TypeCheckObjC.h

//===--- TypeCheckObjC.h - Type Checking for ObjC interop -------*- C++ -*-===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//
//
// This file provides utilities for type-checking interoperability with
// Objective-C.
//
//===----------------------------------------------------------------------===//
#ifndef SWIFT_SEMA_TYPE_CHECK_OBJC_H
#define SWIFT_SEMA_TYPE_CHECK_OBJC_H

#include "swift/AST/ForeignErrorConvention.h"
#include "llvm/ADT/Optional.h"

namespace swift {

class ASTContext;
class SubscriptDecl;
class TypeChecker;
class ValueDecl;
class VarDecl;

using llvm::Optional;

/// Describes the reason why are we trying to apply @objc to a declaration.
///
/// Should only affect diagnostics. If you change this enum, also change
/// the OBJC_ATTR_SELECT macro in DiagnosticsSema.def.
class ObjCReason {
public:
  // The kind of reason.
  enum Kind {
    /// Has the '@cdecl' attribute.
    ExplicitlyCDecl,
    /// Has the 'dynamic' modifier.
    ExplicitlyDynamic,
    /// Has an explicit '@objc' attribute.
    ExplicitlyObjC,
    /// Has an explicit '@IBOutlet' attribute.
    ExplicitlyIBOutlet,
    /// Has an explicit '@IBAction' attribute.
    ExplicitlyIBAction,
    /// Has an explicit '@NSManaged' attribute.
    ExplicitlyNSManaged,
    /// Is a member of an @objc protocol.
    MemberOfObjCProtocol,
    /// Implicitly-introduced @objc.
    ImplicitlyObjC,
    /// Is an override of an @objc member.
    OverridesObjC,
    /// Is a witness to an @objc protocol requirement.
    WitnessToObjC,
    /// Has an explicit '@IBInspectable' attribute.
    ExplicitlyIBInspectable,
    /// Has an explicit '@GKInspectable' attribute.
    ExplicitlyGKInspectable,
    /// Is it a member of an @objc extension of a class.
    MemberOfObjCExtension,
    /// Is it a member of an @objcMembers class.
    MemberOfObjCMembersClass,
    /// A member of an Objective-C-defined class or subclass.
    MemberOfObjCSubclass,
    /// An accessor to a property.
    Accessor,
  };

private:
  Kind kind;

  /// When the kind is \c WitnessToObjC, the requirement being witnessed.
  ValueDecl * decl = nullptr;

  ObjCReason(Kind kind, ValueDecl *decl) : kind(kind), decl(decl) { }

public:
  /// Implicit conversion from the trivial reason kinds.
  ObjCReason(Kind kind) : kind(kind) {
    assert(kind != WitnessToObjC && "Use ObjCReason::witnessToObjC()");
  }

  /// Retrieve the kind of requirement.
  operator Kind() const { return kind; }

  /// Form a reason specifying that we have a witness to the given @objc
  /// requirement.
  static ObjCReason witnessToObjC(ValueDecl *requirement) {
    return ObjCReason(WitnessToObjC, requirement);
  }

  /// When the entity should be @objc because it is a witness to an @objc
  /// requirement, retrieve the requirement.
  ValueDecl *getObjCRequirement() const {
    assert(kind == WitnessToObjC);
    return decl;
  }
};

/// Determine whether we should diagnose conflicts due to inferring @objc
/// with this particular reason.
bool shouldDiagnoseObjCReason(ObjCReason reason, ASTContext &ctx);

/// Return the %select discriminator for the OBJC_ATTR_SELECT macro used to
/// complain about the correct attribute during @objc inference.
unsigned getObjCDiagnosticAttrKind(ObjCReason reason);

/// Figure out if a declaration should be exported to Objective-C.
Optional<ObjCReason> shouldMarkAsObjC(TypeChecker &TC,
                                      const ValueDecl *VD,
                                      bool allowImplicit = false);

/// Record whether the given declaration is @objc, and why.
void markAsObjC(TypeChecker &TC, ValueDecl *D,
                Optional<ObjCReason> isObjC,
                Optional<ForeignErrorConvention> errorConvention = llvm::None);

/// Determine whether the given variable can be represented in Objective-C.
bool isRepresentableInObjC(const VarDecl *VD, ObjCReason Reason);

/// Determine whether the given subscript can be represented in Objective-C.
bool isRepresentableInObjC(const SubscriptDecl *SD, ObjCReason Reason);

} // end namespace swift

#endif // SWIFT_SEMA_TYPE_CHECK_OBJC_H