//===-- UncheckedOptionalAccessModel.h --------------------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
//  This file defines a dataflow analysis that detects unsafe uses of optional
//  values.
//
//===----------------------------------------------------------------------===//

#ifndef CLANG_ANALYSIS_FLOWSENSITIVE_MODELS_UNCHECKEDOPTIONALACCESSMODEL_H
#define CLANG_ANALYSIS_FLOWSENSITIVE_MODELS_UNCHECKEDOPTIONALACCESSMODEL_H

#include "clang/AST/ASTContext.h"
#include "clang/AST/Stmt.h"
#include "clang/Analysis/FlowSensitive/DataflowAnalysis.h"
#include "clang/Analysis/FlowSensitive/DataflowEnvironment.h"
#include "clang/Analysis/FlowSensitive/MatchSwitch.h"
#include "clang/Analysis/FlowSensitive/NoopLattice.h"
#include "clang/Basic/SourceLocation.h"
#include <vector>

namespace clang {
namespace dataflow {

// FIXME: Explore using an allowlist-approach, where constructs supported by the
// analysis are always enabled and additional constructs are enabled through the
// `Options`.
struct UncheckedOptionalAccessModelOptions {
  /// Ignore optionals reachable through overloaded `operator*` or `operator->`
  /// (other than those of the optional type itself). The analysis does not
  /// equate the results of such calls, so it can't identify when their results
  /// are used safely (across calls), resulting in false positives in all such
  /// cases. Note: this option does not cover access through `operator[]`.
  bool IgnoreSmartPointerDereference = false;
};

/// Dataflow analysis that models whether optionals hold values or not.
///
/// Models the `std::optional`, `absl::optional`, and `base::Optional` types.
class UncheckedOptionalAccessModel
    : public DataflowAnalysis<UncheckedOptionalAccessModel, NoopLattice> {
public:
  UncheckedOptionalAccessModel(
      ASTContext &AstContext, UncheckedOptionalAccessModelOptions Options = {});

  /// Returns a matcher for the optional classes covered by this model.
  static ast_matchers::DeclarationMatcher optionalClassDecl();

  static NoopLattice initialElement() { return {}; }

  void transfer(const Stmt *Stmt, NoopLattice &State, Environment &Env);

  bool compareEquivalent(QualType Type, const Value &Val1,
                         const Environment &Env1, const Value &Val2,
                         const Environment &Env2) override;

  bool merge(QualType Type, const Value &Val1, const Environment &Env1,
             const Value &Val2, const Environment &Env2, Value &MergedVal,
             Environment &MergedEnv) override;

private:
  MatchSwitch<TransferState<NoopLattice>> TransferMatchSwitch;
};

class UncheckedOptionalAccessDiagnoser {
public:
  UncheckedOptionalAccessDiagnoser(
      UncheckedOptionalAccessModelOptions Options = {});

  std::vector<SourceLocation> diagnose(ASTContext &Context, const Stmt *Stmt,
                                       const Environment &Env);

private:
  MatchSwitch<const Environment, std::vector<SourceLocation>>
      DiagnoseMatchSwitch;
};

} // namespace dataflow
} // namespace clang

#endif // CLANG_ANALYSIS_FLOWSENSITIVE_MODELS_UNCHECKEDOPTIONALACCESSMODEL_H