clang-tools-extra/clangd/FindTarget.cpp

   1 //===--- FindTarget.cpp - What does an AST node refer to? -----------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #include "FindTarget.h"
  10 #include "AST.h"
  11 #include "HeuristicResolver.h"
  12 #include "support/Logger.h"
  13 #include "clang/AST/ASTTypeTraits.h"
  14 #include "clang/AST/Decl.h"
  15 #include "clang/AST/DeclBase.h"
  16 #include "clang/AST/DeclCXX.h"
  17 #include "clang/AST/DeclTemplate.h"
  18 #include "clang/AST/DeclVisitor.h"
  19 #include "clang/AST/DeclarationName.h"
  20 #include "clang/AST/Expr.h"
  21 #include "clang/AST/ExprCXX.h"
  22 #include "clang/AST/ExprConcepts.h"
  23 #include "clang/AST/ExprObjC.h"
  24 #include "clang/AST/NestedNameSpecifier.h"
  25 #include "clang/AST/PrettyPrinter.h"
  26 #include "clang/AST/RecursiveASTVisitor.h"
  27 #include "clang/AST/StmtVisitor.h"
  28 #include "clang/AST/TemplateBase.h"
  29 #include "clang/AST/Type.h"
  30 #include "clang/AST/TypeLoc.h"
  31 #include "clang/AST/TypeLocVisitor.h"
  32 #include "clang/AST/TypeVisitor.h"
  33 #include "clang/Basic/LangOptions.h"
  34 #include "clang/Basic/SourceLocation.h"
  35 #include "clang/Basic/SourceManager.h"
  36 #include "clang/Basic/Specifiers.h"
  37 #include "llvm/ADT/STLExtras.h"
  38 #include "llvm/ADT/SmallVector.h"
  39 #include "llvm/ADT/StringExtras.h"
  40 #include "llvm/Support/Casting.h"
  41 #include "llvm/Support/Compiler.h"
  42 #include "llvm/Support/raw_ostream.h"
  43 #include <iterator>
  44 #include <string>
  45 #include <utility>
  46 #include <vector>
  47
  48 namespace clang {
  49 namespace clangd {
  50 namespace {
  51
  52 LLVM_ATTRIBUTE_UNUSED std::string nodeToString(const DynTypedNode &N) {
  53   std::string S = std::string(N.getNodeKind().asStringRef());
  54   {
  55     llvm::raw_string_ostream OS(S);
  56     OS << ": ";
  57     N.print(OS, PrintingPolicy(LangOptions()));
  58   }
  59   std::replace(S.begin(), S.end(), '\n', ' ');
  60   return S;
  61 }
  62
  63 const NamedDecl *getTemplatePattern(const NamedDecl *D) {
  64   if (const CXXRecordDecl *CRD = dyn_cast<CXXRecordDecl>(D)) {
  65     if (const auto *Result = CRD->getTemplateInstantiationPattern())
  66       return Result;
  67     // getTemplateInstantiationPattern returns null if the Specialization is
  68     // incomplete (e.g. the type didn't need to be complete), fall back to the
  69     // primary template.
  70     if (CRD->getTemplateSpecializationKind() == TSK_Undeclared)
  71       if (const auto *Spec = dyn_cast<ClassTemplateSpecializationDecl>(CRD))
  72         return Spec->getSpecializedTemplate()->getTemplatedDecl();
  73   } else if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
  74     return FD->getTemplateInstantiationPattern();
  75   } else if (auto *VD = dyn_cast<VarDecl>(D)) {
  76     // Hmm: getTIP returns its arg if it's not an instantiation?!
  77     VarDecl *T = VD->getTemplateInstantiationPattern();
  78     return (T == D) ? nullptr : T;
  79   } else if (const auto *ED = dyn_cast<EnumDecl>(D)) {
  80     return ED->getInstantiatedFromMemberEnum();
  81   } else if (isa<FieldDecl>(D) || isa<TypedefNameDecl>(D)) {
  82     if (const auto *Parent = llvm::dyn_cast<NamedDecl>(D->getDeclContext()))
  83       if (const DeclContext *ParentPat =
  84               dyn_cast_or_null<DeclContext>(getTemplatePattern(Parent)))
  85         for (const NamedDecl *BaseND : ParentPat->lookup(D->getDeclName()))
  86           if (!BaseND->isImplicit() && BaseND->getKind() == D->getKind())
  87             return BaseND;
  88   } else if (const auto *ECD = dyn_cast<EnumConstantDecl>(D)) {
  89     if (const auto *ED = dyn_cast<EnumDecl>(ECD->getDeclContext())) {
  90       if (const EnumDecl *Pattern = ED->getInstantiatedFromMemberEnum()) {
  91         for (const NamedDecl *BaseECD : Pattern->lookup(ECD->getDeclName()))
  92           return BaseECD;
  93       }
  94     }
  95   }
  96   return nullptr;
  97 }
  98
  99 // Returns true if the `TypedefNameDecl` should not be reported.
 100 bool shouldSkipTypedef(const TypedefNameDecl *TD) {
 101   // These should be treated as keywords rather than decls - the typedef is an
 102   // odd implementation detail.
 103   if (TD == TD->getASTContext().getObjCInstanceTypeDecl() ||
 104       TD == TD->getASTContext().getObjCIdDecl())
 105     return true;
 106   return false;
 107 }
 108
 109 // TargetFinder locates the entities that an AST node refers to.
 110 //
 111 // Typically this is (possibly) one declaration and (possibly) one type, but
 112 // may be more:
 113 //  - for ambiguous nodes like OverloadExpr
 114 //  - if we want to include e.g. both typedefs and the underlying type
 115 //
 116 // This is organized as a set of mutually recursive helpers for particular node
 117 // types, but for most nodes this is a short walk rather than a deep traversal.
 118 //
 119 // It's tempting to do e.g. typedef resolution as a second normalization step,
 120 // after finding the 'primary' decl etc. But we do this monolithically instead
 121 // because:
 122 //  - normalization may require these traversals again (e.g. unwrapping a
 123 //    typedef reveals a decltype which must be traversed)
 124 //  - it doesn't simplify that much, e.g. the first stage must still be able
 125 //    to yield multiple decls to handle OverloadExpr
 126 //  - there are cases where it's required for correctness. e.g:
 127 //      template<class X> using pvec = vector<x*>; pvec<int> x;
 128 //    There's no Decl `pvec<int>`, we must choose `pvec<X>` or `vector<int*>`
 129 //    and both are lossy. We must know upfront what the caller ultimately wants.
 130 struct TargetFinder {
 131   using RelSet = DeclRelationSet;
 132   using Rel = DeclRelation;
 133
 134 private:
 135   const HeuristicResolver *Resolver;
 136   llvm::SmallDenseMap<const NamedDecl *,
 137                       std::pair<RelSet, /*InsertionOrder*/ size_t>>
 138       Decls;
 139   llvm::SmallDenseMap<const Decl *, RelSet> Seen;
 140   RelSet Flags;
 141
 142   template <typename T> void debug(T &Node, RelSet Flags) {
 143     dlog("visit [{0}] {1}", Flags, nodeToString(DynTypedNode::create(Node)));
 144   }
 145
 146   void report(const NamedDecl *D, RelSet Flags) {
 147     dlog("--> [{0}] {1}", Flags, nodeToString(DynTypedNode::create(*D)));
 148     auto It = Decls.try_emplace(D, std::make_pair(Flags, Decls.size()));
 149     // If already exists, update the flags.
