diff --git a/src/abstract_tree/assignment.rs b/src/abstract_tree/assignment.rs
index 0dd7425..e0e7668 100644
--- a/src/abstract_tree/assignment.rs
+++ b/src/abstract_tree/assignment.rs
@@ -58,17 +58,24 @@ impl AbstractTree for Assignment {
         let statement_node = node.child(child_count - 1).unwrap();
         let statement = Statement::from_syntax_node(source, statement_node, context)?;
 
+        if let Some((_previous_value, previous_type)) = context.variables()?.get(identifier.inner())
+        {
+            let type_check = previous_type.check(&statement.expected_type(context)?);
+
+            if let Err(error) = type_check {
+                return Err(error.with_context(
+                    statement_node.start_position(),
+                    source[statement_node.byte_range()].to_string(),
+                ));
+            }
+        }
+
         if let Some(type_definition) = &type_definition {
             let statement_type = statement.expected_type(context)?;
 
             match operator {
                 AssignmentOperator::Equal => {
-                    type_definition.inner().check(
-                        &statement_type,
-                        context,
-                        statement_node,
-                        source,
-                    )?;
+                    type_definition.inner().check(&statement_type)?;
                 }
                 AssignmentOperator::PlusEqual => {
                     let identifier_type = identifier.expected_type(context)?;
@@ -76,21 +83,11 @@ impl AbstractTree for Assignment {
                     if let Type::List(item_type) = type_definition.inner() {
                         println!("{item_type}");
 
-                        item_type.check(&identifier_type, context, identifier_node, source)?;
-                        item_type.check(&statement_type, context, statement_node, source)?;
+                        item_type.check(&identifier_type)?;
+                        item_type.check(&statement_type)?;
                     } else {
-                        type_definition.inner().check(
-                            &identifier_type,
-                            context,
-                            identifier_node,
-                            source,
-                        )?;
-                        type_definition.inner().check(
-                            &statement_type,
-                            context,
-                            statement_node,
-                            source,
-                        )?;
+                        type_definition.inner().check(&identifier_type)?;
+                        type_definition.inner().check(&statement_type)?;
                     }
                 }
                 AssignmentOperator::MinusEqual => todo!(),
@@ -128,11 +125,8 @@ impl AbstractTree for Assignment {
             }
             AssignmentOperator::Equal => value,
         };
-        let new_value_type = new_value.r#type(context)?;
 
-        context
-            .variables_mut()?
-            .insert(key.clone(), (new_value, new_value_type));
+        context.set(key.clone(), new_value)?;
 
         Ok(Value::Empty)
     }
diff --git a/src/abstract_tree/for.rs b/src/abstract_tree/for.rs
index 65e7ce5..6421f0a 100644
--- a/src/abstract_tree/for.rs
+++ b/src/abstract_tree/for.rs
@@ -59,7 +59,7 @@ impl AbstractTree for For {
 
                 iter_context
                     .variables_mut()?
-                    .insert(key.clone(), (value.clone(), value.r#type(context)?));
+                    .insert(key.clone(), (value.clone(), value.r#type()));
 
                 self.block.run(source, &mut iter_context).map(|_value| ())
             })?;
@@ -69,7 +69,7 @@ impl AbstractTree for For {
             for value in values.iter() {
                 loop_context
                     .variables_mut()?
-                    .insert(key.clone(), (value.clone(), value.r#type(context)?));
+                    .insert(key.clone(), (value.clone(), value.r#type()));
 
                 self.block.run(source, &mut loop_context.clone())?;
             }
diff --git a/src/abstract_tree/function_call.rs b/src/abstract_tree/function_call.rs
index ea12a62..17e68c3 100644
--- a/src/abstract_tree/function_call.rs
+++ b/src/abstract_tree/function_call.rs
@@ -52,9 +52,9 @@ impl AbstractTree for FunctionCall {
                 let argument_type = argument.expected_type(context)?;
 
                 if let Type::Function { return_type, .. } = argument_type {
-                    r#type.check(&return_type, context, node, source)?;
+                    r#type.check(&return_type)?;
                 } else {
-                    r#type.check(&argument_type, context, node, source)?;
+                    r#type.check(&argument_type)?;
                 }
             }
         }
diff --git a/src/abstract_tree/identifier.rs b/src/abstract_tree/identifier.rs
index 5145189..c8a70a7 100644
--- a/src/abstract_tree/identifier.rs
+++ b/src/abstract_tree/identifier.rs
@@ -43,7 +43,7 @@ impl AbstractTree for Identifier {
 
