Symbol tags in SymbolInformation, WorkspaceSymbol, CallHierarchyItem and TypeHierarchyItem

clang-tools-extra/clangd/ClangdLSPServer.h

@@ -243,7 +243,7 @@ class ClangdLSPServer : private ClangdServer::Callbacks,
   /// Used to indicate the ClangdLSPServer is being destroyed.
   std::atomic<bool> IsBeingDestroyed = {false};
 
-  // FIXME: The caching is a temporary solution to get corresponding clangd 
+  // FIXME: The caching is a temporary solution to get corresponding clangd
   // diagnostic from a LSP diagnostic.
   // Ideally, ClangdServer can generate an identifier for each diagnostic,
   // emit them via the LSP's data field (which was newly added in LSP 3.16).

clang-tools-extra/clangd/FindSymbols.cpp

@@ -13,7 +13,10 @@
 #include "Quality.h"
 #include "SourceCode.h"
 #include "index/Index.h"
+#include "index/Symbol.h"
+#include "index/SymbolLocation.h"
 #include "support/Logger.h"
+#include "clang/AST/Decl.h"
 #include "clang/AST/DeclFriend.h"
 #include "clang/AST/DeclTemplate.h"
 #include "clang/Index/IndexSymbol.h"
@@ -135,6 +138,42 @@ bool isFinal(const Decl *D) {
   return false;
 }
 
+// A method "overrides" if:
+// 1. It overrides at least one method
+// 2. At least one of the overridden methods is virtual (but NOT pure
+// virtual)
+bool isOverrides(const NamedDecl *ND) {
+  if (const auto *MD = llvm::dyn_cast<CXXMethodDecl>(ND)) {
+    if (MD->size_overridden_methods() == 0)
+      return false;
+
+    for (const auto *Overridden : MD->overridden_methods()) {
+      // Check if the overridden method is virtual but not pure virtual
+      if (Overridden->isVirtual() && !Overridden->isPureVirtual())
+        return true;
+    }
+  }
+  return false;
+}
+
+// A method "implements" pure virtual methods from base classes if:
+// 1. It overrides at least one method
+// 2. It is NOT itself pure virtual (i.e., it has a concrete implementation)
+// 3. ALL overridden methods are pure virtual
+bool isImplements(const NamedDecl *ND) {
+  if (const auto *MD = llvm::dyn_cast<CXXMethodDecl>(ND)) {
+    if (MD->size_overridden_methods() == 0 || MD->isPureVirtual())
+      return false;
+
+    for (const auto *Overridden : MD->overridden_methods()) {
+      if (!Overridden->isPureVirtual())
+        return false;
+    }
+    return true;
+  }
+  return false;
+}
+
 // Indicates whether declaration D is a unique definition (as opposed to a
 // declaration).
 bool isUniqueDefinition(const NamedDecl *Decl) {
@@ -153,6 +192,51 @@ bool isUniqueDefinition(const NamedDecl *Decl) {
          isa<TemplateTemplateParmDecl>(Decl) || isa<ObjCCategoryDecl>(Decl) ||
          isa<ObjCImplDecl>(Decl);
 }
+
+// Filter symbol tags based on the presence of other tags and the kind of
+// symbol. This is needed to avoid redundant tags, e.g. Overrides implies
+// Virtual and Implements implies Overrides/Virtual.
+SymbolTags filterSymbolTags(SymbolTags ST) {
+  const SymbolTags VirtualMask = toSymbolTagBitmask(SymbolTag::Virtual);
+  const SymbolTags OverridesMask = toSymbolTagBitmask(SymbolTag::Overrides);
+  const SymbolTags ImplementsMask = toSymbolTagBitmask(SymbolTag::Implements);
+  const SymbolTags AbstractMask = toSymbolTagBitmask(SymbolTag::Abstract);
+  const SymbolTags FinalMask = toSymbolTagBitmask(SymbolTag::Final);
+
+  const SymbolTags RemoveVirtualAndOverrides = VirtualMask | OverridesMask;
+
+  // Implements implies both Overrides and Virtual.
+  if (ST & ImplementsMask)
+    ST &= ~RemoveVirtualAndOverrides;
+
+  // Final also suppresses both Virtual and Overrides in this model.
+  if (ST & FinalMask)
+    ST &= ~RemoveVirtualAndOverrides;
+
+  // Overrides or Abstract each imply Virtual.
+  if (ST & (OverridesMask | AbstractMask))
+    ST &= ~VirtualMask;
+
+  return ST;
+}
+
+bool isCXXClassMethod(const clang::clangd::Symbol &S) {
+  using clang::index::SymbolKind;
+  using clang::index::SymbolLanguage;
+
+  if (S.SymInfo.Lang != SymbolLanguage::CXX)
+    return false;
+
+  return llvm::is_contained({SymbolKind::InstanceMethod,
+                             SymbolKind::StaticMethod, SymbolKind::Constructor,
+                             SymbolKind::Destructor,
+                             SymbolKind::ConversionFunction},
+                            S.SymInfo.Kind);
+}
+
+template <typename E> constexpr E enumIncrement(E Value) {
+  return static_cast<E>(static_cast<std::underlying_type_t<E>>(Value) + 1);
+}
 } // namespace
 
