3 files changed, 112 insertions, 63 deletions

diff --git a/makefile b/makefile
index b8484a7..5207a11 100644
--- a/makefile
+++ b/makefile
@@ -212,7 +212,7 @@ clean:
 
 # Test Moonscript compiler
 .PHONY: test
-test: release
+test: debug
         @echo "Compiling Moonscript codes..."
         @$(START_TIME)
         @./$(BIN_NAME) $(TEST_INPUT) -t $(TEST_OUTPUT)
diff --git a/spec/inputs/backcall.moon b/spec/inputs/backcall.moon
index 30a0f8f..5f53f9e 100644
--- a/spec/inputs/backcall.moon
+++ b/spec/inputs/backcall.moon
@@ -107,3 +107,7 @@ alert "hi"
 
 x = 123 |> a |> b or 456 |> c |> d or a.if\then("abc") or a?.b\c?(123) or x\y
 
+y = 1 + # 2 |> a ^ c |> b(3,_) ^ 4 * -123 |> f |> f1 or 123
+
+nil
+
diff --git a/src/MoonP/moon_compiler.cpp b/src/MoonP/moon_compiler.cpp
index 36b6b11..189a428 100644
--- a/src/MoonP/moon_compiler.cpp
+++ b/src/MoonP/moon_compiler.cpp
@@ -43,7 +43,7 @@ inline std::string s(std::string_view sv) {
 }
 
 const std::string_view version() {
-        return "0.3.13"sv;
+        return "0.3.14"sv;
 }
 
 // name of table stored in lua registry
@@ -1612,79 +1612,123 @@ private:
                 out.push_back(join(temp, ", "sv));
         }
 
