swift-mirror/lib/AST/LookupVisibleDecls.cpp

//===--- LookupVisibleDecls - Swift Name Lookup Routines ------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2015 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See http://swift.org/LICENSE.txt for license information
// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//
//
// This file implements the lookupVisibleDecls interface for visiting named
// declarations.
//
//===----------------------------------------------------------------------===//


#include "swift/AST/NameLookup.h"
#include "swift/AST/AST.h"
#include "swift/AST/ASTVisitor.h"

using namespace swift;

VisibleDeclConsumer::~VisibleDeclConsumer() {
  // Anchor the vtable.
}

namespace {
enum class LookupKind {
  /// An unqualified lookup of all visible decls in a DeclContext.
  Unqualified,

  /// Lookup of all visible members of a given object (of non-metatype type).
  Qualified,

  /// Lookup of all visible members of a given metatype.
  QualifiedOnMetatype
};
} // unnamed namespace

static void DoGlobalExtensionLookup(Type BaseType,
                                    VisibleDeclConsumer &Consumer,
                                    ArrayRef<ValueDecl*> BaseMembers,
                                    const Module *CurModule,
                                    const Module *BaseModule,
                                    LookupKind LK) {
  SmallVector<ValueDecl *, 4> found;
  
  auto nominal = BaseType->getAnyNominal();
  if (!nominal)
    return;

  // Add the members from the type itself to the list of results.
  for (auto member : BaseMembers) {
    if (auto *FD = dyn_cast<FuncDecl>(member)) {
      // Can not call static functions on non-metatypes.
      if (LK != LookupKind::QualifiedOnMetatype && FD->isStatic())
        continue;
    }
    if (LK == LookupKind::QualifiedOnMetatype && isa<VarDecl>(member)) {
      // FIXME: static variables
      continue;
    }
    if (LK == LookupKind::Qualified && isa<TypeAliasDecl>(member)) {
      // Can only access nested typealiases with unqualified lookup or on
      // metatypes.
      // FIXME: other nominal types?  rdar://14489286
      continue;
    }
    found.push_back(member);
  }

  // Look in each extension of this type.
  for (auto extension : nominal->getExtensions()) {
    for (auto member : extension->getMembers()) {
      auto vd = dyn_cast<ValueDecl>(member);
      if (!vd)
        continue;

      found.push_back(vd);
    }
  }

  // Handle shadowing.
  removeShadowedDecls(found, CurModule);

  // Report the declarations we found to the consumer.
  for (auto decl : found)
    Consumer.foundDecl(decl);
}

namespace {
  typedef llvm::SmallPtrSet<TypeDecl *, 8> VisitedSet;
}

static void doMemberLookup(Type BaseTy,
                           VisibleDeclConsumer &Consumer,
                           const DeclContext *CurrDC,
                           LookupKind LK,
                           VisitedSet &Visited);
static void lookupTypeMembers(Type BaseType,
                              VisibleDeclConsumer &Consumer,
                              const DeclContext *CurrDC,
                              LookupKind LK);

static void lookupVisibleMemberDecls(Type BaseTy,
                                     VisibleDeclConsumer &Consumer,
                                     const DeclContext *CurrDC,
                                     LookupKind LK) {
  VisitedSet Visited;
  doMemberLookup(BaseTy, Consumer, CurrDC, LK, Visited);
}

/// \brief Lookup a member 'Name' in 'BaseTy' within the context
/// of a given module 'M'.  This operation corresponds to a standard "dot"
/// lookup operation like "a.b" where 'this' is the type of 'a'.  This
/// operation is only valid after name binding.
///
/// \param OnlyInstanceMembers Only instance members should be found by
/// name lookup.
static void doMemberLookup(Type BaseTy,
                           VisibleDeclConsumer &Consumer,
                           const DeclContext *CurrDC,
                           LookupKind LK,
                           VisitedSet &Visited) {
  // Just look through l-valueness.  It doesn't affect name lookup.
  BaseTy = BaseTy->getRValueType();