     fn expected_type(&self, context: &Map) -> Result<Type> {
         if let Some((value, _)) = context.variables()?.get(&self.0) {
-            value.r#type(context)
+            Ok(value.r#type())
         } else {
             for built_in_function in BUILT_IN_FUNCTIONS {
                 if self.0 == built_in_function.name() {
diff --git a/src/abstract_tree/index_assignment.rs b/src/abstract_tree/index_assignment.rs
index 61e7a77..4830ac3 100644
--- a/src/abstract_tree/index_assignment.rs
+++ b/src/abstract_tree/index_assignment.rs
@@ -85,7 +85,7 @@ impl AbstractTree for IndexAssignment {
             }
             AssignmentOperator::Equal => value,
         };
-        let new_value_type = new_value.r#type(context)?;
+        let new_value_type = new_value.r#type();
 
         index_context
             .variables_mut()?
diff --git a/src/abstract_tree/type_defintion.rs b/src/abstract_tree/type_defintion.rs
index 46bb084..8957e3a 100644
--- a/src/abstract_tree/type_defintion.rs
+++ b/src/abstract_tree/type_defintion.rs
@@ -67,7 +67,7 @@ pub enum Type {
 }
 
 impl Type {
-    pub fn check(&self, other: &Type, context: &Map, node: Node, source: &str) -> Result<()> {
+    pub fn check(&self, other: &Type) -> Result<()> {
         match (self, other) {
             (Type::Any, _)
             | (_, Type::Any)
@@ -83,7 +83,7 @@ impl Type {
             | (Type::Float, Type::Number)
             | (Type::String, Type::String) => Ok(()),
             (Type::List(self_item_type), Type::List(other_item_type)) => {
-                self_item_type.check(&other_item_type, context, node, source)
+                self_item_type.check(&other_item_type)
             }
             (
                 Type::Function {
@@ -100,18 +100,16 @@ impl Type {
                     .zip(other_parameter_types.iter());
 
                 for (self_parameter_type, other_parameter_type) in parameter_type_pairs {
-                    self_parameter_type.check(&other_parameter_type, context, node, source)?;
+                    self_parameter_type.check(&other_parameter_type)?;
                 }
 
-                self_return_type.check(other_return_type, context, node, source)?;
+                self_return_type.check(other_return_type)?;
 
                 Ok(())
             }
             _ => Err(Error::TypeCheck {
                 expected: self.clone(),
                 actual: other.clone(),
-                location: node.start_position(),
-                source: source[node.byte_range()].to_string(),
             }),
         }
     }
diff --git a/src/abstract_tree/value_node.rs b/src/abstract_tree/value_node.rs
index e459274..906b1b0 100644
--- a/src/abstract_tree/value_node.rs
+++ b/src/abstract_tree/value_node.rs
@@ -132,7 +132,7 @@ impl AbstractTree for ValueNode {
 
                     for (key, statement) in key_statement_pairs {
                         let value = statement.run(source, context)?;
-                        let value_type = value.r#type(context)?;
+                        let value_type = value.r#type();
 
                         variables.insert(key.clone(), (value, value_type));
                     }
diff --git a/src/built_in_functions/type.rs b/src/built_in_functions/type.rs
index 4ac9582..388e679 100644
--- a/src/built_in_functions/type.rs
+++ b/src/built_in_functions/type.rs
@@ -7,11 +7,11 @@ impl BuiltInFunction for TypeFunction {
         "type"
     }
 
-    fn run(&self, arguments: &[Value], context: &Map) -> Result<Value> {
+    fn run(&self, arguments: &[Value], _context: &Map) -> Result<Value> {
         Error::expect_argument_amount(self, 1, arguments.len())?;
 
         if arguments.len() == 1 {
-            let type_definition = arguments.first().unwrap().r#type(context)?;
+            let type_definition = arguments.first().unwrap().r#type();
             let type_text = type_definition.to_string();
             let text_without_brackets = &type_text[1..type_text.len() - 1];
 
@@ -20,7 +20,7 @@ impl BuiltInFunction for TypeFunction {
             let mut answers = Vec::new();
 
             for value in arguments {
-                let type_definition = value.r#type(context)?;
+                let type_definition = value.r#type();
                 let type_text = type_definition.to_string();
                 let text_without_brackets = &type_text[1..type_text.len() - 1];
                 let text_as_value = Value::String(text_without_brackets.to_string());
diff --git a/src/error.rs b/src/error.rs
index dca82bb..26f07f8 100644
--- a/src/error.rs
+++ b/src/error.rs
@@ -13,6 +13,12 @@ pub type Result<T> = std::result::Result<T, Error>;
 
 #[derive(Clone, PartialEq)]
 pub enum Error {
+    WithContext {
+        error: Box<Error>,
+        location: Point,
+        source: String,
+    },
+
     UnexpectedSyntaxNode {
         expected: &'static str,
         actual: &'static str,
@@ -23,13 +29,6 @@ pub enum Error {
     TypeCheck {
         expected: Type,
         actual: Type,
-        location: Point,
-        source: String,
-    },
-
-    RuntimeTypeCheck {
-        expected: Type,
-        actual: Type,
     },
 
