Merge pull request #47454 from vnen/gdscript-lambda

modules/gdscript/gdscript.h

@@ -270,6 +270,7 @@ public:
 class GDScriptInstance : public ScriptInstance {
 	friend class GDScript;
 	friend class GDScriptFunction;
+	friend class GDScriptLambdaCallable;
 	friend class GDScriptCompiler;
 	friend struct GDScriptUtilityFunctionsDefinitions;
 

modules/gdscript/gdscript_analyzer.cpp

@@ -856,6 +856,7 @@ void GDScriptAnalyzer::resolve_node(GDScriptParser::Node *p_node) {
 		case GDScriptParser::Node::DICTIONARY:
 		case GDScriptParser::Node::GET_NODE:
 		case GDScriptParser::Node::IDENTIFIER:
+		case GDScriptParser::Node::LAMBDA:
 		case GDScriptParser::Node::LITERAL:
 		case GDScriptParser::Node::PRELOAD:
 		case GDScriptParser::Node::SELF:
@@ -1458,6 +1459,9 @@ void GDScriptAnalyzer::reduce_expression(GDScriptParser::ExpressionNode *p_expre
 		case GDScriptParser::Node::IDENTIFIER:
 			reduce_identifier(static_cast<GDScriptParser::IdentifierNode *>(p_expression));
 			break;
+		case GDScriptParser::Node::LAMBDA:
+			reduce_lambda(static_cast<GDScriptParser::LambdaNode *>(p_expression));
+			break;
 		case GDScriptParser::Node::LITERAL:
 			reduce_literal(static_cast<GDScriptParser::LiteralNode *>(p_expression));
 			break;
@@ -2061,6 +2065,12 @@ void GDScriptAnalyzer::reduce_call(GDScriptParser::CallNode *p_call, bool is_awa
 		is_self = true;
 	} else if (callee_type == GDScriptParser::Node::SUBSCRIPT) {
 		GDScriptParser::SubscriptNode *subscript = static_cast<GDScriptParser::SubscriptNode *>(p_call->callee);
+		if (subscript->base == nullptr) {
+			// Invalid syntax, error already set on parser.
+			p_call->set_datatype(call_type);
+			mark_node_unsafe(p_call);
+			return;
+		}
 		if (!subscript->is_attribute) {
 			// Invalid call. Error already sent in parser.
 			// TODO: Could check if Callable here.
@@ -2097,6 +2107,8 @@ void GDScriptAnalyzer::reduce_call(GDScriptParser::CallNode *p_call, bool is_awa
 
 		if (is_self && parser->current_function != nullptr && parser->current_function->is_static && !is_static) {
 			push_error(vformat(R"*(Cannot call non-static function "%s()" from static function "%s()".)*", p_call->function_name, parser->current_function->identifier->name), p_call->callee);
+		} else if (is_self && !is_static && !lambda_stack.is_empty()) {
+			push_error(vformat(R"*(Cannot call non-static function "%s()" from a lambda function.)*", p_call->function_name), p_call->callee);
 		}
 
 		call_type = return_type;
@@ -2219,6 +2231,8 @@ void GDScriptAnalyzer::reduce_get_node(GDScriptParser::GetNodeNode *p_get_node)
 
 	if (!ClassDB::is_parent_class(GDScriptParser::get_real_class_name(parser->current_class->base_type.native_type), result.native_type)) {
 		push_error(R"*(Cannot use shorthand "get_node()" notation ("$") on a class that isn't a node.)*", p_get_node);
+	} else if (!lambda_stack.is_empty()) {
+		push_error(R"*(Cannot use shorthand "get_node()" notation ("$") inside a lambda. Use a captured variable instead.)*", p_get_node);
 	}
 
 	p_get_node->set_datatype(result);
@@ -2346,6 +2360,7 @@ void GDScriptAnalyzer::reduce_identifier_from_base(GDScriptParser::IdentifierNod
 				case GDScriptParser::ClassNode::Member::ENUM_VALUE:
 					p_identifier->is_constant = true;
 					p_identifier->reduced_value = member.enum_value.value;
+					p_identifier->source = GDScriptParser::IdentifierNode::MEMBER_CONSTANT;
 					break;
 				case GDScriptParser::ClassNode::Member::VARIABLE:
 					p_identifier->source = GDScriptParser::IdentifierNode::MEMBER_VARIABLE;
@@ -2446,42 +2461,65 @@ void GDScriptAnalyzer::reduce_identifier(GDScriptParser::IdentifierNode *p_ident
 		}
 	}
 
+	bool found_source = false;
 	// Check if identifier is local.
 	// If that's the case, the declaration already was solved before.
 	switch (p_identifier->source) {
 		case GDScriptParser::IdentifierNode::FUNCTION_PARAMETER:
 			p_identifier->set_datatype(p_identifier->parameter_source->get_datatype());
-			return;
+			found_source = true;
+			break;
 		case GDScriptParser::IdentifierNode::LOCAL_CONSTANT:
 		case GDScriptParser::IdentifierNode::MEMBER_CONSTANT:
 			p_identifier->set_datatype(p_identifier->constant_source->get_datatype());
 			p_identifier->is_constant = true;
 			// TODO: Constant should have a value on the node itself.
 			p_identifier->reduced_value = p_identifier->constant_source->initializer->reduced_value;
-			return;
+			found_source = true;
+			break;
 		case GDScriptParser::IdentifierNode::MEMBER_VARIABLE:
 			p_identifier->variable_source->usages++;
 			[[fallthrough]];
 		case GDScriptParser::IdentifierNode::LOCAL_VARIABLE:
 			p_identifier->set_datatype(p_identifier->variable_source->get_datatype());
-			return;
+			found_source = true;
+			break;
 		case GDScriptParser::IdentifierNode::LOCAL_ITERATOR:
 			p_identifier->set_datatype(p_identifier->bind_source->get_datatype());
-			return;
+			found_source = true;
+			break;
 		case GDScriptParser::IdentifierNode::LOCAL_BIND: {
 			GDScriptParser::DataType result = p_identifier->bind_source->get_datatype();
 			result.is_constant = true;
 			p_identifier->set_datatype(result);
-			return;
+			found_source = true;
-		}
+		} break;
 		case GDScriptParser::IdentifierNode::UNDEFINED_SOURCE:
 			break;
 	}
 
 	// Not a local, so check members.
-	reduce_identifier_from_base(p_identifier);
+	if (!found_source) {
-	if (p_identifier->get_datatype().is_set()) {
+		reduce_identifier_from_base(p_identifier);
-		// Found.
+		if (p_identifier->source != GDScriptParser::IdentifierNode::UNDEFINED_SOURCE || p_identifier->get_datatype().is_set()) {
+			// Found.
+			found_source = true;
+		}
+	}
+
+	if (found_source) {
+		// If the identifier is local, check if it's any kind of capture by comparing their source function.
+		// Only capture locals and members and enum values. Constants are still accessible from the lambda using the script reference.
+		if (p_identifier->source == GDScriptParser::IdentifierNode::UNDEFINED_SOURCE || p_identifier->source == GDScriptParser::IdentifierNode::MEMBER_CONSTANT || lambda_stack.is_empty()) {
+			return;
+		}
+
+		GDScriptParser::FunctionNode *function_test = lambda_stack.back()->get()->function;
+		while (function_test != nullptr && function_test != p_identifier->source_function && function_test->source_lambda != nullptr && !function_test->source_lambda->captures_indices.has(p_identifier->name)) {
+			function_test->source_lambda->captures_indices[p_identifier->name] = function_test->source_lambda->captures.size();
+			function_test->source_lambda->captures.push_back(p_identifier);
+			function_test = function_test->source_lambda->parent_function;
+		}
 		return;
 	}
 
@@ -2563,6 +2601,57 @@ void GDScriptAnalyzer::reduce_identifier(GDScriptParser::IdentifierNode *p_ident
 	p_identifier->set_datatype(dummy); // Just so type is set to something.
 }
 