  // Type check metatype references, as in "some_type.some_member".  These are
  // special and can't have extensions.
  if (MetaTypeType *MTT = BaseTy->getAs<MetaTypeType>()) {
    // The metatype represents an arbitrary named type: dig through to the
    // declared type to see what we're dealing with.
    Type Ty = MTT->getInstanceType();

    // Just perform normal dot lookup on the type with the specified
    // member name to see if we find extensions or anything else.  For example,
    // type SomeTy.SomeMember can look up static functions, and can even look
    // up non-static functions as well (thus getting the address of the member).
    doMemberLookup(Ty, Consumer, CurrDC, LookupKind::QualifiedOnMetatype,
                   Visited);
    return;
  }
  
  // Lookup module references, as on some_module.some_member.  These are
  // special and can't have extensions.
  if (ModuleType *MT = BaseTy->getAs<ModuleType>()) {
    MT->getModule()->lookupVisibleDecls(Module::AccessPathTy(), Consumer,
                                        NLKind::QualifiedLookup);
    return;
  }

  // If the base is a protocol, see if this is a reference to a declared
  // protocol member.
  if (ProtocolType *PT = BaseTy->getAs<ProtocolType>()) {
    if (!Visited.insert(PT->getDecl()))
      return;
      
    for (auto Inherited : PT->getDecl()->getInherited())
      doMemberLookup(Inherited.getType(), Consumer, CurrDC, LK, Visited);

    lookupTypeMembers(PT, Consumer, CurrDC, LK);
    return;
  }
  
  // If the base is a protocol composition, see if this is a reference to a
  // declared protocol member in any of the protocols.
  if (auto PC = BaseTy->getAs<ProtocolCompositionType>()) {
    for (auto Proto : PC->getProtocols())
      doMemberLookup(Proto, Consumer, CurrDC, LK, Visited);
    return;
  }

  // Check to see if any of an archetype's requirements have the member.
  if (ArchetypeType *Archetype = BaseTy->getAs<ArchetypeType>()) {
    for (auto Proto : Archetype->getConformsTo())
      doMemberLookup(Proto->getDeclaredType(), Consumer, CurrDC, LK, Visited);

    if (auto superclass = Archetype->getSuperclass())
      doMemberLookup(superclass, Consumer, CurrDC, LK, Visited);
    return;
  }

  do {
    // Look in for members of a nominal type.
    SmallVector<ValueDecl*, 8> ExtensionMethods;
    lookupTypeMembers(BaseTy, Consumer, CurrDC, LK);

    for (ValueDecl *VD : ExtensionMethods) {
      assert((isa<VarDecl>(VD) || isa<SubscriptDecl>(VD)) &&
             "Unexpected extension member");
      Consumer.foundDecl(VD);
    }

    // If we have a class type, look into its base class.
    ClassDecl *CurClass = nullptr;
    if (auto CT = BaseTy->getAs<ClassType>())
      CurClass = CT->getDecl();
    else if (auto BGT = BaseTy->getAs<BoundGenericType>())
      CurClass = dyn_cast<ClassDecl>(BGT->getDecl());
    else if (UnboundGenericType *UGT = BaseTy->getAs<UnboundGenericType>())
      CurClass = dyn_cast<ClassDecl>(UGT->getDecl());

    if (CurClass && CurClass->hasBaseClass()) {
      BaseTy = CurClass->getBaseClass();
    } else {
      break;
    }
  } while (1);

