expect_type_xs: refactor: simplify api

include/xo/reader/expect_type_xs.hpp

@@ -16,11 +16,14 @@ namespace xo {
         public:
             expect_type_xs();
 
-            static std::unique_ptr<expect_type_xs> make();
+            static void start(exprstatestack * p_stack);
 
             virtual void on_symbol_token(const token_type & tk,
                                          exprstatestack * p_stack,
                                          rp<Expression> * p_emit_expr) override;
+
+        private:
+            static std::unique_ptr<expect_type_xs> make();
         };
     } /*namespace scm*/
 } /*namespace xo*/

src/reader/define_xs.cpp

@@ -116,7 +116,7 @@ namespace xo {
             if (this->defxs_type_ == defexprstatetype::def_2) {
                 this->defxs_type_ = defexprstatetype::def_3;
 
-                p_stack->push_exprstate(expect_type_xs::make());
+                expect_type_xs::start(p_stack);
             } else {
                 exprstate::on_colon_token(tk, p_stack);
             }

src/reader/expect_formal_xs.cpp

@@ -60,7 +60,8 @@ namespace xo {
         {
             if (this->formalxs_type_ == formalstatetype::formal_1) {
                 this->formalxs_type_ = formalstatetype::formal_2;
-                p_stack->push_exprstate(expect_type_xs::make());
+                expect_type_xs::start(p_stack);
+                /* control reenters via expect_formal_xs::on_typedescr() */
             } else {
                 exprstate::on_colon_token(tk,
                                           p_stack);

src/reader/expect_type_xs.cpp

@@ -17,6 +17,11 @@ namespace xo {
             return std::make_unique<expect_type_xs>(expect_type_xs());
         }
 
+        void
+        expect_type_xs::start(exprstatestack * p_stack) {
+            p_stack->push_exprstate(expect_type_xs::make());
+        }
+
         expect_type_xs::expect_type_xs()
             : exprstate(exprstatetype::expect_type)
         {}