Hacky implementation of @staticmethod, @property, mb even @classmethod

README.md

@@ -1291,6 +1291,41 @@ print(doesANestedThing())
 
 _**Note:** The implementation of `with` blocks is incomplete; exceptions raised from within a `with` that are not caught within the block will cause `__exit__` to not be called._
 
+### Special Decorators
+
+The compiler implements special handling when the decorators `@staticmethod` and `@property` are used with methods of a class.
+
+`@staticmethod` will mark the decorated method as a regular function - it will not receive an implicit "self" and it will be attached to the `fields` table of the class and instances of that class, rather than the `methods` table.
+
+`@property` will mark the decorated method as a property object. When it is retrieved or assigned to from the class or instance through a dot-accessor (eg. `foo.bar`), the wrapped method will be called intead.
+
+Properties work differently from in Python:
+
+```py
+class Foo():
+    def __init__(self):
+        self._bar = 0
+    @property
+    def bar(self, *setter):
+        if setter:
+            print("Setting bar:", setter[0])
+            self._bar = setter[0]
+        else:
+            print("Getting bar.")
+            return self._bar
+let f = Foo()
+print(f.bar)
+f.bar = 42
+print(f.bar)
+# → Getting bar.
+#   0
+#   Setting bar: 42
+#   Getting bar.
+#   42
+```
+
+_**Note:** Special handling when using `del` on a property is not yet implemented._
+
 ## About the REPL
 
 Kuroko's repl provides an interactive environment for executing code and seeing results.

src/chunk.h

@@ -83,6 +83,8 @@ typedef enum {
 	OP_INVOKE_DELETE,
 	OP_IMPORT_FROM,
 
+	OP_CREATE_PROPERTY,
+
 	OP_CONSTANT_LONG = 128,
 	OP_DEFINE_GLOBAL_LONG,
 	OP_GET_GLOBAL_LONG,

src/compiler.c

@@ -92,6 +92,8 @@ typedef enum {
 	TYPE_METHOD,
 	TYPE_INIT,
 	TYPE_LAMBDA,
+	TYPE_STATIC,
+	TYPE_PROPERTY,
 } FunctionType;
 
 typedef struct Compiler {
@@ -133,6 +135,10 @@ static KrkChunk * currentChunk() {
 #define EMIT_CONSTANT_OP(opc, arg) do { if (arg < 256) { emitBytes(opc, arg); } \
 	else { emitBytes(opc ## _LONG, arg >> 16); emitBytes(arg >> 8, arg); } } while (0)
 
+static int isMethod(int type) {
+	return type == TYPE_METHOD || type == TYPE_INIT || type == TYPE_PROPERTY;
+}
+
 static void initCompiler(Compiler * compiler, FunctionType type) {
 	compiler->enclosing = current;
 	current = compiler;
@@ -159,7 +165,7 @@ static void initCompiler(Compiler * compiler, FunctionType type) {
 		current->function->name = krk_copyString(parser.previous.start, parser.previous.length);
 	}
 
-	if (type == TYPE_INIT || type == TYPE_METHOD) {
+	if (isMethod(type)) {
 		Local * local = &current->locals[current->localCount++];
 		local->depth = 0;
 		local->isCaptured = 0;
@@ -876,7 +882,7 @@ static void function(FunctionType type, size_t blockWidth) {
 
 	beginScope();
 
-	if (type == TYPE_METHOD || type == TYPE_INIT) current->function->requiredArgs = 1;
+	if (isMethod(type)) current->function->requiredArgs = 1;
 
 	int hasCollectors = 0;
 