  // FIXME: Weed out overridden methods.
}

static void lookupTypeMembers(Type BaseType, VisibleDeclConsumer &Consumer,
                              const DeclContext *CurrDC,
                              LookupKind LK) {
  NominalTypeDecl *D;
  SmallVector<ValueDecl*, 2> BaseMembers;
  if (BoundGenericType *BGT = BaseType->getAs<BoundGenericType>()) {
    BaseType = BGT->getDecl()->getDeclaredType();
    D = BGT->getDecl();
  } else if (UnboundGenericType *UGT = BaseType->getAs<UnboundGenericType>()) {
    D = UGT->getDecl();
  } else if (NominalType *NT = BaseType->getAs<NominalType>()) {
    D = NT->getDecl();
  } else {
    return;
  }

  bool LookupFromChildDeclContext = false;
  const DeclContext *TempDC = CurrDC;
  while (!TempDC->isModuleContext()) {
    if (TempDC == D) {
      LookupFromChildDeclContext = true;
      break;
    }
    TempDC = TempDC->getParent();
  }

  if (LookupFromChildDeclContext) {
    // Current decl context is contained inside 'D', so generic parameters
    // are visible.
    if (D->getGenericParams())
      for (auto Param : *D->getGenericParams())
        BaseMembers.push_back(Param.getDecl());
  }

  for (Decl *Member : D->getMembers()) {
    if (ValueDecl *VD = dyn_cast<ValueDecl>(Member)) {
      if (LK == LookupKind::QualifiedOnMetatype && isa<VarDecl>(VD))
        continue;

      if (!LookupFromChildDeclContext) {
        // Current decl context is outside 'D', so 'This' decl is not visible.
        if (auto TAD = dyn_cast<TypeAliasDecl>(VD))
          if (TAD->getName().str() == "This")
            continue;
      }
      BaseMembers.push_back(VD);
    }
  }
  DoGlobalExtensionLookup(BaseType, Consumer, BaseMembers,
                          CurrDC->getParentModule(), D->getParentModule(), LK);
}

namespace {

struct FindLocalVal : public StmtVisitor<FindLocalVal> {
  SourceLoc Loc;
  VisibleDeclConsumer &Consumer;

  FindLocalVal(SourceLoc Loc, VisibleDeclConsumer &Consumer)
    : Loc(Loc), Consumer(Consumer) {}

  bool IntersectsRange(SourceRange R) {
    return R.Start.Value.getPointer() <= Loc.Value.getPointer() &&
           R.End.Value.getPointer() >= Loc.Value.getPointer();
  }

  void checkValueDecl(ValueDecl *D) {
    Consumer.foundDecl(D);
  }

  void checkPattern(const Pattern *Pat) {
    switch (Pat->getKind()) {
    case PatternKind::Tuple:
      for (auto &field : cast<TuplePattern>(Pat)->getFields())
        checkPattern(field.getPattern());
      return;
    case PatternKind::Paren:
      return checkPattern(cast<ParenPattern>(Pat)->getSubPattern());
    case PatternKind::Typed:
      return checkPattern(cast<TypedPattern>(Pat)->getSubPattern());
    case PatternKind::Named:
      return checkValueDecl(cast<NamedPattern>(Pat)->getDecl());
    case PatternKind::NominalType:
      return checkPattern(cast<NominalTypePattern>(Pat)->getSubPattern());
    case PatternKind::OneOfElement: {
      auto *OP = cast<OneOfElementPattern>(Pat);
      if (OP->hasSubPattern())
        checkPattern(OP->getSubPattern());
      return;
    }
    case PatternKind::Var:
      return checkPattern(cast<VarPattern>(Pat)->getSubPattern());
    // Handle non-vars.
    case PatternKind::Isa:
    case PatternKind::Expr:
    case PatternKind::Any:
      return;
    }
  }

  void checkGenericParams(GenericParamList *Params) {
    if (!Params)
      return;

    for (auto P : *Params)
      checkValueDecl(P.getDecl());
  }

  void checkTranslationUnit(const TranslationUnit *TU) {
    for (Decl *D : TU->Decls)
      if (TopLevelCodeDecl *TLCD = dyn_cast<TopLevelCodeDecl>(D))
        visit(TLCD->getBody());
  }

  void visitBreakStmt(BreakStmt *) {}
  void visitContinueStmt(ContinueStmt *) {}
  void visitFallthroughStmt(FallthroughStmt *) {}
  void visitReturnStmt(ReturnStmt *) {}
  void visitIfStmt(IfStmt * S) {
    visit(S->getThenStmt());
    if (S->getElseStmt())
      visit(S->getElseStmt());
  }
  void visitWhileStmt(WhileStmt *S) {
    visit(S->getBody());
  }
  void visitDoWhileStmt(DoWhileStmt *S) {
    visit(S->getBody());
  }

