From b21621692e877e5a44508b90049c2bc75091ebac Mon Sep 17 00:00:00 2001
From: Li Jin <dragon-fly@qq.com>
Date: Wed, 21 May 2025 18:10:32 +0800
Subject: Allowed backcall without parentheses.

---
 doc/docs/doc/README.md         | 10 +++++-----
 doc/docs/zh/doc/README.md      | 10 +++++-----
 spec/inputs/backcall.yue       |  4 ++--
 src/yuescript/yue_ast.cpp      |  6 ++++++
 src/yuescript/yue_ast.h        |  8 +++++++-
 src/yuescript/yue_compiler.cpp | 34 +++++++++++++++++++++++++++++++++-
 src/yuescript/yue_parser.cpp   |  3 ++-
 src/yuescript/yue_parser.h     |  1 +
 8 files changed, 61 insertions(+), 15 deletions(-)

diff --git a/doc/docs/doc/README.md b/doc/docs/doc/README.md
index 502f7b6..4a408fe 100755
--- a/doc/docs/doc/README.md
+++ b/doc/docs/doc/README.md
@@ -1925,22 +1925,22 @@ x * 2
 </pre>
 </YueDisplay>
 
-If you wish to have further code after your backcalls, you can set them aside with a do statement.
+If you wish to have further code after your backcalls, you can set them aside with a do statement. And the parentheses can be omitted with non-fat arrow functions.
 
 ```moonscript
 result, msg = do
-  (data) <- readAsync "filename.txt"
+  data <- readAsync "filename.txt"
   print data
-  (info) <- processAsync data
+  info <- processAsync data
   check info
 print result, msg
 ```
 <YueDisplay>
 <pre>
 result, msg = do
-  (data) <- readAsync "filename.txt"
+  data <- readAsync "filename.txt"
   print data
-  (info) <- processAsync data
+  info <- processAsync data
   check info
 print result, msg
 </pre>
diff --git a/doc/docs/zh/doc/README.md b/doc/docs/zh/doc/README.md
index e5efe3b..d7b8361 100755
--- a/doc/docs/zh/doc/README.md
+++ b/doc/docs/zh/doc/README.md
@@ -1886,22 +1886,22 @@ x * 2
 </pre>
 </YueDisplay>
 
-如果你希望在反向回调处理后继续编写更多其它的代码，你可以使用do语句将不归属反向回调的代码分开。
+如果你希望在反向回调处理后继续编写更多其它的代码，可以使用 do 语句将不属于反向回调的代码分隔开。对于非粗箭头函数的反向回调，回调返回值的括号也是可以省略的。
 
 ```moonscript
 result, msg = do
-  (data) <- readAsync "文件名.txt"
+  data <- readAsync "文件名.txt"
   print data
-  (info) <- processAsync data
+  info <- processAsync data
   check info
 print result, msg
 ```
 <YueDisplay>
 <pre>
 result, msg = do
-  (data) <- readAsync "文件名.txt"
+  data <- readAsync "文件名.txt"
   print data
-  (info) <- processAsync data
+  info <- processAsync data
   check info
 print result, msg
 </pre>
diff --git a/spec/inputs/backcall.yue b/spec/inputs/backcall.yue
index 8aadc71..e6b8c21 100644
--- a/spec/inputs/backcall.yue
+++ b/spec/inputs/backcall.yue
@@ -13,9 +13,9 @@ do
 	x > 2
 
 do
-	(data) <- http?.get "ajaxtest"
+	data <- http?.get "ajaxtest"
 	body[".result"]\html data
-	(processed) <- http.post "ajaxprocess", data
+	processed <- http.post "ajaxprocess", data
 	body[".result"]\append processed
 	<- setTimeout 1000
 	print "done"
diff --git a/src/yuescript/yue_ast.cpp b/src/yuescript/yue_ast.cpp
index 56e3447..fdb1d20 100644
--- a/src/yuescript/yue_ast.cpp
+++ b/src/yuescript/yue_ast.cpp
@@ -331,6 +331,12 @@ std::string Backcall_t::to_string(void* ud) const {
 	temp.emplace_back(value->to_string(ud));
 	return join(temp, " "sv);
 }
+std::string SubBackcall_t::to_string(void* ud) const {
+	str_list temp;
+	temp.emplace_back(arrow->to_string(ud));
+	temp.emplace_back(value->to_string(ud));
+	return join(temp, " "sv);
+}
 std::string PipeBody_t::to_string(void* ud) const {
 	auto info = reinterpret_cast<YueFormat*>(ud);
 	str_list temp;
diff --git a/src/yuescript/yue_ast.h b/src/yuescript/yue_ast.h
index 8501a19..0c15fac 100644
--- a/src/yuescript/yue_ast.h
+++ b/src/yuescript/yue_ast.h
@@ -841,9 +841,15 @@ AST_NODE(UnaryExp)
 	AST_MEMBER(UnaryExp, &ops, &expos, &inExp)
 AST_END(UnaryExp)
 
