diff --git a/dust-lang/src/chunk/disassembler.rs b/dust-lang/src/chunk/disassembler.rs
index 3a73c62..c5edceb 100644
--- a/dust-lang/src/chunk/disassembler.rs
+++ b/dust-lang/src/chunk/disassembler.rs
@@ -46,7 +46,7 @@ use std::{
 
 use colored::{ColoredString, Colorize};
 
-use crate::{value::ConcreteValue, Chunk, Local};
+use crate::{value::ConcreteValue, Chunk, Local, Value};
 
 const INSTRUCTION_COLUMNS: [(&str, usize); 4] =
     [("i", 5), ("POSITION", 12), ("OPERATION", 17), ("INFO", 24)];
@@ -336,7 +336,7 @@ impl<'a, W: Write> Disassembler<'a, W> {
         self.write_centered_with_border(CONSTANT_BORDERS[1])?;
 
         for (index, value) in self.chunk.constants().iter().enumerate() {
-            let is_function = matches!(value, ConcreteValue::Function(_));
+            let is_function = matches!(value, Value::Concrete(ConcreteValue::Function(_)));
             let type_display = value.r#type().to_string();
             let value_display = if is_function {
                 "Function displayed below".to_string()
@@ -353,7 +353,7 @@ impl<'a, W: Write> Disassembler<'a, W> {
 
             self.write_centered_with_border(&constant_display)?;
 
-            if let ConcreteValue::Function(chunk) = value {
+            if let Value::Concrete(ConcreteValue::Function(chunk)) = value {
                 let function_disassembler = chunk
                     .disassembler(self.writer)
                     .style(self.style)
diff --git a/dust-lang/src/chunk/mod.rs b/dust-lang/src/chunk/mod.rs
index 8590176..919d6bd 100644
--- a/dust-lang/src/chunk/mod.rs
+++ b/dust-lang/src/chunk/mod.rs
@@ -17,7 +17,7 @@ use std::io::Write;
 use serde::{Deserialize, Serialize};
 use smallvec::SmallVec;
 
-use crate::{ConcreteValue, DustString, FunctionType, Instruction, Span};
+use crate::{ConcreteValue, DustString, FunctionType, Instruction, Span, Value};
 
 /// In-memory representation of a Dust program or function.
 ///
@@ -28,7 +28,7 @@ pub struct Chunk {
     r#type: FunctionType,
 
     instructions: SmallVec<[(Instruction, Span); 32]>,
-    constants: SmallVec<[ConcreteValue; 16]>,
+    constants: SmallVec<[Value; 16]>,
     locals: SmallVec<[Local; 8]>,
 
     stack_size: usize,
@@ -39,7 +39,7 @@ impl Chunk {
         name: Option<DustString>,
         r#type: FunctionType,
         instructions: SmallVec<[(Instruction, Span); 32]>,
-        constants: SmallVec<[ConcreteValue; 16]>,
+        constants: SmallVec<[Value; 16]>,
         locals: SmallVec<[Local; 8]>,
         stack_size: usize,
     ) -> Self {
@@ -57,7 +57,7 @@ impl Chunk {
         name: Option<DustString>,
         r#type: FunctionType,
         instructions: impl Into<SmallVec<[(Instruction, Span); 32]>>,
-        constants: impl Into<SmallVec<[ConcreteValue; 16]>>,
+        constants: impl Into<SmallVec<[Value; 16]>>,
         locals: impl Into<SmallVec<[Local; 8]>>,
     ) -> Self {
         Self {
@@ -82,7 +82,7 @@ impl Chunk {
         self.instructions.is_empty()
     }
 
-    pub fn constants(&self) -> &SmallVec<[ConcreteValue; 16]> {
+    pub fn constants(&self) -> &SmallVec<[Value; 16]> {
         &self.constants
     }
 
diff --git a/dust-lang/src/compiler/mod.rs b/dust-lang/src/compiler/mod.rs
index e249fb2..6062e6d 100644
--- a/dust-lang/src/compiler/mod.rs
+++ b/dust-lang/src/compiler/mod.rs
@@ -24,7 +24,7 @@ use crate::{
         Not, Return, SetLocal, Test,
     },
     Argument, Chunk, ConcreteValue, DustError, DustString, FunctionType, Instruction, Lexer, Local,
-    NativeFunction, Operation, Scope, Span, Token, TokenKind, Type,
+    NativeFunction, Operation, Scope, Span, Token, TokenKind, Type, Value,
 };
 
 /// Compiles the input and returns a chunk.
@@ -58,7 +58,7 @@ pub fn compile(source: &str) -> Result<Chunk, DustError> {
 pub struct Compiler<'src> {
     self_name: Option<DustString>,
     instructions: SmallVec<[(Instruction, Type, Span); 32]>,
-    constants: SmallVec<[ConcreteValue; 16]>,
+    constants: SmallVec<[Value; 16]>,
     locals: SmallVec<[(Local, Type); 8]>,
     stack_size: usize,
 
@@ -203,11 +203,12 @@ impl<'src> Compiler<'src> {
             .rev()
             .find_map(|(index, (local, _))| {
                 let constant = self.constants.get(local.identifier_index as usize)?;
-                let identifier = if let ConcreteValue::String(identifier) = constant {
-                    identifier
-                } else {
-                    return None;
-                };
+                let identifier =
+                    if let Value::Concrete(ConcreteValue::String(identifier)) = constant {
+                        identifier
+                    } else {
+                        return None;
+                    };
 
                 if identifier == identifier_text {
                     Some(index as u8)
@@ -231,7 +232,7 @@ impl<'src> Compiler<'src> {
     ) -> (u8, u8) {
         log::info!("Declaring local {identifier}");
 
-        let identifier = ConcreteValue::string(identifier);
+        let identifier = Value::Concrete(ConcreteValue::string(identifier));
         let identifier_index = self.push_or_get_constant(identifier);
         let local_index = self.locals.len() as u8;
 
