fixed method/constructor overloading in bytecode generator

Test/JavaSources/Main.java

@@ -16,7 +16,8 @@ public class Main {
         TestRecursion recursion = new TestRecursion(10);
         TestMalicious malicious = new TestMalicious();
         TestLoop loop = new TestLoop();
-
+        TestMethodOverload overload = new TestMethodOverload();
+        
         // constructing a basic class works
         assert empty != null;
         // initializers (and default initializers to 0/null) work
@@ -34,6 +35,12 @@ public class Main {
         // self-referencing methods work.
         assert recursion.fibonacci(15) == 610;
         assert loop.factorial(5) == 120;
+        // methods with the same name but different parameters work
+        assert overload.MethodOverload() == 42;
+        assert overload.MethodOverload(15) == 42 + 15;
+        // constructor overloading works, too.
+        assert (new TestConstructorOverload()).a == 42;
+        assert (new TestConstructorOverload(12)).a == 12;
         // intentionally dodgy expressions work
         assert malicious.assignNegativeIncrement(42) == -42;
         assert malicious.tripleAddition(1, 2, 3) == 6;

Test/JavaSources/TestConstructorOverload.java

@@ -1,13 +1,12 @@
 public class TestConstructorOverload {
 
+    public int a = 42;
+
     TestConstructorOverload() {
+        // nothing here, so a will assume the default value 42.
     }
 
     TestConstructorOverload(int a) {
-    }
+        this.a = a;
-
-    public void test() {
-        int a = 3;
-        TestConstructorOverload test = new TestConstructorOverload(a);
     }
 }

Test/JavaSources/TestMethodOverload.java

@@ -1,14 +1,10 @@
 public class TestMethodOverload {
 
-    public void MethodOverload() {
+    public int MethodOverload() {
+        return 42;
     }
 
-    public void MethodOverload(int a) {
+    public int MethodOverload(int a) {
+        return 42 + a;
     }
-
-    public void test() {
-        int a = 3;
-        MethodOverload(a);
-    }
-    
 }

project.cabal

@@ -18,7 +18,6 @@ executable compiler
     other-modules:      Parser.Lexer,
                         Parser.JavaParser,
                         Ast,
-                        Example,
                         Typecheck,
                         ByteCode.Util,
                         ByteCode.ByteUtil,

src/ByteCode/Builder.hs

@@ -56,10 +56,13 @@ methodBuilder (MethodDeclaration returntype name parameters statement) input = l
             methods = methods input ++ [method]
         }
 
+constructorBuilder :: ClassFileBuilder ConstructorDeclaration
+constructorBuilder (ConstructorDeclaration name parameters statement) = methodBuilder (MethodDeclaration "void" "<init>" parameters statement)
+
 
 methodAssembler :: ClassFileBuilder MethodDeclaration
 methodAssembler (MethodDeclaration returntype name parameters statement) input = let
-        methodConstantIndex = findMethodIndex input name
+        methodConstantIndex = findMethodIndex input (MethodDeclaration returntype name parameters statement) 
     in case methodConstantIndex of
         Nothing -> error ("Cannot find method entry in method pool for method: " ++ name)
         Just index -> let
@@ -84,9 +87,12 @@ methodAssembler (MethodDeclaration returntype name parameters statement) input =
                             methods = pre ++ (assembledMethod : post)
                         }
 
+constructorAssembler :: ClassFileBuilder ConstructorDeclaration
+constructorAssembler (ConstructorDeclaration name parameters statement) = methodAssembler (MethodDeclaration "void" "<init>" parameters statement)
+
 
 classBuilder :: ClassFileBuilder Class
-classBuilder (Class name methods fields) _ = let
+classBuilder (Class name constructors methods fields) _ = let
         baseConstants = [
             ClassInfo 4,
             MethodRefInfo 1 3,
@@ -108,15 +114,15 @@ classBuilder (Class name methods fields) _ = let
             attributes = []
         }
 
-        -- if a class has no constructor, inject an empty one.
-        methodsWithInjectedConstructor = injectDefaultConstructor methods
         -- for every constructor, prepend all initialization assignments for fields.
-        methodsWithInjectedInitializers = injectFieldInitializers name fields methodsWithInjectedConstructor
+        constructorsWithInitializers = injectFieldInitializers name fields constructors
 