+void GDScriptAnalyzer::reduce_lambda(GDScriptParser::LambdaNode *p_lambda) {
+	// Lambda is always a Callable.
+	GDScriptParser::DataType lambda_type;
+	lambda_type.type_source = GDScriptParser::DataType::ANNOTATED_INFERRED;
+	lambda_type.kind = GDScriptParser::DataType::BUILTIN;
+	lambda_type.builtin_type = Variant::CALLABLE;
+	p_lambda->set_datatype(lambda_type);
+
+	if (p_lambda->function == nullptr) {
+		return;
+	}
+
+	GDScriptParser::FunctionNode *previous_function = parser->current_function;
+	parser->current_function = p_lambda->function;
+
+	lambda_stack.push_back(p_lambda);
+
+	for (int i = 0; i < p_lambda->function->parameters.size(); i++) {
+		resolve_parameter(p_lambda->function->parameters[i]);
+	}
+
+	resolve_suite(p_lambda->function->body);
+
+	int captures_amount = p_lambda->captures.size();
+	if (captures_amount > 0) {
+		// Create space for lambda parameters.
+		// At the beginning to not mess with optional parameters.
+		int param_count = p_lambda->function->parameters.size();
+		p_lambda->function->parameters.resize(param_count + captures_amount);
+		for (int i = param_count - 1; i >= 0; i--) {
+			p_lambda->function->parameters.write[i + captures_amount] = p_lambda->function->parameters[i];
+			p_lambda->function->parameters_indices[p_lambda->function->parameters[i]->identifier->name] = i + captures_amount;
+		}
+
+		// Add captures as extra parameters at the beginning.
+		for (int i = 0; i < p_lambda->captures.size(); i++) {
+			GDScriptParser::IdentifierNode *capture = p_lambda->captures[i];
+			GDScriptParser::ParameterNode *capture_param = parser->alloc_node<GDScriptParser::ParameterNode>();
+			capture_param->identifier = capture;
+			capture_param->usages = capture->usages;
+			capture_param->set_datatype(capture->get_datatype());
+
+			p_lambda->function->parameters.write[i] = capture_param;
+			p_lambda->function->parameters_indices[capture->name] = i;
+		}
+	}
+
+	lambda_stack.pop_back();
+	parser->current_function = previous_function;
+}
+
 void GDScriptAnalyzer::reduce_literal(GDScriptParser::LiteralNode *p_literal) {
 	p_literal->reduced_value = p_literal->value;
 	p_literal->is_constant = true;

modules/gdscript/gdscript_analyzer.h

@@ -42,6 +42,7 @@ class GDScriptAnalyzer {
 	HashMap<String, Ref<GDScriptParserRef>> depended_parsers;
 
 	const GDScriptParser::EnumNode *current_enum = nullptr;
+	List<const GDScriptParser::LambdaNode *> lambda_stack;
 
 	Error resolve_inheritance(GDScriptParser::ClassNode *p_class, bool p_recursive = true);
 	GDScriptParser::DataType resolve_datatype(GDScriptParser::TypeNode *p_type);
@@ -82,6 +83,7 @@ class GDScriptAnalyzer {
 	void reduce_get_node(GDScriptParser::GetNodeNode *p_get_node);
 	void reduce_identifier(GDScriptParser::IdentifierNode *p_identifier, bool can_be_builtin = false);
 	void reduce_identifier_from_base(GDScriptParser::IdentifierNode *p_identifier, GDScriptParser::DataType *p_base = nullptr);
+	void reduce_lambda(GDScriptParser::LambdaNode *p_lambda);
 	void reduce_literal(GDScriptParser::LiteralNode *p_literal);
 	void reduce_preload(GDScriptParser::PreloadNode *p_preload);
 	void reduce_self(GDScriptParser::SelfNode *p_self);

modules/gdscript/gdscript_byte_codegen.cpp

@@ -383,6 +383,18 @@ GDScriptFunction *GDScriptByteCodeGenerator::write_end() {
 		function->_methods_count = 0;
 	}
 
+	if (lambdas_map.size()) {
+		function->lambdas.resize(lambdas_map.size());
+		function->_lambdas_ptr = function->lambdas.ptrw();
+		function->_lambdas_count = lambdas_map.size();
+		for (const Map<GDScriptFunction *, int>::Element *E = lambdas_map.front(); E; E = E->next()) {
+			function->lambdas.write[E->get()] = E->key();
+		}
+	} else {
+		function->_lambdas_ptr = nullptr;
+		function->_lambdas_count = 0;
+	}
+
 	if (debug_stack) {
 		function->stack_debug = stack_debug;
 	}
@@ -1118,6 +1130,17 @@ void GDScriptByteCodeGenerator::write_call_script_function(const Address &p_targ
 	append(p_function_name);
 }
 
+void GDScriptByteCodeGenerator::write_lambda(const Address &p_target, GDScriptFunction *p_function, const Vector<Address> &p_captures) {
+	append(GDScriptFunction::OPCODE_CREATE_LAMBDA, 1 + p_captures.size());
+	for (int i = 0; i < p_captures.size(); i++) {
+		append(p_captures[i]);
+	}
+
+	append(p_target);
+	append(p_captures.size());
+	append(p_function);
+}
+
 void GDScriptByteCodeGenerator::write_construct(const Address &p_target, Variant::Type p_type, const Vector<Address> &p_arguments) {
 	// Try to find an appropriate constructor.
 	bool all_have_type = true;

modules/gdscript/gdscript_byte_codegen.h

@@ -93,6 +93,7 @@ class GDScriptByteCodeGenerator : public GDScriptCodeGenerator {
 	Map<Variant::ValidatedUtilityFunction, int> utilities_map;
 	Map<GDScriptUtilityFunctions::FunctionPtr, int> gds_utilities_map;
 	Map<MethodBind *, int> method_bind_map;
+	Map<GDScriptFunction *, int> lambdas_map;
 
 	// Lists since these can be nested.
 	List<int> if_jmp_addrs;
@@ -293,6 +294,15 @@ class GDScriptByteCodeGenerator : public GDScriptCodeGenerator {
 		return pos;
 	}
 
+	int get_lambda_function_pos(GDScriptFunction *p_lambda_function) {
+		if (lambdas_map.has(p_lambda_function)) {
+			return lambdas_map[p_lambda_function];
+		}
+		int pos = lambdas_map.size();
+		lambdas_map[p_lambda_function] = pos;
+		return pos;
+	}
+
 	void alloc_ptrcall(int p_params) {
 		if (p_params >= ptrcall_max) {
 			ptrcall_max = p_params;
@@ -386,6 +396,10 @@ class GDScriptByteCodeGenerator : public GDScriptCodeGenerator {
 		opcodes.push_back(get_method_bind_pos(p_method));
 	}
 
+	void append(GDScriptFunction *p_lambda_function) {
+		opcodes.push_back(get_lambda_function_pos(p_lambda_function));
+	}
+
 	void patch_jump(int p_address) {
 		opcodes.write[p_address] = opcodes.size();
 	}
@@ -452,6 +466,7 @@ public:
 	virtual void write_call_self(const Address &p_target, const StringName &p_function_name, const Vector<Address> &p_arguments) override;
 	virtual void write_call_self_async(const Address &p_target, const StringName &p_function_name, const Vector<Address> &p_arguments) override;
 	virtual void write_call_script_function(const Address &p_target, const Address &p_base, const StringName &p_function_name, const Vector<Address> &p_arguments) override;
+	virtual void write_lambda(const Address &p_target, GDScriptFunction *p_function, const Vector<Address> &p_captures) override;
 	virtual void write_construct(const Address &p_target, Variant::Type p_type, const Vector<Address> &p_arguments) override;
 	virtual void write_construct_array(const Address &p_target, const Vector<Address> &p_arguments) override;
 	virtual void write_construct_typed_array(const Address &p_target, const GDScriptDataType &p_element_type, const Vector<Address> &p_arguments) override;

modules/gdscript/gdscript_codegen.h

@@ -127,6 +127,7 @@ public:
 	virtual void write_call_self(const Address &p_target, const StringName &p_function_name, const Vector<Address> &p_arguments) = 0;
 	virtual void write_call_self_async(const Address &p_target, const StringName &p_function_name, const Vector<Address> &p_arguments) = 0;
 	virtual void write_call_script_function(const Address &p_target, const Address &p_base, const StringName &p_function_name, const Vector<Address> &p_arguments) = 0;
+	virtual void write_lambda(const Address &p_target, GDScriptFunction *p_function, const Vector<Address> &p_captures) = 0;
 	virtual void write_construct(const Address &p_target, Variant::Type p_type, const Vector<Address> &p_arguments) = 0;
 	virtual void write_construct_array(const Address &p_target, const Vector<Address> &p_arguments) = 0;
 	virtual void write_construct_typed_array(const Address &p_target, const GDScriptDataType &p_element_type, const Vector<Address> &p_arguments) = 0;

modules/gdscript/gdscript_compiler.cpp

@@ -1091,6 +1091,34 @@ GDScriptCodeGenerator::Address GDScriptCompiler::_parse_expression(CodeGen &code
 			}
 			return GDScriptCodeGenerator::Address(); // Assignment does not return a value.
 		} break;
+		case GDScriptParser::Node::LAMBDA: {
+			const GDScriptParser::LambdaNode *lambda = static_cast<const GDScriptParser::LambdaNode *>(p_expression);
+			GDScriptCodeGenerator::Address result = codegen.add_temporary(_gdtype_from_datatype(lambda->get_datatype()));
+
+			Vector<GDScriptCodeGenerator::Address> captures;
+			captures.resize(lambda->captures.size());
+			for (int i = 0; i < lambda->captures.size(); i++) {
+				captures.write[i] = _parse_expression(codegen, r_error, lambda->captures[i]);
+				if (r_error) {
+					return GDScriptCodeGenerator::Address();
+				}
+			}
+
+			GDScriptFunction *function = _parse_function(r_error, codegen.script, codegen.class_node, lambda->function, false, true);
+			if (r_error) {
+				return GDScriptCodeGenerator::Address();
+			}
+
+			gen->write_lambda(result, function, captures);
+
+			for (int i = 0; i < captures.size(); i++) {
+				if (captures[i].mode == GDScriptCodeGenerator::Address::TEMPORARY) {
+					gen->pop_temporary();
+				}
+			}
+
+			return result;
+		} break;
 		default: {
 			ERR_FAIL_V_MSG(GDScriptCodeGenerator::Address(), "Bug in bytecode compiler, unexpected node in parse tree while parsing expression."); // Unreachable code.
 		} break;
@@ -1804,8 +1832,8 @@ Error GDScriptCompiler::_parse_block(CodeGen &codegen, const GDScriptParser::Sui
 	return OK;
 }
 