@@ -253,7 +254,7 @@ impl<'src> Compiler<'src> {
             })
     }
 
-    fn push_or_get_constant(&mut self, value: ConcreteValue) -> u8 {
+    fn push_or_get_constant(&mut self, value: Value) -> u8 {
         if let Some(index) = self
             .constants
             .iter()
@@ -405,7 +406,7 @@ impl<'src> Compiler<'src> {
         position: Span,
     ) -> Result<(), CompileError> {
         let r#type = constant.r#type();
-        let constant_index = self.push_or_get_constant(constant);
+        let constant_index = self.push_or_get_constant(Value::Concrete(constant));
         let destination = self.next_register();
         let load_constant = Instruction::load_constant(destination, constant_index, false);
 
@@ -1618,7 +1619,7 @@ impl<'src> Compiler<'src> {
 
         let function_end = function_compiler.previous_position.1;
         let chunk = function_compiler.finish(None, value_parameters.clone());
-        let function = ConcreteValue::function(chunk);
+        let function = Value::Concrete(ConcreteValue::function(chunk));
         let constant_index = self.push_or_get_constant(function);
         let destination = self.next_register();
         let function_type = FunctionType {
diff --git a/dust-lang/src/lib.rs b/dust-lang/src/lib.rs
index 0c7f7cc..f965f05 100644
--- a/dust-lang/src/lib.rs
+++ b/dust-lang/src/lib.rs
@@ -47,9 +47,7 @@ pub use crate::lexer::{lex, LexError, Lexer};
 pub use crate::native_function::{NativeFunction, NativeFunctionError};
 pub use crate::r#type::{EnumType, FunctionType, StructType, Type, TypeConflict};
 pub use crate::token::{Token, TokenKind, TokenOwned};
-pub use crate::value::{
-    AbstractValue, ConcreteValue, DustString, RangeValue, Value, ValueError, ValueRef,
-};
+pub use crate::value::{AbstractValue, ConcreteValue, DustString, RangeValue, Value, ValueError};
 pub use crate::vm::{run, Vm, VmError};
 
 use std::fmt::Display;
diff --git a/dust-lang/src/native_function/assertion.rs b/dust-lang/src/native_function/assertion.rs
index 7fe89d0..8e9e3e2 100644
--- a/dust-lang/src/native_function/assertion.rs
+++ b/dust-lang/src/native_function/assertion.rs
@@ -3,11 +3,11 @@ use std::panic;
 use annotate_snippets::{Level, Renderer, Snippet};
 use smallvec::SmallVec;
 
-use crate::{DustString, NativeFunctionError, Value, ValueRef, Vm};
+use crate::{DustString, NativeFunctionError, Value, Vm};
 
 pub fn panic(
     vm: &Vm,
-    arguments: SmallVec<[ValueRef; 4]>,
+    arguments: SmallVec<[&Value; 4]>,
 ) -> Result<Option<Value>, NativeFunctionError> {
     let mut message: Option<DustString> = None;
 
diff --git a/dust-lang/src/native_function/io.rs b/dust-lang/src/native_function/io.rs
index f163b0d..c2c16ee 100644
--- a/dust-lang/src/native_function/io.rs
+++ b/dust-lang/src/native_function/io.rs
@@ -2,12 +2,9 @@ use std::io::{stdin, stdout, Write};
 
 use smallvec::SmallVec;
 
-use crate::{ConcreteValue, NativeFunctionError, Value, ValueRef, Vm};
+use crate::{ConcreteValue, NativeFunctionError, Value, Vm};
 
-pub fn read_line(
-    vm: &Vm,
-    _: SmallVec<[ValueRef; 4]>,
-) -> Result<Option<Value>, NativeFunctionError> {
+pub fn read_line(vm: &Vm, _: SmallVec<[&Value; 4]>) -> Result<Option<Value>, NativeFunctionError> {
     let mut buffer = String::new();
 
     match stdin().read_line(&mut buffer) {
@@ -27,7 +24,7 @@ pub fn read_line(
 
 pub fn write(
     vm: &Vm,
-    arguments: SmallVec<[ValueRef; 4]>,
+    arguments: SmallVec<[&Value; 4]>,
 ) -> Result<Option<Value>, NativeFunctionError> {
     let mut stdout = stdout();
 
@@ -50,7 +47,7 @@ pub fn write(
 
 pub fn write_line(
     vm: &Vm,
-    arguments: SmallVec<[ValueRef; 4]>,
+    arguments: SmallVec<[&Value; 4]>,
 ) -> Result<Option<Value>, NativeFunctionError> {
     let mut stdout = stdout();
 
diff --git a/dust-lang/src/native_function/mod.rs b/dust-lang/src/native_function/mod.rs
index 30cd8cb..c1b50d4 100644
--- a/dust-lang/src/native_function/mod.rs
+++ b/dust-lang/src/native_function/mod.rs
@@ -15,7 +15,7 @@ use std::{
 use serde::{Deserialize, Serialize};
 use smallvec::{smallvec, SmallVec};
 
-use crate::{AnnotatedError, FunctionType, Span, Type, Value, ValueRef, Vm, VmError};
+use crate::{AnnotatedError, FunctionType, Span, Type, Value, Vm, VmError};
 
 macro_rules! define_native_function {
     ($(($name:ident, $bytes:literal, $str:expr, $type:expr, $function:expr)),*) => {
@@ -33,7 +33,7 @@ macro_rules! define_native_function {
             pub fn call<'a>(
                 &self,
                 vm: &Vm<'a>,
-                arguments: SmallVec<[ValueRef<'a>; 4]>,
+                arguments: SmallVec<[&Value; 4]>,
             ) -> Result<Option<Value>, NativeFunctionError> {
                 match self {
                     $(
diff --git a/dust-lang/src/native_function/string.rs b/dust-lang/src/native_function/string.rs
index 03caf7e..8857025 100644
--- a/dust-lang/src/native_function/string.rs
+++ b/dust-lang/src/native_function/string.rs
@@ -1,10 +1,10 @@
 use smallvec::SmallVec;
 
-use crate::{ConcreteValue, NativeFunctionError, Value, ValueRef, Vm};
+use crate::{ConcreteValue, NativeFunctionError, Value, Vm};
 
 pub fn to_string(
     vm: &Vm,
-    arguments: SmallVec<[ValueRef; 4]>,
+    arguments: SmallVec<[&Value; 4]>,
 ) -> Result<Option<Value>, NativeFunctionError> {
     if arguments.len() != 1 {
         return Err(NativeFunctionError::ExpectedArgumentCount {
diff --git a/dust-lang/src/value/abstract_value.rs b/dust-lang/src/value/abstract_value.rs
index 0407fb5..8e7de63 100644
--- a/dust-lang/src/value/abstract_value.rs
+++ b/dust-lang/src/value/abstract_value.rs
@@ -1,11 +1,14 @@
 use std::fmt::{self, Display, Formatter};
 
