Update error message, add Int.__eq__

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

src/obj/int.rs

@@ -13,6 +13,22 @@ pub struct IntObj {
 
 thread_local! {
     static VTABLE: VTable = VTableBuilder::default()
+        .with_builtin("__eq__", |machine, _| {
+            let rhs_ptr: ObjPtr = machine.stack_pop()?;
+            let lhs_ptr: ObjPtr = machine.stack_pop()?;
+            let lhs = lhs_ptr.as_any().downcast_ref::<IntObj>();
+            let rhs = rhs_ptr.as_any().downcast_ref::<IntObj>();
+            let result = if let (Some(lhs), Some(rhs)) = (lhs, rhs) {
+                lhs.value() == rhs.value()
+            } else if let (Some(lhs), Some(rhs)) = (lhs, rhs_ptr.as_any().downcast_ref::<FloatObj>()) {
+                // implicit upcast for this comparison allowed
+                lhs.value() as Float == rhs.value()
+            } else {
+                false
+            };
+            machine.stack_push(BoolObj::new(result))?;
+            Ok(BuiltinExit::Return)
+        })
         .with_builtin("__splat__", |machine, _| {
             let rhs_ptr: ObjPtr = machine.stack_pop()?;
             let lhs_ptr: ObjPtr = machine.stack_pop()?;

src/vm/error.rs

@@ -15,7 +15,7 @@ pub enum RuntimeError {
     #[error("cannot call value '{0}'")]
     CannotCall(String),
 
-    #[error("expected {0} value")]
+    #[error("expected {0}")]
     WrongValue(String),
 
     #[error("at {0}")]