     /// The 'assert' macro did not resolve successfully.
@@ -148,6 +147,14 @@ pub enum Error {
 }
 
 impl Error {
+    pub fn with_context(self, location: Point, source: String) -> Self {
+        Error::WithContext {
+            error: Box::new(self),
+            location,
+            source,
+        }
+    }
+
     pub fn expect_syntax_node(source: &str, expected: &'static str, actual: Node) -> Result<()> {
         if expected == actual.kind() {
             Ok(())
@@ -368,19 +375,15 @@ impl fmt::Display for Error {
             Syntax { source, location } => {
                 write!(f, "Syntax error at {location}, this is not valid: {source}")
             }
-            TypeCheck {
-                expected,
-                actual,
+            TypeCheck { expected, actual } => write!(
+                f,
+                "Type check error. Expected type {expected} but got type {actual}."
+            ),
+            WithContext {
+                error,
                 location,
                 source,
-            } => write!(
-                f,
-                "Type check error at {location}. Expected type {expected} but got type {actual}: {source}."
-            ),
-            RuntimeTypeCheck { expected, actual } => write!(
-                f,
-                "Type check error. Expected type {expected} but got value with type {actual}."
-            ),
+            } => write!(f, "{error} Occured at {location}: \"{source}\""),
         }
     }
 }
diff --git a/src/main.rs b/src/main.rs
index 3201348..75fb151 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -12,7 +12,7 @@ use tree_sitter::Parser as TSParser;
 
 use std::{borrow::Cow, fs::read_to_string};
 
-use dust_lang::{evaluate_with_context, language, Interpreter, Map, Value};
+use dust_lang::{evaluate_with_context, language, Interpreter, Map, Type, Value};
 
 /// Command-line arguments to be parsed.
 #[derive(Parser, Debug)]
@@ -63,16 +63,16 @@ fn main() {
         context
             .variables_mut()
             .unwrap()
-            .insert("input".to_string(), Value::String(input));
+            .insert("input".to_string(), (Value::String(input), Type::String));
     }
 
     if let Some(path) = args.input_path {
         let file_contents = read_to_string(path).unwrap();
 
-        context
-            .variables_mut()
-            .unwrap()
-            .insert("input".to_string(), Value::String(file_contents));
+        context.variables_mut().unwrap().insert(
+            "input".to_string(),
+            (Value::String(file_contents), Type::String),
+        );
     }
 
     let mut parser = TSParser::new();
diff --git a/src/value/function.rs b/src/value/function.rs
index 63cc4ab..0aebc08 100644
--- a/src/value/function.rs
+++ b/src/value/function.rs
@@ -76,7 +76,7 @@ impl Function {
 
         for ((identifier, argument_type), expression) in parameter_argument_pairs {
             let value = expression.run(source, context)?;
-            let value_type = value.r#type(context)?;
+            let value_type = value.r#type();
 
             match argument_type {
                 Type::Any => {}
diff --git a/src/value/map.rs b/src/value/map.rs
index 1d71bb0..8dd8d68 100644
--- a/src/value/map.rs
+++ b/src/value/map.rs
@@ -41,6 +41,20 @@ impl Map {
         Ok(self.variables.read()?)
     }
 
+    pub fn set(&self, key: String, value: Value) -> Result<Option<(Value, Type)>> {
+        let value_type = value.r#type();
+        let previous = self
+            .variables
+            .write()?
+            .insert(key, (value, value_type.clone()));
+
+        if let Some((_previous_value, previous_type)) = previous.clone() {
+            previous_type.check(&value_type)?;
+        }
+
+        Ok(previous)
+    }
+
     pub fn variables_mut(&self) -> Result<RwLockWriteGuard<BTreeMap<String, (Value, Type)>>> {
         Ok(self.variables.write()?)
     }
diff --git a/src/value/mod.rs b/src/value/mod.rs
index dc6cc98..cea810e 100644
--- a/src/value/mod.rs
+++ b/src/value/mod.rs
@@ -42,17 +42,17 @@ pub enum Value {
 }
 
 impl Value {
-    pub fn r#type(&self, context: &Map) -> Result<Type> {
+    pub fn r#type(&self) -> Type {
         let r#type = match self {
             Value::List(list) => {
                 let mut previous_type = None;
 
                 for value in list.items().iter() {
-                    let value_type = value.r#type(context)?;
+                    let value_type = value.r#type();
 
                     if let Some(previous) = &previous_type {
                         if &value_type != previous {
-                            return Ok(Type::List(Box::new(Type::Any)));
+                            return Type::List(Box::new(Type::Any));
                         }
                     }
 
@@ -74,7 +74,7 @@ impl Value {
             Value::Empty => Type::Empty,
         };
 
-        Ok(r#type)
+        r#type
     }
 
     pub fn is_string(&self) -> bool {