 150     if (!It.second)
 151       It.first->second.first |= Flags;
 152   }
 153
 154 public:
 155   TargetFinder(const HeuristicResolver *Resolver) : Resolver(Resolver) {}
 156
 157   llvm::SmallVector<std::pair<const NamedDecl *, RelSet>, 1> takeDecls() const {
 158     using ValTy = std::pair<const NamedDecl *, RelSet>;
 159     llvm::SmallVector<ValTy, 1> Result;
 160     Result.resize(Decls.size());
 161     for (const auto &Elem : Decls)
 162       Result[Elem.second.second] = {Elem.first, Elem.second.first};
 163     return Result;
 164   }
 165
 166   void add(const Decl *Dcl, RelSet Flags) {
 167     const NamedDecl *D = llvm::dyn_cast_or_null<NamedDecl>(Dcl);
 168     if (!D)
 169       return;
 170     debug(*D, Flags);
 171
 172     // Avoid recursion (which can arise in the presence of heuristic
 173     // resolution of dependent names) by exiting early if we have
 174     // already seen this decl with all flags in Flags.
 175     auto Res = Seen.try_emplace(D);
 176     if (!Res.second && Res.first->second.contains(Flags))
 177       return;
 178     Res.first->second |= Flags;
 179
 180     if (const UsingDirectiveDecl *UDD = llvm::dyn_cast<UsingDirectiveDecl>(D))
 181       D = UDD->getNominatedNamespaceAsWritten();
 182
 183     if (const TypedefNameDecl *TND = dyn_cast<TypedefNameDecl>(D)) {
 184       add(TND->getUnderlyingType(), Flags | Rel::Underlying);
 185       Flags |= Rel::Alias; // continue with the alias.
 186     } else if (const UsingDecl *UD = dyn_cast<UsingDecl>(D)) {
 187       // no Underlying as this is a non-renaming alias.
 188       for (const UsingShadowDecl *S : UD->shadows())
 189         add(S->getUnderlyingDecl(), Flags);
 190       Flags |= Rel::Alias; // continue with the alias.
 191     } else if (const UsingEnumDecl *UED = dyn_cast<UsingEnumDecl>(D)) {
 192       add(UED->getEnumDecl(), Flags);
 193       Flags |= Rel::Alias; // continue with the alias.
 194     } else if (const auto *NAD = dyn_cast<NamespaceAliasDecl>(D)) {
 195       add(NAD->getUnderlyingDecl(), Flags | Rel::Underlying);
 196       Flags |= Rel::Alias; // continue with the alias
 197     } else if (const UnresolvedUsingValueDecl *UUVD =
 198                    dyn_cast<UnresolvedUsingValueDecl>(D)) {
 199       if (Resolver) {
 200         for (const NamedDecl *Target : Resolver->resolveUsingValueDecl(UUVD)) {
 201           add(Target, Flags); // no Underlying as this is a non-renaming alias
 202         }
 203       }
 204       Flags |= Rel::Alias; // continue with the alias
 205     } else if (isa<UnresolvedUsingTypenameDecl>(D)) {
 206       // FIXME: improve common dependent scope using name lookup in primary
 207       // templates.
 208       Flags |= Rel::Alias;
 209     } else if (const UsingShadowDecl *USD = dyn_cast<UsingShadowDecl>(D)) {
 210       // Include the Introducing decl, but don't traverse it. This may end up
 211       // including *all* shadows, which we don't want.
 212       report(USD->getIntroducer(), Flags | Rel::Alias);
 213       // Shadow decls are synthetic and not themselves interesting.
 214       // Record the underlying decl instead, if allowed.
 215       D = USD->getTargetDecl();
 216     } else if (const auto *DG = dyn_cast<CXXDeductionGuideDecl>(D)) {
 217       D = DG->getDeducedTemplate();
 218     } else if (const ObjCImplementationDecl *IID =
 219                    dyn_cast<ObjCImplementationDecl>(D)) {
 220       // Treat ObjC{Interface,Implementation}Decl as if they were a decl/def
 221       // pair as long as the interface isn't implicit.
 222       if (const auto *CID = IID->getClassInterface())
 223         if (const auto *DD = CID->getDefinition())
 224           if (!DD->isImplicitInterfaceDecl())
 225             D = DD;
 226     } else if (const ObjCCategoryImplDecl *CID =
 227                    dyn_cast<ObjCCategoryImplDecl>(D)) {
 228       // Treat ObjC{Category,CategoryImpl}Decl as if they were a decl/def pair.
 229       D = CID->getCategoryDecl();
 230     }
 231     if (!D)
 232       return;
 233
 234     if (const Decl *Pat = getTemplatePattern(D)) {
 235       assert(Pat != D);
 236       add(Pat, Flags | Rel::TemplatePattern);
 237       // Now continue with the instantiation.
 238       Flags |= Rel::TemplateInstantiation;
 239     }
 240
 241     report(D, Flags);
 242   }
 243
 244   void add(const Stmt *S, RelSet Flags) {
 245     if (!S)
 246       return;
 247     debug(*S, Flags);
 248     struct Visitor : public ConstStmtVisitor<Visitor> {
 249       TargetFinder &Outer;
 250       RelSet Flags;
 251       Visitor(TargetFinder &Outer, RelSet Flags) : Outer(Outer), Flags(Flags) {}
 252
 253       void VisitCallExpr(const CallExpr *CE) {
 254         Outer.add(CE->getCalleeDecl(), Flags);
 255       }
 256       void VisitConceptSpecializationExpr(const ConceptSpecializationExpr *E) {
 257         Outer.add(E->getNamedConcept(), Flags);
 258       }
 259       void VisitDeclRefExpr(const DeclRefExpr *DRE) {
 260         const Decl *D = DRE->getDecl();
 261         // UsingShadowDecl allows us to record the UsingDecl.
 262         // getFoundDecl() returns the wrong thing in other cases (templates).
 263         if (auto *USD = llvm::dyn_cast<UsingShadowDecl>(DRE->getFoundDecl()))
 264           D = USD;
 265         Outer.add(D, Flags);
 266       }
 267       void VisitMemberExpr(const MemberExpr *ME) {
 268         const Decl *D = ME->getMemberDecl();
 269         if (auto *USD =
 270                 llvm::dyn_cast<UsingShadowDecl>(ME->getFoundDecl().getDecl()))
 271           D = USD;
 272         Outer.add(D, Flags);
 273       }
 274       void VisitOverloadExpr(const OverloadExpr *OE) {
 275         for (auto *D : OE->decls())
 276           Outer.add(D, Flags);
 277       }
 278       void VisitSizeOfPackExpr(const SizeOfPackExpr *SE) {
 279         Outer.add(SE->getPack(), Flags);
 280       }
 281       void VisitCXXConstructExpr(const CXXConstructExpr *CCE) {
 282         Outer.add(CCE->getConstructor(), Flags);
 283       }
 284       void VisitDesignatedInitExpr(const DesignatedInitExpr *DIE) {
 285         for (const DesignatedInitExpr::Designator &D :
 286              llvm::reverse(DIE->designators()))
 287           if (D.isFieldDesignator()) {
 288             Outer.add(D.getField(), Flags);
 289             // We don't know which designator was intended, we assume the outer.
