//===--- ITCDecl.cpp - Iterative Type Checker for Declarations ------------===//
//
// 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 implements the portions of the IterativeTypeChecker
//  class that involve declarations.
//
//===----------------------------------------------------------------------===//
#include "GenericTypeResolver.h"
#include "TypeChecker.h"
#include "swift/Sema/IterativeTypeChecker.h"
#include "swift/AST/ASTContext.h"
#include "swift/AST/Decl.h"
#include "swift/AST/ExistentialLayout.h"
#include <tuple>
using namespace swift;

//===----------------------------------------------------------------------===//
// Inheritance clause handling
//===----------------------------------------------------------------------===//
static std::tuple<TypeResolutionOptions, DeclContext *,
                  MutableArrayRef<TypeLoc>>
decomposeInheritedClauseDecl(
  llvm::PointerUnion<TypeDecl *, ExtensionDecl *> decl) {
  TypeResolutionOptions options;
  DeclContext *dc;
  MutableArrayRef<TypeLoc> inheritanceClause;
  if (auto typeDecl = decl.dyn_cast<TypeDecl *>()) {
    inheritanceClause = typeDecl->getInherited();
    if (auto nominal = dyn_cast<NominalTypeDecl>(typeDecl)) {
      dc = nominal;
      options |= TypeResolutionFlags::GenericSignature;
      options |= TypeResolutionFlags::InheritanceClause;
      options |= TypeResolutionFlags::AllowUnavailableProtocol;
    } else {
      dc = typeDecl->getDeclContext();

      if (isa<GenericTypeParamDecl>(typeDecl)) {
        // For generic parameters, we want name lookup to look at just the
        // signature of the enclosing entity.
        if (auto nominal = dyn_cast<NominalTypeDecl>(dc)) {
          dc = nominal;
          options |= TypeResolutionFlags::GenericSignature;
        } else if (auto ext = dyn_cast<ExtensionDecl>(dc)) {
          dc = ext;
          options |= TypeResolutionFlags::GenericSignature;
        } else if (auto func = dyn_cast<AbstractFunctionDecl>(dc)) {
          dc = func;
          options |= TypeResolutionFlags::GenericSignature;
        } else if (!dc->isModuleScopeContext()) {
          // Skip the generic parameter's context entirely.
          dc = dc->getParent();
        }
      }
    }
  } else {
    auto ext = decl.get<ExtensionDecl *>();
    inheritanceClause = ext->getInherited();
    dc = ext;
    options |= TypeResolutionFlags::GenericSignature;
    options |= TypeResolutionFlags::InheritanceClause;
    options |= TypeResolutionFlags::AllowUnavailableProtocol;
  }

  return std::make_tuple(options, dc, inheritanceClause);
}

static std::tuple<TypeResolutionOptions, DeclContext *, TypeLoc *>
decomposeInheritedClauseEntry(
  TypeCheckRequest::InheritedClauseEntryPayloadType entry) {
  TypeResolutionOptions options;
  DeclContext *dc;
  MutableArrayRef<TypeLoc> inheritanceClause;
  std::tie(options, dc, inheritanceClause)
    = decomposeInheritedClauseDecl(entry.first);
  return std::make_tuple(options, dc, &inheritanceClause[entry.second]);
}

bool IterativeTypeChecker::isResolveInheritedClauseEntrySatisfied(
       TypeCheckRequest::InheritedClauseEntryPayloadType payload) {
  TypeLoc &inherited = *std::get<2>(decomposeInheritedClauseEntry(payload));
  return !inherited.getType().isNull();
}

void IterativeTypeChecker::processResolveInheritedClauseEntry(
       TypeCheckRequest::InheritedClauseEntryPayloadType payload,
       UnsatisfiedDependency unsatisfiedDependency) {
  TypeResolutionOptions options;
  DeclContext *dc;
  TypeLoc *inherited;
  std::tie(options, dc, inherited) = decomposeInheritedClauseEntry(payload);

  // FIXME: Declaration validation is overkill. Sink it down into type
  // resolution when it is actually needed.
  if (auto nominal = dyn_cast<NominalTypeDecl>(dc))
    TC.validateDeclForNameLookup(nominal);
  else if (auto ext = dyn_cast<ExtensionDecl>(dc)) {
    TC.validateExtension(ext);
  }

