[clangd] Split findDefs/highlights into XRefs, from ClangdUnit. NFC

Going to add unit tests in the next patch. (Haha!) But seriously there's
some work to do first - need to extract the markers-in-source-code
parser from CodeComplete test and make it more flexible, to allow
annotated ranges etc.

git-svn-id: https://llvm.org/svn/llvm-project/clang-tools-extra/trunk@321087 91177308-0d34-0410-b5e6-96231b3b80d8

6 files changed, 307 insertions, 260 deletions

diff --git a/clangd/CMakeLists.txt b/clangd/CMakeLists.txt
index 69a0c684..df242da5 100644
--- a/clangd/CMakeLists.txt
+++ b/clangd/CMakeLists.txt
@@ -20,6 +20,7 @@ add_clang_library(clangDaemon
   ProtocolHandlers.cpp
   SourceCode.cpp
   Trace.cpp
+  XRefs.cpp
   index/FileIndex.cpp
   index/Index.cpp
   index/MemIndex.cpp
diff --git a/clangd/ClangdServer.cpp b/clangd/ClangdServer.cpp
index 4a9ee699..129fc074 100644
--- a/clangd/ClangdServer.cpp
+++ b/clangd/ClangdServer.cpp
@@ -8,7 +8,9 @@
 //===-------------------------------------------------------------------===//
 
 #include "ClangdServer.h"
+#include "CodeComplete.h"
 #include "SourceCode.h"
+#include "XRefs.h"
 #include "clang/Format/Format.h"
 #include "clang/Frontend/CompilerInstance.h"
 #include "clang/Frontend/CompilerInvocation.h"
diff --git a/clangd/ClangdUnit.cpp b/clangd/ClangdUnit.cpp
index 5f45b2f4..f735e09f 100644
--- a/clangd/ClangdUnit.cpp
+++ b/clangd/ClangdUnit.cpp
@@ -267,268 +267,15 @@ ParsedAST::Build(const Context &Ctx,
 namespace {
 
 SourceLocation getMacroArgExpandedLocation(const SourceManager &Mgr,
-                                           const FileEntry *FE,
-                                           unsigned Offset) {
-  SourceLocation FileLoc = Mgr.translateFileLineCol(FE, 1, 1);
-  return Mgr.getMacroArgExpandedLocation(FileLoc.getLocWithOffset(Offset));
-}
-
-SourceLocation getMacroArgExpandedLocation(const SourceManager &Mgr,
                                            const FileEntry *FE, Position Pos) {
   SourceLocation InputLoc =
       Mgr.translateFileLineCol(FE, Pos.line + 1, Pos.character + 1);
   return Mgr.getMacroArgExpandedLocation(InputLoc);
 }
 
-/// Finds declarations locations that a given source location refers to.
-class DeclarationAndMacrosFinder : public index::IndexDataConsumer {
-  std::vector<const Decl *> Decls;
-  std::vector<const MacroInfo *> MacroInfos;
-  const SourceLocation &SearchedLocation;
-  const ASTContext &AST;
-  Preprocessor &PP;
-
-public:
-  DeclarationAndMacrosFinder(raw_ostream &OS,
-                             const SourceLocation &SearchedLocation,
-                             ASTContext &AST, Preprocessor &PP)
-      : SearchedLocation(SearchedLocation), AST(AST), PP(PP) {}
-
-  std::vector<const Decl *> takeDecls() {
-    // Don't keep the same declaration multiple times.
-    // This can happen when nodes in the AST are visited twice.
-    std::sort(Decls.begin(), Decls.end());
-    auto Last = std::unique(Decls.begin(), Decls.end());
-    Decls.erase(Last, Decls.end());
-    return std::move(Decls);
-  }
-
-  std::vector<const MacroInfo *> takeMacroInfos() {
-    // Don't keep the same Macro info multiple times.
