carbon-lang/explorer/ast/bindings.h

// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
// Exceptions. See /LICENSE for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception

#ifndef CARBON_EXPLORER_AST_BINDINGS_H_
#define CARBON_EXPLORER_AST_BINDINGS_H_

#include <map>
#include <utility>

#include "explorer/common/nonnull.h"
#include "llvm/ADT/ArrayRef.h"

namespace Carbon {

class Arena;
class ImplBinding;
class GenericBinding;
class Value;

using BindingMap =
    std::map<Nonnull<const GenericBinding*>, Nonnull<const Value*>>;
using ImplWitnessMap =
    std::map<Nonnull<const ImplBinding*>, Nonnull<const Value*>>;

// A set of evaluated bindings in some context, such as a function or class.
//
// These are shared by a context and all unparameterized entities within that
// context. For example, a class and the name of a method within that class
// will have the same set of bindings.
class Bindings {
 public:
  // Gets an empty set of bindings.
  static auto None() -> Nonnull<const Bindings*>;

  // Makes a set of symbolic identity bindings for the given collection of
  // generic bindings and their impl bindings.
  static auto SymbolicIdentity(
      Nonnull<Arena*> arena,
      llvm::ArrayRef<Nonnull<const GenericBinding*>> bindings)
      -> Nonnull<const Bindings*>;

  // Create an empty set of bindings.
  Bindings() = default;

  // Create an instantiated set of bindings for use during evaluation,
  // containing both arguments and witnesses.
  Bindings(BindingMap args, ImplWitnessMap witnesses)
      : args_(std::move(args)), witnesses_(std::move(witnesses)) {}

  enum NoWitnessesTag { NoWitnesses };

  // Create a set of bindings for use during type-checking, containing only the
  // arguments but not the corresponding witnesses.
  Bindings(BindingMap args, NoWitnessesTag /*unused*/)
      : args_(std::move(args)) {}

  template <typename F>
  auto Decompose(F f) const {
    return f(args_, witnesses_);
  }

  // Add a value, and perhaps a witness, for a generic binding.
  void Add(Nonnull<const GenericBinding*> binding, Nonnull<const Value*> value,
           std::optional<Nonnull<const Value*>> witness);

  // Argument values corresponding to generic bindings.
  auto args() const -> const BindingMap& { return args_; }

  // Witnesses corresponding to impl bindings.
  auto witnesses() const -> const ImplWitnessMap& { return witnesses_; }

  // Determine whether this is an empty set of bindings.
  [[nodiscard]] auto empty() const -> bool {
    return args_.empty() && witnesses_.empty();
  }

 private:
  BindingMap args_;
  ImplWitnessMap witnesses_;
};

}  // namespace Carbon

#endif  // CARBON_EXPLORER_AST_BINDINGS_H_