-Error GDScriptCompiler::_parse_function(GDScript *p_script, const GDScriptParser::ClassNode *p_class, const GDScriptParser::FunctionNode *p_func, bool p_for_ready) {
+GDScriptFunction *GDScriptCompiler::_parse_function(Error &r_error, GDScript *p_script, const GDScriptParser::ClassNode *p_class, const GDScriptParser::FunctionNode *p_func, bool p_for_ready, bool p_for_lambda) {
-	Error error = OK;
+	r_error = OK;
 	CodeGen codegen;
 	codegen.generator = memnew(GDScriptByteCodeGenerator);
 
@@ -1822,7 +1850,11 @@ Error GDScriptCompiler::_parse_function(GDScript *p_script, const GDScriptParser
 	return_type.builtin_type = Variant::NIL;
 
 	if (p_func) {
-		func_name = p_func->identifier->name;
+		if (p_func->identifier) {
+			func_name = p_func->identifier->name;
+		} else {
+			func_name = "<anonymous lambda>";
+		}
 		is_static = p_func->is_static;
 		rpc_mode = p_func->rpc_mode;
 		return_type = _gdtype_from_datatype(p_func->get_datatype(), p_script);
@@ -1853,11 +1885,11 @@ Error GDScriptCompiler::_parse_function(GDScript *p_script, const GDScriptParser
 	}
 
 	// Parse initializer if applies.
-	bool is_implicit_initializer = !p_for_ready && !p_func;
+	bool is_implicit_initializer = !p_for_ready && !p_func && !p_for_lambda;
-	bool is_initializer = p_func && String(p_func->identifier->name) == GDScriptLanguage::get_singleton()->strings._init;
+	bool is_initializer = p_func && !p_for_lambda && String(p_func->identifier->name) == GDScriptLanguage::get_singleton()->strings._init;
-	bool is_for_ready = p_for_ready || (p_func && String(p_func->identifier->name) == "_ready");
+	bool is_for_ready = p_for_ready || (p_func && !p_for_lambda && String(p_func->identifier->name) == "_ready");
 
-	if (is_implicit_initializer || is_for_ready) {
+	if (!p_for_lambda && (is_implicit_initializer || is_for_ready)) {
 		// Initialize class fields.
 		for (int i = 0; i < p_class->members.size(); i++) {
 			if (p_class->members[i].type != GDScriptParser::ClassNode::Member::VARIABLE) {
@@ -1884,10 +1916,10 @@ Error GDScriptCompiler::_parse_function(GDScript *p_script, const GDScriptParser
 						codegen.generator->write_construct_array(dst_address, Vector<GDScriptCodeGenerator::Address>());
 					}
 				}
-				GDScriptCodeGenerator::Address src_address = _parse_expression(codegen, error, field->initializer, false, true);
+				GDScriptCodeGenerator::Address src_address = _parse_expression(codegen, r_error, field->initializer, false, true);
-				if (error) {
+				if (r_error) {
 					memdelete(codegen.generator);
-					return error;
+					return nullptr;
 				}
 
 				codegen.generator->write_assign(dst_address, src_address);
@@ -1914,10 +1946,10 @@ Error GDScriptCompiler::_parse_function(GDScript *p_script, const GDScriptParser
 			codegen.generator->start_parameters();
 			for (int i = p_func->parameters.size() - optional_parameters; i < p_func->parameters.size(); i++) {
 				const GDScriptParser::ParameterNode *parameter = p_func->parameters[i];
-				GDScriptCodeGenerator::Address src_addr = _parse_expression(codegen, error, parameter->default_value, true);
+				GDScriptCodeGenerator::Address src_addr = _parse_expression(codegen, r_error, parameter->default_value, true);
-				if (error) {
+				if (r_error) {
 					memdelete(codegen.generator);
-					return error;
+					return nullptr;
 				}
 				GDScriptCodeGenerator::Address dst_addr = codegen.parameters[parameter->identifier->name];
 				codegen.generator->write_assign_default_parameter(dst_addr, src_addr);
@@ -1928,10 +1960,10 @@ Error GDScriptCompiler::_parse_function(GDScript *p_script, const GDScriptParser
 			codegen.generator->end_parameters();
 		}
 
-		Error err = _parse_block(codegen, p_func->body);
+		r_error = _parse_block(codegen, p_func->body);
-		if (err) {
+		if (r_error) {
 			memdelete(codegen.generator);
-			return err;
+			return nullptr;
 		}
 	}
 
@@ -1957,6 +1989,10 @@ Error GDScriptCompiler::_parse_function(GDScript *p_script, const GDScriptParser
 			signature += "::" + String(func_name);
 		}
 
+		if (p_for_lambda) {
+			signature += "(lambda)";
+		}
+
 		codegen.generator->set_signature(signature);
 	}
 #endif
@@ -1964,8 +2000,10 @@ Error GDScriptCompiler::_parse_function(GDScript *p_script, const GDScriptParser
 	if (p_func) {
 		codegen.generator->set_initial_line(p_func->start_line);
 #ifdef TOOLS_ENABLED
-		p_script->member_lines[func_name] = p_func->start_line;
+		if (!p_for_lambda) {
-		p_script->doc_functions[func_name] = p_func->doc_description;
+			p_script->member_lines[func_name] = p_func->start_line;
+			p_script->doc_functions[func_name] = p_func->doc_description;
+		}
 #endif
 	} else {
 		codegen.generator->set_initial_line(0);
@@ -1994,11 +2032,13 @@ Error GDScriptCompiler::_parse_function(GDScript *p_script, const GDScriptParser
 #endif
 	}
 
-	p_script->member_functions[func_name] = gd_function;
+	if (!p_for_lambda) {
+		p_script->member_functions[func_name] = gd_function;
+	}
 
 	memdelete(codegen.generator);
 
-	return OK;
+	return gd_function;
 }
 
 Error GDScriptCompiler::_parse_setter_getter(GDScript *p_script, const GDScriptParser::ClassNode *p_class, const GDScriptParser::VariableNode *p_variable, bool p_is_setter) {
@@ -2391,7 +2431,8 @@ Error GDScriptCompiler::_parse_class_blocks(GDScript *p_script, const GDScriptPa
 			if (!has_ready && function->identifier->name == "_ready") {
 				has_ready = true;
 			}
-			Error err = _parse_function(p_script, p_class, function);
+			Error err = OK;
+			_parse_function(err, p_script, p_class, function);
 			if (err) {
 				return err;
 			}
@@ -2416,7 +2457,8 @@ Error GDScriptCompiler::_parse_class_blocks(GDScript *p_script, const GDScriptPa
 
 	{
 		// Create an implicit constructor in any case.
-		Error err = _parse_function(p_script, p_class, nullptr);
+		Error err = OK;
+		_parse_function(err, p_script, p_class, nullptr);
 		if (err) {
 			return err;
 		}
@@ -2424,7 +2466,8 @@ Error GDScriptCompiler::_parse_class_blocks(GDScript *p_script, const GDScriptPa
 
 	if (!has_ready && p_class->onready_used) {
 		//create a _ready constructor
-		Error err = _parse_function(p_script, p_class, nullptr, true);
+		Error err = OK;
+		_parse_function(err, p_script, p_class, nullptr, true);
 		if (err) {
 			return err;
 		}

modules/gdscript/gdscript_compiler.h

@@ -128,7 +128,7 @@ class GDScriptCompiler {
 	GDScriptCodeGenerator::Address _parse_match_pattern(CodeGen &codegen, Error &r_error, const GDScriptParser::PatternNode *p_pattern, const GDScriptCodeGenerator::Address &p_value_addr, const GDScriptCodeGenerator::Address &p_type_addr, const GDScriptCodeGenerator::Address &p_previous_test, bool p_is_first, bool p_is_nested);
 	void _add_locals_in_block(CodeGen &codegen, const GDScriptParser::SuiteNode *p_block);
 	Error _parse_block(CodeGen &codegen, const GDScriptParser::SuiteNode *p_block, bool p_add_locals = true);
-	Error _parse_function(GDScript *p_script, const GDScriptParser::ClassNode *p_class, const GDScriptParser::FunctionNode *p_func, bool p_for_ready = false);
+	GDScriptFunction *_parse_function(Error &r_error, GDScript *p_script, const GDScriptParser::ClassNode *p_class, const GDScriptParser::FunctionNode *p_func, bool p_for_ready = false, bool p_for_lambda = false);
 	Error _parse_setter_getter(GDScript *p_script, const GDScriptParser::ClassNode *p_class, const GDScriptParser::VariableNode *p_variable, bool p_is_setter);
 	Error _parse_class_level(GDScript *p_script, const GDScriptParser::ClassNode *p_class, bool p_keep_state);
 	Error _parse_class_blocks(GDScript *p_script, const GDScriptParser::ClassNode *p_class, bool p_keep_state);

modules/gdscript/gdscript_disassembler.cpp

@@ -721,7 +721,7 @@ void GDScriptFunction::disassemble(const Vector<String> &p_code_lines) const {
 				text += "await ";
 				text += DADDR(1);
 