  void visitForStmt(ForStmt *S) {
    if (!IntersectsRange(S->getSourceRange()))
      return;
    visit(S->getBody());
    for (Decl *D : S->getInitializerVarDecls()) {
      if (ValueDecl *VD = dyn_cast<ValueDecl>(D))
        checkValueDecl(VD);
    }
  }
  void visitForEachStmt(ForEachStmt *S) {
    if (!IntersectsRange(S->getSourceRange()))
      return;
    visit(S->getBody());
    checkPattern(S->getPattern());
  }
  void visitBraceStmt(BraceStmt *S) {
    if (!IntersectsRange(S->getSourceRange()))
      return;
    for (auto elem : S->getElements()) {
      if (Stmt *S = elem.dyn_cast<Stmt*>())
        visit(S);
    }
    for (auto elem : S->getElements()) {
      if (Decl *D = elem.dyn_cast<Decl*>()) {
        if (ValueDecl *VD = dyn_cast<ValueDecl>(D))
          checkValueDecl(VD);
      }
    }
  }
  
  void visitSwitchStmt(SwitchStmt *S) {
    if (!IntersectsRange(S->getSourceRange()))
      return;
    for (CaseStmt *C : S->getCases()) {
      visit(C);
    }
  }
  
  void visitCaseStmt(CaseStmt *S) {
    if (!IntersectsRange(S->getSourceRange()))
      return;

    // TODO: Check patterns in pattern-matching case.
    visit(S->getBody());
  }
};
  
} // end anonymous namespace

void swift::lookupVisibleDecls(VisibleDeclConsumer &Consumer,
                               const DeclContext *DC,
                               SourceLoc Loc) {
  const Module &M = *DC->getParentModule();

  // If we are inside of a method, check to see if there are any ivars in scope,
  // and if so, whether this is a reference to one of them.
  while (!DC->isModuleContext()) {
    const ValueDecl *BaseDecl = nullptr;
    const ValueDecl *MetaBaseDecl = nullptr;
    GenericParamList *GenericParams = nullptr;
    Type ExtendedType;
    if (auto FE = dyn_cast<FuncExpr>(DC)) {
      for (auto *P : FE->getArgParamPatterns())
        FindLocalVal(Loc, Consumer).checkPattern(P);

      // Look for local variables; normally, the parser resolves these
      // for us, but it can't do the right thing inside local types.
      // FIXME: when we can parse and typecheck the function body partially for
      // code completion, FE->getBody() check can be removed.
      if (Loc.isValid() && FE->getBody()) {
        FindLocalVal(Loc, Consumer).visit(FE->getBody());
      }

      FuncDecl *FD = FE->getDecl();
      if (FD && FD->getExtensionType()) {
        ExtendedType = FD->getExtensionType();
        BaseDecl = FD->getImplicitThisDecl();
        MetaBaseDecl = ExtendedType->getAnyNominal();
        DC = DC->getParent();

        if (FD->isStatic())
          ExtendedType = MetaTypeType::get(ExtendedType, M.getASTContext());
      }

      // Look in the generic parameters after checking our local declaration.
      if (FD)
        GenericParams = FD->getGenericParams();
    } else if (auto CE = dyn_cast<PipeClosureExpr>(DC)) {
      if (Loc.isValid()) {
        FindLocalVal(Loc, Consumer).visit(CE->getBody());
      }
    } else if (auto ED = dyn_cast<ExtensionDecl>(DC)) {
      ExtendedType = ED->getExtendedType();
      BaseDecl = ExtendedType->getNominalOrBoundGenericNominal();
      MetaBaseDecl = BaseDecl;
    } else if (auto ND = dyn_cast<NominalTypeDecl>(DC)) {
      ExtendedType = ND->getDeclaredType();
      BaseDecl = ND;
      MetaBaseDecl = BaseDecl;
    } else if (auto CD = dyn_cast<ConstructorDecl>(DC)) {
      // Look for local variables; normally, the parser resolves these
      // for us, but it can't do the right thing inside local types.
      if (Loc.isValid()) {
        FindLocalVal(Loc, Consumer).visit(CD->getBody());
      }