 SymbolTags toSymbolTagBitmask(const SymbolTag ST) {
@@ -178,9 +262,15 @@ SymbolTags computeSymbolTags(const NamedDecl &ND) {
   if (isAbstract(&ND))
     Result |= toSymbolTagBitmask(SymbolTag::Abstract);
 
+  if (isOverrides(&ND))
+    Result |= toSymbolTagBitmask(SymbolTag::Overrides);
+
   if (isFinal(&ND))
     Result |= toSymbolTagBitmask(SymbolTag::Final);
 
+  if (isImplements(&ND))
+    Result |= toSymbolTagBitmask(SymbolTag::Implements);
+
   if (not isa<UnresolvedUsingValueDecl>(ND)) {
     // Do not treat an UnresolvedUsingValueDecl as a declaration.
     // It's more common to think of it as a reference to the
@@ -208,26 +298,58 @@ SymbolTags computeSymbolTags(const NamedDecl &ND) {
   return Result;
 }
 
-std::vector<SymbolTag> getSymbolTags(const NamedDecl &ND) {
-  const auto symbolTags = computeSymbolTags(ND);
+std::vector<SymbolTag> expandTagBitmask(const SymbolTags STGS) {
   std::vector<SymbolTag> Tags;
 
-  if (symbolTags == 0)
+  if (STGS == 0)
     return Tags;
 
+  // No filtering required since this function is only used for Symbols from the
+  // index, which have already been filtered in getSymbolTags(const NamedDecl
+  // &ND).
+
   // Iterate through SymbolTag enum values and collect any that are present in
   // the bitmask. SymbolTag values are in the numeric range
   // [FirstTag .. LastTag].
   constexpr unsigned MinTag = static_cast<unsigned>(SymbolTag::FirstTag);
   constexpr unsigned MaxTag = static_cast<unsigned>(SymbolTag::LastTag);
   for (unsigned I = MinTag; I <= MaxTag; ++I) {
     auto ST = static_cast<SymbolTag>(I);
-    if (symbolTags & toSymbolTagBitmask(ST))
+    if (STGS & toSymbolTagBitmask(ST))
       Tags.push_back(ST);
   }
   return Tags;
 }
 
+std::vector<SymbolTag> getSymbolTags(const Symbol &S) {
+  const SymbolTags Tags =
+      isCXXClassMethod(S) ? filterSymbolTags(S.Tags) : S.Tags;
+  return expandTagBitmask(Tags);
+}
+
+std::vector<SymbolTag> getSymbolTags(const NamedDecl &ND) {
+  const auto STGS = computeSymbolTags(ND);
+  SymbolTags FilteredTags = STGS;
+  std::vector<SymbolTag> Tags;
+
+  if (STGS == 0)
+    return Tags;
+
+  // Apply specific filter to the symbol tags only on CXX class methods.
+  if (isa<CXXMethodDecl>(ND))
+    FilteredTags = filterSymbolTags(STGS);
+
+  // Iterate through SymbolTag enum values and collect any that are present in
+  // the bitmask. SymbolTag values are in the numeric range
+  // [FirstTag .. LastTag].
+  for (SymbolTag Tag = SymbolTag::FirstTag; Tag <= SymbolTag::LastTag;
+       Tag = enumIncrement(Tag)) {
+    if (FilteredTags & toSymbolTagBitmask(Tag))
+      Tags.push_back(Tag);
+  }
+  return Tags;
+}
+
 namespace {
 using ScoredSymbolInfo = std::pair<float, SymbolInformation>;
 struct ScoredSymbolGreater {
@@ -359,6 +481,7 @@ getWorkspaceSymbols(llvm::StringRef Query, int Limit,
     Info.score = Relevance.NameMatch > std::numeric_limits<float>::epsilon()
                      ? Score / Relevance.NameMatch
                      : QualScore;
+    Info.tags = getSymbolTags(Sym);
     Top.push({Score, std::move(Info)});
   });
   for (auto &R : std::move(Top).items())

clang-tools-extra/clangd/FindSymbols.h

@@ -12,24 +12,18 @@
 #ifndef LLVM_CLANG_TOOLS_EXTRA_CLANGD_FINDSYMBOLS_H
 #define LLVM_CLANG_TOOLS_EXTRA_CLANGD_FINDSYMBOLS_H
 