-				incr += 2;
+				incr = 2;
 			} break;
 			case OPCODE_AWAIT_RESUME: {
 				text += "await resume ";
@@ -729,6 +729,25 @@ void GDScriptFunction::disassemble(const Vector<String> &p_code_lines) const {
 
 				incr = 2;
 			} break;
+			case OPCODE_CREATE_LAMBDA: {
+				int captures_count = _code_ptr[ip + 1 + instr_var_args];
+				GDScriptFunction *lambda = _lambdas_ptr[_code_ptr[ip + 2 + instr_var_args]];
+
+				text += DADDR(1 + captures_count);
+				text += "create lambda from ";
+				text += lambda->name.operator String();
+				text += "function, captures (";
+
+				for (int i = 0; i < captures_count; i++) {
+					if (i > 0) {
+						text += ", ";
+					}
+					text += DADDR(1 + i);
+				}
+				text += ")";
+
+				incr = 3 + captures_count;
+			} break;
 			case OPCODE_JUMP: {
 				text += "jump ";
 				text += itos(_code_ptr[ip + 1]);

modules/gdscript/gdscript_function.cpp

@@ -150,6 +150,10 @@ GDScriptFunction::GDScriptFunction() {
 }
 
 GDScriptFunction::~GDScriptFunction() {
+	for (int i = 0; i < lambdas.size(); i++) {
+		memdelete(lambdas[i]);
+	}
+
 #ifdef DEBUG_ENABLED
 
 	MutexLock lock(GDScriptLanguage::get_singleton()->lock);

modules/gdscript/gdscript_function.h

@@ -301,6 +301,7 @@ public:
 		OPCODE_CALL_PTRCALL_PACKED_COLOR_ARRAY,
 		OPCODE_AWAIT,
 		OPCODE_AWAIT_RESUME,
+		OPCODE_CREATE_LAMBDA,
 		OPCODE_JUMP,
 		OPCODE_JUMP_IF,
 		OPCODE_JUMP_IF_NOT,
@@ -459,6 +460,8 @@ private:
 	const GDScriptUtilityFunctions::FunctionPtr *_gds_utilities_ptr = nullptr;
 	int _methods_count = 0;
 	MethodBind **_methods_ptr = nullptr;
+	int _lambdas_count = 0;
+	GDScriptFunction **_lambdas_ptr = nullptr;
 	const int *_code_ptr = nullptr;
 	int _code_size = 0;
 	int _argument_count = 0;
@@ -488,6 +491,7 @@ private:
 	Vector<Variant::ValidatedUtilityFunction> utilities;
 	Vector<GDScriptUtilityFunctions::FunctionPtr> gds_utilities;
 	Vector<MethodBind *> methods;
+	Vector<GDScriptFunction *> lambdas;
 	Vector<int> code;
 	Vector<GDScriptDataType> argument_types;
 	GDScriptDataType return_type;

modules/gdscript/gdscript_lambda_callable.cpp

@@ -0,0 +1,95 @@
+/*************************************************************************/
+/*  gdscript_lambda_callable.cpp                                         */
+/*************************************************************************/
+/*                       This file is part of:                           */
+/*                           GODOT ENGINE                                */
+/*                      https://godotengine.org                          */
+/*************************************************************************/
+/* Copyright (c) 2007-2021 Juan Linietsky, Ariel Manzur.                 */
+/* Copyright (c) 2014-2021 Godot Engine contributors (cf. AUTHORS.md).   */
+/*                                                                       */
+/* Permission is hereby granted, free of charge, to any person obtaining */
+/* a copy of this software and associated documentation files (the       */
+/* "Software"), to deal in the Software without restriction, including   */
+/* without limitation the rights to use, copy, modify, merge, publish,   */
+/* distribute, sublicense, and/or sell copies of the Software, and to    */
+/* permit persons to whom the Software is furnished to do so, subject to */
+/* the following conditions:                                             */
+/*                                                                       */
+/* The above copyright notice and this permission notice shall be        */
+/* included in all copies or substantial portions of the Software.       */
+/*                                                                       */
+/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,       */
+/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF    */
+/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.*/
+/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY  */
+/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,  */
+/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE     */
+/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                */
+/*************************************************************************/
+
+#include "gdscript_lambda_callable.h"
+
+#include "core/templates/hashfuncs.h"
+#include "gdscript.h"
+
+bool GDScriptLambdaCallable::compare_equal(const CallableCustom *p_a, const CallableCustom *p_b) {
+	// Lambda callables are only compared by reference.
+	return p_a == p_b;
+}
+
+bool GDScriptLambdaCallable::compare_less(const CallableCustom *p_a, const CallableCustom *p_b) {
+	// Lambda callables are only compared by reference.
+	return p_a < p_b;
+}
+
+uint32_t GDScriptLambdaCallable::hash() const {
+	return h;
+}
+
+String GDScriptLambdaCallable::get_as_text() const {
+	if (function->get_name() != StringName()) {
+		return function->get_name().operator String() + "(lambda)";
+	}
+	return "(anonymous lambda)";
+}
+
+CallableCustom::CompareEqualFunc GDScriptLambdaCallable::get_compare_equal_func() const {
+	return compare_equal;
+}
+
+CallableCustom::CompareLessFunc GDScriptLambdaCallable::get_compare_less_func() const {
+	return compare_less;
+}
+
+ObjectID GDScriptLambdaCallable::get_object() const {
+	return script->get_instance_id();
+}
+
+void GDScriptLambdaCallable::call(const Variant **p_arguments, int p_argcount, Variant &r_return_value, Callable::CallError &r_call_error) const {
+	int captures_amount = captures.size();
+
+	if (captures_amount > 0) {
+		Vector<const Variant *> args;
+		args.resize(p_argcount + captures_amount);
+		for (int i = 0; i < captures_amount; i++) {
+			args.write[i] = &captures[i];
+		}
+		for (int i = 0; i < p_argcount; i++) {
+			args.write[i + captures_amount] = p_arguments[i];
+		}
+
+		r_return_value = function->call(nullptr, args.ptrw(), args.size(), r_call_error);
+		r_call_error.argument -= captures_amount;
+	} else {
+		r_return_value = function->call(nullptr, p_arguments, p_argcount, r_call_error);
+	}
+}
+
+GDScriptLambdaCallable::GDScriptLambdaCallable(Ref<GDScript> p_script, GDScriptFunction *p_function, const Vector<Variant> &p_captures) {
+	script = p_script;
+	function = p_function;
+	captures = p_captures;
+
+	h = (uint32_t)hash_djb2_one_64((uint64_t)this);
+}

modules/gdscript/gdscript_lambda_callable.h

@@ -0,0 +1,65 @@
+/*************************************************************************/
+/*  gdscript_lambda_callable.h                                           */
+/*************************************************************************/
+/*                       This file is part of:                           */
+/*                           GODOT ENGINE                                */
+/*                      https://godotengine.org                          */
+/*************************************************************************/
+/* Copyright (c) 2007-2021 Juan Linietsky, Ariel Manzur.                 */
+/* Copyright (c) 2014-2021 Godot Engine contributors (cf. AUTHORS.md).   */
+/*                                                                       */
+/* Permission is hereby granted, free of charge, to any person obtaining */
+/* a copy of this software and associated documentation files (the       */
+/* "Software"), to deal in the Software without restriction, including   */
+/* without limitation the rights to use, copy, modify, merge, publish,   */
+/* distribute, sublicense, and/or sell copies of the Software, and to    */
+/* permit persons to whom the Software is furnished to do so, subject to */
+/* the following conditions:                                             */
+/*                                                                       */
+/* The above copyright notice and this permission notice shall be        */
+/* included in all copies or substantial portions of the Software.       */
+/*                                                                       */
+/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,       */
+/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF    */
+/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.*/
+/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY  */
+/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,  */
+/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE     */
+/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                */
+/*************************************************************************/
+
+#ifndef GDSCRIPT_LAMBDA_CALLABLE
+#define GDSCRIPT_LAMBDA_CALLABLE
+
+#include "core/object/reference.h"
+#include "core/templates/vector.h"
+#include "core/variant/callable.h"
+#include "core/variant/variant.h"
+
+class GDScript;
+class GDScriptFunction;
+class GDScriptInstance;
+
+class GDScriptLambdaCallable : public CallableCustom {
+	GDScriptFunction *function = nullptr;
+	Ref<GDScript> script;
+	uint32_t h;
+
+	Vector<Variant> captures;
+
+	static bool compare_equal(const CallableCustom *p_a, const CallableCustom *p_b);
+	static bool compare_less(const CallableCustom *p_a, const CallableCustom *p_b);
+
+public:
+	uint32_t hash() const override;
+	String get_as_text() const override;
+	CompareEqualFunc get_compare_equal_func() const override;
+	CompareLessFunc get_compare_less_func() const override;
+	ObjectID get_object() const override;
+	void call(const Variant **p_arguments, int p_argcount, Variant &r_return_value, Callable::CallError &r_call_error) const override;
+
+	GDScriptLambdaCallable(Ref<GDScript> p_script, GDScriptFunction *p_function, const Vector<Variant> &p_captures);
+	virtual ~GDScriptLambdaCallable() = default;
+};
+
+#endif // GDSCRIPT_LAMBDA_CALLABLE

modules/gdscript/gdscript_parser.cpp

@@ -402,6 +402,8 @@ Error GDScriptParser::parse(const String &p_source_code, const String &p_script_
 }
 