-    std::sort(MacroInfos.begin(), MacroInfos.end());
-    auto Last = std::unique(MacroInfos.begin(), MacroInfos.end());
-    MacroInfos.erase(Last, MacroInfos.end());
-    return std::move(MacroInfos);
-  }
-
-  bool
-  handleDeclOccurence(const Decl *D, index::SymbolRoleSet Roles,
-                      ArrayRef<index::SymbolRelation> Relations, FileID FID,
-                      unsigned Offset,
-                      index::IndexDataConsumer::ASTNodeInfo ASTNode) override {
-    if (isSearchedLocation(FID, Offset))
-      Decls.push_back(D);
-    return true;
-  }
-
-private:
-  bool isSearchedLocation(FileID FID, unsigned Offset) const {
-    const SourceManager &SourceMgr = AST.getSourceManager();
-    return SourceMgr.getFileOffset(SearchedLocation) == Offset &&
-           SourceMgr.getFileID(SearchedLocation) == FID;
-  }
-
-  void finish() override {
-    // Also handle possible macro at the searched location.
-    Token Result;
-    if (!Lexer::getRawToken(SearchedLocation, Result, AST.getSourceManager(),
-                            AST.getLangOpts(), false)) {
-      if (Result.is(tok::raw_identifier)) {
-        PP.LookUpIdentifierInfo(Result);
-      }
-      IdentifierInfo *IdentifierInfo = Result.getIdentifierInfo();
-      if (IdentifierInfo && IdentifierInfo->hadMacroDefinition()) {
-        std::pair<FileID, unsigned int> DecLoc =
-            AST.getSourceManager().getDecomposedExpansionLoc(SearchedLocation);
-        // Get the definition just before the searched location so that a macro
-        // referenced in a '#undef MACRO' can still be found.
-        SourceLocation BeforeSearchedLocation = getMacroArgExpandedLocation(
-            AST.getSourceManager(),
-            AST.getSourceManager().getFileEntryForID(DecLoc.first),
-            DecLoc.second - 1);
-        MacroDefinition MacroDef =
-            PP.getMacroDefinitionAtLoc(IdentifierInfo, BeforeSearchedLocation);
-        MacroInfo *MacroInf = MacroDef.getMacroInfo();
-        if (MacroInf) {
-          MacroInfos.push_back(MacroInf);
-        }
-      }
-    }
-  }
-};
-
-/// Finds document highlights that a given list of declarations refers to.
-class DocumentHighlightsFinder : public index::IndexDataConsumer {
-  std::vector<const Decl *> &Decls;
-  std::vector<DocumentHighlight> DocumentHighlights;
-  const ASTContext &AST;
-
-public:
-  DocumentHighlightsFinder(raw_ostream &OS, ASTContext &AST, Preprocessor &PP,
-                           std::vector<const Decl *> &Decls)
-      : Decls(Decls), AST(AST) {}
-  std::vector<DocumentHighlight> takeHighlights() {
-    // Don't keep the same highlight multiple times.
-    // This can happen when nodes in the AST are visited twice.
-    std::sort(DocumentHighlights.begin(), DocumentHighlights.end());
-    auto Last =
-        std::unique(DocumentHighlights.begin(), DocumentHighlights.end());
-    DocumentHighlights.erase(Last, DocumentHighlights.end());
-    return std::move(DocumentHighlights);
-  }
-
-  bool
-  handleDeclOccurence(const Decl *D, index::SymbolRoleSet Roles,
-                      ArrayRef<index::SymbolRelation> Relations, FileID FID,
-                      unsigned Offset,
-                      index::IndexDataConsumer::ASTNodeInfo ASTNode) override {
-    const SourceManager &SourceMgr = AST.getSourceManager();
-    if (SourceMgr.getMainFileID() != FID ||
-        std::find(Decls.begin(), Decls.end(), D) == Decls.end()) {
-      return true;
-    }
-    SourceLocation End;
-    const LangOptions &LangOpts = AST.getLangOpts();
-    SourceLocation StartOfFileLoc = SourceMgr.getLocForStartOfFile(FID);