  // Validate the type of this inherited clause entry.
  // FIXME: Recursion into existing type checker.
  ProtocolRequirementTypeResolver protoResolver;
  GenericTypeToArchetypeResolver archetypeResolver(dc);
  GenericTypeResolver *resolver;
  if (isa<ProtocolDecl>(dc)) {
    resolver = &protoResolver;
  } else {
    resolver = &archetypeResolver;
  }

  if (TC.validateType(*inherited, dc, options, resolver,
                      &unsatisfiedDependency)) {
    inherited->setInvalidType(getASTContext());
  }

  auto type = inherited->getType();
  if (!type.isNull() && !isa<ProtocolDecl>(dc))
    inherited->setType(type->mapTypeOutOfContext());
}

bool IterativeTypeChecker::breakCycleForResolveInheritedClauseEntry(
       TypeCheckRequest::InheritedClauseEntryPayloadType payload) {
  std::get<2>(decomposeInheritedClauseEntry(payload))
    ->setInvalidType(getASTContext());
  return true;
}

//===----------------------------------------------------------------------===//
// Superclass handling
//===----------------------------------------------------------------------===//
bool IterativeTypeChecker::isTypeCheckSuperclassSatisfied(ClassDecl *payload) {
  return payload->LazySemanticInfo.Superclass.getInt();
}

void IterativeTypeChecker::processTypeCheckSuperclass(
       ClassDecl *classDecl,
       UnsatisfiedDependency unsatisfiedDependency) {
  // The superclass should be the first inherited type. However, so
  // long as we see already-resolved types that refer to protocols,
  // skip over them to keep looking for a misplaced superclass. The
  // actual error will be diagnosed when we perform full semantic
  // analysis on the class itself.
  Type superclassType;
  auto inheritedClause = classDecl->getInherited();
  for (unsigned i = 0, n = inheritedClause.size(); i != n; ++i) {
    TypeLoc &inherited = inheritedClause[i];

    // If this inherited type has not been resolved, we depend on it.
    if (unsatisfiedDependency(
          requestResolveInheritedClauseEntry({ classDecl, i }))) {
      return;
    }

    // If this resolved inherited type is existential, keep going.
    if (inherited.getType()->isExistentialType()) continue;

    // If this resolved type is a class, we're done.
    if (inherited.getType()->getClassOrBoundGenericClass()) {
      superclassType = inherited.getType();
      break;
    }
  }

  // Set the superclass type.
  if (classDecl->isInvalid())
    superclassType = ErrorType::get(getASTContext());
  classDecl->setSuperclass(superclassType);
}

bool IterativeTypeChecker::breakCycleForTypeCheckSuperclass(
       ClassDecl *classDecl) {
  classDecl->setSuperclass(ErrorType::get(getASTContext()));
  return true;
}

//===----------------------------------------------------------------------===//
// Raw type handling
//===----------------------------------------------------------------------===//
bool IterativeTypeChecker::isTypeCheckRawTypeSatisfied(EnumDecl *payload) {
  return payload->LazySemanticInfo.RawType.getInt();
}

void IterativeTypeChecker::processTypeCheckRawType(
       EnumDecl *enumDecl,
       UnsatisfiedDependency unsatisfiedDependency) {
  // The raw type should be the first inherited type. However, so
  // long as we see already-resolved types that refer to protocols,
  // skip over them to keep looking for a misplaced raw type. The
  // actual error will be diagnosed when we perform full semantic
  // analysis on the enum itself.
  Type rawType;
  auto inheritedClause = enumDecl->getInherited();
  for (unsigned i = 0, n = inheritedClause.size(); i != n; ++i) {
    TypeLoc &inherited = inheritedClause[i];

    // We depend on having resolved the inherited type.
    if (unsatisfiedDependency(
          requestResolveInheritedClauseEntry({ enumDecl, i }))) {
      return;
    }

    // If this resolved inherited type is existential, keep going.
    if (inherited.getType()->isExistentialType()) continue;

    // Record this raw type.
    rawType = inherited.getType();
    break;
  }

  // Set the raw type.
  enumDecl->setRawType(rawType);
}

bool IterativeTypeChecker::breakCycleForTypeCheckRawType(EnumDecl *enumDecl) {
  enumDecl->setRawType(ErrorType::get(getASTContext()));
  return true;
}

//===----------------------------------------------------------------------===//
// Inherited protocols
//===----------------------------------------------------------------------===//
bool IterativeTypeChecker::isInheritedProtocolsSatisfied(ProtocolDecl *payload){
  auto inheritedClause = payload->getInherited();
  for (unsigned i = 0, n = inheritedClause.size(); i != n; ++i) {
    TypeLoc &inherited = inheritedClause[i];
    if (!inherited.getType()) return false;
  }

  return true;
}

void IterativeTypeChecker::processInheritedProtocols(
       ProtocolDecl *protocol,
       UnsatisfiedDependency unsatisfiedDependency) {
  // Computing the set of inherited protocols depends on the complete
  // inheritance clause.
  // FIXME: Technically, we only need very basic name binding.
  auto inheritedClause = protocol->getInherited();
  bool anyDependencies = false;
  bool diagnosedCircularity = false;
  llvm::SmallSetVector<ProtocolDecl *, 4> allProtocols;
  for (unsigned i = 0, n = inheritedClause.size(); i != n; ++i) {
    TypeLoc &inherited = inheritedClause[i];

