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diff --git a/tiger-compiler/lib/misc/variant.hh b/tiger-compiler/lib/misc/variant.hh
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+/**
+ ** \file misc/variant.hh
+ ** \brief Interface of misc::variant.
+ **
+ ** misc::variant is a wrapper over std::variant that adds
+ ** conversion operators to the original standard variant class.
+ ** misc::variant is used just like std::variant, and you
+ ** won't be disturbed when using it.
+ **/
+
+#pragma once
+
+#include <variant>
+
+namespace misc
+{
+  // Defining some concepts sepecific to variants:
+
+  // Type T can be converted into another type in Ts,
+  // used to set the variant's value.
+  template <typename T, typename... Ts>
+  concept ContainsTypeSet =
+    std::disjunction<std::is_convertible<T, Ts>...>::value;
+
+  // A type in Ts can be converted into T, used to get the variant's value.
+  template <typename T, typename... Ts>
+  concept ContainsTypeGet =
+    std::disjunction<std::is_convertible<Ts, T>...>::value;
+
+  /// Type V is a visitor on each Ts.
+  template <typename V, typename... Ts>
+  concept Visits = std::conjunction<std::is_invocable<V, Ts>...>::value;
+
+  /// A wrapper over std::variant supporting conversion operators.
+  ///
+  /// Constraints:
+  /// - No type may be const-qualified.
+  /// - Each type must be unique.
+  /// - The first type must be default constructible.
+  ///
+  /// Proper declaration form:
+  ///   misc::variant<T, T1, ..., Tn>
+
+  template <typename T, typename... Ts>
+  class variant : public std::variant<T, Ts...>
+  {
+  public:
+    /// The type of this variant.
+    using self_type = variant<T, Ts...>;
+    /// Super type.
+
+    using super_type = std::variant<T, Ts...>;
+
+    /// Constructors.
+    /// \{
+    variant() = default;
+
+    template <typename U>
+      requires ContainsTypeSet<U, T, Ts...>
+    variant(const U& rhs);
+    /// \}
+
+    template <typename U>
+      requires ContainsTypeSet<U, T, Ts...>
+    self_type& operator=(const U&);
+
+    /// \brief Convert this variant to a value of type \a U.
+    ///
+    /// This conversion relies on std::get.  In particular, if the
+    /// conversion fails, a std::bad_variant_access exception is thrown.
+    template <typename U>
+      requires ContainsTypeGet<U, T, Ts...>
+    operator U&();
+
+    /// Likewise, const version.
+    template <typename U>
+      requires ContainsTypeGet<U, T, Ts...>
+    operator const U&() const;
+
+    /** \brief Visit variants of this class.
+     ** std::visit does not handle classes inheriting from std::variant, hence
+     ** these wrappers.
+     ** \{ */
+    template <typename V>
+      requires Visits<V, T, Ts...>
+    auto visit(V&& visitor) const;
+
+    template <typename V, class... Variants>
+    static auto visit(V&& visitor, Variants&&... vars);
+    /** \} */
+  };
+
+  // Here add variadic template recursion on std::get
+  template <typename T, typename... Ts>
+  std::ostream& operator<<(std::ostream& os, const variant<T, Ts...>& obj);
+
+  class PrintVisitor
+  {
+  public:
+    PrintVisitor(std::ostream& os)
+      : os_(os)
+    {}
+
+    template <typename T> std::ostream& operator()(const T& value) const;
+
+  private:
+    std::ostream& os_;
+  };
+} // namespace misc
+
+#include <misc/variant.hxx>