// 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_TOOLCHAIN_CHECK_DEFERRED_DEFINITION_SCOPE_H_
#define CARBON_TOOLCHAIN_CHECK_DEFERRED_DEFINITION_SCOPE_H_

#include "common/array_stack.h"
#include "toolchain/check/scope_stack.h"
#include "toolchain/sem_ir/inst.h"

namespace Carbon::Check {

// A thunk that has been declared but not yet defined.
//
// This type is large, so moves of this type should be avoided.
struct PendingThunk : public MoveOnly<PendingThunk> {
  SemIR::FunctionId signature_id;
  SemIR::FunctionId function_id;
  SemIR::InstId decl_id;
  SemIR::InstId callee_id;
  ScopeStack::SuspendedScope scope;
};

// A stack of the current non-nested deferred definition scopes. For example, in
// this code:
//
// class A {
//   class B {
//     fn F() {
//       class C {
//         // ...
//       }
//     }
//   }
// }
//
// ... we have two non-nested deferred definition scopes: one for class A, and
// one for class C. The scope for class B is nested, so is not tracked.
//
// At the end of each such scope, pending function definitions for functions
// defined inline are processed. At this location, we also generate bodies for
// thunks generated by checking.
class DeferredDefinitionScopeStack {
 public:
  // Push a new scope.
  auto Push() -> void { pending_thunks_.PushArray(); }

  // Pop a scope.
  auto Pop() -> void { pending_thunks_.PopArray(); }

  // Add a pending thunk definition for the current scope.
  auto AddPendingThunk(PendingThunk&& thunk) -> void {
    pending_thunks_.AppendToTop(std::move(thunk));
  }

  // Peek the list of pending thunks in this scope.
  auto PeekPendingThunks() -> llvm::MutableArrayRef<PendingThunk> {
    return pending_thunks_.PeekArray();
  }

 private:
  ArrayStack<PendingThunk> pending_thunks_;
};

}  // namespace Carbon::Check

#endif  // CARBON_TOOLCHAIN_CHECK_DEFERRED_DEFINITION_SCOPE_H_