 290             break;
 291           }
 292       }
 293       void VisitGotoStmt(const GotoStmt *Goto) {
 294         if (auto *LabelDecl = Goto->getLabel())
 295           Outer.add(LabelDecl, Flags);
 296       }
 297       void VisitLabelStmt(const LabelStmt *Label) {
 298         if (auto *LabelDecl = Label->getDecl())
 299           Outer.add(LabelDecl, Flags);
 300       }
 301       void
 302       VisitCXXDependentScopeMemberExpr(const CXXDependentScopeMemberExpr *E) {
 303         if (Outer.Resolver) {
 304           for (const NamedDecl *D : Outer.Resolver->resolveMemberExpr(E)) {
 305             Outer.add(D, Flags);
 306           }
 307         }
 308       }
 309       void VisitDependentScopeDeclRefExpr(const DependentScopeDeclRefExpr *E) {
 310         if (Outer.Resolver) {
 311           for (const NamedDecl *D : Outer.Resolver->resolveDeclRefExpr(E)) {
 312             Outer.add(D, Flags);
 313           }
 314         }
 315       }
 316       void VisitObjCIvarRefExpr(const ObjCIvarRefExpr *OIRE) {
 317         Outer.add(OIRE->getDecl(), Flags);
 318       }
 319       void VisitObjCMessageExpr(const ObjCMessageExpr *OME) {
 320         Outer.add(OME->getMethodDecl(), Flags);
 321       }
 322       void VisitObjCPropertyRefExpr(const ObjCPropertyRefExpr *OPRE) {
 323         if (OPRE->isExplicitProperty())
 324           Outer.add(OPRE->getExplicitProperty(), Flags);
 325         else {
 326           if (OPRE->isMessagingGetter())
 327             Outer.add(OPRE->getImplicitPropertyGetter(), Flags);
 328           if (OPRE->isMessagingSetter())
 329             Outer.add(OPRE->getImplicitPropertySetter(), Flags);
 330         }
 331       }
 332       void VisitObjCProtocolExpr(const ObjCProtocolExpr *OPE) {
 333         Outer.add(OPE->getProtocol(), Flags);
 334       }
 335       void VisitOpaqueValueExpr(const OpaqueValueExpr *OVE) {
 336         Outer.add(OVE->getSourceExpr(), Flags);
 337       }
 338       void VisitPseudoObjectExpr(const PseudoObjectExpr *POE) {
 339         Outer.add(POE->getSyntacticForm(), Flags);
 340       }
 341       void VisitCXXNewExpr(const CXXNewExpr *CNE) {
 342         Outer.add(CNE->getOperatorNew(), Flags);
 343       }
 344       void VisitCXXDeleteExpr(const CXXDeleteExpr *CDE) {
 345         Outer.add(CDE->getOperatorDelete(), Flags);
 346       }
 347     };
 348     Visitor(*this, Flags).Visit(S);
 349   }
 350
 351   void add(QualType T, RelSet Flags) {
 352     if (T.isNull())
 353       return;
 354     debug(T, Flags);
 355     struct Visitor : public TypeVisitor<Visitor> {
 356       TargetFinder &Outer;
 357       RelSet Flags;
 358       Visitor(TargetFinder &Outer, RelSet Flags) : Outer(Outer), Flags(Flags) {}
 359
 360       void VisitTagType(const TagType *TT) {
 361         Outer.add(TT->getAsTagDecl(), Flags);
 362       }
 363
 364       void VisitElaboratedType(const ElaboratedType *ET) {
 365         Outer.add(ET->desugar(), Flags);
 366       }
 367
 368       void VisitUsingType(const UsingType *ET) {
 369         Outer.add(ET->getFoundDecl(), Flags);
 370       }
 371
 372       void VisitInjectedClassNameType(const InjectedClassNameType *ICNT) {
 373         Outer.add(ICNT->getDecl(), Flags);
 374       }
 375
 376       void VisitDecltypeType(const DecltypeType *DTT) {
 377         Outer.add(DTT->getUnderlyingType(), Flags | Rel::Underlying);
 378       }
 379       void VisitDeducedType(const DeducedType *DT) {
 380         // FIXME: In practice this doesn't work: the AutoType you find inside
 381         // TypeLoc never has a deduced type. https://llvm.org/PR42914
 382         Outer.add(DT->getDeducedType(), Flags);
 383       }
 384       void VisitUnresolvedUsingType(const UnresolvedUsingType *UUT) {
 385         Outer.add(UUT->getDecl(), Flags);
 386       }
 387       void VisitDeducedTemplateSpecializationType(
 388           const DeducedTemplateSpecializationType *DTST) {
 389         if (const auto *USD = DTST->getTemplateName().getAsUsingShadowDecl())
 390           Outer.add(USD, Flags);
 391
 392         // FIXME: This is a workaround for https://llvm.org/PR42914,
 393         // which is causing DTST->getDeducedType() to be empty. We
 394         // fall back to the template pattern and miss the instantiation
 395         // even when it's known in principle. Once that bug is fixed,
 396         // the following code can be removed (the existing handling in
 397         // VisitDeducedType() is sufficient).
 398         if (auto *TD = DTST->getTemplateName().getAsTemplateDecl())
 399           Outer.add(TD->getTemplatedDecl(), Flags | Rel::TemplatePattern);
 400       }
 401       void VisitDependentNameType(const DependentNameType *DNT) {
 402         if (Outer.Resolver) {
 403           for (const NamedDecl *ND :
 404                Outer.Resolver->resolveDependentNameType(DNT)) {
 405             Outer.add(ND, Flags);
 406           }
 407         }
 408       }
 409       void VisitDependentTemplateSpecializationType(
 410           const DependentTemplateSpecializationType *DTST) {
 411         if (Outer.Resolver) {
 412           for (const NamedDecl *ND :
 413                Outer.Resolver->resolveTemplateSpecializationType(DTST)) {
 414             Outer.add(ND, Flags);
 415           }
 416         }
 417       }
 418       void VisitTypedefType(const TypedefType *TT) {
 419         if (shouldSkipTypedef(TT->getDecl()))
 420           return;
 421         Outer.add(TT->getDecl(), Flags);
 422       }
 423       void
 424       VisitTemplateSpecializationType(const TemplateSpecializationType *TST) {
 425         // Have to handle these case-by-case.
 426
 427         if (const auto *UTN = TST->getTemplateName().getAsUsingShadowDecl())
 428           Outer.add(UTN, Flags);
 429
 430         // templated type aliases: there's no specialized/instantiated using
 431         // decl to point to. So try to find a decl for the underlying type
 432         // (after substitution), and failing that point to the (templated) using
 433         // decl.