 GDScriptTokenizer::Token GDScriptParser::advance() {
+	lambda_ended = false; // Empty marker since we're past the end in any case.
+
 	if (current.type == GDScriptTokenizer::Token::TK_EOF) {
 		ERR_FAIL_COND_V_MSG(current.type == GDScriptTokenizer::Token::TK_EOF, current, "GDScript parser bug: Trying to advance past the end of stream.");
 	}
@@ -428,7 +430,7 @@ bool GDScriptParser::match(GDScriptTokenizer::Token::Type p_token_type) {
 	return true;
 }
 
-bool GDScriptParser::check(GDScriptTokenizer::Token::Type p_token_type) {
+bool GDScriptParser::check(GDScriptTokenizer::Token::Type p_token_type) const {
 	if (p_token_type == GDScriptTokenizer::Token::IDENTIFIER) {
 		return current.is_identifier();
 	}
@@ -443,7 +445,7 @@ bool GDScriptParser::consume(GDScriptTokenizer::Token::Type p_token_type, const
 	return false;
 }
 
-bool GDScriptParser::is_at_end() {
+bool GDScriptParser::is_at_end() const {
 	return check(GDScriptTokenizer::Token::TK_EOF);
 }
 
@@ -494,16 +496,34 @@ void GDScriptParser::pop_multiline() {
 	tokenizer.set_multiline_mode(multiline_stack.size() > 0 ? multiline_stack.back()->get() : false);
 }
 
-bool GDScriptParser::is_statement_end() {
+bool GDScriptParser::is_statement_end_token() const {
 	return check(GDScriptTokenizer::Token::NEWLINE) || check(GDScriptTokenizer::Token::SEMICOLON) || check(GDScriptTokenizer::Token::TK_EOF);
 }
 
+bool GDScriptParser::is_statement_end() const {
+	return lambda_ended || in_lambda || is_statement_end_token();
+}
+
 void GDScriptParser::end_statement(const String &p_context) {
 	bool found = false;
 	while (is_statement_end() && !is_at_end()) {
 		// Remove sequential newlines/semicolons.
+		if (is_statement_end_token()) {
+			// Only consume if this is an actual token.
+			advance();
+		} else if (lambda_ended) {
+			lambda_ended = false; // Consume this "token".
+			found = true;
+			break;
+		} else {
+			if (!found) {
+				lambda_ended = true; // Mark the lambda as done since we found something else to end the statement.
+				found = true;
+			}
+			break;
+		}
+
 		found = true;
-		advance();
 	}
 	if (!found && !is_at_end()) {
 		push_error(vformat(R"(Expected end of statement after %s, found "%s" instead.)", p_context, current.get_name()));
@@ -1182,6 +1202,51 @@ GDScriptParser::EnumNode *GDScriptParser::parse_enum() {
 	return enum_node;
 }
 
+void GDScriptParser::parse_function_signature(FunctionNode *p_function, SuiteNode *p_body, const String &p_type) {
+	if (!check(GDScriptTokenizer::Token::PARENTHESIS_CLOSE) && !is_at_end()) {
+		bool default_used = false;
+		do {
+			if (check(GDScriptTokenizer::Token::PARENTHESIS_CLOSE)) {
+				// Allow for trailing comma.
+				break;
+			}
+			ParameterNode *parameter = parse_parameter();
+			if (parameter == nullptr) {
+				break;
+			}
+			if (parameter->default_value != nullptr) {
+				default_used = true;
+			} else {
+				if (default_used) {
+					push_error("Cannot have a mandatory parameters after optional parameters.");
+					continue;
+				}
+			}
+			if (p_function->parameters_indices.has(parameter->identifier->name)) {
+				push_error(vformat(R"(Parameter with name "%s" was already declared for this %s.)", parameter->identifier->name, p_type));
+			} else {
+				p_function->parameters_indices[parameter->identifier->name] = p_function->parameters.size();
+				p_function->parameters.push_back(parameter);
+				p_body->add_local(parameter, current_function);
+			}
+		} while (match(GDScriptTokenizer::Token::COMMA));
+	}
+
+	pop_multiline();
+	consume(GDScriptTokenizer::Token::PARENTHESIS_CLOSE, vformat(R"*(Expected closing ")" after %s parameters.)*", p_type));
+
+	if (match(GDScriptTokenizer::Token::FORWARD_ARROW)) {
+		make_completion_context(COMPLETION_TYPE_NAME_OR_VOID, p_function);
+		p_function->return_type = parse_type(true);
+		if (p_function->return_type == nullptr) {
+			push_error(R"(Expected return type or "void" after "->".)");
+		}
+	}
+
+	// TODO: Improve token consumption so it synchronizes to a statement boundary. This way we can get into the function body with unrecognized tokens.
+	consume(GDScriptTokenizer::Token::COLON, vformat(R"(Expected ":" after %s declaration.)", p_type));
+}
+
 GDScriptParser::FunctionNode *GDScriptParser::parse_function() {
 	bool _static = false;
 	if (previous.type == GDScriptTokenizer::Token::STATIC) {
@@ -1205,55 +1270,13 @@ GDScriptParser::FunctionNode *GDScriptParser::parse_function() {
 	function->identifier = parse_identifier();
 	function->is_static = _static;
 
-	push_multiline(true);
-	consume(GDScriptTokenizer::Token::PARENTHESIS_OPEN, R"(Expected opening "(" after function name.)");
-
 	SuiteNode *body = alloc_node<SuiteNode>();
 	SuiteNode *previous_suite = current_suite;
 	current_suite = body;
 
-	if (!check(GDScriptTokenizer::Token::PARENTHESIS_CLOSE) && !is_at_end()) {
+	push_multiline(true);
-		bool default_used = false;
+	consume(GDScriptTokenizer::Token::PARENTHESIS_OPEN, R"(Expected opening "(" after function name.)");
-		do {
+	parse_function_signature(function, body, "function");
-			if (check(GDScriptTokenizer::Token::PARENTHESIS_CLOSE)) {
-				// Allow for trailing comma.
-				break;
-			}
-			ParameterNode *parameter = parse_parameter();
-			if (parameter == nullptr) {
-				break;
-			}
-			if (parameter->default_value != nullptr) {
-				default_used = true;
-			} else {
-				if (default_used) {
-					push_error("Cannot have a mandatory parameters after optional parameters.");
-					continue;
-				}
-			}
-			if (function->parameters_indices.has(parameter->identifier->name)) {
-				push_error(vformat(R"(Parameter with name "%s" was already declared for this function.)", parameter->identifier->name));
-			} else {
-				function->parameters_indices[parameter->identifier->name] = function->parameters.size();
-				function->parameters.push_back(parameter);
-				body->add_local(parameter);
-			}
-		} while (match(GDScriptTokenizer::Token::COMMA));
-	}
-
-	pop_multiline();
-	consume(GDScriptTokenizer::Token::PARENTHESIS_CLOSE, R"*(Expected closing ")" after function parameters.)*");
-
-	if (match(GDScriptTokenizer::Token::FORWARD_ARROW)) {
-		make_completion_context(COMPLETION_TYPE_NAME_OR_VOID, function);
-		function->return_type = parse_type(true);
-		if (function->return_type == nullptr) {
-			push_error(R"(Expected return type or "void" after "->".)");
-		}
-	}
-
-	// TODO: Improve token consumption so it synchronizes to a statement boundary. This way we can get into the function body with unrecognized tokens.
-	consume(GDScriptTokenizer::Token::COLON, R"(Expected ":" after function declaration.)");
 
 	current_suite = previous_suite;
 	function->body = parse_suite("function declaration", body);
@@ -1339,29 +1362,34 @@ bool GDScriptParser::register_annotation(const MethodInfo &p_info, uint32_t p_ta
 	return true;
 }
 
-GDScriptParser::SuiteNode *GDScriptParser::parse_suite(const String &p_context, SuiteNode *p_suite) {
+GDScriptParser::SuiteNode *GDScriptParser::parse_suite(const String &p_context, SuiteNode *p_suite, bool p_for_lambda) {
 	SuiteNode *suite = p_suite != nullptr ? p_suite : alloc_node<SuiteNode>();
 	suite->parent_block = current_suite;
+	suite->parent_function = current_function;
 	current_suite = suite;
 
 	bool multiline = false;
 
-	if (check(GDScriptTokenizer::Token::NEWLINE)) {
+	if (match(GDScriptTokenizer::Token::NEWLINE)) {
 		multiline = true;
 	}
 
 	if (multiline) {
-		consume(GDScriptTokenizer::Token::NEWLINE, vformat(R"(Expected newline after %s.)", p_context));
-
 		if (!consume(GDScriptTokenizer::Token::INDENT, vformat(R"(Expected indented block after %s.)", p_context))) {
 			current_suite = suite->parent_block;
 			return suite;
 		}
 	}
 