-use crate::{vm::Pointer, ConcreteValue, DustString, Value, ValueRef, Vm, VmError};
+use crate::{vm::Pointer, ConcreteValue, DustString, Type, Value, Vm, VmError};
 
 #[derive(Debug, PartialEq, PartialOrd)]
 pub enum AbstractValue {
     FunctionSelf,
-    List { item_pointers: Vec<Pointer> },
+    List {
+        item_type: Type,
+        item_pointers: Vec<Pointer>,
+    },
 }
 
 impl AbstractValue {
@@ -13,10 +16,6 @@ impl AbstractValue {
         Value::Abstract(self)
     }
 
-    pub fn to_value_ref(&self) -> ValueRef {
-        ValueRef::Abstract(self)
-    }
-
     pub fn to_concrete_owned(&self, vm: &Vm) -> ConcreteValue {
         match self {
             AbstractValue::FunctionSelf => ConcreteValue::function(vm.chunk().clone()),
@@ -26,7 +25,7 @@ impl AbstractValue {
                 for pointer in item_pointers {
                     let item_option = vm.follow_pointer_allow_empty(*pointer);
                     let item = match item_option {
-                        Some(value_ref) => value_ref.into_concrete_owned(vm),
+                        Some(value) => value.clone().into_concrete_owned(vm),
                         None => continue,
                     };
 
@@ -65,6 +64,13 @@ impl AbstractValue {
 
         Ok(display)
     }
+
+    pub fn r#type(&self) -> Type {
+        match self {
+            AbstractValue::FunctionSelf => Type::SelfChunk,
+            AbstractValue::List { item_type, .. } => Type::List(Box::new(item_type.clone())),
+        }
+    }
 }
 
 impl Clone for AbstractValue {
@@ -74,8 +80,10 @@ impl Clone for AbstractValue {
         match self {
             AbstractValue::FunctionSelf => AbstractValue::FunctionSelf,
             AbstractValue::List {
+                item_type: r#type,
                 item_pointers: items,
             } => AbstractValue::List {
+                item_type: r#type.clone(),
                 item_pointers: items.clone(),
             },
         }
diff --git a/dust-lang/src/value/concrete_value.rs b/dust-lang/src/value/concrete_value.rs
index 13dd2ca..e0f6491 100644
--- a/dust-lang/src/value/concrete_value.rs
+++ b/dust-lang/src/value/concrete_value.rs
@@ -3,7 +3,7 @@ use std::fmt::{self, Display, Formatter};
 use serde::{Deserialize, Serialize};
 use smartstring::{LazyCompact, SmartString};
 
-use crate::{Chunk, Type, Value, ValueError, ValueRef};
+use crate::{Chunk, Type, Value, ValueError};
 
 use super::RangeValue;
 
@@ -27,10 +27,6 @@ impl ConcreteValue {
         Value::Concrete(self)
     }
 
-    pub fn to_value_ref(&self) -> ValueRef {
-        ValueRef::Concrete(self)
-    }
-
     pub fn function(chunk: Chunk) -> Self {
         ConcreteValue::Function(Box::new(chunk))
     }
diff --git a/dust-lang/src/value/mod.rs b/dust-lang/src/value/mod.rs
index a6f0761..d8105ae 100644
--- a/dust-lang/src/value/mod.rs
+++ b/dust-lang/src/value/mod.rs
@@ -6,25 +6,20 @@ mod range_value;
 pub use abstract_value::AbstractValue;
 pub use concrete_value::{ConcreteValue, DustString};
 pub use range_value::RangeValue;
+use serde::{Deserialize, Serialize};
 
 use std::fmt::{self, Debug, Display, Formatter};
 
-use crate::{Vm, VmError};
+use crate::{Type, Vm, VmError};
 
-#[derive(Clone, Debug, PartialEq, PartialOrd)]
+#[derive(Clone, Debug, PartialEq, PartialOrd, Serialize, Deserialize)]
 pub enum Value {
+    #[serde(skip)]
     Abstract(AbstractValue),
     Concrete(ConcreteValue),
 }
 
 impl Value {
-    pub fn to_ref(&self) -> ValueRef {
-        match self {
-            Value::Abstract(abstract_value) => ValueRef::Abstract(abstract_value),
-            Value::Concrete(concrete_value) => ValueRef::Concrete(concrete_value),
-        }
-    }
-
     pub fn into_concrete_owned(self, vm: &Vm) -> ConcreteValue {
         match self {
             Value::Abstract(abstract_value) => abstract_value.to_concrete_owned(vm),
@@ -39,58 +34,24 @@ impl Value {
             None
         }
     }
-}
 
-impl Display for Value {
-    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
+    pub fn r#type(&self) -> Type {
         match self {
-            Value::Abstract(abstract_value) => write!(f, "{}", abstract_value),
-            Value::Concrete(concrete_value) => write!(f, "{}", concrete_value),
-        }
-    }
-}
-
-#[derive(Clone, Copy, Debug, PartialEq, PartialOrd)]
-pub enum ValueRef<'a> {
-    Abstract(&'a AbstractValue),
-    Concrete(&'a ConcreteValue),
-}
-
-impl ValueRef<'_> {
-    pub fn to_owned(&self) -> Value {
-        match self {
-            ValueRef::Abstract(abstract_value) => Value::Abstract((*abstract_value).clone()),
-            ValueRef::Concrete(concrete_value) => Value::Concrete((*concrete_value).clone()),
+            Value::Abstract(abstract_value) => abstract_value.r#type(),
+            Value::Concrete(concrete_value) => concrete_value.r#type(),
         }
     }
 