-#include "Protocol.h"
 #include "index/Symbol.h"
 #include "clang/AST/Decl.h"
 #include "llvm/ADT/StringRef.h"
 
 namespace clang {
+class NamedDecl;
+
 namespace clangd {
 class ParsedAST;
 class SymbolIndex;
-
-/// A bitmask type representing symbol tags supported by LSP.
-/// \see
-/// https://microsoft.github.io/language-server-protocol/specifications/specification-current/#symbolTag
-using SymbolTags = uint32_t;
-/// Ensure we have enough bits to represent all SymbolTag values.
-static_assert(static_cast<unsigned>(SymbolTag::LastTag) <= 32,
-              "Too many SymbolTags to fit in uint32_t. Change to uint64_t if "
-              "we ever have more than 32 tags.");
+struct Symbol;
+struct SymbolLocation;
 
 /// Helper function for deriving an LSP Location from an index SymbolLocation.
 llvm::Expected<Location> indexToLSPLocation(const SymbolLocation &Loc,
@@ -69,6 +63,19 @@ SymbolTags computeSymbolTags(const NamedDecl &ND);
 /// \p ND The declaration to get tags for.
 std::vector<SymbolTag> getSymbolTags(const NamedDecl &ND);
 
+/// Returns the \c SymbolTag values for the given indexed \p S.
+///
+/// Converts the bitmask stored in \c Symbol::Tags into a flat vector of
+/// \c SymbolTag enum values. For C++ class methods (instance methods, static
+/// methods, constructors, destructors, and conversion functions), a semantic
+/// filter is applied first to remove tags that are implied by higher-priority
+/// tags (e.g. \c Overrides implies \c Virtual, so \c Virtual is suppressed).
+/// For all other symbol kinds the bitmask is expanded as-is.
+///
+/// \param S The indexed symbol whose tags should be returned.
+/// \return A vector of \c SymbolTag values present in \c S.Tags, after
+///         applying any applicable filters.
+std::vector<SymbolTag> getSymbolTags(const Symbol &S);
 } // namespace clangd
 } // namespace clang
 

clang-tools-extra/clangd/Protocol.cpp

@@ -867,6 +867,8 @@ llvm::json::Value toJSON(const SymbolInformation &P) {
   };
   if (P.score)
     O["score"] = *P.score;
+  if (!P.tags.empty())
+    O["tags"] = P.tags;
   return std::move(O);
 }
 
@@ -1445,6 +1447,8 @@ llvm::json::Value toJSON(const TypeHierarchyItem &I) {
 
   if (I.detail)
     Result["detail"] = I.detail;
+  if (!I.tags.empty())
+    Result["tags"] = I.tags;
   return std::move(Result);
 }
 

clang-tools-extra/clangd/Protocol.h

@@ -1115,22 +1115,33 @@ enum class SymbolTag {
   Internal = 6,
   File = 7,
   Static = 8,
-  Abstract = 9,
-  Final = 10,
+  Abstract = 9, // In context of a class and method - this symbol indicates a
+                // pure virtual class or method.
+  Final = 10, // In context of a method - this symbol indicates that the method
+              // cannot be overridden in subclasses.
+              // In context of a class - this symbol indicates that the class is
+              // final and thus cannot be extended.
   Sealed = 11,
   Transient = 12,
   Volatile = 13,
   Synchronized = 14,
-  Virtual = 15,
+  Virtual =
+      15, // In context of a method - this symbol indicates a virtual
+          // method declared and implemented in same class, and thereby it is
+          // not implementing or overriding a method from any base class.
   Nullable = 16,
   NonNull = 17,
   Declaration = 18,
   Definition = 19,
   ReadOnly = 20,
+  Overrides = 21,  // In context of a method - this symbol indicates a method
+                   // overriding a virtual method, implemented in base class.
+  Implements = 22, // In context of a method - this symbol indicates a method
+                   // implementing a pure virtual method from a base class.
 
