src/Typecheck.hs

@@ -2,6 +2,7 @@ module Typecheck where
 import Data.List (find)
 import Data.Maybe
 import Ast
+import Debug.Trace (trace)
 
 typeCheckCompilationUnit :: CompilationUnit -> CompilationUnit
 typeCheckCompilationUnit classes = map (`typeCheckClass` classes) classes
@@ -256,21 +257,27 @@ typeCheckStatement (While cond stmt) symtab classes =
 typeCheckStatement (Block statements) symtab classes =
     let
         processStatements (accSts, currentSymtab, types) stmt =
-            let
-                checkedStmt = typeCheckStatement stmt currentSymtab classes
-                stmtType = getTypeFromStmt checkedStmt
-            in case stmt of
+            case stmt of
                 LocalVariableDeclaration (VariableDeclaration dataType identifier maybeExpr) ->
                     let
+                        alreadyDefined = any (\(id, _) -> id == identifier) currentSymtab
+                        newSymtab = if alreadyDefined
+                                    then error ("Variable " ++ identifier ++ " already defined in this scope.")
+                                    else (identifier, dataType) : currentSymtab
                         checkedExpr = fmap (\expr -> typeCheckExpression expr currentSymtab classes) maybeExpr
-                        newSymtab = (identifier, dataType) : currentSymtab
+                        checkedStmt = typeCheckStatement stmt newSymtab classes
                     in (accSts ++ [checkedStmt], newSymtab, types)
 
-                If {} -> (accSts ++ [checkedStmt], currentSymtab, if stmtType /= "void" then types ++ [stmtType] else types)
-                While _ _ -> (accSts ++ [checkedStmt], currentSymtab, if stmtType /= "void" then types ++ [stmtType] else types)
-                Return _ -> (accSts ++ [checkedStmt], currentSymtab, if stmtType /= "void" then types ++ [stmtType] else types)
-                Block _ -> (accSts ++ [checkedStmt], currentSymtab, if stmtType /= "void" then types ++ [stmtType] else types)
-                _ -> (accSts ++ [checkedStmt], currentSymtab, types)
+                _ ->
+                    let
+                        checkedStmt = typeCheckStatement stmt currentSymtab classes
+                        stmtType = getTypeFromStmt checkedStmt
+                    in case stmt of
+                        If {} -> (accSts ++ [checkedStmt], currentSymtab, if stmtType /= "void" then types ++ [stmtType] else types)
+                        While _ _ -> (accSts ++ [checkedStmt], currentSymtab, if stmtType /= "void" then types ++ [stmtType] else types)
+                        Return _ -> (accSts ++ [checkedStmt], currentSymtab, if stmtType /= "void" then types ++ [stmtType] else types)
+                        Block _ -> (accSts ++ [checkedStmt], currentSymtab, if stmtType /= "void" then types ++ [stmtType] else types)
+                        _ -> (accSts ++ [checkedStmt], currentSymtab, types)
 
         -- Initial accumulator: empty statements list, initial symbol table, empty types list
         (checkedStatements, finalSymtab, collectedTypes) = foldl processStatements ([], symtab, []) statements
@@ -280,6 +287,7 @@ typeCheckStatement (Block statements) symtab classes =
 
     in TypedStatement blockType (Block checkedStatements)
 
+
 typeCheckStatement (Return expr) symtab classes =
   let methodReturnType = fromMaybe (error "Method return type not found in symbol table") (lookup "thisMeth" symtab)
       expr' = case expr of