No more default constructors.

Fixes #296.

src/vm/wren_compiler.c

@@ -2964,7 +2964,7 @@ static void defineMethod(Compiler* compiler, int classSlot, bool isStatic,
 // Returns `true` if it compiled successfully, or `false` if the method couldn't
 // be parsed.
 static bool method(Compiler* compiler, ClassCompiler* classCompiler,
-                   int classSlot, bool* hasConstructor)
+                   int classSlot)
 {
   // TODO: What about foreign constructors?
   bool isForeign = match(compiler, TOKEN_FOREIGN);
@@ -3030,31 +3030,11 @@ static bool method(Compiler* compiler, ClassCompiler* classCompiler,
     
     createConstructor(compiler, &signature, methodSymbol);
     defineMethod(compiler, classSlot, true, constructorSymbol);
-    
-    // We don't need a default constructor anymore.
-    *hasConstructor = true;
   }
 
   return true;
 }
 
-// Defines a default "new()" constructor on the current class.
-//
-// It just invokes "init new()" on the instance. If a base class defines that,
-// it will get invoked. Otherwise, it falls to the default one in Object which
-// does nothing.
-static void createDefaultConstructor(Compiler* compiler, int classSlot)
-{
-  Signature signature = { "new", 3, SIG_INITIALIZER, 0 };
-  int initializerSymbol = signatureSymbol(compiler, &signature);
-  
-  signature.type = SIG_METHOD;
-  int constructorSymbol = signatureSymbol(compiler, &signature);
-  
-  createConstructor(compiler, &signature, initializerSymbol);
-  defineMethod(compiler, classSlot, true, constructorSymbol);
-}
-
 // Compiles a class definition. Assumes the "class" token has already been
 // consumed (along with a possibly preceding "foreign" token).
 static void classDefinition(Compiler* compiler, bool isForeign)
@@ -3117,11 +3097,9 @@ static void classDefinition(Compiler* compiler, bool isForeign)
   consume(compiler, TOKEN_LEFT_BRACE, "Expect '{' after class declaration.");
   matchLine(compiler);
 
-  bool hasConstructor = false;
-  
   while (!match(compiler, TOKEN_RIGHT_BRACE))
   {
-    if (!method(compiler, &classCompiler, slot, &hasConstructor)) break;
+    if (!method(compiler, &classCompiler, slot)) break;
     
     // Don't require a newline after the last definition.
     if (match(compiler, TOKEN_RIGHT_BRACE)) break;
@@ -3129,12 +3107,6 @@ static void classDefinition(Compiler* compiler, bool isForeign)
     consumeLine(compiler, "Expect newline after definition in class.");
   }
   
-  // If no constructor was defined, create a default new() one.
-  if (!hasConstructor)
-  {
-    createDefaultConstructor(compiler, slot);
-  }
-
   // Update the class with the number of fields.
   if (!isForeign)
   {

src/vm/wren_core.c

@@ -213,16 +213,6 @@ static const char* coreLibSource =
 "\n"
 "class Range is Sequence {}\n";
 
-// A simple primitive that just returns "this". Used in a few different places:
-//
-// * The default new() initializer on Object needs no initialization so just
-//   uses this.
-// * String's toString method obviously can use this.
-DEF_PRIMITIVE(return_this)
-{
-  RETURN_VAL(args[0]);
-}
-
 DEF_PRIMITIVE(bool_not)
 {
   RETURN_BOOL(!AS_BOOL(args[0]));
@@ -1258,6 +1248,11 @@ DEF_PRIMITIVE(string_subscript)
   RETURN_ERROR("Subscript ranges for strings are not implemented yet.");
 }
 
+DEF_PRIMITIVE(string_toString)
+{
+  RETURN_VAL(args[0]);
+}
+
 // Creates either the Object or Class class in the core library with [name].
 static ObjClass* defineClass(WrenVM* vm, ObjModule* module, const char* name)
 {
@@ -1282,7 +1277,6 @@ void wrenInitializeCore(WrenVM* vm)
   PRIMITIVE(vm->objectClass, "!", object_not);
   PRIMITIVE(vm->objectClass, "==(_)", object_eqeq);
   PRIMITIVE(vm->objectClass, "!=(_)", object_bangeq);
-  PRIMITIVE(vm->objectClass, "init new()", return_this);
   PRIMITIVE(vm->objectClass, "is(_)", object_is);
   PRIMITIVE(vm->objectClass, "toString", object_toString);
   PRIMITIVE(vm->objectClass, "type", object_type);
@@ -1436,7 +1430,7 @@ void wrenInitializeCore(WrenVM* vm)
   PRIMITIVE(vm->stringClass, "iterateByte_(_)", string_iterateByte);
   PRIMITIVE(vm->stringClass, "iteratorValue(_)", string_iteratorValue);
   PRIMITIVE(vm->stringClass, "startsWith(_)", string_startsWith);
-  PRIMITIVE(vm->stringClass, "toString", return_this);
+  PRIMITIVE(vm->stringClass, "toString", string_toString);
 
   vm->listClass = AS_CLASS(wrenFindVariable(vm, coreModule, "List"));
   PRIMITIVE(vm->listClass->obj.classObj, "new()", list_new);