diff --git a/dust-lang/src/abstract_tree/function_call.rs b/dust-lang/src/abstract_tree/function_call.rs
index 638dd0c..6a1c065 100644
--- a/dust-lang/src/abstract_tree/function_call.rs
+++ b/dust-lang/src/abstract_tree/function_call.rs
@@ -1,3 +1,5 @@
+use std::sync::{Arc, Mutex};
+
 use serde::{Deserialize, Serialize};
 
 use crate::{
@@ -8,11 +10,14 @@ use crate::{
 
 use super::{AbstractNode, Evaluation, Expression, Type, TypeConstructor};
 
-#[derive(Debug, Clone, Eq, PartialEq, PartialOrd, Ord, Serialize, Deserialize)]
+#[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct FunctionCall {
     function: Box<Expression>,
     type_arguments: Option<Vec<TypeConstructor>>,
     value_arguments: Vec<Expression>,
+
+    #[serde(skip)]
+    context: Arc<Mutex<Option<Context>>>,
 }
 
 impl FunctionCall {
@@ -25,6 +30,7 @@ impl FunctionCall {
             function: Box::new(function),
             type_arguments,
             value_arguments,
+            context: Arc::new(Mutex::new(None)),
         }
     }
 
@@ -34,13 +40,15 @@ impl FunctionCall {
 }
 
 impl AbstractNode for FunctionCall {
-    fn define_types(&self, _context: &Context) -> Result<(), ValidationError> {
-        self.function.define_types(_context)?;
+    fn define_types(&self, context: &Context) -> Result<(), ValidationError> {
+        *self.context.lock()? = Some(context.create_child());
+
+        self.function.define_types(context)?;
 
         let mut previous = ();
 
         for expression in &self.value_arguments {
-            previous = expression.define_types(_context)?;
+            previous = expression.define_types(context)?;
         }
 
         Ok(previous)
@@ -128,7 +136,11 @@ impl AbstractNode for FunctionCall {
             arguments.push(evalution);
         }
 
-        let mut function_context = Context::new(Some(&context));
+        let function_context = if let Some(context) = self.context.lock()?.clone() {
+            context
+        } else {
+            panic!("");
+        };
 
         match (function.type_parameters(), self.type_arguments) {
             (Some(type_parameters), Some(type_arguments)) => {
@@ -145,7 +157,7 @@ impl AbstractNode for FunctionCall {
 
         function
             .clone()
-            .call(arguments, &mut function_context, clear_variables)
+            .call(arguments, &function_context, clear_variables)
     }
 
     fn expected_type(&self, context: &Context) -> Result<Option<Type>, ValidationError> {
@@ -220,3 +232,23 @@ impl AbstractNode for FunctionCall {
         }
     }
 }
+
+impl Eq for FunctionCall {}
+
+impl PartialEq for FunctionCall {
+    fn eq(&self, other: &Self) -> bool {
+        todo!()
+    }
+}
+
+impl PartialOrd for FunctionCall {
+    fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
+        todo!()
+    }
+}
+
+impl Ord for FunctionCall {
+    fn cmp(&self, other: &Self) -> std::cmp::Ordering {
+        todo!()
+    }
+}
diff --git a/dust-lang/src/context.rs b/dust-lang/src/context.rs
index 355c3c3..def8209 100644
--- a/dust-lang/src/context.rs
+++ b/dust-lang/src/context.rs
@@ -1,6 +1,6 @@
 use std::{
     collections::HashMap,
-    sync::{Arc, RwLock, RwLockReadGuard},
+    sync::{Arc, RwLock},
 };
 
 use crate::{
@@ -11,37 +11,40 @@ use crate::{
 };
 
 #[derive(Clone, Debug)]
-pub struct Context<'a> {
-    variables: Arc<RwLock<HashMap<Identifier, (VariableData, UsageData)>>>,
-    parent: Option<&'a Context<'a>>,
+pub struct Context {
+    data: Arc<RwLock<ContextData>>,
     is_clean: Arc<RwLock<bool>>,
 }
 
-impl<'a> Context<'a> {
-    pub fn new(parent: Option<&'a Context>) -> Self {
-        Self {
-            variables: Arc::new(RwLock::new(HashMap::new())),
-            parent,
+#[derive(Clone, Debug)]
+struct ContextData {
+    variables: HashMap<Identifier, (VariableData, UsageData)>,
+    parent: Option<Context>,
+}
+
+impl Context {
+    pub fn new(parent: Option<Context>) -> Self {
+        Context {
+            data: Arc::new(RwLock::new(ContextData {
+                variables: HashMap::new(),
+                parent,
+            })),
             is_clean: Arc::new(RwLock::new(true)),
         }
     }
 