-    SourceLocation HightlightStartLoc = StartOfFileLoc.getLocWithOffset(Offset);
-    End =
-        Lexer::getLocForEndOfToken(HightlightStartLoc, 0, SourceMgr, LangOpts);
-    SourceRange SR(HightlightStartLoc, End);
-
-    DocumentHighlightKind Kind = DocumentHighlightKind::Text;
-    if (static_cast<index::SymbolRoleSet>(index::SymbolRole::Write) & Roles)
-      Kind = DocumentHighlightKind::Write;
-    else if (static_cast<index::SymbolRoleSet>(index::SymbolRole::Read) & Roles)
-      Kind = DocumentHighlightKind::Read;
-
-    DocumentHighlights.push_back(getDocumentHighlight(SR, Kind));
-    return true;
-  }
-
-private:
-  DocumentHighlight getDocumentHighlight(SourceRange SR,
-                                         DocumentHighlightKind Kind) {
-    const SourceManager &SourceMgr = AST.getSourceManager();
-    SourceLocation LocStart = SR.getBegin();
-    Position Begin;
-    Begin.line = SourceMgr.getSpellingLineNumber(LocStart) - 1;
-    Begin.character = SourceMgr.getSpellingColumnNumber(LocStart) - 1;
-    Position End;
-    End.line = SourceMgr.getSpellingLineNumber(SR.getEnd()) - 1;
-    End.character = SourceMgr.getSpellingColumnNumber(SR.getEnd()) - 1;
-    Range R = {Begin, End};
-    DocumentHighlight DH;
-    DH.range = R;
-    DH.kind = Kind;
-    return DH;
-  }
-};
 
 } // namespace
 
-llvm::Optional<Location>
-getDeclarationLocation(ParsedAST &AST, const SourceRange &ValSourceRange) {
-  const SourceManager &SourceMgr = AST.getASTContext().getSourceManager();
-  const LangOptions &LangOpts = AST.getASTContext().getLangOpts();
-  SourceLocation LocStart = ValSourceRange.getBegin();
-
-  const FileEntry *F =
-      SourceMgr.getFileEntryForID(SourceMgr.getFileID(LocStart));
-  if (!F)
-    return llvm::None;
-  SourceLocation LocEnd = Lexer::getLocForEndOfToken(ValSourceRange.getEnd(), 0,
-                                                     SourceMgr, LangOpts);
-  Position Begin;
-  Begin.line = SourceMgr.getSpellingLineNumber(LocStart) - 1;
-  Begin.character = SourceMgr.getSpellingColumnNumber(LocStart) - 1;
-  Position End;
-  End.line = SourceMgr.getSpellingLineNumber(LocEnd) - 1;
-  End.character = SourceMgr.getSpellingColumnNumber(LocEnd) - 1;
-  Range R = {Begin, End};
-  Location L;
-
-  StringRef FilePath = F->tryGetRealPathName();
-  if (FilePath.empty())
-    FilePath = F->getName();
-  L.uri = URI::fromFile(FilePath);
-  L.range = R;
-  return L;
-}
-
-std::vector<Location> clangd::findDefinitions(const Context &Ctx,
-                                              ParsedAST &AST, Position Pos) {
-  const SourceManager &SourceMgr = AST.getASTContext().getSourceManager();
-  const FileEntry *FE = SourceMgr.getFileEntryForID(SourceMgr.getMainFileID());
-  if (!FE)
-    return {};
-
-  SourceLocation SourceLocationBeg = getBeginningOfIdentifier(AST, Pos, FE);
-
-  auto DeclMacrosFinder = std::make_shared<DeclarationAndMacrosFinder>(
-      llvm::errs(), SourceLocationBeg, AST.getASTContext(),
-      AST.getPreprocessor());
-  index::IndexingOptions IndexOpts;
-  IndexOpts.SystemSymbolFilter =
-      index::IndexingOptions::SystemSymbolFilterKind::All;
-  IndexOpts.IndexFunctionLocals = true;
-
-  indexTopLevelDecls(AST.getASTContext(), AST.getTopLevelDecls(),
-                     DeclMacrosFinder, IndexOpts);
-
-  std::vector<const Decl *> Decls = DeclMacrosFinder->takeDecls();
-  std::vector<const MacroInfo *> MacroInfos =
-      DeclMacrosFinder->takeMacroInfos();
-  std::vector<Location> Result;
-
-  for (auto Item : Decls) {
-    auto L = getDeclarationLocation(AST, Item->getSourceRange());
-    if (L)
-      Result.push_back(*L);
-  }
-
-  for (auto Item : MacroInfos) {