@@ -885,7 +891,7 @@ static void function(FunctionType type, size_t blockWidth) {
 	if (!check(TOKEN_RIGHT_PAREN)) {
 		do {
 			if (match(TOKEN_SELF)) {
-				if (type != TYPE_INIT && type != TYPE_METHOD) {
+				if (!isMethod(type)) {
 					error("Invalid use of `self` as a function paramenter.");
 				}
 				continue;
@@ -995,6 +1001,9 @@ static void method(size_t blockWidth) {
 		if (!match(TOKEN_EOL) && !match(TOKEN_EOF)) {
 			errorAtCurrent("Expected end of line after class attribut declaration");
 		}
+	} else if (match(TOKEN_PASS)) {
+		/* bah */
+		consume(TOKEN_EOL, "Expected linefeed after 'pass' in class body.");
 	} else {
 		consume(TOKEN_DEF, "expected a definition, got nothing");
 		consume(TOKEN_IDENTIFIER, "expected method name");
@@ -1134,8 +1143,33 @@ static KrkToken decorator(size_t level, FunctionType type) {
 	size_t blockWidth = (parser.previous.type == TOKEN_INDENTATION) ? parser.previous.length : 0;
 	advance(); /* Collect the `@` */
 
+	KrkToken funcName = {0};
+	int haveCallable = 0;
+
+	/* hol'up, let's special case some stuff */
+	KrkToken at_staticmethod = syntheticToken("staticmethod");
+	KrkToken at_property = syntheticToken("property");
+	if (identifiersEqual(&at_staticmethod, &parser.current)) {
+		if (level != 0 || type != TYPE_METHOD) {
+			error("Invalid use of @staticmethod, which must be the top decorator of a class method.");
+			return funcName;
+		}
+		advance();
+		type = TYPE_STATIC;
+		emitBytes(OP_DUP, 0); /* SET_PROPERTY will pop class */
+	} else if (identifiersEqual(&at_property, &parser.current)) {
+		if (level != 0 || type != TYPE_METHOD) {
+			error("Invalid use of @property, which must be the top decorator of a class method.");
+			return funcName;
+		}
+		advance();
+		type = TYPE_PROPERTY;
+		emitBytes(OP_DUP, 0);
+	} else {
 		/* Collect an identifier */
 		expression();
+		haveCallable = 1;
+	}
 
 	consume(TOKEN_EOL, "Expected line feed after decorator.");
 	if (blockWidth) {
@@ -1143,7 +1177,6 @@ static KrkToken decorator(size_t level, FunctionType type) {
 		if (parser.previous.length != blockWidth) error("Expected next line after decorator to have same indentation.");
 	}
 
-	KrkToken funcName = {0};
 	if (check(TOKEN_DEF)) {
 		/* We already checked for block level */
 		advance();
@@ -1160,6 +1193,7 @@ static KrkToken decorator(size_t level, FunctionType type) {
 		return funcName;
 	}
 
+	if (haveCallable)
 		emitBytes(OP_CALL, 1);
 
 	if (level == 0) {
@@ -1168,6 +1202,15 @@ static KrkToken decorator(size_t level, FunctionType type) {
 			declareVariable();
 			size_t ind = (current->scopeDepth > 0) ? 0 : identifierConstant(&funcName);
 			defineVariable(ind);
+		} else if (type == TYPE_STATIC) {
+			size_t ind = identifierConstant(&funcName);
+			EMIT_CONSTANT_OP(OP_SET_PROPERTY, ind);
+			emitByte(OP_POP);
+		} else if (type == TYPE_PROPERTY) {
+			emitByte(OP_CREATE_PROPERTY);
+			size_t ind = identifierConstant(&funcName);
+			EMIT_CONSTANT_OP(OP_SET_PROPERTY, ind);
+			emitByte(OP_POP);
 		} else {
 			size_t ind = identifierConstant(&funcName);
 			EMIT_CONSTANT_OP(OP_METHOD, ind);

src/debug.c

@@ -122,6 +122,7 @@ size_t krk_disassembleInstruction(FILE * f, KrkFunction * func, size_t offset) {
 		SIMPLE(OP_FINALIZE)
 		SIMPLE(OP_IS)
 		SIMPLE(OP_POW)
+		SIMPLE(OP_CREATE_PROPERTY)
 		OPERANDB(OP_DUP,(void)0)
 		OPERANDB(OP_EXPAND_ARGS,EXPAND_ARGS_MORE)
 		CONSTANT(OP_DEFINE_GLOBAL,(void)0)

src/memory.c

@@ -87,6 +87,10 @@ static void freeObject(KrkObj * object) {
 			FREE(KrkBytes, bytes);
 			break;
 		}
+		case OBJ_PROPERTY: {
+			FREE(KrkProperty, object);
+			break;
+		}
 	}
 }
 
