Typecheck function calls

1 files changed, 33 insertions, 8 deletions

diff --git a/src/Compiler.hs b/src/Compiler.hs
index e694d71..0adc4ad 100644
--- a/src/Compiler.hs
+++ b/src/Compiler.hs
@@ -2,6 +2,7 @@ module Compiler where
 
 import qualified Ast as A
 import Control.Monad.State
+import Data.Either (rights)
 import Env
 import Error
 import System.Environment (getEnv, getEnvironment)
@@ -36,11 +37,37 @@ addError e = do
   put (ev, e : errs)
   return $ Right Nothing
 
+-- | @typecheckCall args params@ resolves @args@ and compares it with @params@,
+-- returning a a string describing an error or Nothing in case of type match.
+typecheckCall :: [A.Expr] -> [A.Type] -> State CompState (Maybe String)
+typecheckCall args params
+  | length args /= length params = return $ Just "invalid number of arguments in function call"
+  | length params == 0 = return $ Nothing
+  | otherwise = do
+      -- resolve all args types
+      targs <- fmap rights $ traverse compile args
+      case sequence targs of
+        Just t ->
+          if length t /= length params
+            then -- there was an error in one argument
+              return $ Nothing
+            else
+              if all (\(a, b) -> a == b) $ zip t params -- compare types
+                then return $ Nothing -- all good!
+                else return $ Just "type mismatch in function call" -- TODO: type description
+        Nothing ->
+          -- there was an error in on argument
+          return $ Nothing
+
 compile :: A.Expr -> State CompState CompResult
 compile x = do
   case x of
     (A.Module name pos) -> return $ Right Nothing
-    (A.BinOp _ a b) -> compileAll [a, b] -- XXX
+    (A.Num _ _) -> return $ Right $ Just $ A.Type "u8" -- TODO: placeholder
+    (A.BinOp _ a b) -> do
+      l <- compile a
+      r <- compile b
+      return $ l -- TODO: placeholder
     (A.Func ident params ret body priv pos) -> do
       -- current env
       (ev, errs) <- get
@@ -62,12 +89,11 @@ compile x = do
     (A.Call ident args pos) -> do
       r <- compile ident
       case r of
-        p@(Right (Just (A.FuncType params _))) ->
-          if length args /= length params
-            then addError $ Error ("invalid number of arguments in function call") pos
-            else return $ p
-        Right _ -> addError $ Error ("non callable value in function call") pos
-        Left r -> return $ Right Nothing
+        p@(Right (Just (A.FuncType params rtyp))) -> do
+          r <- typecheckCall args params
+          case r of
+            Just err -> addError $ Error err pos
+            Nothing -> return $ Right rtyp
     (A.Return value pos) -> case value of
       Just v -> compile v
       Nothing -> return $ Right Nothing
@@ -76,7 +102,6 @@ compile x = do
       case getSym ev ident of
         Just (_, t, _) -> return $ Right $ Just t
         Nothing -> addError $ Error ("undefined variable \"" ++ ident ++ "\"") pos
-    _ -> return $ Right Nothing
 
 compileAll :: [A.Expr] -> State CompState CompResult
 compileAll (x : xs) = do