diff --git a/frontends/RainTypes.hs b/frontends/RainTypes.hs
index a03d14f..cc78b1a 100644
--- a/frontends/RainTypes.hs
+++ b/frontends/RainTypes.hs
@@ -140,13 +140,16 @@ matchParamPass = everywhereM ((mkM matchParamPassProc) `extM` matchParamPassFunc
              then return e
              else doCast index formalType actualType e
 
-    --Adds a cast between two types if it is safe to do so, otherwise gives an error
     doCast :: Int -> A.Type -> A.Type -> A.Expression -> PassM A.Expression
-    doCast index to from item
+    doCast index = coerceType $ " for parameter (zero-based): " ++ (show index)
+
+--Adds a cast between two types if it is safe to do so, otherwise gives an error
+coerceType :: String -> A.Type -> A.Type -> A.Expression -> PassM A.Expression
+coerceType customMsg to from item
       = if isImplicitConversionRain from to
           then return $ A.Conversion (findMeta item) A.DefaultConversion to item
           else dieP (findMeta item) $ "Could not perform implicit cast from supplied type: " ++ (show from) ++
-            " to expected type: " ++ (show to) ++ " for parameter (zero-based): " ++ (show index)
+            " to expected type: " ++ (show to) ++ customMsg
 
 
 -- | Checks the types in expressions
@@ -213,3 +216,19 @@ checkExpressionTypes = everywhereASTM checkExpression
     
     haveOrder :: A.Type -> Bool
     haveOrder = isIntegerType
+
+-- | Checks the types in assignments
+checkAssignmentTypes :: Data t => t -> PassM t
+checkAssignmentTypes = everywhereASTM checkAssignment
+  where
+    checkAssignment :: A.Process -> PassM A.Process
+    checkAssignment ass@(A.Assign m [v] (A.ExpressionList m' [e]))
+      = do trhs <- typeOfExpression e
+           tlhs <- typeOfVariable v
+           if (tlhs == trhs)
+             then return ass
+             else do rhs' <- coerceType " in assignment" tlhs trhs e
+                     return $ A.Assign m [v] (A.ExpressionList m' [rhs'])
+    checkAssignment (A.Assign {}) = dieInternal "Rain checker found occam-style assignment"
+    checkAssignment st = return st
+
diff --git a/frontends/RainTypesTest.hs b/frontends/RainTypesTest.hs
index 785e09a..4c776cc 100644
--- a/frontends/RainTypesTest.hs
+++ b/frontends/RainTypesTest.hs
@@ -160,8 +160,40 @@ checkExpressionTest = TestList
   ,passSame 2103 A.Int64 $ Cast A.Int64 (Var "xu8")
   ,passSame 2104 A.Int64 $ Cast A.Int64 $ Cast A.Int32 $ Cast A.UInt16 $ Var "xu8"  
   ,passSame 2105 A.UInt64 $ Cast A.UInt64 (Var "xu8")
+  
+  --Assignments:
+  ,passAssignSame 3000 "x" (Var "x")
+  ,passAssignSame 3001 "xu8" (Var "xu8")
+  ,passAssignSame 3002 "b" (Var "b")
+  ,passAssignSame 3003 "x" $ Dy (Var "x") A.Plus (Var "x")
+  ,passAssignSame 3004 "b" $ Dy (Var "x8") A.Eq (Var "x8")
+  ,passAssignSame 3004 "x" $ Mon A.MonadicMinus (Var "x")
+
+  ,passAssign 3100 "x" (Cast A.Int64 $ Var "xu8") (Var "xu8")
+  ,failAssign 3101 "xu8" (Var "x")
+  ,failAssign 3102 "x" (Var "b")
+  ,failAssign 3103 "b" (Var "x")
+  ,failAssign 3104 "x8" (Var "xu8")
+  ,failAssign 3105 "xu8" (Var "x8")
  ]
  where
+  passAssign :: Int -> String -> ExprHelper -> ExprHelper -> Test
+  passAssign n lhs exp src = TestCase $ testPassWithCheck ("checkExpressionTest " ++ show n) 
+    (tag3 A.Assign DontCare [variablePattern lhs] $ tag2 A.ExpressionList DontCare [buildExprPattern exp])
+    (checkAssignmentTypes $ src')
+    state refeed
+    where
+      src' = A.Assign m [variable lhs] $ A.ExpressionList m [buildExpr src]
+    
+      refeed :: A.Process -> Assertion
+      refeed changed = if (src' /= changed) then testPass ("checkExpressionTest refeed " ++ show n) (mkPattern changed) (checkAssignmentTypes changed) state else return ()
+  
+  passAssignSame :: Int -> String -> ExprHelper -> Test
+  passAssignSame n s e = passAssign n s e e
+  
+  failAssign :: Int -> String -> ExprHelper -> Test
+  failAssign n lhs src = TestCase $ testPassShouldFail ("checkExpressionTest " ++ show n) (checkAssignmentTypes $ A.Assign m [variable lhs] $ A.ExpressionList m [buildExpr src]) state
+ 
   passSame :: Int -> A.Type -> ExprHelper -> Test
   passSame n t e = pass n t e e