-    pub fn create_child<'b>(&'b self) -> Context<'b> {
-        Context::new(Some(self))
-    }
-
-    pub fn inner(
-        &self,
-    ) -> Result<RwLockReadGuard<HashMap<Identifier, (VariableData, UsageData)>>, PoisonError> {
-        Ok(self.variables.read()?)
+    pub fn create_child(&self) -> Context {
+        Context::new(Some(self.clone()))
     }
 
     pub fn contains(&self, identifier: &Identifier) -> Result<bool, PoisonError> {
         log::trace!("Checking that {identifier} exists.");
 
-        if self.variables.read()?.contains_key(identifier) {
+        let data = self.data.read()?;
+
+        if data.variables.contains_key(identifier) {
             Ok(true)
-        } else if let Some(parent) = self.parent {
+        } else if let Some(parent) = &data.parent {
             parent.contains(identifier)
         } else {
             Ok(false)
@@ -49,16 +52,18 @@ impl<'a> Context<'a> {
     }
 
     pub fn get_type(&self, identifier: &Identifier) -> Result<Option<Type>, ValidationError> {
-        if let Some((data, _)) = self.variables.read()?.get(identifier) {
-            log::trace!("Getting {identifier}'s type.");
+        log::trace!("Getting {identifier}'s type.");
 
+        let data = self.data.read()?;
+
+        if let Some((data, _)) = data.variables.get(identifier) {
             let r#type = match data {
                 VariableData::Type(r#type) => r#type.clone(),
                 VariableData::Value(value) => value.r#type(self)?,
             };
 
             Ok(Some(r#type.clone()))
-        } else if let Some(parent) = self.parent {
+        } else if let Some(parent) = &data.parent {
             parent.get_type(identifier)
         } else {
             Ok(None)
@@ -66,16 +71,16 @@ impl<'a> Context<'a> {
     }
 
     pub fn use_value(&self, identifier: &Identifier) -> Result<Option<Value>, PoisonError> {
-        if let Some((VariableData::Value(value), usage_data)) =
-            self.variables.read()?.get(identifier)
-        {
-            log::trace!("Using {identifier}'s value.");
+        log::trace!("Using {identifier}'s value.");
 
+        let data = self.data.read()?;
+
+        if let Some((VariableData::Value(value), usage_data)) = data.variables.get(identifier) {
             usage_data.inner().write()?.actual += 1;
             *self.is_clean.write()? = false;
 
             Ok(Some(value.clone()))
-        } else if let Some(parent) = self.parent {
+        } else if let Some(parent) = &data.parent {
             parent.use_value(identifier)
         } else {
             Ok(None)
@@ -83,27 +88,14 @@ impl<'a> Context<'a> {
     }
 
     pub fn get_value(&self, identifier: &Identifier) -> Result<Option<Value>, PoisonError> {
-        if let Some((VariableData::Value(value), _)) = self.variables.read()?.get(identifier) {
-            log::trace!("Getting {identifier}'s value.");
+        log::trace!("Getting {identifier}'s value.");
 
+        let data = self.data.read()?;
+
+        if let Some((VariableData::Value(value), _)) = data.variables.get(identifier) {
             Ok(Some(value.clone()))
-        } else if let Some(parent) = self.parent {
-            parent.get_value(identifier)
-        } else {
-            Ok(None)
-        }
-    }
-
-    pub fn get_data(
-        &self,
-        identifier: &Identifier,
-    ) -> Result<Option<(VariableData, UsageData)>, PoisonError> {
-        if let Some(full_data) = self.variables.read()?.get(identifier) {
-            log::trace!("Getting {identifier}'s value.");
-
-            Ok(Some(full_data.clone()))
-        } else if let Some(parent) = self.parent {
-            parent.get_data(identifier)
+        } else if let Some(parent) = &data.parent {
+            parent.use_value(identifier)
         } else {
             Ok(None)
         }
@@ -112,8 +104,9 @@ impl<'a> Context<'a> {
     pub fn set_type(&self, identifier: Identifier, r#type: Type) -> Result<(), PoisonError> {
         log::debug!("Setting {identifier} to type {}.", r#type);
 
-        self.variables
+        self.data
             .write()?
+            .variables
             .insert(identifier, (VariableData::Type(r#type), UsageData::new()));
 
         Ok(())
@@ -122,27 +115,43 @@ impl<'a> Context<'a> {
     pub fn set_value(&self, identifier: Identifier, value: Value) -> Result<(), PoisonError> {
         log::debug!("Setting {identifier} to value {value}.");
 