-        -- add fields, then method bodies to the classfile. After all referable names are known,
+        -- add fields, then method bodies, then constructor bodies to the classfile. After all referable names are known,
-        -- assemble the methods into bytecode.
+        -- assemble the methods and constructors into bytecode.
-        classFileWithFields = foldr fieldBuilder nakedClassFile fields
+        fieldsAdded = foldr fieldBuilder nakedClassFile fields
-        classFileWithMethods = foldr methodBuilder classFileWithFields methodsWithInjectedInitializers
+        methodsAdded = foldr methodBuilder fieldsAdded methods
-        classFileWithAssembledMethods = foldr methodAssembler classFileWithMethods methodsWithInjectedInitializers
+        constructorsAdded = foldr constructorBuilder methodsAdded constructorsWithInitializers
+        methodsAssembled = foldr methodAssembler constructorsAdded methods
+        constructorsAssembled = foldr constructorAssembler methodsAssembled constructorsWithInitializers
     in
-        classFileWithAssembledMethods
+        constructorsAssembled

src/ByteCode/Util.hs

@@ -1,3 +1,5 @@
+{-# OPTIONS_GHC -Wno-unrecognised-pragmas #-}
+{-# HLINT ignore "Use lambda-case" #-}
 module ByteCode.Util where
 
 import Data.Int
@@ -131,11 +133,12 @@ comparisonOffset anything_else = Nothing
 isComparisonOperation :: Operation -> Bool
 isComparisonOperation op = isJust (comparisonOffset op)
 
-findMethodIndex :: ClassFile -> String -> Maybe Int
+findMethodIndex :: ClassFile -> MethodDeclaration -> Maybe Int
-findMethodIndex classFile name = let
+findMethodIndex classFile (MethodDeclaration rtype name params stmt) = let
         constants = constantPool classFile
+        descriptor = methodDescriptor (MethodDeclaration rtype name params stmt)
     in
-        findIndex (\method -> memberInfoIsMethod constants method && memberInfoName constants method == name) (methods classFile)
+        findIndex (\method -> memberInfoIsMethod constants method && memberInfoName constants method == name && memberInfoDescriptor constants method == descriptor) (methods classFile)
 
 findClassIndex :: [ConstantInfo] -> String -> Maybe Int
 findClassIndex constants name = let
@@ -211,16 +214,11 @@ findMemberIndex constants (cname, fname, ftype) = let
         allMembers = getKnownMembers constants
         desiredMember = find (\(index, (c, f, ft)) -> (c, f, ft) == (cname, fname, ftype)) allMembers
     in
-        fmap (\(index, _) -> index) desiredMember
+        fmap fst desiredMember
 
-injectDefaultConstructor :: [MethodDeclaration] -> [MethodDeclaration]
+injectFieldInitializers :: String -> [VariableDeclaration] -> [ConstructorDeclaration] -> [ConstructorDeclaration]
-injectDefaultConstructor pre
+injectFieldInitializers classname vars constructors = let
-    | any (\(MethodDeclaration _ name _ _) -> name == "<init>") pre = pre
+        initializers = mapMaybe (\variable -> case variable of
-    | otherwise = pre ++ [MethodDeclaration "void" "<init>" [] (TypedStatement "void" (Block []))]
-
-injectFieldInitializers :: String -> [VariableDeclaration] -> [MethodDeclaration] -> [MethodDeclaration]
-injectFieldInitializers classname vars pre = let
-        initializers = mapMaybe (\(variable) -> case variable of
                 VariableDeclaration dtype name (Just initializer) -> Just (
                         TypedStatement dtype (
                             StatementExpressionStatement (
@@ -235,10 +233,11 @@ injectFieldInitializers classname vars pre = let
                 otherwise -> Nothing
             ) vars
     in
-        map (\method -> case method of
+        map (\con -> let
-                MethodDeclaration "void" "<init>" params (TypedStatement "void" (Block statements)) -> MethodDeclaration "void" "<init>" params (TypedStatement "void" (Block (initializers ++ statements)))
+                    ConstructorDeclaration classname params (TypedStatement "void" (Block statements)) = con
-                _ -> method
+                in
-            ) pre
+                    ConstructorDeclaration classname params (TypedStatement "void" (Block (initializers ++ statements)))
+            ) constructors
 
 -- effect of one instruction/operation on the stack
 operationStackCost :: [ConstantInfo] -> Operation -> Int