+	int error_count = 0;
+
 	do {
 		Node *statement = parse_statement();
 		if (statement == nullptr) {
+			if (error_count++ > 100) {
+				push_error("Too many statement errors.", suite);
+				break;
+			}
 			continue;
 		}
 		suite->statements.push_back(statement);
@@ -1374,7 +1402,7 @@ GDScriptParser::SuiteNode *GDScriptParser::parse_suite(const String &p_context,
 				if (local.type != SuiteNode::Local::UNDEFINED) {
 					push_error(vformat(R"(There is already a %s named "%s" declared in this scope.)", local.get_name(), variable->identifier->name));
 				}
-				current_suite->add_local(variable);
+				current_suite->add_local(variable, current_function);
 				break;
 			}
 			case Node::CONSTANT: {
@@ -1389,19 +1417,29 @@ GDScriptParser::SuiteNode *GDScriptParser::parse_suite(const String &p_context,
 					}
 					push_error(vformat(R"(There is already a %s named "%s" declared in this scope.)", name, constant->identifier->name));
 				}
-				current_suite->add_local(constant);
+				current_suite->add_local(constant, current_function);
 				break;
 			}
 			default:
 				break;
 		}
 
-	} while (multiline && !check(GDScriptTokenizer::Token::DEDENT) && !is_at_end());
+	} while (multiline && !check(GDScriptTokenizer::Token::DEDENT) && !lambda_ended && !is_at_end());
 
 	if (multiline) {
-		consume(GDScriptTokenizer::Token::DEDENT, vformat(R"(Missing unindent at the end of %s.)", p_context));
+		if (!lambda_ended) {
+			consume(GDScriptTokenizer::Token::DEDENT, vformat(R"(Missing unindent at the end of %s.)", p_context));
+
+		} else {
+			match(GDScriptTokenizer::Token::DEDENT);
+		}
+	} else if (previous.type == GDScriptTokenizer::Token::SEMICOLON) {
+		consume(GDScriptTokenizer::Token::NEWLINE, vformat(R"(Expected newline after ";" at the end of %s.)", p_context));
 	}
 
+	if (p_for_lambda) {
+		lambda_ended = true;
+	}
 	current_suite = suite->parent_block;
 	return suite;
 }
@@ -1458,6 +1496,10 @@ GDScriptParser::Node *GDScriptParser::parse_statement() {
 					push_error(R"(Constructor cannot return a value.)");
 				}
 				n_return->return_value = parse_expression(false);
+			} else if (in_lambda && !is_statement_end_token()) {
+				// Try to parse it anyway as this might not be the statement end in a lambda.
+				// If this fails the expression will be nullptr, but that's the same as no return, so it's fine.
+				n_return->return_value = parse_expression(false);
 			}
 			result = n_return;
 
@@ -1486,10 +1528,18 @@ GDScriptParser::Node *GDScriptParser::parse_statement() {
 		default: {
 			// Expression statement.
 			ExpressionNode *expression = parse_expression(true); // Allow assignment here.
+			bool has_ended_lambda = false;
 			if (expression == nullptr) {
-				push_error(vformat(R"(Expected statement, found "%s" instead.)", previous.get_name()));
+				if (in_lambda) {
+					// If it's not a valid expression beginning, it might be the continuation of the outer expression where this lambda is.
+					lambda_ended = true;
+					has_ended_lambda = true;
+				} else {
+					push_error(vformat(R"(Expected statement, found "%s" instead.)", previous.get_name()));
+				}
 			}
 			end_statement("expression");
+			lambda_ended = lambda_ended || has_ended_lambda;
 			result = expression;
 
 #ifdef DEBUG_ENABLED
@@ -1513,7 +1563,7 @@ GDScriptParser::Node *GDScriptParser::parse_statement() {
 	if (unreachable && result != nullptr) {
 		current_suite->has_unreachable_code = true;
 		if (current_function) {
-			push_warning(result, GDScriptWarning::UNREACHABLE_CODE, current_function->identifier->name);
+			push_warning(result, GDScriptWarning::UNREACHABLE_CODE, current_function->identifier ? current_function->identifier->name : "<anonymous lambda>");
 		} else {
 			// TODO: Properties setters and getters with unreachable code are not being warned
 		}
@@ -1598,7 +1648,7 @@ GDScriptParser::ForNode *GDScriptParser::parse_for() {
 
 	SuiteNode *suite = alloc_node<SuiteNode>();
 	if (n_for->variable) {
-		suite->add_local(SuiteNode::Local(n_for->variable));
+		suite->add_local(SuiteNode::Local(n_for->variable, current_function));
 	}
 	suite->parent_for = n_for;
 
@@ -1753,7 +1803,7 @@ GDScriptParser::MatchBranchNode *GDScriptParser::parse_match_branch() {
 		branch->patterns[0]->binds.get_key_list(&binds);
 
 		for (List<StringName>::Element *E = binds.front(); E != nullptr; E = E->next()) {
-			SuiteNode::Local local(branch->patterns[0]->binds[E->get()]);
+			SuiteNode::Local local(branch->patterns[0]->binds[E->get()], current_function);
 			suite->add_local(local);
 		}
 	}
@@ -1953,7 +2003,7 @@ GDScriptParser::ExpressionNode *GDScriptParser::parse_precedence(Precedence p_pr
 	// Completion can appear whenever an expression is expected.
 	make_completion_context(COMPLETION_IDENTIFIER, nullptr);
 
-	GDScriptTokenizer::Token token = advance();
+	GDScriptTokenizer::Token token = current;
 	ParseFunction prefix_rule = get_rule(token.type)->prefix;
 
 	if (prefix_rule == nullptr) {
@@ -1961,6 +2011,8 @@ GDScriptParser::ExpressionNode *GDScriptParser::parse_precedence(Precedence p_pr
 		return nullptr;
 	}
 
+	advance(); // Only consume the token if there's a valid rule.
+
 	ExpressionNode *previous_operand = (this->*prefix_rule)(nullptr, p_can_assign);
 
 	while (p_precedence <= get_rule(current.type)->precedence) {
@@ -2002,6 +2054,8 @@ GDScriptParser::ExpressionNode *GDScriptParser::parse_identifier(ExpressionNode
 
 	if (current_suite != nullptr && current_suite->has_local(identifier->name)) {
 		const SuiteNode::Local &declaration = current_suite->get_local(identifier->name);
+
+		identifier->source_function = declaration.source_function;
 		switch (declaration.type) {
 			case SuiteNode::Local::CONSTANT:
 				identifier->source = IdentifierNode::LOCAL_CONSTANT;
@@ -2055,6 +2109,9 @@ GDScriptParser::ExpressionNode *GDScriptParser::parse_self(ExpressionNode *p_pre
 	if (current_function && current_function->is_static) {
 		push_error(R"(Cannot use "self" inside a static function.)");
 	}
+	if (in_lambda) {
+		push_error(R"(Cannot use "self" inside a lambda.)");
+	}
 	SelfNode *self = alloc_node<SelfNode>();
 	self->current_class = current_class;
 	return self;
@@ -2488,7 +2545,7 @@ GDScriptParser::ExpressionNode *GDScriptParser::parse_attribute(ExpressionNode *
 
 	if (for_completion) {
 		bool is_builtin = false;
-		if (p_previous_operand->type == Node::IDENTIFIER) {
+		if (p_previous_operand && p_previous_operand->type == Node::IDENTIFIER) {
 			const IdentifierNode *id = static_cast<const IdentifierNode *>(p_previous_operand);
 			Variant::Type builtin_type = get_builtin_type(id->name);
 			if (builtin_type < Variant::VARIANT_MAX) {
@@ -2675,6 +2732,65 @@ GDScriptParser::ExpressionNode *GDScriptParser::parse_preload(ExpressionNode *p_
 	return preload;
 }
 
+GDScriptParser::ExpressionNode *GDScriptParser::parse_lambda(ExpressionNode *p_previous_operand, bool p_can_assign) {
+	LambdaNode *lambda = alloc_node<LambdaNode>();
+	lambda->parent_function = current_function;
+	FunctionNode *function = alloc_node<FunctionNode>();
+	function->source_lambda = lambda;
+
+	function->is_static = current_function != nullptr ? current_function->is_static : false;
+
+	if (match(GDScriptTokenizer::Token::IDENTIFIER)) {
+		function->identifier = parse_identifier();
+	}
+
+	bool multiline_context = multiline_stack.back()->get();
+
+	// Reset the multiline stack since we don't want the multiline mode one in the lambda body.
+	push_multiline(false);
+	if (multiline_context) {
+		tokenizer.push_expression_indented_block();
+	}
+
+	push_multiline(true); // For the parameters.
+	if (function->identifier) {
+		consume(GDScriptTokenizer::Token::PARENTHESIS_OPEN, R"(Expected opening "(" after lambda name.)");
+	} else {
+		consume(GDScriptTokenizer::Token::PARENTHESIS_OPEN, R"(Expected opening "(" after "func".)");
+	}
+
+	FunctionNode *previous_function = current_function;
+	current_function = function;
+
+	SuiteNode *body = alloc_node<SuiteNode>();
+	SuiteNode *previous_suite = current_suite;
+	current_suite = body;
+
+	parse_function_signature(function, body, "lambda");
+
+	current_suite = previous_suite;
+
+	bool previous_in_lambda = in_lambda;
+	in_lambda = true;
+
+	function->body = parse_suite("lambda declaration", body, true);
+
+	pop_multiline();
+
+	if (multiline_context) {
+		// If we're in multiline mode, we want to skip the spurious DEDENT and NEWLINE tokens.
+		while (check(GDScriptTokenizer::Token::DEDENT) || check(GDScriptTokenizer::Token::INDENT) || check(GDScriptTokenizer::Token::NEWLINE)) {
+			current = tokenizer.scan(); // Not advance() since we don't want to change the previous token.
+		}
+		tokenizer.pop_expression_indented_block();
+	}
+
+	current_function = previous_function;
+	in_lambda = previous_in_lambda;
+	lambda->function = function;
+	return lambda;
+}
+
 GDScriptParser::ExpressionNode *GDScriptParser::parse_invalid_token(ExpressionNode *p_previous_operand, bool p_can_assign) {
 	// Just for better error messages.
 	GDScriptTokenizer::Token::Type invalid = previous.type;
@@ -3019,7 +3135,7 @@ GDScriptParser::ParseRule *GDScriptParser::get_rule(GDScriptTokenizer::Token::Ty
 		{ nullptr,                                          nullptr,                                        PREC_NONE }, // CONST,
 		{ nullptr,                                          nullptr,                                        PREC_NONE }, // ENUM,
 		{ nullptr,                                          nullptr,                                        PREC_NONE }, // EXTENDS,
-		{ nullptr,                                          nullptr,                                        PREC_NONE }, // FUNC,
+		{ &GDScriptParser::parse_lambda,                    nullptr,                                        PREC_NONE }, // FUNC,
 		{ nullptr,                                          &GDScriptParser::parse_binary_operator,      	PREC_CONTENT_TEST }, // IN,
 		{ nullptr,                                          &GDScriptParser::parse_binary_operator,      	PREC_TYPE_TEST }, // IS,
 		{ nullptr,                                          nullptr,                                        PREC_NONE }, // NAMESPACE,
@@ -3755,6 +3871,10 @@ void GDScriptParser::TreePrinter::print_dictionary(DictionaryNode *p_dictionary)
 }
 