@@ -178,6 +182,11 @@ static void blackenObject(KrkObj * object) {
 			markArray(&tuple->values);
 			break;
 		}
+		case OBJ_PROPERTY: {
+			KrkProperty * property = (KrkProperty *)object;
+			krk_markValue(property->method);
+			break;
+		}
 		case OBJ_NATIVE:
 		case OBJ_STRING:
 		case OBJ_BYTES:

src/object.c

@@ -248,6 +248,12 @@ KrkUpvalue * krk_newUpvalue(int slot) {
 	return upvalue;
 }
 
+KrkProperty * krk_newProperty(KrkValue method) {
+	KrkProperty * property = ALLOCATE_OBJECT(KrkProperty, OBJ_PROPERTY);
+	property->method = method;
+	return property;
+}
+
 KrkClass * krk_newClass(KrkString * name, KrkClass * baseClass) {
 	KrkClass * _class = ALLOCATE_OBJECT(KrkClass, OBJ_CLASS);
 	_class->name = name;

src/object.h

@@ -28,6 +28,8 @@
 
 #define IS_TUPLE(value)    isObjType(value, OBJ_TUPLE)
 #define AS_TUPLE(value)    ((KrkTuple *)AS_OBJECT(value))
+#define IS_PROPERTY(value) isObjType(value, OBJ_PROPERTY)
+#define AS_PROPERTY(value) ((KrkProperty *)AS_OBJECT(value))
 
 typedef enum {
 	OBJ_FUNCTION,
@@ -40,6 +42,7 @@ typedef enum {
 	OBJ_BOUND_METHOD,
 	OBJ_TUPLE,
 	OBJ_BYTES,
+	OBJ_PROPERTY,
 } ObjType;
 
 struct Obj {
@@ -173,6 +176,11 @@ typedef struct {
 	KrkValueArray values;
 } KrkTuple;
 
+typedef struct {
+	KrkObj obj;
+	KrkValue method;
+} KrkProperty;
+
 typedef struct {
 	KrkInstance inst;
 	KrkValueArray values;
@@ -200,6 +208,7 @@ extern KrkClass *       krk_newClass(KrkString * name, KrkClass * base);
 extern KrkInstance *    krk_newInstance(KrkClass * _class);
 extern KrkBoundMethod * krk_newBoundMethod(KrkValue receiver, KrkObj * method);
 extern KrkTuple *       krk_newTuple(size_t length);
+extern KrkProperty * krk_newProperty(KrkValue method);
 
 extern void * krk_unicodeString(KrkString * string);
 extern uint32_t krk_unicodeCodepoint(KrkString * string, size_t index);

src/vm.c

@@ -1411,6 +1411,7 @@ KrkValue krk_callSimple(KrkValue value, int argCount, int isMethod) {
 	} else if (result == 1) {
 		return krk_runNext();
 	}
+	if (!IS_NONE(vm.currentException)) return NONE_VAL();
 	return krk_runtimeError(vm.exceptions.typeError, "Invalid internal method call: %d ('%s')", result, krk_typeName(value));
 }
 