-    SourceRange SR(Item->getDefinitionLoc(), Item->getDefinitionEndLoc());
-    auto L = getDeclarationLocation(AST, SR);
-    if (L)
-      Result.push_back(*L);
-  }
-
-  return Result;
-}
-
-std::vector<DocumentHighlight>
-clangd::findDocumentHighlights(const Context &Ctx, ParsedAST &AST,
-                               Position Pos) {
-  const SourceManager &SourceMgr = AST.getASTContext().getSourceManager();
-  const FileEntry *FE = SourceMgr.getFileEntryForID(SourceMgr.getMainFileID());
-  if (!FE)
-    return {};
-
-  SourceLocation SourceLocationBeg = getBeginningOfIdentifier(AST, Pos, FE);
-
-  auto DeclMacrosFinder = std::make_shared<DeclarationAndMacrosFinder>(
-      llvm::errs(), SourceLocationBeg, AST.getASTContext(),
-      AST.getPreprocessor());
-  index::IndexingOptions IndexOpts;
-  IndexOpts.SystemSymbolFilter =
-      index::IndexingOptions::SystemSymbolFilterKind::All;
-  IndexOpts.IndexFunctionLocals = true;
-
-  // Macro occurences are not currently handled.
-  indexTopLevelDecls(AST.getASTContext(), AST.getTopLevelDecls(),
-                     DeclMacrosFinder, IndexOpts);
-
-  std::vector<const Decl *> SelectedDecls = DeclMacrosFinder->takeDecls();
-
-  auto DocHighlightsFinder = std::make_shared<DocumentHighlightsFinder>(
-      llvm::errs(), AST.getASTContext(), AST.getPreprocessor(), SelectedDecls);
-
-  indexTopLevelDecls(AST.getASTContext(), AST.getTopLevelDecls(),
-                     DocHighlightsFinder, IndexOpts);
-
-  return DocHighlightsFinder->takeHighlights();
-}
-
 void ParsedAST::ensurePreambleDeclsDeserialized() {
   if (PreambleDeclsDeserialized || !Preamble)
     return;
diff --git a/clangd/ClangdUnit.h b/clangd/ClangdUnit.h
index a8110de4..47902c54 100644
--- a/clangd/ClangdUnit.h
+++ b/clangd/ClangdUnit.h
@@ -258,13 +258,6 @@ private:
 SourceLocation getBeginningOfIdentifier(ParsedAST &Unit, const Position &Pos,
                                         const FileEntry *FE);
 
-/// Get definition of symbol at a specified \p Pos.
-std::vector<Location> findDefinitions(const Context &Ctx, ParsedAST &AST,
-                                      Position Pos);
-
-std::vector<DocumentHighlight>
-findDocumentHighlights(const Context &Ctx, ParsedAST &AST, Position Pos);
-
 /// For testing/debugging purposes. Note that this method deserializes all
 /// unserialized Decls, so use with care.
 void dumpAST(ParsedAST &AST, llvm::raw_ostream &OS);
diff --git a/clangd/XRefs.cpp b/clangd/XRefs.cpp
new file mode 100644
index 00000000..9bd4131b
--- /dev/null
+++ b/clangd/XRefs.cpp
@@ -0,0 +1,270 @@
+//===--- XRefs.cpp ----------------------------------------------*- C++-*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===---------------------------------------------------------------------===//
+#include "XRefs.h"
+#include "clang/Index/IndexDataConsumer.h"
+#include "clang/Index/IndexingAction.h"
+namespace clang {
+namespace clangd {
+using namespace llvm;
+namespace {
+
+/// Finds declarations locations that a given source location refers to.
+class DeclarationAndMacrosFinder : public index::IndexDataConsumer {
+  std::vector<const Decl *> Decls;
+  std::vector<const MacroInfo *> MacroInfos;
+  const SourceLocation &SearchedLocation;
+  const ASTContext &AST;
+  Preprocessor &PP;
+
+public:
+  DeclarationAndMacrosFinder(raw_ostream &OS,
+                             const SourceLocation &SearchedLocation,
+                             ASTContext &AST, Preprocessor &PP)
+      : SearchedLocation(SearchedLocation), AST(AST), PP(PP) {}
+
+  std::vector<const Decl *> takeDecls() {
+    // Don't keep the same declaration multiple times.