 void GDScriptParser::TreePrinter::print_expression(ExpressionNode *p_expression) {
+	if (p_expression == nullptr) {
+		push_text("<invalid expression>");
+		return;
+	}
 	switch (p_expression->type) {
 		case Node::ARRAY:
 			print_array(static_cast<ArrayNode *>(p_expression));
@@ -3783,6 +3903,9 @@ void GDScriptParser::TreePrinter::print_expression(ExpressionNode *p_expression)
 		case Node::IDENTIFIER:
 			print_identifier(static_cast<IdentifierNode *>(p_expression));
 			break;
+		case Node::LAMBDA:
+			print_lambda(static_cast<LambdaNode *>(p_expression));
+			break;
 		case Node::LITERAL:
 			print_literal(static_cast<LiteralNode *>(p_expression));
 			break;
@@ -3842,12 +3965,17 @@ void GDScriptParser::TreePrinter::print_for(ForNode *p_for) {
 	decrease_indent();
 }
 
-void GDScriptParser::TreePrinter::print_function(FunctionNode *p_function) {
+void GDScriptParser::TreePrinter::print_function(FunctionNode *p_function, const String &p_context) {
 	for (const List<AnnotationNode *>::Element *E = p_function->annotations.front(); E != nullptr; E = E->next()) {
 		print_annotation(E->get());
 	}
-	push_text("Function ");
+	push_text(p_context);
-	print_identifier(p_function->identifier);
+	push_text(" ");
+	if (p_function->identifier) {
+		print_identifier(p_function->identifier);
+	} else {
+		push_text("<anonymous>");
+	}
 	push_text("( ");
 	for (int i = 0; i < p_function->parameters.size(); i++) {
 		if (i > 0) {
@@ -3901,6 +4029,18 @@ void GDScriptParser::TreePrinter::print_if(IfNode *p_if, bool p_is_elif) {
 	}
 }
 
+void GDScriptParser::TreePrinter::print_lambda(LambdaNode *p_lambda) {
+	print_function(p_lambda->function, "Lambda");
+	push_text("| captures [ ");
+	for (int i = 0; i < p_lambda->captures.size(); i++) {
+		if (i > 0) {
+			push_text(" , ");
+		}
+		push_text(p_lambda->captures[i]->name.operator String());
+	}
+	push_line(" ]");
+}
+
 void GDScriptParser::TreePrinter::print_literal(LiteralNode *p_literal) {
 	// Prefix for string types.
 	switch (p_literal->value.get_type()) {

modules/gdscript/gdscript_parser.h

@@ -76,6 +76,7 @@ public:
 	struct GetNodeNode;
 	struct IdentifierNode;
 	struct IfNode;
+	struct LambdaNode;
 	struct LiteralNode;
 	struct MatchNode;
 	struct MatchBranchNode;
@@ -267,6 +268,7 @@ public:
 			GET_NODE,
 			IDENTIFIER,
 			IF,
+			LAMBDA,
 			LITERAL,
 			MATCH,
 			MATCH_BRANCH,
@@ -728,6 +730,7 @@ public:
 		bool is_coroutine = false;
 		MultiplayerAPI::RPCMode rpc_mode = MultiplayerAPI::RPC_MODE_DISABLED;
 		MethodInfo info;
+		LambdaNode *source_lambda = nullptr;
 #ifdef TOOLS_ENABLED
 		Vector<Variant> default_arg_values;
 		String doc_description;
@@ -771,6 +774,7 @@ public:
 			VariableNode *variable_source;
 			IdentifierNode *bind_source;
 		};
+		FunctionNode *source_function = nullptr;
 
 		int usages = 0; // Useful for binds/iterator variable.
 
@@ -789,6 +793,21 @@ public:
 		}
 	};
 
+	struct LambdaNode : public ExpressionNode {
+		FunctionNode *function = nullptr;
+		FunctionNode *parent_function = nullptr;
+		Vector<IdentifierNode *> captures;
+		Map<StringName, int> captures_indices;
+
+		bool has_name() const {
+			return function && function->identifier;
+		}
+
+		LambdaNode() {
+			type = LAMBDA;
+		}
+	};
+
 	struct LiteralNode : public ExpressionNode {
 		Variant value;
 
@@ -942,6 +961,7 @@ public:
 				IdentifierNode *bind;
 			};
 			StringName name;
+			FunctionNode *source_function = nullptr;
 
 			int start_line = 0, end_line = 0;
 			int start_column = 0, end_column = 0;
@@ -951,10 +971,11 @@ public:
 			String get_name() const;
 
 			Local() {}
-			Local(ConstantNode *p_constant) {
+			Local(ConstantNode *p_constant, FunctionNode *p_source_function) {
 				type = CONSTANT;
 				constant = p_constant;
 				name = p_constant->identifier->name;
+				source_function = p_source_function;
 
 				start_line = p_constant->start_line;
 				end_line = p_constant->end_line;
@@ -963,10 +984,11 @@ public:
 				leftmost_column = p_constant->leftmost_column;
 				rightmost_column = p_constant->rightmost_column;
 			}
-			Local(VariableNode *p_variable) {
+			Local(VariableNode *p_variable, FunctionNode *p_source_function) {
 				type = VARIABLE;
 				variable = p_variable;
 				name = p_variable->identifier->name;
+				source_function = p_source_function;
 
 				start_line = p_variable->start_line;
 				end_line = p_variable->end_line;
@@ -975,10 +997,11 @@ public:
 				leftmost_column = p_variable->leftmost_column;
 				rightmost_column = p_variable->rightmost_column;
 			}
-			Local(ParameterNode *p_parameter) {
+			Local(ParameterNode *p_parameter, FunctionNode *p_source_function) {
 				type = PARAMETER;
 				parameter = p_parameter;
 				name = p_parameter->identifier->name;
+				source_function = p_source_function;
 
 				start_line = p_parameter->start_line;
 				end_line = p_parameter->end_line;
@@ -987,10 +1010,11 @@ public:
 				leftmost_column = p_parameter->leftmost_column;
 				rightmost_column = p_parameter->rightmost_column;
 			}
-			Local(IdentifierNode *p_identifier) {
+			Local(IdentifierNode *p_identifier, FunctionNode *p_source_function) {
 				type = FOR_VARIABLE;
 				bind = p_identifier;
 				name = p_identifier->name;
+				source_function = p_source_function;
 
 				start_line = p_identifier->start_line;
 				end_line = p_identifier->end_line;
@@ -1015,9 +1039,9 @@ public:
 		bool has_local(const StringName &p_name) const;
 		const Local &get_local(const StringName &p_name) const;
 		template <class T>
-		void add_local(T *p_local) {
+		void add_local(T *p_local, FunctionNode *p_source_function) {
 			locals_indices[p_local->identifier->name] = locals.size();
-			locals.push_back(Local(p_local));
+			locals.push_back(Local(p_local, p_source_function));
 		}
 		void add_local(const Local &p_local) {
 			locals_indices[p_local.name] = locals.size();
@@ -1191,6 +1215,8 @@ private:
 	CompletionCall completion_call;
 	List<CompletionCall> completion_call_stack;
 	bool passed_cursor = false;
+	bool in_lambda = false;
+	bool lambda_ended = false; // Marker for when a lambda ends, to apply an end of statement if needed.
 
 	typedef bool (GDScriptParser::*AnnotationAction)(const AnnotationNode *p_annotation, Node *p_target);
 	struct AnnotationInfo {
@@ -1278,10 +1304,11 @@ private:
 
