Merge pull request #231 from koto-lang/object-improvements

Introduce trait-based objects

CHANGELOG.md

@@ -49,7 +49,8 @@ The Koto project adheres to
 
 #### Internals
 
-- `MetaMapBuilder` is now available to simplify the creation of `MetaMap`s. 
+- The `KotoObject` trait has been introduced to simplify creating custom object 
+  types, replacing `ExternalValue`.
 - Preludes are now available in the `koto` and `koto_runtime` crates.
 - `Ptr<T>` and `PtrMut<T>` wrappers have been introduced as the core memory
   types for the runtime, replacing uses of `Rc<T>` and `Rc<RefCell<T>>`.
@@ -96,7 +97,7 @@ The Koto project adheres to
 
 - `Value` no longer implements `fmt::Display`, instead `value_to_string` can be
   called on `Koto` or the Vm to get a string.
-- `Value::ExternalValue` is now `Value::External`.
+- `Value::ExternalValue` has been replaced by `Value::Object`.
 - `ValueTuple::data` has been removed, with a `Deref` impl to `&[Value]` taking
   its place.
 - Type strings and strings returned by `KotoFile` implementations are now 
@@ -136,8 +137,6 @@ The Koto project adheres to
     # You can use:
     "hello"[2..4]
     ```
-- The `Value::ExternalData` variant has been removed, `ExternalValue` can be
-  used instead. 
 
 ### Fixed
 

Cargo.toml

@@ -49,6 +49,8 @@ smallvec = { version = "1.10.0", features = ["const_generics", "union"] }
 tempfile = "3.1"
 # A crate for getting the crate binary in an integration test.
 test_bin = "0.4.0"
+# derive(Error)
+thiserror = "1.0.44"
 # A native Rust encoder and decoder of TOML-formatted files and streams.
 toml = { version = "0.5.6", features = ["preserve_order"] }
 # Powerful library for word wrapping, indenting, and dedenting strings

core/memory/src/rc/ptr_mut.rs

@@ -48,6 +48,13 @@ impl<T: ?Sized> PtrMut<T> {
     pub fn try_borrow_mut(&self) -> Result<BorrowMut<'_, T>, BorrowMutError> {
         self.0.try_borrow_mut().map(BorrowMut)
     }
+
+    /// Returns true if the two `PtsMut`s point to the same allocation
+    ///
+    /// See also: [std::rc::Rc::ptr_eq]
+    pub fn ptr_eq(this: &Self, other: &Self) -> bool {
+        Rc::ptr_eq(&this.0, &other.0)
+    }
 }
 
 impl<T> From<T> for PtrMut<T> {

core/runtime/Cargo.toml

@@ -24,6 +24,7 @@ downcast-rs = { workspace = true }
 indexmap = { workspace = true }
 rustc-hash = { workspace = true }
 smallvec = { workspace = true }
+thiserror = { workspace = true }
 unicode-segmentation = { workspace = true }
 
 [target.'cfg(not(target_arch = "wasm32"))'.dependencies]