Add new base object stuff, gc dependency

I'm not writing my own GC, it's a huge pain in Rust. I'm using the gc
library instead.

Base object stuff implementation is here too. Hopefully going to start
using ObjPtr instead of Value next.

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

src/object.rs

@@ -4,24 +4,25 @@
 #![allow(dead_code)]
 
 use crate::syn::ast::SpStmt;
-use crate::vm::{error::Result, machine::Machine};
+use crate::vm::{error::*, machine::Machine};
 use crate::{scope::Scope, syn::span::Span, vm::inst::SpInst};
-use std::cell::RefCell;
-use std::collections::{BTreeMap, HashMap};
+use gc::{unsafe_empty_trace, Finalize, Gc, Trace};
+use std::collections::HashMap;
 use std::fmt::{self, Debug, Display};
-use std::rc::{Rc, Weak};
+use std::rc::Rc;
 
+pub type ObjPtr = Gc<dyn Obj>;
 pub type Str = String;
 pub type Int = i64;
 pub type Float = f64;
-pub type VTable = HashMap<String, Value>;
+pub type VTable = HashMap<String, ObjPtr>;
 
 // /////////////////////////////////////////////////////////////////////////////
 // Quote
 // /////////////////////////////////////////////////////////////////////////////
 
 /// A handle to a quote pointing to an element in a `QuoteTable`.
-#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Finalize)]
 pub struct Quote(usize);
 
 impl Quote {
@@ -30,6 +31,10 @@ impl Quote {
     }
 }
 
+unsafe impl Trace for Quote {
+    unsafe_empty_trace!();
+}
+
 /// A table of compiled quotes, their expression trees, and their spans.
 #[derive(Debug, Clone, Default)]
 pub struct QuoteTable {
@@ -135,12 +140,16 @@ pub enum BuiltinExit {
     Return,
 }
 
-#[derive(Clone)]
+#[derive(Clone, Finalize)]
 pub struct BuiltinFn {
     name: Rc<String>,
     fun: Rc<BuiltinFnPtr>,
 }
 
+unsafe impl Trace for BuiltinFn {
+    unsafe_empty_trace!();
+}
+
 impl PartialEq for BuiltinFn {
     fn eq(&self, other: &Self) -> bool {
         (&self.fun as *const _ as usize) == (&other.fun as *const _ as usize)
@@ -172,3 +181,179 @@ impl Debug for BuiltinFn {
         )
     }
 }
+
+/// An object that has a vtable and common functions.
+pub trait Obj: Trace + Finalize {
+    /// Gets the vtable for this object.
+    fn vtable(&self) -> &VTable;
+
+    /// Gets the vtable for this object, mutably.
+    fn vtable_mut(&mut self) -> &mut VTable;
+
+    /// Calls this object.
+    fn call(&self, machine: &mut Machine) -> Result<()>;
+
+    /// Gets a value in the vtable.
+    ///
+    /// This has a default implementation, so it probably doesn't need to be
+    /// implemented.
+    fn get(&self, key: &str) -> Option<ObjPtr> {
+        self.vtable().get(key).cloned()
+    }
+
+    /// Sets a value in the vtable.
+    ///
+    /// This has a default implementation, so it probably doesn't need to be
+    /// implemented.
+    fn set(&mut self, key: String, value: ObjPtr) -> Option<ObjPtr> {
+        self.vtable_mut().insert(key, value)
+    }
+}
+
+macro_rules! vtable {
+    ($($key:expr => $value:expr),* $(,)?) => {{
+        VTable::from(
+            [
+                $(
+                    ($key.to_string(), $value)
+                ),*
+            ]
+        )
+    }};
+}
+
+#[derive(Trace, Finalize)]
+pub struct FloatObj {
+    value: Float,
+    vtable: VTable,
+}
+
+impl Obj for FloatObj {
+    fn vtable(&self) -> &VTable {
+        &self.vtable
+    }
+
+    fn vtable_mut(&mut self) -> &mut VTable {
+        &mut self.vtable
+    }
+
+    fn call(&self, _: &mut Machine) -> Result<()> {
+        Err(RuntimeError::CannotCall("float value".to_string()))
+    }
+}
+
+#[derive(Trace, Finalize)]
+pub struct IntObj {
+    value: Int,
+    vtable: VTable,
+}
+
+impl IntObj {
+    pub fn new(value: Int) -> Self {
+        IntObj {
+            value,
+            vtable: vtable! {},
+        }
+    }
+}
+
+impl Obj for IntObj {
+    fn vtable(&self) -> &VTable {
+        &self.vtable
+    }
+
+    fn vtable_mut(&mut self) -> &mut VTable {
+        &mut self.vtable
+    }
+
+    fn call(&self, _: &mut Machine) -> Result<()> {
+        Err(RuntimeError::CannotCall("int value".to_string()))
+    }
+}
+
+#[derive(Trace, Finalize)]
+pub struct StrObj {
+    value: String,
+    vtable: VTable,
+}
+
+impl StrObj {
+    pub fn new(value: String) -> Self {
+        StrObj {
+            value,
+            vtable: vtable! {},
+        }
+    }
+}
+
+impl Obj for StrObj {
+    fn vtable(&self) -> &VTable {
+        &self.vtable
+    }
+
+    fn vtable_mut(&mut self) -> &mut VTable {
+        &mut self.vtable
+    }
+
+    fn call(&self, _: &mut Machine) -> Result<()> {
+        Err(RuntimeError::CannotCall("string value".to_string()))
+    }
+}
+
+#[derive(Trace, Finalize)]
+pub struct QuoteObj {
+    value: Quote,
+    vtable: VTable,
+}
+
+impl QuoteObj {
+    pub fn new(value: Quote) -> Self {
+        QuoteObj {
+            value,
+            vtable: vtable! {},
+        }
+    }
+}
+
+impl Obj for QuoteObj {
+    fn vtable(&self) -> &VTable {
+        &self.vtable
+    }
+
+    fn vtable_mut(&mut self) -> &mut VTable {
+        &mut self.vtable
+    }
+
+    fn call(&self, _: &mut Machine) -> Result<()> {
+        Err(RuntimeError::CannotCall("quote value".to_string()))
+    }
+}
+
+#[derive(Trace, Finalize)]
+pub struct BuiltinFnObj {
+    value: BuiltinFn,
+    vtable: VTable,
+}
+
+impl BuiltinFnObj {
+    pub fn new(value: BuiltinFn) -> Self {
+        BuiltinFnObj {
+            value,
+            vtable: vtable! {},
+        }
+    }
+}
+
+impl Obj for BuiltinFnObj {
+    fn vtable(&self) -> &VTable {
+        &self.vtable
+    }
+
+    fn vtable_mut(&mut self) -> &mut VTable {
+        &mut self.vtable
+    }
+
+    fn call(&self, _: &mut Machine) -> Result<()> {
+        Err(RuntimeError::CannotCall("quote value".to_string()))
+    }
+}