-    pub fn into_concrete_owned(self, vm: &Vm) -> ConcreteValue {
-        match self {
-            ValueRef::Abstract(abstract_value) => abstract_value.to_concrete_owned(vm),
-            ValueRef::Concrete(concrete_value) => concrete_value.clone(),
-        }
-    }
-
-    pub fn display(&self, vm: &Vm) -> Result<DustString, VmError> {
-        match self {
-            ValueRef::Abstract(abstract_value) => abstract_value.to_dust_string(vm),
-            ValueRef::Concrete(concrete_value) => Ok(concrete_value.to_dust_string()),
-        }
-    }
-
-    #[inline(always)]
-    pub fn add(&self, other: ValueRef) -> Result<Value, ValueError> {
+    pub fn add(&self, other: &Value) -> Result<Value, ValueError> {
         match (self, other) {
-            (ValueRef::Concrete(left), ValueRef::Concrete(right)) => {
-                left.add(right).map(Value::Concrete)
-            }
+            (Value::Concrete(left), Value::Concrete(right)) => left.add(right).map(Value::Concrete),
             _ => Err(ValueError::CannotAdd(self.to_owned(), other.to_owned())),
         }
     }
 
-    pub fn subtract(&self, other: ValueRef) -> Result<Value, ValueError> {
+    pub fn subtract(&self, other: &Value) -> Result<Value, ValueError> {
         match (self, other) {
-            (ValueRef::Concrete(left), ValueRef::Concrete(right)) => {
+            (Value::Concrete(left), Value::Concrete(right)) => {
                 left.subtract(right).map(Value::Concrete)
             }
             _ => Err(ValueError::CannotSubtract(
@@ -100,9 +61,9 @@ impl ValueRef<'_> {
         }
     }
 
-    pub fn multiply(&self, other: ValueRef) -> Result<Value, ValueError> {
+    pub fn multiply(&self, other: &Value) -> Result<Value, ValueError> {
         match (self, other) {
-            (ValueRef::Concrete(left), ValueRef::Concrete(right)) => {
+            (Value::Concrete(left), Value::Concrete(right)) => {
                 left.multiply(right).map(Value::Concrete)
             }
             _ => Err(ValueError::CannotMultiply(
@@ -112,18 +73,18 @@ impl ValueRef<'_> {
         }
     }
 
-    pub fn divide(&self, other: ValueRef) -> Result<Value, ValueError> {
+    pub fn divide(&self, other: &Value) -> Result<Value, ValueError> {
         match (self, other) {
-            (ValueRef::Concrete(left), ValueRef::Concrete(right)) => {
+            (Value::Concrete(left), Value::Concrete(right)) => {
                 left.divide(right).map(Value::Concrete)
             }
             _ => Err(ValueError::CannotDivide(self.to_owned(), other.to_owned())),
         }
     }
 
-    pub fn modulo(&self, other: ValueRef) -> Result<Value, ValueError> {
+    pub fn modulo(&self, other: &Value) -> Result<Value, ValueError> {
         match (self, other) {
-            (ValueRef::Concrete(left), ValueRef::Concrete(right)) => {
+            (Value::Concrete(left), Value::Concrete(right)) => {
                 left.modulo(right).map(Value::Concrete)
             }
             _ => Err(ValueError::CannotModulo(self.to_owned(), other.to_owned())),
@@ -132,51 +93,58 @@ impl ValueRef<'_> {
 
     pub fn negate(&self) -> Result<Value, ValueError> {
         match self {
-            ValueRef::Concrete(concrete_value) => concrete_value.negate().map(Value::Concrete),
+            Value::Concrete(concrete_value) => concrete_value.negate().map(Value::Concrete),
             _ => Err(ValueError::CannotNegate(self.to_owned())),
         }
     }
 
     pub fn not(&self) -> Result<Value, ValueError> {
         match self {
-            ValueRef::Concrete(concrete_value) => concrete_value.not().map(Value::Concrete),
+            Value::Concrete(concrete_value) => concrete_value.not().map(Value::Concrete),
             _ => Err(ValueError::CannotNot(self.to_owned())),
         }
     }
 
-    pub fn equal(&self, other: ValueRef) -> Result<Value, ValueError> {
+    pub fn equal(&self, other: &Value) -> Result<Value, ValueError> {
         match (self, other) {
-            (ValueRef::Concrete(left), ValueRef::Concrete(right)) => {
+            (Value::Concrete(left), Value::Concrete(right)) => {
                 left.equal(right).map(Value::Concrete)
             }
             _ => Err(ValueError::CannotCompare(self.to_owned(), other.to_owned())),
         }
     }
 
-    pub fn less(&self, other: ValueRef) -> Result<Value, ValueError> {
+    pub fn less(&self, other: &Value) -> Result<Value, ValueError> {
         match (self, other) {
-            (ValueRef::Concrete(left), ValueRef::Concrete(right)) => {
+            (Value::Concrete(left), Value::Concrete(right)) => {
                 left.less_than(right).map(Value::Concrete)
             }
             _ => Err(ValueError::CannotCompare(self.to_owned(), other.to_owned())),
         }
     }
 
-    pub fn less_equal(&self, other: ValueRef) -> Result<Value, ValueError> {
+    pub fn less_equal(&self, other: &Value) -> Result<Value, ValueError> {
         match (self, other) {
-            (ValueRef::Concrete(left), ValueRef::Concrete(right)) => {
+            (Value::Concrete(left), Value::Concrete(right)) => {
                 left.less_than_or_equal(right).map(Value::Concrete)
             }
             _ => Err(ValueError::CannotCompare(self.to_owned(), other.to_owned())),
         }
     }
+
+    pub fn display(&self, vm: &Vm) -> Result<DustString, VmError> {
+        match self {
+            Value::Abstract(abstract_value) => abstract_value.to_dust_string(vm),
+            Value::Concrete(concrete_value) => Ok(concrete_value.to_dust_string()),
+        }
+    }
 }
 