+    // This can happen when nodes in the AST are visited twice.
+    std::sort(Decls.begin(), Decls.end());
+    auto Last = std::unique(Decls.begin(), Decls.end());
+    Decls.erase(Last, Decls.end());
+    return std::move(Decls);
+  }
+
+  std::vector<const MacroInfo *> takeMacroInfos() {
+    // Don't keep the same Macro info multiple times.
+    std::sort(MacroInfos.begin(), MacroInfos.end());
+    auto Last = std::unique(MacroInfos.begin(), MacroInfos.end());
+    MacroInfos.erase(Last, MacroInfos.end());
+    return std::move(MacroInfos);
+  }
+
+  bool
+  handleDeclOccurence(const Decl *D, index::SymbolRoleSet Roles,
+                      ArrayRef<index::SymbolRelation> Relations, FileID FID,
+                      unsigned Offset,
+                      index::IndexDataConsumer::ASTNodeInfo ASTNode) override {
+    if (isSearchedLocation(FID, Offset))
+      Decls.push_back(D);
+    return true;
+  }
+
+private:
+  bool isSearchedLocation(FileID FID, unsigned Offset) const {
+    const SourceManager &SourceMgr = AST.getSourceManager();
+    return SourceMgr.getFileOffset(SearchedLocation) == Offset &&
+           SourceMgr.getFileID(SearchedLocation) == FID;
+  }
+
+  void finish() override {
+    // Also handle possible macro at the searched location.
+    Token Result;
+    auto &Mgr = AST.getSourceManager();
+    if (!Lexer::getRawToken(SearchedLocation, Result, Mgr, AST.getLangOpts(),
+                            false)) {
+      if (Result.is(tok::raw_identifier)) {
+        PP.LookUpIdentifierInfo(Result);
+      }
+      IdentifierInfo *IdentifierInfo = Result.getIdentifierInfo();
+      if (IdentifierInfo && IdentifierInfo->hadMacroDefinition()) {
+        std::pair<FileID, unsigned int> DecLoc =
+            Mgr.getDecomposedExpansionLoc(SearchedLocation);
+        // Get the definition just before the searched location so that a macro
+        // referenced in a '#undef MACRO' can still be found.
+        SourceLocation BeforeSearchedLocation = Mgr.getMacroArgExpandedLocation(
+            Mgr.getLocForStartOfFile(DecLoc.first)
+                .getLocWithOffset(DecLoc.second - 1));
+        MacroDefinition MacroDef =
+            PP.getMacroDefinitionAtLoc(IdentifierInfo, BeforeSearchedLocation);
+        MacroInfo *MacroInf = MacroDef.getMacroInfo();
+        if (MacroInf) {
+          MacroInfos.push_back(MacroInf);
+        }
+      }
+    }
+  }
+};
+
+llvm::Optional<Location>
+getDeclarationLocation(ParsedAST &AST, const SourceRange &ValSourceRange) {
+  const SourceManager &SourceMgr = AST.getASTContext().getSourceManager();
+  const LangOptions &LangOpts = AST.getASTContext().getLangOpts();
+  SourceLocation LocStart = ValSourceRange.getBegin();
+
+  const FileEntry *F =
+      SourceMgr.getFileEntryForID(SourceMgr.getFileID(LocStart));
+  if (!F)
+    return llvm::None;
+  SourceLocation LocEnd = Lexer::getLocForEndOfToken(ValSourceRange.getEnd(), 0,
+                                                     SourceMgr, LangOpts);
+  Position Begin;
+  Begin.line = SourceMgr.getSpellingLineNumber(LocStart) - 1;
+  Begin.character = SourceMgr.getSpellingColumnNumber(LocStart) - 1;
+  Position End;
+  End.line = SourceMgr.getSpellingLineNumber(LocEnd) - 1;
+  End.character = SourceMgr.getSpellingColumnNumber(LocEnd) - 1;
+  Range R = {Begin, End};
+  Location L;
+
+  StringRef FilePath = F->tryGetRealPathName();
+  if (FilePath.empty())
+    FilePath = F->getName();