    // We depend on having resolved the inherited type.
    if (unsatisfiedDependency(
          requestResolveInheritedClauseEntry({ protocol, i }))) {
      anyDependencies = true;
      continue;
    }

    // Collect existential types.
    // FIXME: We'd prefer to keep what the user wrote here.
    if (inherited.getType()->isExistentialType()) {
      auto layout = inherited.getType()->getExistentialLayout();
      for (auto inheritedProtocolTy: layout.getProtocols()) {
        auto *inheritedProtocol = inheritedProtocolTy->getDecl();

        if (inheritedProtocol == protocol ||
            inheritedProtocol->inheritsFrom(protocol)) {
          if (!diagnosedCircularity) {
            diagnose(protocol,
                     diag::circular_protocol_def, protocol->getName().str())
                    .fixItRemove(inherited.getSourceRange());
            diagnosedCircularity = true;
          }
          continue;
        }
        allProtocols.insert(inheritedProtocol);
      }
    }
  }

  // If we enumerated any dependencies, we can't complete this request.
  if (anyDependencies)
    return;
}

bool IterativeTypeChecker::breakCycleForInheritedProtocols(
       ProtocolDecl *protocol) {
  // FIXME: We'd like to drop just the problematic protocols, not
  // everything.
  return true;
}

//===----------------------------------------------------------------------===//
// Resolve a type declaration
//===----------------------------------------------------------------------===//
bool IterativeTypeChecker::isResolveTypeDeclSatisfied(TypeDecl *typeDecl) {
  auto *dc = typeDecl->getDeclContext();

  if (typeDecl->hasInterfaceType())
    return true;

  if (auto typeAliasDecl = dyn_cast<TypeAliasDecl>(typeDecl)) {
    if (typeAliasDecl->getDeclContext()->isModuleScopeContext() &&
        typeAliasDecl->getGenericParams() == nullptr) {
      return typeAliasDecl->hasInterfaceType();
    }
  }

  // If this request can *never* be satisfied due to recursion,
  // return success and fail elsewhere.
  if (typeDecl->isBeingValidated())
    return true;

  while (dc) {
    if (auto nominal = dyn_cast<NominalTypeDecl>(dc)) {
      if (nominal->isBeingValidated())
        return true;
      if (nominal->hasInterfaceType())
        return false;
    } else if (auto ext = dyn_cast<ExtensionDecl>(dc)) {
      if (ext->isBeingValidated())
        return true;
      if (ext->hasValidationStarted())
        return false;
    } else {
      break;
    }
    dc = dc->getParent();
  }

  // Ok, we can try calling validateDecl().
  return false;
}

void IterativeTypeChecker::processResolveTypeDecl(
       TypeDecl *typeDecl,
       UnsatisfiedDependency unsatisfiedDependency) {
  if (auto typeAliasDecl = dyn_cast<TypeAliasDecl>(typeDecl)) {
    if (typeAliasDecl->getDeclContext()->isModuleScopeContext() &&
        typeAliasDecl->getGenericParams() == nullptr) {
      TypeResolutionOptions options =
                                   TypeResolutionFlags::TypeAliasUnderlyingType;
      if (!typeAliasDecl->getDeclContext()->isCascadingContextForLookup(
            /*functionsAreNonCascading*/true)) {
        options |= TypeResolutionFlags::KnownNonCascadingDependency;
      }

      // Note: recursion into old type checker is okay when passing in an
      // unsatisfied-dependency callback.
      GenericTypeToArchetypeResolver resolver(typeAliasDecl);
      if (TC.validateType(typeAliasDecl->getUnderlyingTypeLoc(), typeAliasDecl,
                          options, &resolver, &unsatisfiedDependency)) {
        typeAliasDecl->setInvalid();
        typeAliasDecl->getUnderlyingTypeLoc().setInvalidType(getASTContext());
      }

      if (typeAliasDecl->getUnderlyingTypeLoc().wasValidated()) {
        typeAliasDecl->setUnderlyingType(
            typeAliasDecl->getUnderlyingTypeLoc().getType());
      }

      return;
    }

    // Fall through.
  }

  // FIXME: Recursion into the old type checker.
  TC.validateDecl(typeDecl);
}

bool IterativeTypeChecker::breakCycleForResolveTypeDecl(TypeDecl *typeDecl) {
  if (auto typeAliasDecl = dyn_cast<TypeAliasDecl>(typeDecl)) {
    typeAliasDecl->setInvalid();
    typeAliasDecl->setInterfaceType(ErrorType::get(getASTContext()));
    typeAliasDecl->getUnderlyingTypeLoc().setInvalidType(getASTContext());
    return true;
  }

  // FIXME: Generalize this.
  return false;
}