-impl Display for ValueRef<'_> {
+impl Display for Value {
     fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
         match self {
-            ValueRef::Abstract(abstract_value) => write!(f, "{}", abstract_value),
-            ValueRef::Concrete(concrete_value) => write!(f, "{}", concrete_value),
+            Value::Abstract(abstract_value) => write!(f, "{}", abstract_value),
+            Value::Concrete(concrete_value) => write!(f, "{}", concrete_value),
         }
     }
 }
diff --git a/dust-lang/src/vm/mod.rs b/dust-lang/src/vm/mod.rs
index 896bc32..d6035d4 100644
--- a/dust-lang/src/vm/mod.rs
+++ b/dust-lang/src/vm/mod.rs
@@ -4,6 +4,7 @@ mod runners;
 use std::{
     fmt::{self, Display, Formatter},
     io, iter,
+    rc::Rc,
 };
 
 use runners::Runner;
@@ -11,10 +12,10 @@ use smallvec::SmallVec;
 
 use crate::{
     compile, instruction::*, AbstractValue, AnnotatedError, Chunk, ConcreteValue, DustError,
-    NativeFunctionError, Span, Value, ValueError, ValueRef,
+    NativeFunctionError, Span, Value, ValueError,
 };
 
-pub fn run(source: &str) -> Result<Option<ConcreteValue>, DustError> {
+pub fn run(source: &str) -> Result<Option<Value>, DustError> {
     let chunk = compile(source)?;
     let vm = Vm::new(source, &chunk, None, None);
 
@@ -35,7 +36,7 @@ pub struct Vm<'a> {
     ip: usize,
     last_assigned_register: Option<u8>,
     source: &'a str,
-    return_value: Option<ConcreteValue>,
+    return_value: Option<Value>,
 }
 
 impl<'a> Vm<'a> {
@@ -85,26 +86,31 @@ impl<'a> Vm<'a> {
         position
     }
 
-    pub fn run(mut self) -> Option<ConcreteValue> {
+    pub fn run(mut self) -> Option<Value> {
         while self.ip < self.runners.len() && self.return_value.is_none() {
-            let runner = self.runners[self.ip];
-
-            runner.run(&mut self);
+            self.execute_next_runner();
         }
 
         self.return_value
     }
 
-    pub(crate) fn follow_pointer(&self, pointer: Pointer) -> ValueRef {
+    pub fn execute_next_runner(&mut self) {
+        assert!(
+            self.ip < self.runners.len(),
+            "Runtime Error: IP out of bounds"
+        );
+
+        let runner = self.runners[self.ip];
+
+        runner.run(self);
+    }
+
+    pub(crate) fn follow_pointer(&self, pointer: Pointer) -> &Value {
         log::trace!("Follow pointer {pointer}");
 
         match pointer {
             Pointer::Stack(register_index) => self.open_register(register_index),
-            Pointer::Constant(constant_index) => {
-                let constant = self.get_constant(constant_index);
-
-                ValueRef::Concrete(constant)
-            }
+            Pointer::Constant(constant_index) => self.get_constant(constant_index),
             Pointer::ParentStack(register_index) => {
                 assert!(self.parent.is_some(), "Vm Error: Expected parent");
 
@@ -113,15 +119,12 @@ impl<'a> Vm<'a> {
             Pointer::ParentConstant(constant_index) => {
                 assert!(self.parent.is_some(), "Vm Error: Expected parent");
 
-                self.parent
-                    .unwrap()
-                    .get_constant(constant_index)
-                    .to_value_ref()
+                self.parent.unwrap().get_constant(constant_index)
             }
         }
     }
 
-    pub(crate) fn follow_pointer_allow_empty(&self, pointer: Pointer) -> Option<ValueRef> {
+    pub(crate) fn follow_pointer_allow_empty(&self, pointer: Pointer) -> Option<&Value> {
         log::trace!("Follow pointer {pointer}");
 
         match pointer {
@@ -129,7 +132,7 @@ impl<'a> Vm<'a> {
             Pointer::Constant(constant_index) => {
                 let constant = self.get_constant(constant_index);
 
-                Some(ValueRef::Concrete(constant))
+                Some(constant)
             }
             Pointer::ParentStack(register_index) => {
                 assert!(self.parent.is_some(), "Vm Error: Expected parent");
@@ -141,18 +144,14 @@ impl<'a> Vm<'a> {
             Pointer::ParentConstant(constant_index) => {
                 assert!(self.parent.is_some(), "Vm Error: Expected parent");
 
-                let constant = self
-                    .parent
-                    .unwrap()
-                    .get_constant(constant_index)
-                    .to_value_ref();
+                let constant = self.parent.unwrap().get_constant(constant_index);
 
                 Some(constant)
             }
         }
     }
 
-    fn open_register(&self, register_index: u8) -> ValueRef {
+    fn open_register(&self, register_index: u8) -> &Value {
         log::trace!("Open register R{register_index}");
 
         let register_index = register_index as usize;
@@ -165,13 +164,13 @@ impl<'a> Vm<'a> {
         let register = &self.stack[register_index];
 
         match register {
-            Register::Value(value) => value.to_ref(),
+            Register::Value(value) => value,
             Register::Pointer(pointer) => self.follow_pointer(*pointer),
             Register::Empty => panic!("VM Error: Register {register_index} is empty"),
         }
     }
 
-    fn open_register_allow_empty(&self, register_index: u8) -> Option<ValueRef> {
+    fn open_register_allow_empty(&self, register_index: u8) -> Option<&Value> {
         log::trace!("Open register R{register_index}");
 
         let register_index = register_index as usize;
@@ -184,7 +183,7 @@ impl<'a> Vm<'a> {
         let register = &self.stack[register_index];
 
         match register {
-            Register::Value(value) => Some(value.to_ref()),
+            Register::Value(value) => Some(value),
             Register::Pointer(pointer) => Some(self.follow_pointer(*pointer)),
             Register::Empty => None,
         }
@@ -209,9 +208,9 @@ impl<'a> Vm<'a> {
     }
 
     /// DRY helper to get a value from an Argument
-    fn get_argument(&self, index: u8, is_constant: bool) -> ValueRef {
+    fn get_argument(&self, index: u8, is_constant: bool) -> &Value {
         if is_constant {
-            self.get_constant(index).to_value_ref()
+            self.get_constant(index)
         } else {
             self.open_register(index)
         }
@@ -229,7 +228,7 @@ impl<'a> Vm<'a> {
         self.stack[to_register] = register;
     }
 
-    fn get_constant(&self, constant_index: u8) -> &ConcreteValue {
+    fn get_constant(&self, constant_index: u8) -> &Value {
         let constant_index = constant_index as usize;
         let constants = self.chunk.constants();
 
diff --git a/dust-lang/src/vm/runners.rs b/dust-lang/src/vm/runners.rs
index 9fb33ac..9eb8c9a 100644
--- a/dust-lang/src/vm/runners.rs
+++ b/dust-lang/src/vm/runners.rs
@@ -1,6 +1,8 @@
+use std::{borrow::BorrowMut, cell::RefCell, rc::Rc};
+
 use smallvec::SmallVec;
 