-        let mut variables = self.variables.write()?;
-        let old_usage_data = variables
+        let mut data = self.data.write()?;
+        let usage_data = data
+            .variables
             .remove(&identifier)
-            .map(|(_, usage_data)| usage_data);
+            .map(|(_, usage_data)| usage_data)
+            .unwrap_or(UsageData::new());
 
-        if let Some(usage_data) = old_usage_data {
-            variables.insert(identifier, (VariableData::Value(value), usage_data));
-        } else {
-            variables.insert(identifier, (VariableData::Value(value), UsageData::new()));
-        }
+        data.variables
+            .insert(identifier, (VariableData::Value(value), usage_data));
 
         Ok(())
     }
 
+    pub fn add_expected_use(&self, identifier: &Identifier) -> Result<bool, PoisonError> {
+        let data = self.data.read()?;
+
+        if let Some((_, usage_data)) = data.variables.get(identifier) {
+            log::trace!("Adding expected use for variable {identifier}.");
+
+            usage_data.inner().write()?.expected += 1;
+
+            Ok(true)
+        } else if let Some(parent) = &data.parent {
+            parent.add_expected_use(identifier)
+        } else {
+            Ok(false)
+        }
+    }
+
     pub fn clean(&self) -> Result<(), PoisonError> {
         if *self.is_clean.read()? {
             return Ok(());
         }
 
-        self.variables
+        self.data
             .write()?
+            .variables
             .retain(|identifier, (value_data, usage_data)| {
                 if let VariableData::Value(_) = value_data {
                     let usage = usage_data.inner().read().unwrap();
@@ -165,33 +174,7 @@ impl<'a> Context<'a> {
     }
 
     pub fn is_clean(&mut self) -> Result<bool, PoisonError> {
-        if *self.is_clean.read()? {
-            Ok(true)
-        } else {
-            for (_, (_, usage_data)) in self.variables.read()?.iter() {
-                let usage_data = usage_data.inner().read().unwrap();
-
-                if usage_data.actual > usage_data.expected {
-                    return Ok(false);
-                }
-            }
-
-            Ok(true)
-        }
-    }
-
-    pub fn add_expected_use(&self, identifier: &Identifier) -> Result<bool, PoisonError> {
-        if let Some((_, usage_data)) = self.variables.read()?.get(identifier) {
-            log::trace!("Adding expected use for variable {identifier}.");
-
-            usage_data.inner().write()?.expected += 1;
-
-            Ok(true)
-        } else if let Some(parent) = self.parent {
-            parent.add_expected_use(identifier)
-        } else {
-            Ok(false)
-        }
+        Ok(*self.is_clean.read()?)
     }
 }
 
diff --git a/dust-lang/src/lib.rs b/dust-lang/src/lib.rs
index fbd6cf4..23761c0 100644
--- a/dust-lang/src/lib.rs
+++ b/dust-lang/src/lib.rs
@@ -38,13 +38,13 @@ pub fn interpret_without_std(
     interpreter.run(Arc::from(source_id.to_string()), Arc::from(source))
 }
 
-pub struct Interpreter<'a> {
-    context: Context<'a>,
+pub struct Interpreter {
+    context: Context,
     sources: Arc<RwLock<Vec<(Arc<str>, Arc<str>)>>>,
 }
 
-impl<'a> Interpreter<'a> {
-    pub fn new(context: Context<'a>) -> Self {
+impl Interpreter {
+    pub fn new(context: Context) -> Self {
         Interpreter {
             context,
             sources: Arc::new(RwLock::new(Vec::new())),
diff --git a/dust-lang/src/value.rs b/dust-lang/src/value.rs
index 78e78bc..b589286 100644
--- a/dust-lang/src/value.rs
+++ b/dust-lang/src/value.rs
@@ -731,7 +731,7 @@ impl Function {
     pub fn call(
         self,
         value_arguments: Vec<Value>,
-        context: &mut Context,
+        context: &Context,
         manage_memory: bool,
     ) -> Result<Option<Evaluation>, RuntimeError> {
         for ((identifier, _), value) in self
diff --git a/dust-shell/src/cli.rs b/dust-shell/src/cli.rs
index 0bf2ab0..2650c50 100644
--- a/dust-shell/src/cli.rs
+++ b/dust-shell/src/cli.rs
@@ -15,7 +15,7 @@ use reedline::{
     SqliteBackedHistory,
 };
 
-pub fn run_shell<'a>(context: Context<'a>) -> Result<(), io::Error> {
+pub fn run_shell(context: Context) -> Result<(), io::Error> {
     let mut interpreter = Interpreter::new(context.clone());
     let mut keybindings = default_emacs_keybindings();