 434         if (TST->isTypeAlias()) {
 435           Outer.add(TST->getAliasedType(), Flags | Rel::Underlying);
 436           // Don't *traverse* the alias, which would result in traversing the
 437           // template of the underlying type.
 438           Outer.report(
 439               TST->getTemplateName().getAsTemplateDecl()->getTemplatedDecl(),
 440               Flags | Rel::Alias | Rel::TemplatePattern);
 441         }
 442         // specializations of template template parameters aren't instantiated
 443         // into decls, so they must refer to the parameter itself.
 444         else if (const auto *Parm =
 445                      llvm::dyn_cast_or_null<TemplateTemplateParmDecl>(
 446                          TST->getTemplateName().getAsTemplateDecl()))
 447           Outer.add(Parm, Flags);
 448         // class template specializations have a (specialized) CXXRecordDecl.
 449         else if (const CXXRecordDecl *RD = TST->getAsCXXRecordDecl())
 450           Outer.add(RD, Flags); // add(Decl) will despecialize if needed.
 451         else {
 452           // fallback: the (un-specialized) declaration from primary template.
 453           if (auto *TD = TST->getTemplateName().getAsTemplateDecl())
 454             Outer.add(TD->getTemplatedDecl(), Flags | Rel::TemplatePattern);
 455         }
 456       }
 457       void VisitTemplateTypeParmType(const TemplateTypeParmType *TTPT) {
 458         Outer.add(TTPT->getDecl(), Flags);
 459       }
 460       void VisitObjCInterfaceType(const ObjCInterfaceType *OIT) {
 461         Outer.add(OIT->getDecl(), Flags);
 462       }
 463     };
 464     Visitor(*this, Flags).Visit(T.getTypePtr());
 465   }
 466
 467   void add(const NestedNameSpecifier *NNS, RelSet Flags) {
 468     if (!NNS)
 469       return;
 470     debug(*NNS, Flags);
 471     switch (NNS->getKind()) {
 472     case NestedNameSpecifier::Namespace:
 473       add(NNS->getAsNamespace(), Flags);
 474       return;
 475     case NestedNameSpecifier::NamespaceAlias:
 476       add(NNS->getAsNamespaceAlias(), Flags);
 477       return;
 478     case NestedNameSpecifier::Identifier:
 479       if (Resolver) {
 480         add(QualType(Resolver->resolveNestedNameSpecifierToType(NNS), 0),
 481             Flags);
 482       }
 483       return;
 484     case NestedNameSpecifier::TypeSpec:
 485     case NestedNameSpecifier::TypeSpecWithTemplate:
 486       add(QualType(NNS->getAsType(), 0), Flags);
 487       return;
 488     case NestedNameSpecifier::Global:
 489       // This should be TUDecl, but we can't get a pointer to it!
 490       return;
 491     case NestedNameSpecifier::Super:
 492       add(NNS->getAsRecordDecl(), Flags);
 493       return;
 494     }
 495     llvm_unreachable("unhandled NestedNameSpecifier::SpecifierKind");
 496   }
 497
 498   void add(const CXXCtorInitializer *CCI, RelSet Flags) {
 499     if (!CCI)
 500       return;
 501     debug(*CCI, Flags);
 502
 503     if (CCI->isAnyMemberInitializer())
 504       add(CCI->getAnyMember(), Flags);
 505     // Constructor calls contain a TypeLoc node, so we don't handle them here.
 506   }
 507
 508   void add(const TemplateArgument &Arg, RelSet Flags) {
 509     // Only used for template template arguments.
 510     // For type and non-type template arguments, SelectionTree
 511     // will hit a more specific node (e.g. a TypeLoc or a
 512     // DeclRefExpr).
 513     if (Arg.getKind() == TemplateArgument::Template ||
 514         Arg.getKind() == TemplateArgument::TemplateExpansion) {
 515       if (TemplateDecl *TD =
 516               Arg.getAsTemplateOrTemplatePattern().getAsTemplateDecl()) {
 517         report(TD, Flags);
 518       }
 519       if (const auto *USD =
 520               Arg.getAsTemplateOrTemplatePattern().getAsUsingShadowDecl())
 521         add(USD, Flags);
 522     }
 523   }
 524 };
 525
 526 } // namespace
 527
 528 llvm::SmallVector<std::pair<const NamedDecl *, DeclRelationSet>, 1>
 529 allTargetDecls(const DynTypedNode &N, const HeuristicResolver *Resolver) {
 530   dlog("allTargetDecls({0})", nodeToString(N));
 531   TargetFinder Finder(Resolver);
 532   DeclRelationSet Flags;
 533   if (const Decl *D = N.get<Decl>())
 534     Finder.add(D, Flags);
 535   else if (const Stmt *S = N.get<Stmt>())
 536     Finder.add(S, Flags);
 537   else if (const NestedNameSpecifierLoc *NNSL = N.get<NestedNameSpecifierLoc>())
 538     Finder.add(NNSL->getNestedNameSpecifier(), Flags);
 539   else if (const NestedNameSpecifier *NNS = N.get<NestedNameSpecifier>())
 540     Finder.add(NNS, Flags);
 541   else if (const TypeLoc *TL = N.get<TypeLoc>())
 542     Finder.add(TL->getType(), Flags);
 543   else if (const QualType *QT = N.get<QualType>())
 544     Finder.add(*QT, Flags);
 545   else if (const CXXCtorInitializer *CCI = N.get<CXXCtorInitializer>())
 546     Finder.add(CCI, Flags);
 547   else if (const TemplateArgumentLoc *TAL = N.get<TemplateArgumentLoc>())
 548     Finder.add(TAL->getArgument(), Flags);
 549   else if (const CXXBaseSpecifier *CBS = N.get<CXXBaseSpecifier>())
 550     Finder.add(CBS->getTypeSourceInfo()->getType(), Flags);
 551   else if (const ObjCProtocolLoc *PL = N.get<ObjCProtocolLoc>())
 552     Finder.add(PL->getProtocol(), Flags);
 553   return Finder.takeDecls();
 554 }
 555
 556 llvm::SmallVector<const NamedDecl *, 1>
 557 targetDecl(const DynTypedNode &N, DeclRelationSet Mask,
 558            const HeuristicResolver *Resolver) {
 559   llvm::SmallVector<const NamedDecl *, 1> Result;
 560   for (const auto &Entry : allTargetDecls(N, Resolver)) {
 561     if (!(Entry.second & ~Mask))
 562       Result.push_back(Entry.first);
 563   }
 564   return Result;
 565 }
 566
 567 llvm::SmallVector<const NamedDecl *, 1>
 568 explicitReferenceTargets(DynTypedNode N, DeclRelationSet Mask,
 569                          const HeuristicResolver *Resolver) {
 570   assert(!(Mask & (DeclRelation::TemplatePattern |
 571                    DeclRelation::TemplateInstantiation)) &&
 572          "explicitReferenceTargets handles templates on its own");
 573   auto Decls = allTargetDecls(N, Resolver);
 574
 575   // We prefer to return template instantiation, but fallback to template
 576   // pattern if instantiation is not available.
