diff --git a/schala-lang/src/eval.rs b/schala-lang/src/eval.rs
index 7979e9b..d6f2b00 100644
--- a/schala-lang/src/eval.rs
+++ b/schala-lang/src/eval.rs
@@ -1,3 +1,4 @@
+use std::cell::RefCell;
 use std::rc::Rc;
 use std::fmt::Write;
 use std::io;
@@ -6,9 +7,11 @@ use itertools::Itertools;
 
 use util::StateStack;
 use ast_reducing::{ReducedAST, Stmt, Expr, Lit, Func};
+use typechecking::TypeContext;
 
 pub struct State<'a> {
-  values: StateStack<'a, Rc<String>, ValueEntry>
+  values: StateStack<'a, Rc<String>, ValueEntry>,
+  type_context_handle: Option<Rc<RefCell<TypeContext>>>,
 }
 
 macro_rules! builtin_binding {
@@ -18,12 +21,12 @@ macro_rules! builtin_binding {
 }
 
 impl<'a> State<'a> {
-  pub fn new() -> State<'a> {
+  pub fn new(type_context_handle: Option<Rc<RefCell<TypeContext>>>) -> State<'a> {
     let mut values = StateStack::new(Some(format!("global")));
     builtin_binding!("print", values);
     builtin_binding!("println", values);
     builtin_binding!("getline", values);
-    State { values }
+    State { values, type_context_handle }
   }
 
   pub fn debug_print(&self) -> String {
@@ -415,7 +418,10 @@ impl<'a> State<'a> {
         if params.len() != args.len() {
           return Err(format!("calling a {}-argument function with {} args", params.len(), args.len()))
         }
-        let mut func_state = State { values: self.values.new_frame(name.map(|n| format!("{}", n))) };
+        let mut func_state = State {
+          values: self.values.new_frame(name.map(|n| format!("{}", n))),
+          type_context_handle: self.type_context_handle.clone(),
+        };
         for (param, val) in params.into_iter().zip(args.into_iter()) {
           let val = func_state.expression(val)?;
           func_state.values.insert(param, ValueEntry::Binding { constant: true, val });
@@ -518,7 +524,7 @@ mod eval_tests {
 
   macro_rules! fresh_env {
     ($string:expr, $correct:expr) => {
-      let mut state = State::new();
+      let mut state = State::new(None);
       let all_output = state.evaluate(parse(tokenize($string)).0.unwrap().reduce(), true);
       let ref output = all_output.last().unwrap();
       assert_eq!(**output, Ok($correct.to_string()));
diff --git a/schala-lang/src/lib.rs b/schala-lang/src/lib.rs
index 1038827..e8d0e1d 100644
--- a/schala-lang/src/lib.rs
+++ b/schala-lang/src/lib.rs
@@ -10,6 +10,9 @@ extern crate schala_repl;
 #[macro_use]
 extern crate schala_codegen;
 
+use std::cell::RefCell;
+use std::rc::Rc;
+
 use itertools::Itertools;
 use schala_repl::{ProgrammingLanguageInterface, EvalOptions, TraceArtifact, UnfinishedComputation, FinishedComputation};
 
@@ -31,14 +34,15 @@ mod eval;
 #[PipelineSteps(tokenizing, parsing, symbol_table, typechecking, ast_reducing, eval)]
 pub struct Schala {
   state: eval::State<'static>,
-  type_context: typechecking::TypeContext
+  type_context: Rc<RefCell<typechecking::TypeContext>>,
 }
 
 impl Schala {
   pub fn new() -> Schala {
+    let type_context = Rc::new(RefCell::new(typechecking::TypeContext::new()));
     Schala {
-      state: eval::State::new(),
-      type_context: typechecking::TypeContext::new(),
+      type_context: type_context.clone(),
+      state: eval::State::new(Some(type_context)),
     }
   }
 }
@@ -70,9 +74,10 @@ fn parsing(_handle: &mut Schala, input: Vec<tokenizing::Token>, comp: Option<&mu
 }
 
 fn symbol_table(handle: &mut Schala, input: parsing::AST, comp: Option<&mut UnfinishedComputation>) -> Result<parsing::AST, String> {
-  match handle.type_context.add_top_level_types(&input) {
+  let add = handle.type_context.borrow_mut().add_top_level_types(&input);
+  match add {
     Ok(()) => {
-      let artifact = TraceArtifact::new("symbol_table", handle.type_context.debug_symbol_table());
+      let artifact = TraceArtifact::new("symbol_table", handle.type_context.borrow().debug_symbol_table());
       comp.map(|comp| comp.add_artifact(artifact));
       Ok(input)
     },
@@ -81,7 +86,7 @@ fn symbol_table(handle: &mut Schala, input: parsing::AST, comp: Option<&mut Unfi
 }
 
 fn typechecking(handle: &mut Schala, input: parsing::AST, comp: Option<&mut UnfinishedComputation>) -> Result<parsing::AST, String> {
-  match handle.type_context.type_check_ast(&input) {
+  match handle.type_context.borrow_mut().type_check_ast(&input) {
     Ok(ty) => {
       comp.map(|comp| comp.add_artifact(TraceArtifact::new("type_check", format!("{:?}", ty))));
       Ok(input)