 	GDScriptTokenizer::Token advance();
 	bool match(GDScriptTokenizer::Token::Type p_token_type);
-	bool check(GDScriptTokenizer::Token::Type p_token_type);
+	bool check(GDScriptTokenizer::Token::Type p_token_type) const;
 	bool consume(GDScriptTokenizer::Token::Type p_token_type, const String &p_error_message);
-	bool is_at_end();
+	bool is_at_end() const;
-	bool is_statement_end();
+	bool is_statement_end_token() const;
+	bool is_statement_end() const;
 	void end_statement(const String &p_context);
 	void synchronize();
 	void push_multiline(bool p_state);
@@ -1299,7 +1326,8 @@ private:
 	EnumNode *parse_enum();
 	ParameterNode *parse_parameter();
 	FunctionNode *parse_function();
-	SuiteNode *parse_suite(const String &p_context, SuiteNode *p_suite = nullptr);
+	void parse_function_signature(FunctionNode *p_function, SuiteNode *p_body, const String &p_type);
+	SuiteNode *parse_suite(const String &p_context, SuiteNode *p_suite = nullptr, bool p_for_lambda = false);
 	// Annotations
 	AnnotationNode *parse_annotation(uint32_t p_valid_targets);
 	bool register_annotation(const MethodInfo &p_info, uint32_t p_target_kinds, AnnotationAction p_apply, int p_optional_arguments = 0, bool p_is_vararg = false);
@@ -1354,6 +1382,7 @@ private:
 	ExpressionNode *parse_await(ExpressionNode *p_previous_operand, bool p_can_assign);
 	ExpressionNode *parse_attribute(ExpressionNode *p_previous_operand, bool p_can_assign);
 	ExpressionNode *parse_subscript(ExpressionNode *p_previous_operand, bool p_can_assign);
+	ExpressionNode *parse_lambda(ExpressionNode *p_previous_operand, bool p_can_assign);
 	ExpressionNode *parse_invalid_token(ExpressionNode *p_previous_operand, bool p_can_assign);
 	TypeNode *parse_type(bool p_allow_void = false);
 #ifdef TOOLS_ENABLED
@@ -1415,10 +1444,11 @@ public:
 		void print_expression(ExpressionNode *p_expression);
 		void print_enum(EnumNode *p_enum);
 		void print_for(ForNode *p_for);
-		void print_function(FunctionNode *p_function);
+		void print_function(FunctionNode *p_function, const String &p_context = "Function");
 		void print_get_node(GetNodeNode *p_get_node);
 		void print_if(IfNode *p_if, bool p_is_elif = false);
 		void print_identifier(IdentifierNode *p_identifier);
+		void print_lambda(LambdaNode *p_lambda);
 		void print_literal(LiteralNode *p_literal);
 		void print_match(MatchNode *p_match);
 		void print_match_branch(MatchBranchNode *p_match_branch);

modules/gdscript/gdscript_tokenizer.cpp

@@ -242,6 +242,16 @@ void GDScriptTokenizer::set_multiline_mode(bool p_state) {
 	multiline_mode = p_state;
 }
 
+void GDScriptTokenizer::push_expression_indented_block() {
+	indent_stack_stack.push_back(indent_stack);
+}
+
+void GDScriptTokenizer::pop_expression_indented_block() {
+	ERR_FAIL_COND(indent_stack_stack.size() == 0);
+	indent_stack = indent_stack_stack.back()->get();
+	indent_stack_stack.pop_back();
+}
+
 int GDScriptTokenizer::get_cursor_line() const {
 	return cursor_line;
 }

modules/gdscript/gdscript_tokenizer.h

@@ -217,6 +217,7 @@ private:
 	Token last_newline;
 	int pending_indents = 0;
 	List<int> indent_stack;
+	List<List<int>> indent_stack_stack; // For lambdas, which require manipulating the indentation point.
 	List<char32_t> paren_stack;
 	char32_t indent_char = '\0';
 	int position = 0;
@@ -263,6 +264,8 @@ public:
 	void set_multiline_mode(bool p_state);
 	bool is_past_cursor() const;
 	static String get_token_name(Token::Type p_token_type);
+	void push_expression_indented_block(); // For lambdas, or blocks inside expressions.
+	void pop_expression_indented_block(); // For lambdas, or blocks inside expressions.
 
 	GDScriptTokenizer();
 };

modules/gdscript/gdscript_vm.cpp

@@ -33,6 +33,7 @@
 #include "core/core_string_names.h"
 #include "core/os/os.h"
 #include "gdscript.h"
+#include "gdscript_lambda_callable.h"
 
 Variant *GDScriptFunction::_get_variant(int p_address, GDScriptInstance *p_instance, Variant *p_stack, String &r_error) const {
 	int address = p_address & ADDR_MASK;
@@ -232,6 +233,7 @@ String GDScriptFunction::_get_call_error(const Callable::CallError &p_err, const
 		&&OPCODE_CALL_PTRCALL_PACKED_COLOR_ARRAY,    \
 		&&OPCODE_AWAIT,                              \
 		&&OPCODE_AWAIT_RESUME,                       \
+		&&OPCODE_CREATE_LAMBDA,                      \
 		&&OPCODE_JUMP,                               \
 		&&OPCODE_JUMP_IF,                            \
 		&&OPCODE_JUMP_IF_NOT,                        \
@@ -1452,13 +1454,17 @@ Variant GDScriptFunction::call(GDScriptInstance *p_instance, const Variant **p_a
 				if (err.error != Callable::CallError::CALL_OK) {
 					String methodstr = *methodname;
 					String basestr = _get_var_type(base);
+					bool is_callable = false;
 
 					if (methodstr == "call") {
-						if (argc >= 1) {
+						if (argc >= 1 && base->get_type() != Variant::CALLABLE) {
 							methodstr = String(*argptrs[0]) + " (via call)";
 							if (err.error == Callable::CallError::CALL_ERROR_INVALID_ARGUMENT) {
 								err.argument += 1;
 							}
+						} else {
+							methodstr = base->operator String() + " (Callable)";
+							is_callable = true;
 						}
 					} else if (methodstr == "free") {
 						if (err.error == Callable::CallError::CALL_ERROR_INVALID_METHOD) {
@@ -1478,7 +1484,7 @@ Variant GDScriptFunction::call(GDScriptInstance *p_instance, const Variant **p_a
 							}
 						}
 					}
-					err_text = _get_call_error(err, "function '" + methodstr + "' in base '" + basestr + "'", (const Variant **)argptrs);
+					err_text = _get_call_error(err, "function '" + methodstr + (is_callable ? "" : "' in base '" + basestr) + "'", (const Variant **)argptrs);
 					OPCODE_BREAK;
 				}
 #endif
@@ -2057,6 +2063,34 @@ Variant GDScriptFunction::call(GDScriptInstance *p_instance, const Variant **p_a
 			}
 			DISPATCH_OPCODE;
 
+			OPCODE(OPCODE_CREATE_LAMBDA) {
+				CHECK_SPACE(2 + instr_arg_count);
+
+				ip += instr_arg_count;
+
+				int captures_count = _code_ptr[ip + 1];
+				GD_ERR_BREAK(captures_count < 0);
+
+				int lambda_index = _code_ptr[ip + 2];
+				GD_ERR_BREAK(lambda_index < 0 || lambda_index >= _lambdas_count);
+				GDScriptFunction *lambda = _lambdas_ptr[lambda_index];
+
+				Vector<Variant> captures;
+				captures.resize(captures_count);
+				for (int i = 0; i < captures_count; i++) {
+					GET_INSTRUCTION_ARG(arg, i);
+					captures.write[i] = *arg;
+				}
+
+				GDScriptLambdaCallable *callable = memnew(GDScriptLambdaCallable(Ref<GDScript>(script), lambda, captures));
+
+				GET_INSTRUCTION_ARG(result, captures_count);
+				*result = Callable(callable);
+
+				ip += 3;
+			}
+			DISPATCH_OPCODE;
+
 			OPCODE(OPCODE_JUMP) {
 				CHECK_SPACE(2);
 				int to = _code_ptr[ip + 1];

modules/gdscript/tests/test_gdscript.cpp

@@ -66,7 +66,7 @@ static void test_tokenizer(const String &p_code, const Vector<String> &p_lines)
 		StringBuilder token;
 		token += " --> "; // Padding for line number.
 
-		for (int l = current.start_line; l <= current.end_line; l++) {
+		for (int l = current.start_line; l <= current.end_line && l <= p_lines.size(); l++) {
 			print_line(vformat("%04d %s", l, p_lines[l - 1]).replace("\t", tab));
 		}
 
@@ -118,6 +118,18 @@ static void test_parser(const String &p_code, const String &p_script_path, const
 			print_line(vformat("%02d:%02d: %s", error.line, error.column, error.message));
 		}
 	}
+
+	GDScriptAnalyzer analyzer(&parser);
+	analyzer.analyze();
+
+	if (err != OK) {
+		const List<GDScriptParser::ParserError> &errors = parser.get_errors();
+		for (const List<GDScriptParser::ParserError>::Element *E = errors.front(); E != nullptr; E = E->next()) {
+			const GDScriptParser::ParserError &error = E->get();
+			print_line(vformat("%02d:%02d: %s", error.line, error.column, error.message));
+		}
+	}
+
 #ifdef TOOLS_ENABLED
 	GDScriptParser::TreePrinter printer;
 	printer.print_tree(parser);