 577   Mask |= DeclRelation::TemplatePattern | DeclRelation::TemplateInstantiation;
 578
 579   llvm::SmallVector<const NamedDecl *, 1> TemplatePatterns;
 580   llvm::SmallVector<const NamedDecl *, 1> Targets;
 581   bool SeenTemplateInstantiations = false;
 582   for (auto &D : Decls) {
 583     if (D.second & ~Mask)
 584       continue;
 585     if (D.second & DeclRelation::TemplatePattern) {
 586       TemplatePatterns.push_back(D.first);
 587       continue;
 588     }
 589     if (D.second & DeclRelation::TemplateInstantiation)
 590       SeenTemplateInstantiations = true;
 591     Targets.push_back(D.first);
 592   }
 593   if (!SeenTemplateInstantiations)
 594     Targets.insert(Targets.end(), TemplatePatterns.begin(),
 595                    TemplatePatterns.end());
 596   return Targets;
 597 }
 598
 599 namespace {
 600 llvm::SmallVector<ReferenceLoc> refInDecl(const Decl *D,
 601                                           const HeuristicResolver *Resolver) {
 602   struct Visitor : ConstDeclVisitor<Visitor> {
 603     Visitor(const HeuristicResolver *Resolver) : Resolver(Resolver) {}
 604
 605     const HeuristicResolver *Resolver;
 606     llvm::SmallVector<ReferenceLoc> Refs;
 607
 608     void VisitUsingDirectiveDecl(const UsingDirectiveDecl *D) {
 609       // We want to keep it as non-declaration references, as the
 610       // "using namespace" declaration doesn't have a name.
 611       Refs.push_back(ReferenceLoc{D->getQualifierLoc(),
 612                                   D->getIdentLocation(),
 613                                   /*IsDecl=*/false,
 614                                   {D->getNominatedNamespaceAsWritten()}});
 615     }
 616
 617     void VisitUsingDecl(const UsingDecl *D) {
 618       // "using ns::identifier;" is a non-declaration reference.
 619       Refs.push_back(ReferenceLoc{
 620           D->getQualifierLoc(), D->getLocation(), /*IsDecl=*/false,
 621           explicitReferenceTargets(DynTypedNode::create(*D),
 622                                    DeclRelation::Underlying, Resolver)});
 623     }
 624
 625     void VisitNamespaceAliasDecl(const NamespaceAliasDecl *D) {
 626       // For namespace alias, "namespace Foo = Target;", we add two references.
 627       // Add a declaration reference for Foo.
 628       VisitNamedDecl(D);
 629       // Add a non-declaration reference for Target.
 630       Refs.push_back(ReferenceLoc{D->getQualifierLoc(),
 631                                   D->getTargetNameLoc(),
 632                                   /*IsDecl=*/false,
 633                                   {D->getAliasedNamespace()}});
 634     }
 635
 636     void VisitNamedDecl(const NamedDecl *ND) {
 637       // We choose to ignore {Class, Function, Var, TypeAlias}TemplateDecls. As
 638       // as their underlying decls, covering the same range, will be visited.
 639       if (llvm::isa<ClassTemplateDecl>(ND) ||
 640           llvm::isa<FunctionTemplateDecl>(ND) ||
 641           llvm::isa<VarTemplateDecl>(ND) ||
 642           llvm::isa<TypeAliasTemplateDecl>(ND))
 643         return;
 644       // FIXME: decide on how to surface destructors when we need them.
 645       if (llvm::isa<CXXDestructorDecl>(ND))
 646         return;
 647       // Filter anonymous decls, name location will point outside the name token
 648       // and the clients are not prepared to handle that.
 649       if (ND->getDeclName().isIdentifier() &&
 650           !ND->getDeclName().getAsIdentifierInfo())
 651         return;
 652       Refs.push_back(ReferenceLoc{getQualifierLoc(*ND),
 653                                   ND->getLocation(),
 654                                   /*IsDecl=*/true,
 655                                   {ND}});
 656     }
 657
 658     void VisitCXXDeductionGuideDecl(const CXXDeductionGuideDecl *DG) {
 659       // The class template name in a deduction guide targets the class
 660       // template.
 661       Refs.push_back(ReferenceLoc{DG->getQualifierLoc(),
 662                                   DG->getNameInfo().getLoc(),
 663                                   /*IsDecl=*/false,
 664                                   {DG->getDeducedTemplate()}});
 665     }
 666
 667     void VisitObjCMethodDecl(const ObjCMethodDecl *OMD) {
 668       // The name may have several tokens, we can only report the first.
 669       Refs.push_back(ReferenceLoc{NestedNameSpecifierLoc(),
 670                                   OMD->getSelectorStartLoc(),
 671                                   /*IsDecl=*/true,
 672                                   {OMD}});
 673     }
 674
 675     void VisitObjCCategoryDecl(const ObjCCategoryDecl *OCD) {
 676       // getLocation is the extended class's location, not the category's.
 677       Refs.push_back(ReferenceLoc{NestedNameSpecifierLoc(),
 678                                   OCD->getLocation(),
 679                                   /*IsDecl=*/false,
 680                                   {OCD->getClassInterface()}});
 681       Refs.push_back(ReferenceLoc{NestedNameSpecifierLoc(),
 682                                   OCD->getCategoryNameLoc(),
 683                                   /*IsDecl=*/true,
 684                                   {OCD}});
 685     }
 686
 687     void VisitObjCCategoryImplDecl(const ObjCCategoryImplDecl *OCID) {
 688       Refs.push_back(ReferenceLoc{NestedNameSpecifierLoc(),
 689                                   OCID->getLocation(),
 690                                   /*IsDecl=*/false,
 691                                   {OCID->getClassInterface()}});
 692       Refs.push_back(ReferenceLoc{NestedNameSpecifierLoc(),
 693                                   OCID->getCategoryNameLoc(),
 694                                   /*IsDecl=*/true,
 695                                   {OCID->getCategoryDecl()}});
 696     }
 697   };
 698
 699   Visitor V{Resolver};
 700   V.Visit(D);
 701   return V.Refs;
 702 }
 703
 704 llvm::SmallVector<ReferenceLoc> refInStmt(const Stmt *S,
 705                                           const HeuristicResolver *Resolver) {
 706   struct Visitor : ConstStmtVisitor<Visitor> {
 707     Visitor(const HeuristicResolver *Resolver) : Resolver(Resolver) {}
 708
 709     const HeuristicResolver *Resolver;
 710     // FIXME: handle more complicated cases: more ObjC, designated initializers.