-use crate::{AbstractValue, ConcreteValue, NativeFunction, Value, ValueRef};
+use crate::{AbstractValue, ConcreteValue, NativeFunction, Type, Value};
 
 use super::{Instruction, InstructionData, Pointer, Register, Vm};
 
@@ -56,8 +58,7 @@ pub const RUNNER_LOGIC_TABLE: [RunnerLogic; 24] = [
     r#return,
 ];
 
-#[allow(clippy::needless_lifetimes)]
-pub fn r#move<'b, 'c>(vm: &'b mut Vm<'c>, instruction_data: InstructionData) {
+pub fn r#move(vm: &mut Vm, instruction_data: InstructionData) {
     let InstructionData { b, c, .. } = instruction_data;
     let from_register_has_value = vm
         .stack
@@ -71,9 +72,7 @@ pub fn r#move<'b, 'c>(vm: &'b mut Vm<'c>, instruction_data: InstructionData) {
 
     vm.ip += 1;
 
-    let next = vm.runners[vm.ip];
-
-    next.run(vm);
+    vm.execute_next_runner();
 }
 
 #[allow(clippy::needless_lifetimes)]
@@ -93,9 +92,7 @@ pub fn close<'b, 'c>(vm: &'b mut Vm<'c>, instruction_data: InstructionData) {
 
     vm.ip += 1;
 
-    let next = vm.runners[vm.ip];
-
-    next.run(vm);
+    vm.execute_next_runner();
 }
 
 #[allow(clippy::needless_lifetimes)]
@@ -112,9 +109,7 @@ pub fn load_boolean<'b, 'c>(vm: &'b mut Vm<'c>, instruction_data: InstructionDat
         vm.ip += 1;
     }
 
-    let next = vm.runners[vm.ip];
-
-    next.run(vm);
+    vm.execute_next_runner();
 }
 
 #[allow(clippy::needless_lifetimes)]
@@ -130,20 +125,29 @@ pub fn load_constant<'b, 'c>(vm: &'b mut Vm<'c>, instruction_data: InstructionDa
         vm.ip += 1;
     }
 
-    let next = vm.runners[vm.ip];
-
-    next.run(vm);
+    vm.execute_next_runner();
 }
 
 #[allow(clippy::needless_lifetimes)]
 pub fn load_list<'b, 'c>(vm: &'b mut Vm<'c>, instruction_data: InstructionData) {
     let InstructionData { a, b, .. } = instruction_data;
-    let mut item_pointers = Vec::new();
+    let mut item_pointers = Vec::with_capacity((a - b) as usize);
     let stack = vm.stack.as_slice();
+    let mut item_type = Type::Any;
 
     for register_index in b..a {
-        if let Register::Empty = stack[register_index as usize] {
-            continue;
+        match &stack[register_index as usize] {
+            Register::Empty => continue,
+            Register::Value(value) => {
+                if item_type == Type::Any {
+                    item_type = value.r#type();
+                }
+            }
+            Register::Pointer(pointer) => {
+                if item_type == Type::Any {
+                    item_type = vm.follow_pointer(*pointer).r#type();
+                }
+            }
         }
 
         let pointer = Pointer::Stack(register_index);
@@ -151,16 +155,18 @@ pub fn load_list<'b, 'c>(vm: &'b mut Vm<'c>, instruction_data: InstructionData)
         item_pointers.push(pointer);
     }
 
-    let list_value = AbstractValue::List { item_pointers }.to_value();
+    let list_value = AbstractValue::List {
+        item_type,
+        item_pointers,
+    }
+    .to_value();
     let register = Register::Value(list_value);
 
     vm.set_register(a, register);
 
     vm.ip += 1;
 
-    let next = vm.runners[vm.ip];
-
-    next.run(vm);
+    vm.execute_next_runner();
 }
 
 #[allow(clippy::needless_lifetimes)]
@@ -172,9 +178,7 @@ pub fn load_self<'b, 'c>(vm: &'b mut Vm<'c>, instruction_data: InstructionData)
 
     vm.ip += 1;
 
-    let next = vm.runners[vm.ip];
-
-    next.run(vm);
+    vm.execute_next_runner();
 }
 
 #[allow(clippy::needless_lifetimes)]
@@ -187,9 +191,7 @@ pub fn get_local<'b, 'c>(vm: &'b mut Vm<'c>, instruction_data: InstructionData)
 
     vm.ip += 1;
 
-    let next = vm.runners[vm.ip];
-
-    next.run(vm);
+    vm.execute_next_runner();
 }
 
 #[allow(clippy::needless_lifetimes)]
@@ -202,9 +204,7 @@ pub fn set_local<'b, 'c>(vm: &'b mut Vm<'c>, instruction_data: InstructionData)
 
     vm.ip += 1;
 
-    let next = vm.runners[vm.ip];
-
-    next.run(vm);
+    vm.execute_next_runner();
 }
 
 #[allow(clippy::needless_lifetimes)]
@@ -220,7 +220,7 @@ pub fn add<'b, 'c>(vm: &'b mut Vm<'c>, instruction_data: InstructionData) {
     let left = vm.get_argument(b, b_is_constant);
     let right = vm.get_argument(c, c_is_constant);
     let sum = match (left, right) {
-        (ValueRef::Concrete(left), ValueRef::Concrete(right)) => match (left, right) {
+        (Value::Concrete(left), Value::Concrete(right)) => match (left, right) {
             (ConcreteValue::Integer(left), ConcreteValue::Integer(right)) => {
                 ConcreteValue::Integer(left + right).to_value()
             }
@@ -234,9 +234,7 @@ pub fn add<'b, 'c>(vm: &'b mut Vm<'c>, instruction_data: InstructionData) {
 
     vm.ip += 1;
 
-    let next = vm.runners[vm.ip];
-
-    next.run(vm);
+    vm.execute_next_runner();
 }
 