+  L.uri = URI::fromFile(FilePath);
+  L.range = R;
+  return L;
+}
+
+} // namespace
+
+std::vector<Location> findDefinitions(const Context &Ctx, ParsedAST &AST,
+                                      Position Pos) {
+  const SourceManager &SourceMgr = AST.getASTContext().getSourceManager();
+  const FileEntry *FE = SourceMgr.getFileEntryForID(SourceMgr.getMainFileID());
+  if (!FE)
+    return {};
+
+  SourceLocation SourceLocationBeg = getBeginningOfIdentifier(AST, Pos, FE);
+
+  auto DeclMacrosFinder = std::make_shared<DeclarationAndMacrosFinder>(
+      llvm::errs(), SourceLocationBeg, AST.getASTContext(),
+      AST.getPreprocessor());
+  index::IndexingOptions IndexOpts;
+  IndexOpts.SystemSymbolFilter =
+      index::IndexingOptions::SystemSymbolFilterKind::All;
+  IndexOpts.IndexFunctionLocals = true;
+
+  indexTopLevelDecls(AST.getASTContext(), AST.getTopLevelDecls(),
+                     DeclMacrosFinder, IndexOpts);
+
+  std::vector<const Decl *> Decls = DeclMacrosFinder->takeDecls();
+  std::vector<const MacroInfo *> MacroInfos =
+      DeclMacrosFinder->takeMacroInfos();
+  std::vector<Location> Result;
+
+  for (auto Item : Decls) {
+    auto L = getDeclarationLocation(AST, Item->getSourceRange());
+    if (L)
+      Result.push_back(*L);
+  }
+
+  for (auto Item : MacroInfos) {
+    SourceRange SR(Item->getDefinitionLoc(), Item->getDefinitionEndLoc());
+    auto L = getDeclarationLocation(AST, SR);
+    if (L)
+      Result.push_back(*L);
+  }
+
+  return Result;
+}
+
+namespace {
+
+/// Finds document highlights that a given list of declarations refers to.
+class DocumentHighlightsFinder : public index::IndexDataConsumer {
+  std::vector<const Decl *> &Decls;
+  std::vector<DocumentHighlight> DocumentHighlights;
+  const ASTContext &AST;
+
+public:
+  DocumentHighlightsFinder(raw_ostream &OS, ASTContext &AST, Preprocessor &PP,
+                           std::vector<const Decl *> &Decls)
+      : Decls(Decls), AST(AST) {}
+  std::vector<DocumentHighlight> takeHighlights() {
+    // Don't keep the same highlight multiple times.
+    // This can happen when nodes in the AST are visited twice.
+    std::sort(DocumentHighlights.begin(), DocumentHighlights.end());
+    auto Last =
+        std::unique(DocumentHighlights.begin(), DocumentHighlights.end());
+    DocumentHighlights.erase(Last, DocumentHighlights.end());
+    return std::move(DocumentHighlights);
+  }
+
+  bool
+  handleDeclOccurence(const Decl *D, index::SymbolRoleSet Roles,
+                      ArrayRef<index::SymbolRelation> Relations, FileID FID,
+                      unsigned Offset,
+                      index::IndexDataConsumer::ASTNodeInfo ASTNode) override {
+    const SourceManager &SourceMgr = AST.getSourceManager();
+    if (SourceMgr.getMainFileID() != FID ||
+        std::find(Decls.begin(), Decls.end(), D) == Decls.end()) {
+      return true;
+    }
+    SourceLocation End;
+    const LangOptions &LangOpts = AST.getLangOpts();
+    SourceLocation StartOfFileLoc = SourceMgr.getLocForStartOfFile(FID);
+    SourceLocation HightlightStartLoc = StartOfFileLoc.getLocWithOffset(Offset);
+    End =
+        Lexer::getLocForEndOfToken(HightlightStartLoc, 0, SourceMgr, LangOpts);
+    SourceRange SR(HightlightStartLoc, End);
+
+    DocumentHighlightKind Kind = DocumentHighlightKind::Text;
+    if (static_cast<index::SymbolRoleSet>(index::SymbolRole::Write) & Roles)
+      Kind = DocumentHighlightKind::Write;
