typecheck (without modes), unique mode

include/mode_check.hpp

@@ -1,2 +1,79 @@
 #pragma once
 
+#include "parsing_tree.hpp"
+
+#include <map>
+#include <source_location>
+
+namespace mode_check {
+
+using namespace types;
+
+struct VarState {
+  VarState(Mode mode, size_t count = 0) : mode(mode), count(count) {}
+
+  Mode mode;
+  size_t count = 0;
+};
+
+struct State {
+  friend struct Context;
+
+  State() { vars_stack.emplace_back(); }
+
+  std::optional<VarState *> get_var_state(const std::string &name,
+                                          bool last_context_only = false) {
+    for (auto vars_it = vars_stack.rbegin(); vars_it != vars_stack.rend();
+         ++vars_it) {
+      auto var_it = vars_it->find(name);
+      if (var_it == vars_it->end()) {
+        if (last_context_only) {
+          break;
+        }
+
+        continue;
+      }
+      return &var_it->second;
+    }
+
+    utils::throw_error("NO_VAR");
+    return std::nullopt;
+  }
+
+  void add_var(std::string name, Mode mode = Mode()) {
+    vars_stack.back().insert({std::move(name), VarState{mode}});
+    // TODO: check existance
+  }
+
+private:
+  void enter_context() { vars_stack.emplace_back(); }
+
+  void exit_context() { vars_stack.pop_back(); }
+
+private:
+  vector<map<string, VarState>> vars_stack;
+};
+
+struct Context {
+  Context(State &state) : state_(state) { state_.enter_context(); }
+
+  ~Context() { state_.exit_context(); }
+
+private:
+  State &state_;
+};
+
+// struct ExclVarScope {
+//   ExclVarScope(std::string name, State &state)
+//       : name_(std::move(name)), state_(state) {}
+
+//   ~ExclVarScope() {}
+
+// private:
+//   std::string name_;
+//   State &state_;
+// };
+
+void check_expr(nodes::ExprPtr expr, State &state);
+
+} // mode_check