 #[allow(clippy::needless_lifetimes)]
@@ -252,7 +250,7 @@ pub fn subtract<'b, 'c>(vm: &'b mut Vm<'c>, instruction_data: InstructionData) {
     let left = vm.get_argument(b, b_is_constant);
     let right = vm.get_argument(c, c_is_constant);
     let difference = match (left, right) {
-        (ValueRef::Concrete(left), ValueRef::Concrete(right)) => match (left, right) {
+        (Value::Concrete(left), Value::Concrete(right)) => match (left, right) {
             (ConcreteValue::Integer(left), ConcreteValue::Integer(right)) => {
                 ConcreteValue::Integer(left - right).to_value()
             }
@@ -266,9 +264,7 @@ pub fn subtract<'b, 'c>(vm: &'b mut Vm<'c>, instruction_data: InstructionData) {
 
     vm.ip += 1;
 
-    let next = vm.runners[vm.ip];
-
-    next.run(vm);
+    vm.execute_next_runner();
 }
 
 #[allow(clippy::needless_lifetimes)]
@@ -284,7 +280,7 @@ pub fn multiply<'b, 'c>(vm: &'b mut Vm<'c>, instruction_data: InstructionData) {
     let left = vm.get_argument(b, b_is_constant);
     let right = vm.get_argument(c, c_is_constant);
     let product = match (left, right) {
-        (ValueRef::Concrete(left), ValueRef::Concrete(right)) => match (left, right) {
+        (Value::Concrete(left), Value::Concrete(right)) => match (left, right) {
             (ConcreteValue::Integer(left), ConcreteValue::Integer(right)) => {
                 ConcreteValue::Integer(left * right).to_value()
             }
@@ -298,9 +294,7 @@ pub fn multiply<'b, 'c>(vm: &'b mut Vm<'c>, instruction_data: InstructionData) {
 
     vm.ip += 1;
 
-    let next = vm.runners[vm.ip];
-
-    next.run(vm);
+    vm.execute_next_runner();
 }
 
 #[allow(clippy::needless_lifetimes)]
@@ -316,7 +310,7 @@ pub fn divide<'b, 'c>(vm: &'b mut Vm<'c>, instruction_data: InstructionData) {
     let left = vm.get_argument(b, b_is_constant);
     let right = vm.get_argument(c, c_is_constant);
     let quotient = match (left, right) {
-        (ValueRef::Concrete(left), ValueRef::Concrete(right)) => match (left, right) {
+        (Value::Concrete(left), Value::Concrete(right)) => match (left, right) {
             (ConcreteValue::Integer(left), ConcreteValue::Integer(right)) => {
                 ConcreteValue::Integer(left / right).to_value()
             }
@@ -330,9 +324,7 @@ pub fn divide<'b, 'c>(vm: &'b mut Vm<'c>, instruction_data: InstructionData) {
 
     vm.ip += 1;
 
-    let next = vm.runners[vm.ip];
-
-    next.run(vm);
+    vm.execute_next_runner();
 }
 
 #[allow(clippy::needless_lifetimes)]
@@ -348,7 +340,7 @@ pub fn modulo<'b, 'c>(vm: &'b mut Vm<'c>, instruction_data: InstructionData) {
     let left = vm.get_argument(b, b_is_constant);
     let right = vm.get_argument(c, c_is_constant);
     let remainder = match (left, right) {
-        (ValueRef::Concrete(left), ValueRef::Concrete(right)) => match (left, right) {
+        (Value::Concrete(left), Value::Concrete(right)) => match (left, right) {
             (ConcreteValue::Integer(left), ConcreteValue::Integer(right)) => {
                 ConcreteValue::Integer(left % right).to_value()
             }
@@ -362,9 +354,7 @@ pub fn modulo<'b, 'c>(vm: &'b mut Vm<'c>, instruction_data: InstructionData) {
 
     vm.ip += 1;
 
-    let next = vm.runners[vm.ip];
-
-    next.run(vm);
+    vm.execute_next_runner();
 }
 
 #[allow(clippy::needless_lifetimes)]
@@ -376,7 +366,7 @@ pub fn test<'b, 'c>(vm: &'b mut Vm<'c>, instruction_data: InstructionData) {
         ..
     } = instruction_data;
     let value = vm.get_argument(b, b_is_constant);
-    let boolean = if let ValueRef::Concrete(ConcreteValue::Boolean(boolean)) = value {
+    let boolean = if let Value::Concrete(ConcreteValue::Boolean(boolean)) = value {
         *boolean
     } else {
         panic!(
@@ -392,9 +382,7 @@ pub fn test<'b, 'c>(vm: &'b mut Vm<'c>, instruction_data: InstructionData) {
         vm.ip += 1;
     }
 
-    let next = vm.runners[vm.ip];
-
-    next.run(vm);
+    vm.execute_next_runner();
 }
 
 #[allow(clippy::needless_lifetimes)]
@@ -407,7 +395,7 @@ pub fn test_set<'b, 'c>(vm: &'b mut Vm<'c>, instruction_data: InstructionData) {
         ..
     } = instruction_data;
     let value = vm.get_argument(b, b_is_constant);
-    let boolean = if let ValueRef::Concrete(ConcreteValue::Boolean(boolean)) = value {
+    let boolean = if let Value::Concrete(ConcreteValue::Boolean(boolean)) = value {
         *boolean
     } else {
         panic!(
@@ -432,9 +420,7 @@ pub fn test_set<'b, 'c>(vm: &'b mut Vm<'c>, instruction_data: InstructionData) {
         vm.ip += 1;
     }
 
-    let next = vm.runners[vm.ip];
-
-    next.run(vm);
+    vm.execute_next_runner();
 }
 
 #[allow(clippy::needless_lifetimes)]
@@ -457,13 +443,10 @@ pub fn equal<'b, 'c>(vm: &'b mut Vm<'c>, instruction_data: InstructionData) {
         vm.ip += 1;
     }
 
-    let next = vm.runners[vm.ip];
-
-    next.run(vm);
+    vm.execute_next_runner();
 }
 
-#[allow(clippy::needless_lifetimes)]
-pub fn less<'b, 'c>(vm: &'b mut Vm<'c>, instruction_data: InstructionData) {
+pub fn less(vm: &mut Vm, instruction_data: InstructionData) {
     let InstructionData {
         b,
         c,
@@ -482,9 +465,7 @@ pub fn less<'b, 'c>(vm: &'b mut Vm<'c>, instruction_data: InstructionData) {
         vm.ip += 1;
     }
 