-        void transformExp(Exp_t* exp, str_list& out, ExpUsage usage, ExpList_t* assignList = nullptr) {
-                auto x = exp;
-                const auto& opValues = exp->opValues.objects();
-                for (auto it = opValues.begin(); it != opValues.end(); ++it) {
+        ast_ptr<false, Exp_t> transformBackcall(Value_t* first, node_container::const_iterator begin, node_container::const_iterator end) {
+                auto arg = first->new_ptr<Exp_t>();
+                arg->value.set(first);
+                for (auto it = begin; it != end; ++it) {
                         auto opValue = static_cast<exp_op_value_t*>(*it);
-                        if (opValue->op.is<BackcallOperator_t>()) {
-                                if (auto chainValue = opValue->value->item.as<ChainValue_t>()) {
-                                        auto newExp = x->new_ptr<Exp_t>();
-                                        {
-                                                auto arg = x->new_ptr<Exp_t>();
-                                                arg->value.set(exp->value);
-                                                for (auto i = opValues.begin(); i != it; ++i) {
-                                                        arg->opValues.push_back(*i);
-                                                }
-                                                auto next = it; ++next;
-                                                for (auto i = next; i != opValues.end(); ++i) {
-                                                        newExp->opValues.push_back(*i);
+                        if (auto chainValue = opValue->value->item.as<ChainValue_t>()) {
+                                auto newArg = first->new_ptr<Exp_t>();
+                                {
+                                        if (isChainValueCall(chainValue)) {
+                                                auto last = chainValue->items.back();
+                                                _ast_list* args = nullptr;
+                                                if (auto invoke = ast_cast<InvokeArgs_t>(last)) {
+                                                        args = &invoke->args;
+                                                } else {
+                                                        args = &(ast_to<Invoke_t>(last)->args);
                                                 }
-                                                if (isChainValueCall(chainValue)) {
-                                                        auto last = chainValue->items.back();
-                                                        _ast_list* args = nullptr;
-                                                        if (auto invoke = ast_cast<InvokeArgs_t>(last)) {
-                                                                args = &invoke->args;
-                                                        } else {
-                                                                args = &(ast_to<Invoke_t>(last)->args);
-                                                        }
-                                                        bool findPlaceHolder = false;
-                                                        for (auto a : args->objects()) {
-                                                                bool lintGlobal = _config.lintGlobalVariable;
-                                                                _config.lintGlobalVariable = false;
-                                                                auto name = singleVariableFrom(a);
-                                                                _config.lintGlobalVariable = lintGlobal;
-                                                                if (name == "_"sv) {
-                                                                        if (!findPlaceHolder) {
-                                                                                args->swap(a, arg);
-                                                                                findPlaceHolder = true;
-                                                                        } else {
-                                                                                throw std::logic_error(_info.errorMessage("backcall placeholder can be used only in one place"sv, a));
-                                                                        }
+                                                bool findPlaceHolder = false;
+                                                for (auto a : args->objects()) {
+                                                        bool lintGlobal = _config.lintGlobalVariable;
+                                                        _config.lintGlobalVariable = false;
+                                                        auto name = singleVariableFrom(a);
+                                                        _config.lintGlobalVariable = lintGlobal;
+                                                        if (name == "_"sv) {
+                                                                if (!findPlaceHolder) {
+                                                                        args->swap(a, arg);
+                                                                        findPlaceHolder = true;
+                                                                } else {
+                                                                        throw std::logic_error(_info.errorMessage("backcall placeholder can be used only in one place"sv, a));
                                                                 }
                                                         }
-                                                        if (!findPlaceHolder) {
-                                                                args->push_front(arg);
-                                                        }
-                                                } else {
-                                                        auto invoke = x->new_ptr<Invoke_t>();
-                                                        invoke->args.push_front(arg);
-                                                        chainValue->items.push_back(invoke);
                                                 }
-                                                auto value = x->new_ptr<Value_t>();
-                                                value->item.set(chainValue);
-                                                newExp->value.set(value);
-                                        }
-                                        if (newExp->opValues.size() == 0) {
-                                                if (usage == ExpUsage::Assignment) {
-                                                        auto assign = x->new_ptr<Assign_t>();
-                                                        assign->values.push_back(newExp);
-                                                        auto assignment = x->new_ptr<ExpListAssign_t>();
-                                                        assignment->expList.set(assignList);
-                                                        assignment->action.set(assign);
-                                                        transformAssignment(assignment, out);
-                                                } else {
-                                                        transformChainValue(chainValue, out, usage);
+                                                if (!findPlaceHolder) {
+                                                        args->push_front(arg);
                                                 }
                                         } else {
-                                                transformExp(newExp, out, usage, assignList);
+                                                auto invoke = first->new_ptr<Invoke_t>();
+                                                invoke->args.push_front(arg);
+                                                chainValue->items.push_back(invoke);
+                                        }
+                                        auto value = first->new_ptr<Value_t>();
+                                        value->item.set(chainValue);
+                                        newArg->value.set(value);
+                                        arg.set(newArg);
+                                }
+                        } else {
+                                throw std::logic_error(_info.errorMessage("backcall operator must be followed by chain value"sv, opValue->value));
+                        }
+                }
+                return arg;
+        }
+
+        void transformExp(Exp_t* exp, str_list& out, ExpUsage usage, ExpList_t* assignList = nullptr) {
+                const auto& opValues = exp->opValues.objects();
+                for (auto it = opValues.begin(); it != opValues.end(); ++it) {
+                        auto opValue = static_cast<exp_op_value_t*>(*it);
+                        if (opValue->op.is<BackcallOperator_t>()) {
+                                auto end = std::find_if_not(it, opValues.end(), [](ast_node* node) {
+                                        return static_cast<exp_op_value_t*>(node)->op.is<BackcallOperator_t>();
+                                });
+                                ast_ptr<false, Exp_t> backcall;
+                                if (it == opValues.begin()) {
+                                        auto first = exp->value.get();
+                                        backcall = transformBackcall(first, it, end);
+                                        for (auto i = end; i != opValues.end(); ++i) {
+                                                backcall->opValues.push_back(*i);
                                         }
-                                        return;
                                 } else {
-                                        throw std::logic_error(_info.errorMessage("backcall operator must be followed by chain value"sv, opValue->value));
+                                        auto prev = it; --prev;
+                                        auto first = static_cast<exp_op_value_t*>(*prev)->value.get();
+                                        backcall = transformBackcall(first, it, end);
+                                        for (auto i = opValues.begin(); i != it; ++i) {
+                                                backcall->opValues.push_back(*i);
+                                        }
+                                        static_cast<exp_op_value_t*>(backcall->opValues.back())->value.set(backcall->value);
+                                        backcall->value.set(exp->value);
+                                        for (auto i = end; i != opValues.end(); ++i) {
+                                                backcall->opValues.push_back(*i);
+                                        }
+                                }
+                                auto x = exp;
+                                switch (usage) {
+                                        case ExpUsage::Assignment: {
+                                                auto assignment = x->new_ptr<ExpListAssign_t>();
+                                                auto assign = x->new_ptr<Assign_t>();
+                                                assign->values.push_back(backcall);
+                                                assignment->action.set(assign);
+                                                assignment->expList.set(assignList);
+                                                transformAssignment(assignment, out);
+                                                return;
+                                        }
+                                        case ExpUsage::Common: {
+                                                if (backcall->opValues.empty() && backcall->value->item.is<ChainValue_t>()) {
+                                                        transformChainValue(backcall->value->item.to<ChainValue_t>(), out, ExpUsage::Common);
+                                                } else {
+                                                        transformExp(backcall, out, ExpUsage::Closure);
+                                                        out.back().insert(0, indent());
+                                                        out.back().append(nlr(x));
+                                                }
+                                                return;
+                                        }
+                                        case ExpUsage::Return: {
+                                                auto ret = x->new_ptr<Return_t>();
+                                                auto expListLow = x->new_ptr<ExpListLow_t>();
+                                                expListLow->exprs.push_back(backcall);
+                                                ret->valueList.set(expListLow);
+                                                transformReturn(ret, out);
+                                                return;
+                                        }
+                                        case ExpUsage::Closure: {
+                                                transformExp(backcall, out, ExpUsage::Closure);
+                                                return;
+                                        }
+                                        default: assert(false); return;
                                 }
                         }
                 }
+                assert(usage == ExpUsage::Closure);
                 str_list temp;
                 transformValue(exp->value, temp);
                 for (auto _opValue : exp->opValues.objects()) {
@@ -2954,6 +2998,7 @@ private:
                         case ExpUsage::Return:
                                 out.push_back(indent() + s("return "sv) + join(temp) + nll(chainList.front()));
                                 break;
+                        case ExpUsage::Assignment: assert(false); break;
                         default:
                                 out.push_back(join(temp));
                                 break;