+    else if (static_cast<index::SymbolRoleSet>(index::SymbolRole::Read) & Roles)
+      Kind = DocumentHighlightKind::Read;
+
+    DocumentHighlights.push_back(getDocumentHighlight(SR, Kind));
+    return true;
+  }
+
+private:
+  DocumentHighlight getDocumentHighlight(SourceRange SR,
+                                         DocumentHighlightKind Kind) {
+    const SourceManager &SourceMgr = AST.getSourceManager();
+    SourceLocation LocStart = SR.getBegin();
+    Position Begin;
+    Begin.line = SourceMgr.getSpellingLineNumber(LocStart) - 1;
+    Begin.character = SourceMgr.getSpellingColumnNumber(LocStart) - 1;
+    Position End;
+    End.line = SourceMgr.getSpellingLineNumber(SR.getEnd()) - 1;
+    End.character = SourceMgr.getSpellingColumnNumber(SR.getEnd()) - 1;
+    Range R = {Begin, End};
+    DocumentHighlight DH;
+    DH.range = R;
+    DH.kind = Kind;
+    return DH;
+  }
+};
+
+} // namespace
+
+std::vector<DocumentHighlight>
+findDocumentHighlights(const Context &Ctx, ParsedAST &AST, Position Pos) {
+  const SourceManager &SourceMgr = AST.getASTContext().getSourceManager();
+  const FileEntry *FE = SourceMgr.getFileEntryForID(SourceMgr.getMainFileID());
+  if (!FE)
+    return {};
+
+  SourceLocation SourceLocationBeg = getBeginningOfIdentifier(AST, Pos, FE);
+
+  auto DeclMacrosFinder = std::make_shared<DeclarationAndMacrosFinder>(
+      llvm::errs(), SourceLocationBeg, AST.getASTContext(),
+      AST.getPreprocessor());
+  index::IndexingOptions IndexOpts;
+  IndexOpts.SystemSymbolFilter =
+      index::IndexingOptions::SystemSymbolFilterKind::All;
+  IndexOpts.IndexFunctionLocals = true;
+
+  // Macro occurences are not currently handled.
+  indexTopLevelDecls(AST.getASTContext(), AST.getTopLevelDecls(),
+                     DeclMacrosFinder, IndexOpts);
+
+  std::vector<const Decl *> SelectedDecls = DeclMacrosFinder->takeDecls();
+
+  auto DocHighlightsFinder = std::make_shared<DocumentHighlightsFinder>(
+      llvm::errs(), AST.getASTContext(), AST.getPreprocessor(), SelectedDecls);
+
+  indexTopLevelDecls(AST.getASTContext(), AST.getTopLevelDecls(),
+                     DocHighlightsFinder, IndexOpts);
+
+  return DocHighlightsFinder->takeHighlights();
+}
+
+} // namespace clangd
+} // namespace clang
diff --git a/clangd/XRefs.h b/clangd/XRefs.h
new file mode 100644
index 00000000..04518a19
--- /dev/null
+++ b/clangd/XRefs.h
@@ -0,0 +1,34 @@
+//===--- XRefs.h ------------------------------------------------*- C++-*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===---------------------------------------------------------------------===//
+//
+// Features that traverse references between symbols.
+//
+//===---------------------------------------------------------------------===//
+#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANGD_XREFS_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANGD_XREFS_H
+
+#include "ClangdUnit.h"
+#include "Context.h"
+#include "Protocol.h"
+#include <vector>
+
+namespace clang {
+namespace clangd {
+
+/// Get definition of symbol at a specified \p Pos.
+std::vector<Location> findDefinitions(const Context &Ctx, ParsedAST &AST,
+                                      Position Pos);
+
+/// Returns highlights for all usages of a symbol at \p Pos.
+std::vector<DocumentHighlight>
+findDocumentHighlights(const Context &Ctx, ParsedAST &AST, Position Pos);
+
+} // namespace clangd
+} // namespace clang
+#endif