+AST_NODE(SubBackcall)
+	ast_ptr<true, FnArrowBack_t> arrow;
+	ast_ptr<true, ChainValue_t> value;
+	AST_MEMBER(SubBackcall, &arrow, &value)
+AST_END(SubBackcall)
+
 AST_NODE(ExpListAssign)
 	ast_ptr<true, ExpList_t> expList;
-	ast_sel<false, Update_t, Assign_t> action;
+	ast_sel<false, Update_t, Assign_t, SubBackcall_t> action;
 	AST_MEMBER(ExpListAssign, &expList, &action)
 AST_END(ExpListAssign)
 
diff --git a/src/yuescript/yue_compiler.cpp b/src/yuescript/yue_compiler.cpp
index 5cd2804..60ed7ac 100644
--- a/src/yuescript/yue_compiler.cpp
+++ b/src/yuescript/yue_compiler.cpp
@@ -78,7 +78,7 @@ static std::unordered_set<std::string> Metamethods = {
 	"close"s // Lua 5.4
 };
 
-const std::string_view version = "0.28.1"sv;
+const std::string_view version = "0.28.2"sv;
 const std::string_view extension = "yue"sv;
 
 class CompileError : public std::logic_error {
@@ -4878,6 +4878,38 @@ private:
 				newBlock->statements.push_back(toAst<Statement_t>("if "s + okVar + " then return ... else error ..."s, x));
 				transformBlock(newBlock, out, usage, assignList, isRoot);
 				return;
+			} else if (auto expListAssign = stmt->content.as<ExpListAssign_t>();
+				expListAssign && expListAssign->action && expListAssign->action.is<SubBackcall_t>()) {
+				auto x = *nodes.begin();
+				auto newBlock = x->new_ptr<Block_t>();
+				if (it != nodes.begin()) {
+					for (auto i = nodes.begin(); i != it; ++i) {
+						newBlock->statements.push_back(*i);
+					}
+				}
+				auto doBackcall = static_cast<SubBackcall_t*>(expListAssign->action.get());
+				auto backcall = expListAssign->new_ptr<Backcall_t>();
+				auto argsDef = backcall->new_ptr<FnArgsDef_t>();
+				try {
+					auto defList = toAst<FnArgDefList_t>(YueFormat{}.toString(expListAssign->expList), expListAssign->expList);
+					argsDef->defList.set(defList);
+				} catch (const std::exception&) {
+					throw CompileError("backcall syntax error", backcall);
+				}
+				backcall->argsDef.set(argsDef);
+				backcall->arrow.set(doBackcall->arrow);
+				backcall->value.set(doBackcall->value);
+				auto newStmt = backcall->new_ptr<Statement_t>();
+				newStmt->content.set(backcall);
+				newStmt->comments.dup(stmt->comments);
+				newStmt->appendix.set(stmt->appendix);
+				newBlock->statements.push_back(newStmt);
+				auto ait = it;
+				for (auto i = ++ait; i != nodes.end(); ++i) {
+					newBlock->statements.push_back(*i);
+				}
+				transformBlock(newBlock, out, usage, assignList, isRoot);
+				return;
 			}
 			if (auto local = stmt->content.as<Local_t>()) {
 				if (!local->collected) {
diff --git a/src/yuescript/yue_parser.cpp b/src/yuescript/yue_parser.cpp
index 045e2c7..cd1fd48 100644
--- a/src/yuescript/yue_parser.cpp
+++ b/src/yuescript/yue_parser.cpp
@@ -889,6 +889,7 @@ YueParser::YueParser() {
 
 	FnArrowBack = '<' >> set("-=");
 	Backcall = -(FnArgsDef >> space) >> FnArrowBack >> space >> ChainValue;
+	SubBackcall = FnArrowBack >> space >> ChainValue;
 
 	PipeBody = Seperator >>
 		pipe_operator >> space >> UnaryExp >>
@@ -946,7 +947,7 @@ YueParser::YueParser() {
 		UnaryValue | TblComprehension | Comprehension |
 		FunLit | Num | VarArg;
 
-	ExpListAssign = ExpList >> -(space >> (Update | Assign)) >> not_(space >> '=');
+	ExpListAssign = ExpList >> -(space >> (Update | Assign | SubBackcall)) >> not_(space >> '=');
 
 	IfLine = IfType >> space >> IfCond;
 	WhileLine = WhileType >> space >> Exp;
diff --git a/src/yuescript/yue_parser.h b/src/yuescript/yue_parser.h
index 63afcb9..4488685 100644
--- a/src/yuescript/yue_parser.h
+++ b/src/yuescript/yue_parser.h
@@ -321,6 +321,7 @@ private:
 	AST_RULE(ShortTabAppending);
 	AST_RULE(FnArrowBack);
 	AST_RULE(Backcall);
+	AST_RULE(SubBackcall);
 	AST_RULE(PipeBody);
 	AST_RULE(ExpListLow);
 	AST_RULE(ExpList);
-- 
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