-    let next = vm.runners[vm.ip];
-
-    next.run(vm);
+    vm.execute_next_runner();
 }
 
 #[allow(clippy::needless_lifetimes)]
@@ -507,9 +488,7 @@ pub fn less_equal<'b, 'c>(vm: &'b mut Vm<'c>, instruction_data: InstructionData)
         vm.ip += 1;
     }
 
-    let next = vm.runners[vm.ip];
-
-    next.run(vm);
+    vm.execute_next_runner();
 }
 
 #[allow(clippy::needless_lifetimes)]
@@ -522,12 +501,12 @@ pub fn negate<'b, 'c>(vm: &'b mut Vm<'c>, instruction_data: InstructionData) {
     } = instruction_data;
     let argument = vm.get_argument(b, b_is_constant);
     let negated = match argument {
-        ValueRef::Concrete(value) => match value {
+        Value::Concrete(value) => match value {
             ConcreteValue::Float(float) => ConcreteValue::Float(-float),
             ConcreteValue::Integer(integer) => ConcreteValue::Integer(-integer),
             _ => panic!("Value Error: Cannot negate value"),
         },
-        ValueRef::Abstract(_) => panic!("VM Error: Cannot negate value"),
+        Value::Abstract(_) => panic!("VM Error: Cannot negate value"),
     };
     let register = Register::Value(Value::Concrete(negated));
 
@@ -535,9 +514,7 @@ pub fn negate<'b, 'c>(vm: &'b mut Vm<'c>, instruction_data: InstructionData) {
 
     vm.ip += 1;
 
-    let next = vm.runners[vm.ip];
-
-    next.run(vm);
+    vm.execute_next_runner();
 }
 
 #[allow(clippy::needless_lifetimes)]
@@ -550,7 +527,7 @@ pub fn not<'b, 'c>(vm: &'b mut Vm<'c>, instruction_data: InstructionData) {
     } = instruction_data;
     let argument = vm.get_argument(b, b_is_constant);
     let not = match argument {
-        ValueRef::Concrete(ConcreteValue::Boolean(boolean)) => ConcreteValue::Boolean(!boolean),
+        Value::Concrete(ConcreteValue::Boolean(boolean)) => ConcreteValue::Boolean(!boolean),
         _ => panic!("VM Error: Expected boolean value for NOT operation"),
     };
     let register = Register::Value(Value::Concrete(not));
@@ -559,9 +536,7 @@ pub fn not<'b, 'c>(vm: &'b mut Vm<'c>, instruction_data: InstructionData) {
 
     vm.ip += 1;
 
-    let next = vm.runners[vm.ip];
-
-    next.run(vm);
+    vm.execute_next_runner();
 }
 
 #[allow(clippy::needless_lifetimes)]
@@ -576,9 +551,7 @@ pub fn jump<'c>(vm: &mut Vm<'c>, instruction_data: InstructionData) {
         vm.ip -= offset
     }
 
-    let next = vm.runners[vm.ip];
-
-    next.run(vm);
+    vm.execute_next_runner();
 }
 
 #[allow(clippy::needless_lifetimes)]
@@ -591,9 +564,9 @@ pub fn call<'b, 'c>(vm: &'b mut Vm<'c>, instruction_data: InstructionData) {
         ..
     } = instruction_data;
     let function = vm.get_argument(b, b_is_constant);
-    let mut function_vm = if let ValueRef::Concrete(ConcreteValue::Function(chunk)) = function {
+    let mut function_vm = if let Value::Concrete(ConcreteValue::Function(chunk)) = function {
         Vm::new(vm.source, chunk, Some(vm), None)
-    } else if let ValueRef::Abstract(AbstractValue::FunctionSelf) = function {
+    } else if let Value::Abstract(AbstractValue::FunctionSelf) = function {
         Vm::new(vm.source, vm.chunk, Some(vm), Some(vm.runners.clone()))
     } else {
         panic!("VM Error: Expected function")
@@ -620,16 +593,14 @@ pub fn call<'b, 'c>(vm: &'b mut Vm<'c>, instruction_data: InstructionData) {
     let return_value = function_vm.run();
 
     if let Some(concrete_value) = return_value {
-        let register = Register::Value(concrete_value.to_value());
+        let register = Register::Value(concrete_value);
 
         vm.set_register(a, register);
     }
 
     vm.ip += 1;
 
-    let next = vm.runners[vm.ip];
-
-    next.run(vm);
+    vm.execute_next_runner();
 }
 
 #[allow(clippy::needless_lifetimes)]
@@ -637,12 +608,12 @@ pub fn call_native<'b, 'c>(vm: &'b mut Vm<'c>, instruction_data: InstructionData
     let InstructionData { a, b, c, .. } = instruction_data;
     let first_argument_index = (a - c) as usize;
     let argument_range = first_argument_index..a as usize;
-    let mut arguments: SmallVec<[ValueRef; 4]> = SmallVec::new();
+    let mut arguments: SmallVec<[&Value; 4]> = SmallVec::new();
 
     for register_index in argument_range {
         let register = &vm.stack[register_index];
         let value = match register {
-            Register::Value(value) => value.to_ref(),
+            Register::Value(value) => value,
             Register::Pointer(pointer) => {
                 let value_option = vm.follow_pointer_allow_empty(*pointer);
 
@@ -668,9 +639,7 @@ pub fn call_native<'b, 'c>(vm: &'b mut Vm<'c>, instruction_data: InstructionData
 
     vm.ip += 1;
 
-    let next = vm.runners[vm.ip];
-
-    next.run(vm);
+    vm.execute_next_runner();
 }
 
 #[allow(clippy::needless_lifetimes)]
@@ -682,7 +651,7 @@ pub fn r#return<'b, 'c>(vm: &'b mut Vm<'c>, instruction_data: InstructionData) {
     }
 
     if let Some(register_index) = &vm.last_assigned_register {
-        let return_value = vm.open_register(*register_index).into_concrete_owned(vm);
+        let return_value = vm.open_register(*register_index).clone();
 
         vm.return_value = Some(return_value);
     } else {