 711     llvm::SmallVector<ReferenceLoc> Refs;
 712
 713     void VisitConceptSpecializationExpr(const ConceptSpecializationExpr *E) {
 714       Refs.push_back(ReferenceLoc{E->getNestedNameSpecifierLoc(),
 715                                   E->getConceptNameLoc(),
 716                                   /*IsDecl=*/false,
 717                                   {E->getNamedConcept()}});
 718     }
 719
 720     void VisitDeclRefExpr(const DeclRefExpr *E) {
 721       Refs.push_back(ReferenceLoc{E->getQualifierLoc(),
 722                                   E->getNameInfo().getLoc(),
 723                                   /*IsDecl=*/false,
 724                                   {E->getFoundDecl()}});
 725     }
 726
 727     void VisitDependentScopeDeclRefExpr(const DependentScopeDeclRefExpr *E) {
 728       Refs.push_back(ReferenceLoc{
 729           E->getQualifierLoc(), E->getNameInfo().getLoc(), /*IsDecl=*/false,
 730           explicitReferenceTargets(DynTypedNode::create(*E), {}, Resolver)});
 731     }
 732
 733     void VisitMemberExpr(const MemberExpr *E) {
 734       // Skip destructor calls to avoid duplication: TypeLoc within will be
 735       // visited separately.
 736       if (llvm::isa<CXXDestructorDecl>(E->getFoundDecl().getDecl()))
 737         return;
 738       Refs.push_back(ReferenceLoc{E->getQualifierLoc(),
 739                                   E->getMemberNameInfo().getLoc(),
 740                                   /*IsDecl=*/false,
 741                                   {E->getFoundDecl()}});
 742     }
 743
 744     void
 745     VisitCXXDependentScopeMemberExpr(const CXXDependentScopeMemberExpr *E) {
 746       Refs.push_back(ReferenceLoc{
 747           E->getQualifierLoc(), E->getMemberNameInfo().getLoc(),
 748           /*IsDecl=*/false,
 749           explicitReferenceTargets(DynTypedNode::create(*E), {}, Resolver)});
 750     }
 751
 752     void VisitOverloadExpr(const OverloadExpr *E) {
 753       Refs.push_back(ReferenceLoc{E->getQualifierLoc(),
 754                                   E->getNameInfo().getLoc(),
 755                                   /*IsDecl=*/false,
 756                                   llvm::SmallVector<const NamedDecl *, 1>(
 757                                       E->decls().begin(), E->decls().end())});
 758     }
 759
 760     void VisitSizeOfPackExpr(const SizeOfPackExpr *E) {
 761       Refs.push_back(ReferenceLoc{NestedNameSpecifierLoc(),
 762                                   E->getPackLoc(),
 763                                   /*IsDecl=*/false,
 764                                   {E->getPack()}});
 765     }
 766
 767     void VisitObjCPropertyRefExpr(const ObjCPropertyRefExpr *E) {
 768       Refs.push_back(ReferenceLoc{
 769           NestedNameSpecifierLoc(), E->getLocation(),
 770           /*IsDecl=*/false,
 771           // Select the getter, setter, or @property depending on the call.
 772           explicitReferenceTargets(DynTypedNode::create(*E), {}, Resolver)});
 773     }
 774
 775     void VisitObjCIvarRefExpr(const ObjCIvarRefExpr *OIRE) {
 776       Refs.push_back(ReferenceLoc{NestedNameSpecifierLoc(),
 777                                   OIRE->getLocation(),
 778                                   /*IsDecl=*/false,
 779                                   {OIRE->getDecl()}});
 780     }
 781
 782     void VisitObjCMessageExpr(const ObjCMessageExpr *E) {
 783       // The name may have several tokens, we can only report the first.
 784       Refs.push_back(ReferenceLoc{NestedNameSpecifierLoc(),
 785                                   E->getSelectorStartLoc(),
 786                                   /*IsDecl=*/false,
 787                                   {E->getMethodDecl()}});
 788     }
 789
 790     void VisitDesignatedInitExpr(const DesignatedInitExpr *DIE) {
 791       for (const DesignatedInitExpr::Designator &D : DIE->designators()) {
 792         if (!D.isFieldDesignator())
 793           continue;
 794
 795         Refs.push_back(ReferenceLoc{NestedNameSpecifierLoc(),
 796                                     D.getFieldLoc(),
 797                                     /*IsDecl=*/false,
 798                                     {D.getField()}});
 799       }
 800     }
 801
 802     void VisitGotoStmt(const GotoStmt *GS) {
 803       Refs.push_back(ReferenceLoc{NestedNameSpecifierLoc(),
 804                                   GS->getLabelLoc(),
 805                                   /*IsDecl=*/false,
 806                                   {GS->getLabel()}});
 807     }
 808
 809     void VisitLabelStmt(const LabelStmt *LS) {
 810       Refs.push_back(ReferenceLoc{NestedNameSpecifierLoc(),
 811                                   LS->getIdentLoc(),
 812                                   /*IsDecl=*/true,
 813                                   {LS->getDecl()}});
 814     }
 815   };
 816
 817   Visitor V{Resolver};
 818   V.Visit(S);
 819   return V.Refs;
 820 }
 821
 822 llvm::SmallVector<ReferenceLoc>
 823 refInTypeLoc(TypeLoc L, const HeuristicResolver *Resolver) {
 824   struct Visitor : TypeLocVisitor<Visitor> {
 825     Visitor(const HeuristicResolver *Resolver) : Resolver(Resolver) {}
 826
 827     const HeuristicResolver *Resolver;
 828     llvm::SmallVector<ReferenceLoc> Refs;
 829
 830     void VisitElaboratedTypeLoc(ElaboratedTypeLoc L) {
 831       // We only know about qualifier, rest if filled by inner locations.
 832       size_t InitialSize = Refs.size();
 833       Visit(L.getNamedTypeLoc().getUnqualifiedLoc());
 834       size_t NewSize = Refs.size();
 835       // Add qualifier for the newly-added refs.
 836       for (unsigned I = InitialSize; I < NewSize; ++I) {
 837         ReferenceLoc *Ref = &Refs[I];
 838         // Fill in the qualifier.
 839         assert(!Ref->Qualifier.hasQualifier() && "qualifier already set");
 840         Ref->Qualifier = L.getQualifierLoc();
 841       }
 842     }
 843
 844     void VisitUsingTypeLoc(UsingTypeLoc L) {
 845       Refs.push_back(ReferenceLoc{NestedNameSpecifierLoc(),
 846                                   L.getLocalSourceRange().getBegin(),
 847                                   /*IsDecl=*/false,
 848                                   {L.getFoundDecl()}});
 849     }
 850
 851     void VisitTagTypeLoc(TagTypeLoc L) {
 852       Refs.push_back(ReferenceLoc{NestedNameSpecifierLoc(),
 853                                   L.getNameLoc(),
 854                                   /*IsDecl=*/false,
 855                                   {L.getDecl()}});
 856     }
 857
 858     void VisitTemplateTypeParmTypeLoc(TemplateTypeParmTypeLoc L) {
 859       Refs.push_back(ReferenceLoc{NestedNameSpecifierLoc(),
 860                                   L.getNameLoc(),
 861                                   /*IsDecl=*/false,
 862                                   {L.getDecl()}});
 863     }
 864
 865     void VisitTemplateSpecializationTypeLoc(TemplateSpecializationTypeLoc L) {
 866       // We must ensure template type aliases are included in results if they
 867       // were written in the source code, e.g. in
 868       //    template <class T> using valias = vector<T>;
 869       //    ^valias<int> x;
 870       // 'explicitReferenceTargets' will return:
 871       //    1. valias with mask 'Alias'.