@@ -4133,6 +4134,10 @@ static int valueGetProperty(KrkString * name) {
 	if (IS_INSTANCE(krk_peek(0))) {
 		KrkInstance * instance = AS_INSTANCE(krk_peek(0));
 		if (krk_tableGet(&instance->fields, OBJECT_VAL(name), &value)) {
+			if (IS_PROPERTY(value)) {
+				krk_push(krk_callSimple(AS_PROPERTY(value)->method, 1, 0));
+				return 1;
+			}
 			krk_pop();
 			krk_push(value);
 			return 1;
@@ -4142,6 +4147,10 @@ static int valueGetProperty(KrkString * name) {
 		KrkClass * _class = AS_CLASS(krk_peek(0));
 		if (krk_tableGet(&_class->fields, OBJECT_VAL(name), &value) ||
 			krk_tableGet(&_class->methods, OBJECT_VAL(name), &value)) {
+			if (IS_PROPERTY(value)) {
+				krk_push(krk_callSimple(AS_PROPERTY(value)->method, 1, 0));
+				return 1;
+			}
 			krk_pop();
 			krk_push(value);
 			return 1;
@@ -4584,12 +4593,17 @@ static KrkValue run() {
 			case OP_SET_PROPERTY_LONG:
 			case OP_SET_PROPERTY: {
 				KrkString * name = READ_STRING(operandWidth);
-				if (IS_INSTANCE(krk_peek(1))) {
-					KrkInstance * instance = AS_INSTANCE(krk_peek(1));
-					krk_tableSet(&instance->fields, OBJECT_VAL(name), krk_peek(0));
-				} else if (IS_CLASS(krk_peek(1))) {
-					KrkClass * _class = AS_CLASS(krk_peek(1));
-					krk_tableSet(&_class->fields, OBJECT_VAL(name), krk_peek(0));
+				KrkTable * table = NULL;
+				if (IS_INSTANCE(krk_peek(1))) table = &AS_INSTANCE(krk_peek(1))->fields;
+				else if (IS_CLASS(krk_peek(1))) table = &AS_CLASS(krk_peek(1))->fields;
+				if (table) {
+					KrkValue previous;
+					if (krk_tableGet(table, OBJECT_VAL(name), &previous) && IS_PROPERTY(previous)) {
+						krk_push(krk_callSimple(AS_PROPERTY(previous)->method, 2, 0));
+						break;
+					} else {
+						krk_tableSet(table, OBJECT_VAL(name), krk_peek(0));
+					}
 				} else {
 					krk_runtimeError(vm.exceptions.attributeError, "'%s' object has no attribute '%s'", krk_typeName(krk_peek(0)), name->chars);
 					goto _finishException;
@@ -4754,6 +4768,12 @@ static KrkValue run() {
 				krk_push(handler);
 				break;
 			}
+			case OP_CREATE_PROPERTY: {
+				KrkProperty * newProperty = krk_newProperty(krk_peek(0));
+				krk_pop();
+				krk_push(OBJECT_VAL(newProperty));
+				break;
+			}
 		}
 		if (likely(!(vm.flags & KRK_HAS_EXCEPTION))) continue;
 _finishException:

test/testClassMethod.krk

@@ -1,14 +1,9 @@
-def staticmethod(func):
-    def _wrapper(*args,**kwargs):
-        return func(None,*args,**kwargs)
-    return _wrapper
-
 class Foo():
     def amethod():
         print("If this were Python, I'd be impossible to call.")
     @staticmethod
     def astatic():
-        print("Since `None` is always implicit, it's been set by @staticmethod here to None:", self)
+        print("these are special now")
 
 # This doesn't work because amethod is unbound and needs an instance.
 try:

test/testClassMethod.krk.expect

@@ -1,3 +1,3 @@
 amethod() takes exactly 1 argument (0 given)
 If this were Python, I'd be impossible to call.
-Since `None` is always implicit, it's been set by @staticmethod here to None: None
+these are special now

test/testSpecialDecorators.krk

@@ -0,0 +1,39 @@
+
+def classmethod(func):
+    def bindClassMethod(callee, *args):
+        if args: raise ValueError("can not reassign class method")
+        let cls = callee if isinstance(callee, type) else callee.__class__
+        def _bound(*args, **kwargs):
+            return func(None, cls, *args, **kwargs)
+        return _bound
+    return bindClassMethod
+
+class Foo(object):
+    myBar = 42
+    @staticmethod
+    def foo():
+        print("No args!")
+    @property
+    def bar(*setter):
+        if setter:
+            print("Called as a setter:", setter)
+            self.myBar = setter[0]
+        return self.myBar
+    @property
+    @classmethod
+    def fromString(cls, string):
+        print(cls, string)
+
+class Bar(Foo):
+
+Foo.foo()
+print(Foo().bar)
+let f = Foo()
+f.myBar = 48
+print(f.bar)
+f.bar = 102
+print(f.bar)
+
+Foo.fromString("test")
+f.fromString("test")
+Bar.fromString("test")

test/testSpecialDecorators.krk.expect

@@ -0,0 +1,8 @@
+No args!
+42
+48
+Called as a setter: [102]
+102
+<type 'Foo'> test
+<type 'Foo'> test
+<type 'Bar'> test