diff --git a/schala-lang/language/src/typechecking.rs b/schala-lang/language/src/typechecking.rs
index 834601f..52b6dba 100644
--- a/schala-lang/language/src/typechecking.rs
+++ b/schala-lang/language/src/typechecking.rs
@@ -28,6 +28,7 @@ enum TConst {
   Int,
   Float,
   StringT,
+  Bool,
 }
 
 impl TConst {
@@ -80,12 +81,17 @@ impl TypeContext {
 
   fn infer_expr_type(&mut self, expr_type: &ExpressionType) -> InferResult<MonoType> {
     use self::ExpressionType::*;
-    match expr_type {
-      NatLiteral(_) => Ok(MonoType::Const(TConst::Nat)),
-      FloatLiteral(_) => Ok(MonoType::Const(TConst::Float)),
-      StringLiteral(_) => Ok(MonoType::Const(TConst::StringT)),
-      _ => Ok(MonoType::Const(TConst::user("unimplemented")))
-    }
+    Ok(match expr_type {
+      NatLiteral(_) => MonoType::Const(TConst::Nat),
+      FloatLiteral(_) => MonoType::Const(TConst::Float),
+      StringLiteral(_) => MonoType::Const(TConst::StringT),
+      BoolLiteral(_) => MonoType::Const(TConst::Bool),
+      _ => MonoType::Const(TConst::user("unimplemented"))
+    })
+  }
+
+  fn unify(t1: MonoType, t2: MonoType) -> InferResult<MonoType> {
+    unimplemented!()
   }
 }