 872       //    2. 'vector<int>' with mask 'Underlying'.
 873       //  we want to return only #1 in this case.
 874       Refs.push_back(ReferenceLoc{
 875           NestedNameSpecifierLoc(), L.getTemplateNameLoc(), /*IsDecl=*/false,
 876           explicitReferenceTargets(DynTypedNode::create(L.getType()),
 877                                    DeclRelation::Alias, Resolver)});
 878     }
 879     void VisitDeducedTemplateSpecializationTypeLoc(
 880         DeducedTemplateSpecializationTypeLoc L) {
 881       Refs.push_back(ReferenceLoc{
 882           NestedNameSpecifierLoc(), L.getNameLoc(), /*IsDecl=*/false,
 883           explicitReferenceTargets(DynTypedNode::create(L.getType()),
 884                                    DeclRelation::Alias, Resolver)});
 885     }
 886
 887     void VisitInjectedClassNameTypeLoc(InjectedClassNameTypeLoc TL) {
 888       Refs.push_back(ReferenceLoc{NestedNameSpecifierLoc(),
 889                                   TL.getNameLoc(),
 890                                   /*IsDecl=*/false,
 891                                   {TL.getDecl()}});
 892     }
 893
 894     void VisitDependentTemplateSpecializationTypeLoc(
 895         DependentTemplateSpecializationTypeLoc L) {
 896       Refs.push_back(
 897           ReferenceLoc{L.getQualifierLoc(), L.getTemplateNameLoc(),
 898                        /*IsDecl=*/false,
 899                        explicitReferenceTargets(
 900                            DynTypedNode::create(L.getType()), {}, Resolver)});
 901     }
 902
 903     void VisitDependentNameTypeLoc(DependentNameTypeLoc L) {
 904       Refs.push_back(
 905           ReferenceLoc{L.getQualifierLoc(), L.getNameLoc(),
 906                        /*IsDecl=*/false,
 907                        explicitReferenceTargets(
 908                            DynTypedNode::create(L.getType()), {}, Resolver)});
 909     }
 910
 911     void VisitTypedefTypeLoc(TypedefTypeLoc L) {
 912       if (shouldSkipTypedef(L.getTypedefNameDecl()))
 913         return;
 914       Refs.push_back(ReferenceLoc{NestedNameSpecifierLoc(),
 915                                   L.getNameLoc(),
 916                                   /*IsDecl=*/false,
 917                                   {L.getTypedefNameDecl()}});
 918     }
 919
 920     void VisitObjCInterfaceTypeLoc(ObjCInterfaceTypeLoc L) {
 921       Refs.push_back(ReferenceLoc{NestedNameSpecifierLoc(),
 922                                   L.getNameLoc(),
 923                                   /*IsDecl=*/false,
 924                                   {L.getIFaceDecl()}});
 925     }
 926   };
 927
 928   Visitor V{Resolver};
 929   V.Visit(L.getUnqualifiedLoc());
 930   return V.Refs;
 931 }
 932
 933 class ExplicitReferenceCollector
 934     : public RecursiveASTVisitor<ExplicitReferenceCollector> {
 935 public:
 936   ExplicitReferenceCollector(llvm::function_ref<void(ReferenceLoc)> Out,
 937                              const HeuristicResolver *Resolver)
 938       : Out(Out), Resolver(Resolver) {
 939     assert(Out);
 940   }
 941
 942   bool VisitTypeLoc(TypeLoc TTL) {
 943     if (TypeLocsToSkip.count(TTL.getBeginLoc()))
 944       return true;
 945     visitNode(DynTypedNode::create(TTL));
 946     return true;
 947   }
 948
 949   bool TraverseElaboratedTypeLoc(ElaboratedTypeLoc L) {
 950     // ElaboratedTypeLoc will reports information for its inner type loc.
 951     // Otherwise we loose information about inner types loc's qualifier.
 952     TypeLoc Inner = L.getNamedTypeLoc().getUnqualifiedLoc();
 953     TypeLocsToSkip.insert(Inner.getBeginLoc());
 954     return RecursiveASTVisitor::TraverseElaboratedTypeLoc(L);
 955   }
 956
 957   bool VisitStmt(Stmt *S) {
 958     visitNode(DynTypedNode::create(*S));
 959     return true;
 960   }
 961
 962   bool TraverseOpaqueValueExpr(OpaqueValueExpr *OVE) {
 963     visitNode(DynTypedNode::create(*OVE));
 964     // Not clear why the source expression is skipped by default...
 965     // FIXME: can we just make RecursiveASTVisitor do this?
 966     return RecursiveASTVisitor::TraverseStmt(OVE->getSourceExpr());
 967   }
 968
 969   bool TraversePseudoObjectExpr(PseudoObjectExpr *POE) {
 970     visitNode(DynTypedNode::create(*POE));
 971     // Traverse only the syntactic form to find the *written* references.
 972     // (The semantic form also contains lots of duplication)
 973     return RecursiveASTVisitor::TraverseStmt(POE->getSyntacticForm());
 974   }
 975
 976   // We re-define Traverse*, since there's no corresponding Visit*.
 977   // TemplateArgumentLoc is the only way to get locations for references to
 978   // template template parameters.
 979   bool TraverseTemplateArgumentLoc(TemplateArgumentLoc A) {
 980     switch (A.getArgument().getKind()) {
 981     case TemplateArgument::Template:
 982     case TemplateArgument::TemplateExpansion:
 983       reportReference(ReferenceLoc{A.getTemplateQualifierLoc(),
 984                                    A.getTemplateNameLoc(),
 985                                    /*IsDecl=*/false,
 986                                    {A.getArgument()
 987                                         .getAsTemplateOrTemplatePattern()
 988                                         .getAsTemplateDecl()}},
 989                       DynTypedNode::create(A.getArgument()));
 990       break;
 991     case TemplateArgument::Declaration:
 992       break; // FIXME: can this actually happen in TemplateArgumentLoc?
 993     case TemplateArgument::Integral:
 994     case TemplateArgument::Null:
 995     case TemplateArgument::NullPtr:
 996       break; // no references.
 997     case TemplateArgument::Pack:
 998     case TemplateArgument::Type:
 999     case TemplateArgument::Expression:
1000       break; // Handled by VisitType and VisitExpression.
1001     };
1002     return RecursiveASTVisitor::TraverseTemplateArgumentLoc(A);
1003   }
1004
1005   bool VisitDecl(Decl *D) {
1006     visitNode(DynTypedNode::create(*D));
1007     return true;
1008   }
1009
1010   // We have to use Traverse* because there is no corresponding Visit*.
1011   bool TraverseNestedNameSpecifierLoc(NestedNameSpecifierLoc L) {
1012     if (!L.getNestedNameSpecifier())
1013       return true;
1014     visitNode(DynTypedNode::create(L));
1015     // Inner type is missing information about its qualifier, skip it.
