T: Obj + ?Sized + Send + Sync,
+{
     gc: Gc<RwLock<T>>,
 }
 
-impl<T: Obj + ?Sized + Send + Sync> Clone for ObjRef<T> {
+impl<T> Clone for ObjRef<T>
+where
+    T: Obj + ?Sized + Send + Sync,
+{
     fn clone(&self) -> Self {
-        ObjRef { gc: self.gc.clone() }
+        ObjRef {
+            gc: self.gc.clone(),
+        }
     }
 }
 
@@ -61,7 +77,10 @@ impl<T: Obj + ?Sized + Send + Sync> Clone for ObjRef<T> {
 // impl ObjRef
 //
 
-impl<T: Obj + ?Sized + Send + Sync> ObjRef<T> {
+impl<T> ObjRef<T>
+where
+    T: Obj + ?Sized + Send + Sync,
+{
     /// Check object reference equality.
     pub fn ref_eq(&self, other: &Self) -> bool {
         let lhs: &RwLock<T> = &*self.gc.get();
@@ -70,7 +89,10 @@ impl<T: Obj + ?Sized + Send + Sync> ObjRef<T> {
     }
 }
 
-impl<T: Obj + Send + Sync + 'static> ObjRef<T> {
+impl<T> ObjRef<T>
+where
+    T: Obj + Send + Sync + 'static,
+{
     pub fn new(obj: T) -> Self {
         ObjRef {
             gc: Gc::new(RwLock::new(obj)),