add placeholder support for backcall statement.

2 files changed, 36 insertions, 4 deletions

diff --git a/spec/inputs/backcall.moon b/spec/inputs/backcall.moon
index f5d0046..3aedba9 100644
--- a/spec/inputs/backcall.moon
+++ b/spec/inputs/backcall.moon
@@ -41,6 +41,16 @@ do
         x * 2
 
 do
+        (x)<- map _,{1,2,3}
+        x * 2
+
+do
+        (x)<- filter _, do
+                (x)<- map _,{1,2,3,4}
+                x * 2
+        x > 2
+
+do
         (data)<- http?.get "ajaxtest"
         body[".result"]\html data
         (processed)<- http.post "ajaxprocess", data
diff --git a/src/MoonP/moon_compiler.cpp b/src/MoonP/moon_compiler.cpp
index 64152cf..a39bfd0 100644
--- a/src/MoonP/moon_compiler.cpp
+++ b/src/MoonP/moon_compiler.cpp
@@ -32,7 +32,7 @@ inline std::string s(std::string_view sv) {
 }
 
 const char* moonScriptVersion() {
-        return "0.5.0-r0.1.3";
+        return "0.5.0-r0.1.4";
 }
 
 class MoonCompilerImpl {
@@ -1516,7 +1516,10 @@ private:
                                                         }
                                                         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);
@@ -1747,10 +1750,29 @@ private:
                                 }
                                 if (isChainValueCall(backcall->value)) {
                                         auto last = backcall->value->items.back();
-                                        if (auto invoke = ast_cast<Invoke_t>(last)) {
-                                                invoke->args.push_back(arg);
+                                        _ast_list* args = nullptr;
+                                        if (auto invoke = ast_cast<InvokeArgs_t>(last)) {
+                                                args = &invoke->args;
                                         } else {
-                                                ast_to<InvokeArgs_t>(last)->args.push_back(arg);
+                                                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));
+                                                        }
+                                                }
+                                        }
+                                        if (!findPlaceHolder) {
+                                                args->push_back(arg);
                                         }
                                 } else {
                                         auto invoke = x->new_ptr<Invoke_t>();