diff --git a/reid/src/ast/process.rs b/reid/src/ast/process.rs
index 3667bb4..44cb533 100644
--- a/reid/src/ast/process.rs
+++ b/reid/src/ast/process.rs
@@ -44,8 +44,6 @@ impl ast::Module {
             }
         }
 
-        // TODO do something with state here
-
         mir::Module {
             name: self.name.clone(),
             imports,
diff --git a/reid/src/mir/typecheck.rs b/reid/src/mir/typecheck.rs
index 18f33e3..46e7b2f 100644
--- a/reid/src/mir/typecheck.rs
+++ b/reid/src/mir/typecheck.rs
@@ -38,6 +38,8 @@ pub enum ErrorKind {
     InvalidAmountParameters(String, usize, usize),
     #[error("Unable to infer type {0}")]
     TypeNotInferrable(TypeKind),
+    #[error("Expected branch type to be {0}, found {1} instead")]
+    BranchTypesDiffer(TypeKind, TypeKind),
 }
 
 /// Struct used to implement a type-checking pass that can be performed on the
@@ -118,7 +120,7 @@ impl Block {
                     let res = expression.typecheck(&mut state, &hints, Some(var_t_resolved));
 
                     // If expression resolution itself was erronous, resolve as
-                    // Unknown.
+                    // Unknown and note error.
                     let res = state.or_else(res, Vague(Unknown), expression.1);
 
                     // Make sure the expression and variable type really is the same
@@ -286,8 +288,8 @@ impl Expression {
                     rhs.typecheck(state, &hints, Some(collapsed)).ok();
                 }
 
-                let res = lhs_type.binop_type(&op, &rhs_type)?;
-                Ok(res)
+                let both_t = lhs_type.collapse_into(&rhs_type)?;
+                Ok(both_t.binop_type(op))
             }
             ExprKind::FunctionCall(function_call) => {
                 let true_function = state
@@ -338,7 +340,6 @@ impl Expression {
                 }
             }
             ExprKind::If(IfExpression(cond, lhs, rhs)) => {
-                // TODO make sure cond_res is Boolean here
                 let cond_res = cond.typecheck(state, &hints, Some(Bool));
                 let cond_t = state.or_else(cond_res, Vague(Unknown), cond.1);
                 state.ok(cond_t.collapse_into(&Bool), cond.1);
@@ -351,11 +352,15 @@ impl Expression {
                     let res = else_block.typecheck(state, &hints, hint_t);
                     state.or_else(res, Vague(Unknown), else_block.meta)
                 } else {
-                    // TODO assert that then_ret_t is Void
-                    Vague(Unknown)
+                    // Else return type is Void if it does not exist
+                    Void
                 };
 
-                let collapsed = then_ret_t.collapse_into(&else_ret_t)?;
+                // Make sure then and else -blocks have the same return type
+                let collapsed = then_ret_t
+                    .collapse_into(&else_ret_t)
+                    .or(Err(ErrorKind::BranchTypesDiffer(then_ret_t, else_ret_t)))?;
+
                 if let Some(rhs) = rhs {
                     // If rhs existed, typecheck both sides to perform type
                     // coercion.
@@ -391,6 +396,8 @@ impl Literal {
                 (L::U64(_), U64) => self,
                 (L::U128(_), U128) => self,
                 (L::Bool(_), Bool) => self,
+                // TODO make sure that v is actually able to fit in the
+                // requested type
                 (L::Vague(VagueL::Number(v)), I8) => L::I8(v as i8),
                 (L::Vague(VagueL::Number(v)), I16) => L::I16(v as i16),
                 (L::Vague(VagueL::Number(v)), I32) => L::I32(v as i32),
@@ -430,17 +437,6 @@ impl TypeKind {
         }
     }
 
-    fn binop_type(&self, op: &BinaryOperator, other: &TypeKind) -> Result<TypeKind, ErrorKind> {
-        let res = self.collapse_into(other)?;
-        Ok(match op {
-            BinaryOperator::Add => res,
-            BinaryOperator::Minus => res,
-            BinaryOperator::Mult => res,
-            BinaryOperator::And => res,
-            BinaryOperator::Cmp(_) => Bool,
-        })
-    }
-
     fn resolve_hinted(&self, hints: &TypeRefs) -> TypeKind {
         match self {
             Vague(TypeRef(idx)) => hints.retrieve_type(*idx).unwrap(),
diff --git a/reid/src/mir/typerefs.rs b/reid/src/mir/typerefs.rs
index 81fb400..cbad7ab 100644
--- a/reid/src/mir/typerefs.rs
+++ b/reid/src/mir/typerefs.rs
@@ -194,12 +194,6 @@ impl<'outer> ScopeTypeRefs<'outer> {
         rhs: &mut TypeRef<'outer>,
     ) -> Option<TypeRef<'outer>> {
         let ty = lhs.narrow(rhs)?;
-        Some(match op {
-            BinaryOperator::Add => ty,
-            BinaryOperator::Minus => ty,
-            BinaryOperator::Mult => ty,
-            BinaryOperator::And => self.from_type(&TypeKind::Bool).unwrap(),
-            BinaryOperator::Cmp(_) => self.from_type(&TypeKind::Bool).unwrap(),
-        })
+        self.from_type(&ty.as_type().binop_type(op))
     }
 }
diff --git a/reid/src/mir/types.rs b/reid/src/mir/types.rs
index ba9c8ff..5d96293 100644
--- a/reid/src/mir/types.rs
+++ b/reid/src/mir/types.rs
@@ -9,7 +9,24 @@ pub enum ReturnTypeOther {
     NoBlockReturn(Metadata),
 }
 
+impl TypeKind {
+    /// Return the type that is the result of a binary operator between two
+    /// values of this type
+    pub fn binop_type(&self, op: &BinaryOperator) -> TypeKind {
+        // TODO make some type of mechanism that allows to binop two values of
+        // differing types..
+        match op {
+            BinaryOperator::Add => *self,
+            BinaryOperator::Minus => *self,
+            BinaryOperator::Mult => *self,
+            BinaryOperator::And => TypeKind::Bool,
+            BinaryOperator::Cmp(_) => TypeKind::Bool,
+        }
+    }
+}
+
 pub trait ReturnType {
+    /// Return the return type of this node
     fn return_type(&self) -> Result<(ReturnKind, TypeKind), ReturnTypeOther>;
 }
 
@@ -24,9 +41,6 @@ impl ReturnType for Block {
             }
         }
 
-        // TODO should actually probably prune all instructions after this one
-        // as to not cause problems in codegen later (when unable to delete the
-        // block)
         if let Some((ReturnKind::Hard, ret_ty)) = early_return {
             return Ok((ReturnKind::Hard, ret_ty));
         }