From 641de5e4f68385da3b53bfc532c2d6585a6d958d Mon Sep 17 00:00:00 2001
From: "Juan J. Martinez" <jjm@usebox.net>
Date: Sun, 14 Aug 2022 19:19:26 +0100
Subject: Limit lambdas to only use local variables

Dynamic allocation (and hence closures) is not supported.
---
 src/Ast.hs      |  4 ++--
 src/Compiler.hs |  6 ++++--
 src/Parser.hs   | 10 +++++-----
 3 files changed, 11 insertions(+), 9 deletions(-)

(limited to 'src')

diff --git a/src/Ast.hs b/src/Ast.hs
index c2bae9e..aa6a5c8 100644
--- a/src/Ast.hs
+++ b/src/Ast.hs
@@ -23,8 +23,8 @@ data Expr
   = Num Integer SourcePos
   | BinOp Op Expr Expr
   | Var Ident SourcePos
-  | -- fn [params] return body private pos
-    Func Ident [FuncParam] (Maybe Type) [Expr] Bool SourcePos
+  | -- fn [params] return body private anomyous pos
+    Func Ident [FuncParam] (Maybe Type) [Expr] Bool Bool SourcePos
   | Call Expr [Expr] SourcePos
   | Return (Maybe Expr) SourcePos
   | Module String SourcePos
diff --git a/src/Compiler.hs b/src/Compiler.hs
index f9c0eed..0d90143 100644
--- a/src/Compiler.hs
+++ b/src/Compiler.hs
@@ -86,7 +86,7 @@ compile x = do
       l <- compile a
       r <- compile b
       return $ l -- TODO: placeholder
-    (A.Func ident params ret body priv pos) -> do
+    (A.Func ident params ret body priv anon pos) -> do
       -- current env
       (ev, errs) <- get
       -- updated with the function
@@ -94,8 +94,10 @@ compile x = do
         return $ case addSymUniq ev (ident, ftype, pos) of
           Left err -> (ev, err : errs)
           Right ev -> (ev, errs)
+      -- lambdas can only access local variables (closures aren't supported)
+      fev <- return $ if anon then emptyEnv else ev
       -- with parameters
-      (nev, errs) <- return $ foldlEither addSymUniq (addEnv ev, errs) params
+      (nev, errs) <- return $ foldlEither addSymUniq (addEnv fev, errs) params
       -- helper for return
       nev <- return $ addSym nev ("$fn$", ftype, pos)
       put (nev, errs)
diff --git a/src/Parser.hs b/src/Parser.hs
index 1c21700..851b4c0 100644
--- a/src/Parser.hs
+++ b/src/Parser.hs
@@ -59,8 +59,8 @@ arg = do
   t <- type' <?> "type"
   return $ (i, t, pos)
 
-fdef :: Ident -> Bool -> SourcePos -> Parser Expr
-fdef ident priv pos = do
+fdef :: Ident -> Bool -> Bool -> SourcePos -> Parser Expr
+fdef ident priv anon pos = do
   args <- parens $ commaSep arg
   rtyp <-
     optionMaybe
@@ -70,7 +70,7 @@ fdef ident priv pos = do
           return $ rtyp
       )
   body <- braces $ many statement
-  return $ Func ident args rtyp body priv pos
+  return $ Func ident args rtyp body priv anon pos
 
 function :: Parser Expr
 function = do
@@ -78,7 +78,7 @@ function = do
   priv <- optionMaybe $ reserved "private"
   reserved "def"
   ident <- identifier
-  fdef ident (isJust priv) pos
+  fdef ident (isJust priv) False pos
 
 lambdaId :: SourcePos -> Ident
 lambdaId s =
@@ -87,7 +87,7 @@ lambdaId s =
 lambda :: Parser Expr
 lambda = do
   pos <- getPosition
-  fdef (lambdaId pos) True pos
+  fdef (lambdaId pos) True True pos
 
 return' :: Parser Expr
 return' = do
-- 
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