Remove expression list in parser

We don't need exprs non-terminal after implement statements.

ast.cpp

@@ -70,47 +70,36 @@ class NullStmtNode : public StmtNode {
 
 class ReturnStmtNode : public StmtNode {
  public:
-  ReturnStmtNode(std::vector<std::unique_ptr<ExprNode>>&& exprs)
-      : exprs_{std::move(exprs)} {}
+  ReturnStmtNode(std::unique_ptr<ExprNode> expr) : expr_{std::move(expr)} {}
 
   void CodeGen() const override {
     output << " ret ";
-    for (const auto& expr : exprs_) {
-      expr->CodeGen();
-    }
+    expr_->CodeGen();
   }
 
   void Dump(int pad) const override {
-    for (const auto& expr : exprs_) {
-      expr->Dump(pad);
-    }
+    std::cout << Pad(pad) << "(ret" << std::endl;
+    expr_->Dump(pad + 2);
+    std::cout << Pad(pad) << ')' << std::endl;
   }
 
  protected:
-  std::vector<std::unique_ptr<ExprNode>> exprs_;
+  std::unique_ptr<ExprNode> expr_;
 };
 
 /// @note Any expression can be turned into a statement by adding a semicolon
 /// to the end of the expression.
 class ExprStmtNode : public StmtNode {
  public:
-  ExprStmtNode(std::vector<std::unique_ptr<ExprNode>>&& exprs)
-      : exprs_{std::move(exprs)} {}
-
-  void CodeGen() const override {
-    for (const auto& expr : exprs_) {
-      expr->CodeGen();
-    }
-  }
+  ExprStmtNode(std::unique_ptr<ExprNode> expr) : expr_{std::move(expr)} {}
 
+  void CodeGen() const override {}
   void Dump(int pad) const override {
-    for (const auto& expr : exprs_) {
-      expr->Dump(pad);
-    }
+    expr_->Dump(pad);
   }
 
  protected:
-  std::vector<std::unique_ptr<ExprNode>> exprs_;
+  std::unique_ptr<ExprNode> expr_;
 };
 
 class IdExprNode : public ExprNode {

parser.y

@@ -39,7 +39,6 @@ std::ofstream output;
 ;
 
 %nterm <std::unique_ptr<ExprNode>> expr
-%nterm <std::vector<std::unique_ptr<ExprNode>>> exprs
 %nterm <std::unique_ptr<StmtNode>> stmt
 %nterm <std::vector<std::unique_ptr<StmtNode>>> stmts
 %nterm <std::vector<std::unique_ptr<StmtNode>>> main_func
@@ -69,18 +68,10 @@ stmts: stmts stmt {
   ;
 
 stmt: ';' { $$ = std::make_unique<NullStmtNode>(); }
-    | RETURN exprs ';' { $$ = std::make_unique<ReturnStmtNode>($2); }
-    | exprs ';' { $$ = std::make_unique<ExprStmtNode>($1); }
+    | RETURN expr ';' { $$ = std::make_unique<ReturnStmtNode>($2); }
+    | expr ';' { $$ = std::make_unique<ExprStmtNode>($1); }
     ;
 
-exprs: exprs expr {
-    auto exprs = $1;
-    exprs.push_back($2);
-    $$ = std::move(exprs);
-  }
-  | epsilon { $$ = std::vector<std::unique_ptr<ExprNode>>{}; }
-  ;
-
 expr: ID { $$ = std::make_unique<IdExprNode>($1); }
   | NUM { $$ = std::make_unique<IntConstExprNode>($1); }
   | expr '+' expr { $$ = std::make_unique<PlusExprNode>($1, $3); }

test/arithmetic.c

@@ -1,4 +1,4 @@
-int main () {
+int main() {
   1 + 2;
   1 - 2;
   1 * 2;