      BaseDecl = CD->getImplicitThisDecl();
      ExtendedType = CD->getDeclContext()->getDeclaredTypeOfContext();
      if (NominalType *NT = ExtendedType->getAs<NominalType>())
        MetaBaseDecl = NT->getDecl();
      else if (auto UGT = ExtendedType->getAs<UnboundGenericType>())
        MetaBaseDecl = UGT->getDecl();
      DC = DC->getParent();
    } else if (auto DD = dyn_cast<DestructorDecl>(DC)) {
      // Look for local variables; normally, the parser resolves these
      // for us, but it can't do the right thing inside local types.
      if (Loc.isValid()) {
        FindLocalVal(Loc, Consumer).visit(CD->getBody());
      }

      BaseDecl = DD->getImplicitThisDecl();
      ExtendedType = DD->getDeclContext()->getDeclaredTypeOfContext();
      if (NominalType *NT = ExtendedType->getAs<NominalType>())
        MetaBaseDecl = NT->getDecl();
      else if (auto UGT = ExtendedType->getAs<UnboundGenericType>())
        MetaBaseDecl = UGT->getDecl();
      DC = DC->getParent();
    }

    if (BaseDecl) {
      lookupVisibleMemberDecls(ExtendedType, Consumer, DC,
                               LookupKind::Unqualified);
    }

    // Check the generic parameters for something with the given name.
    if (GenericParams) {
      FindLocalVal(Loc, Consumer).checkGenericParams(GenericParams);
    }

    DC = DC->getParent();
  }

  if (Loc.isValid()) {
    if (auto TU = dyn_cast<TranslationUnit>(&M)) {
      // Look for local variables in top-level code; normally, the parser
      // resolves these for us, but it can't do the right thing for
      // local types.
      FindLocalVal(Loc, Consumer).checkTranslationUnit(TU);
    }
  }

  // Track whether we've already searched the Clang modules.
  // FIXME: This is a weird hack. We either need to filter within the
  // Clang module importer, or we need to change how this works.
  bool searchedClangModule = false;
  
  // Do a local lookup within the current module.
  M.lookupVisibleDecls(Module::AccessPathTy(), Consumer,
                       NLKind::UnqualifiedLookup);
  searchedClangModule = isa<ClangModule>(&M);

  // The builtin module has no imports.
  if (isa<BuiltinModule>(M)) return;
  
  const TranslationUnit &TU = cast<TranslationUnit>(M);

  // Scrape through all of the imports looking for additional results.
  // FIXME: Implement DAG-based shadowing rules.
  llvm::SmallPtrSet<Module *, 16> Visited;
  for (auto &ImpEntry : TU.getImportedModules()) {
    if (!Visited.insert(ImpEntry.second))
      continue;

    // FIXME: Only searching Clang modules once.
    if (isa<ClangModule>(ImpEntry.second)) {
      if (searchedClangModule)
        continue;

      searchedClangModule = true;
    }

    ImpEntry.second->lookupVisibleDecls(ImpEntry.first, Consumer,
                                        NLKind::UnqualifiedLookup);
  }

  // Look for a module with the given name.
  // FIXME: Modules aren't ValueDecls
  //Consumer.foundDecl(&M);
  //for (const auto &ImpEntry : TU.getImportedModules())
  //  Consumer.foundDecl(&ImpEntry.second);
}

void swift::lookupVisibleDecls(VisibleDeclConsumer &Consumer, Type BaseTy,
                               const DeclContext *CurrDC) {
  lookupVisibleMemberDecls(BaseTy, Consumer, CurrDC, LookupKind::Qualified);
}