   // Update as needed
   FirstTag = Deprecated,
-  LastTag = ReadOnly
+  LastTag = Implements
 };
 llvm::json::Value toJSON(SymbolTag);
 /// Represents programming constructs like variables, classes, interfaces etc.
@@ -1548,6 +1559,9 @@ struct TypeHierarchyItem {
   /// The kind of this item.
   SymbolKind kind;
 
+  /// The symbol tags for this item.
+  std::vector<SymbolTag> tags;
+
   /// More detail for this item, e.g. the signature of a function.
   std::optional<std::string> detail;
 

clang-tools-extra/clangd/XRefs.cpp

@@ -1818,8 +1818,9 @@ declToHierarchyItem(const NamedDecl &ND, llvm::StringRef TUPath) {
 
   HierarchyItem HI;
   HI.name = printName(Ctx, ND);
-  // FIXME: Populate HI.detail the way we do in symbolToHierarchyItem?
+  HI.detail = printQualifiedName(ND);
   HI.kind = SK;
+  HI.tags = getSymbolTags(ND);
   HI.range = Range{sourceLocToPosition(SM, DeclRange->getBegin()),
                    sourceLocToPosition(SM, DeclRange->getEnd())};
   HI.selectionRange = Range{NameBegin, NameEnd};
@@ -1872,6 +1873,7 @@ static std::optional<HierarchyItem> symbolToHierarchyItem(const Symbol &S,
   HI.name = std::string(S.Name);
   HI.detail = (S.Scope + S.Name).str();
   HI.kind = indexSymbolKindToSymbolKind(S.SymInfo);
+  HI.tags = getSymbolTags(S);
   HI.selectionRange = Loc->range;
   // FIXME: Populate 'range' correctly
   // (https://github.com/clangd/clangd/issues/59).
@@ -1897,8 +1899,6 @@ symbolToCallHierarchyItem(const Symbol &S, PathRef TUPath) {
   if (!Result)
     return Result;
   Result->data = S.ID.str();
-  if (S.Flags & Symbol::Deprecated)
-    Result->tags.push_back(SymbolTag::Deprecated);
   return Result;
 }
 
@@ -2144,7 +2144,7 @@ static void unwrapFindType(
     return;
 
   // If there's a specific type alias, point at that rather than unwrapping.
-  if (const auto* TDT = T->getAs<TypedefType>())
+  if (const auto *TDT = T->getAs<TypedefType>())
     return Out.push_back(QualType(TDT, 0));
 
   // Pointers etc => pointee type.
@@ -2307,24 +2307,23 @@ getTypeHierarchy(ParsedAST &AST, Position Pos, int ResolveLevels,
 
 std::optional<std::vector<TypeHierarchyItem>>
 superTypes(const TypeHierarchyItem &Item, const SymbolIndex *Index) {
-  std::vector<TypeHierarchyItem> Results;
-  if (!Item.data.parents)
+  if (!Index || !Item.data.parents)
     return std::nullopt;
-  if (Item.data.parents->empty())
-    return Results;
   LookupRequest Req;
   llvm::DenseMap<SymbolID, const TypeHierarchyItem::ResolveParams *> IDToData;
   for (const auto &Parent : *Item.data.parents) {
     Req.IDs.insert(Parent.symbolID);
     IDToData[Parent.symbolID] = &Parent;
   }
+  std::vector<TypeHierarchyItem> Results;
   Index->lookup(Req, [&Item, &Results, &IDToData](const Symbol &S) {
     if (auto THI = symbolToTypeHierarchyItem(S, Item.uri.file())) {
       THI->data = *IDToData.lookup(S.ID);
       Results.emplace_back(std::move(*THI));
     }
   });
-  return Results;
+  return Results.empty() ? std::nullopt
+                         : std::make_optional(std::move(Results));
 }
 
 std::vector<TypeHierarchyItem> subTypes(const TypeHierarchyItem &Item,

clang-tools-extra/clangd/XRefs.h

@@ -132,7 +132,8 @@ std::vector<TypeHierarchyItem> getTypeHierarchy(
     const SymbolIndex *Index = nullptr, PathRef TUPath = PathRef{});
 
 /// Returns direct parents of a TypeHierarchyItem using SymbolIDs stored inside
-/// the item.
+/// the item. Returns nullopt if the item does not have parents or if
+/// the index is not provided.
 std::optional<std::vector<TypeHierarchyItem>>
 superTypes(const TypeHierarchyItem &Item, const SymbolIndex *Index);
 /// Returns direct children of a TypeHierarchyItem.