1016     if (auto TL = L.getTypeLoc())
1017       TypeLocsToSkip.insert(TL.getBeginLoc());
1018     return RecursiveASTVisitor::TraverseNestedNameSpecifierLoc(L);
1019   }
1020
1021   bool TraverseObjCProtocolLoc(ObjCProtocolLoc ProtocolLoc) {
1022     visitNode(DynTypedNode::create(ProtocolLoc));
1023     return true;
1024   }
1025
1026   bool TraverseConstructorInitializer(CXXCtorInitializer *Init) {
1027     visitNode(DynTypedNode::create(*Init));
1028     return RecursiveASTVisitor::TraverseConstructorInitializer(Init);
1029   }
1030
1031 private:
1032   /// Obtain information about a reference directly defined in \p N. Does not
1033   /// recurse into child nodes, e.g. do not expect references for constructor
1034   /// initializers
1035   ///
1036   /// Any of the fields in the returned structure can be empty, but not all of
1037   /// them, e.g.
1038   ///   - for implicitly generated nodes (e.g. MemberExpr from range-based-for),
1039   ///     source location information may be missing,
1040   ///   - for dependent code, targets may be empty.
1041   ///
1042   /// (!) For the purposes of this function declarations are not considered to
1043   ///     be references. However, declarations can have references inside them,
1044   ///     e.g. 'namespace foo = std' references namespace 'std' and this
1045   ///     function will return the corresponding reference.
1046   llvm::SmallVector<ReferenceLoc> explicitReference(DynTypedNode N) {
1047     if (auto *D = N.get<Decl>())
1048       return refInDecl(D, Resolver);
1049     if (auto *S = N.get<Stmt>())
1050       return refInStmt(S, Resolver);
1051     if (auto *NNSL = N.get<NestedNameSpecifierLoc>()) {
1052       // (!) 'DeclRelation::Alias' ensures we do not loose namespace aliases.
1053       return {ReferenceLoc{
1054           NNSL->getPrefix(), NNSL->getLocalBeginLoc(), false,
1055           explicitReferenceTargets(
1056               DynTypedNode::create(*NNSL->getNestedNameSpecifier()),
1057               DeclRelation::Alias, Resolver)}};
1058     }
1059     if (const TypeLoc *TL = N.get<TypeLoc>())
1060       return refInTypeLoc(*TL, Resolver);
1061     if (const CXXCtorInitializer *CCI = N.get<CXXCtorInitializer>()) {
1062       // Other type initializers (e.g. base initializer) are handled by visiting
1063       // the typeLoc.
1064       if (CCI->isAnyMemberInitializer()) {
1065         return {ReferenceLoc{NestedNameSpecifierLoc(),
1066                              CCI->getMemberLocation(),
1067                              /*IsDecl=*/false,
1068                              {CCI->getAnyMember()}}};
1069       }
1070     }
1071     if (const ObjCProtocolLoc *PL = N.get<ObjCProtocolLoc>())
1072       return {ReferenceLoc{NestedNameSpecifierLoc(),
1073                            PL->getLocation(),
1074                            /*IsDecl=*/false,
1075                            {PL->getProtocol()}}};
1076
1077     // We do not have location information for other nodes (QualType, etc)
1078     return {};
1079   }
1080
1081   void visitNode(DynTypedNode N) {
1082     for (auto &R : explicitReference(N))
1083       reportReference(std::move(R), N);
1084   }
1085
1086   void reportReference(ReferenceLoc &&Ref, DynTypedNode N) {
1087     // Strip null targets that can arise from invalid code.
1088     // (This avoids having to check for null everywhere we insert)
1089     llvm::erase_value(Ref.Targets, nullptr);
1090     // Our promise is to return only references from the source code. If we lack
1091     // location information, skip these nodes.
1092     // Normally this should not happen in practice, unless there are bugs in the
1093     // traversals or users started the traversal at an implicit node.
1094     if (Ref.NameLoc.isInvalid()) {
1095       dlog("invalid location at node {0}", nodeToString(N));
1096       return;
1097     }
1098     Out(Ref);
1099   }
1100
1101   llvm::function_ref<void(ReferenceLoc)> Out;
1102   const HeuristicResolver *Resolver;
1103   /// TypeLocs starting at these locations must be skipped, see
1104   /// TraverseElaboratedTypeSpecifierLoc for details.
1105   llvm::DenseSet<SourceLocation> TypeLocsToSkip;
1106 };
1107 } // namespace
1108
1109 void findExplicitReferences(const Stmt *S,
1110                             llvm::function_ref<void(ReferenceLoc)> Out,
1111                             const HeuristicResolver *Resolver) {
1112   assert(S);
1113   ExplicitReferenceCollector(Out, Resolver).TraverseStmt(const_cast<Stmt *>(S));
1114 }
1115 void findExplicitReferences(const Decl *D,
1116                             llvm::function_ref<void(ReferenceLoc)> Out,
1117                             const HeuristicResolver *Resolver) {
1118   assert(D);
1119   ExplicitReferenceCollector(Out, Resolver).TraverseDecl(const_cast<Decl *>(D));
1120 }
1121 void findExplicitReferences(const ASTContext &AST,
1122                             llvm::function_ref<void(ReferenceLoc)> Out,
1123                             const HeuristicResolver *Resolver) {
1124   ExplicitReferenceCollector(Out, Resolver)
1125       .TraverseAST(const_cast<ASTContext &>(AST));
1126 }
1127
1128 llvm::raw_ostream &operator<<(llvm::raw_ostream &OS, DeclRelation R) {
1129   switch (R) {
1130 #define REL_CASE(X)                                                            \
1131   case DeclRelation::X:                                                        \
1132     return OS << #X;
1133     REL_CASE(Alias);
1134     REL_CASE(Underlying);
1135     REL_CASE(TemplateInstantiation);
1136     REL_CASE(TemplatePattern);
1137 #undef REL_CASE
1138   }
1139   llvm_unreachable("Unhandled DeclRelation enum");
1140 }
1141 llvm::raw_ostream &operator<<(llvm::raw_ostream &OS, DeclRelationSet RS) {
1142   const char *Sep = "";
1143   for (unsigned I = 0; I < RS.S.size(); ++I) {
1144     if (RS.S.test(I)) {
1145       OS << Sep << static_cast<DeclRelation>(I);
1146       Sep = "|";
1147     }
1148   }
1149   return OS;
1150 }
1151
1152 llvm::raw_ostream &operator<<(llvm::raw_ostream &OS, ReferenceLoc R) {
1153   // note we cannot print R.NameLoc without a source manager.
1154   OS << "targets = {";
1155   llvm::SmallVector<std::string> Targets;
1156   for (const NamedDecl *T : R.Targets) {
1157     llvm::raw_string_ostream Target(Targets.emplace_back());
1158     Target << printQualifiedName(*T) << printTemplateSpecializationArgs(*T);
1159   }
1160   llvm::sort(Targets);
1161   OS << llvm::join(Targets, ", ");
1162   OS << "}";
1163   if (R.Qualifier) {
1164     OS << ", qualifier = '";
1165     R.Qualifier.getNestedNameSpecifier()->print(OS,
1166                                                 PrintingPolicy(LangOptions()));
1167     OS << "'";
1168   }
1169   if (R.IsDecl)
1170     OS << ", decl";
1171   return OS;
1172 }
1173
1174 } // namespace clangd
1175 } // namespace clang