clang-tools-extra/clangd/Hover.cpp

   1 //===--- Hover.cpp - Information about code at the cursor location --------===//
   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 "Hover.h"
  10
  11 #include "AST.h"
  12 #include "CodeCompletionStrings.h"
  13 #include "Config.h"
  14 #include "FindTarget.h"
  15 #include "Headers.h"
  16 #include "IncludeCleaner.h"
  17 #include "ParsedAST.h"
  18 #include "Selection.h"
  19 #include "SourceCode.h"
  20 #include "clang-include-cleaner/Analysis.h"
  21 #include "clang-include-cleaner/IncludeSpeller.h"
  22 #include "clang-include-cleaner/Types.h"
  23 #include "index/SymbolCollector.h"
  24 #include "support/Logger.h"
  25 #include "support/Markup.h"
  26 #include "support/Trace.h"
  27 #include "clang/AST/ASTContext.h"
  28 #include "clang/AST/ASTDiagnostic.h"
  29 #include "clang/AST/ASTTypeTraits.h"
  30 #include "clang/AST/Attr.h"
  31 #include "clang/AST/Decl.h"
  32 #include "clang/AST/DeclBase.h"
  33 #include "clang/AST/DeclCXX.h"
  34 #include "clang/AST/DeclObjC.h"
  35 #include "clang/AST/DeclTemplate.h"
  36 #include "clang/AST/Expr.h"
  37 #include "clang/AST/ExprCXX.h"
  38 #include "clang/AST/OperationKinds.h"
  39 #include "clang/AST/PrettyPrinter.h"
  40 #include "clang/AST/RecordLayout.h"
  41 #include "clang/AST/Type.h"
  42 #include "clang/Basic/CharInfo.h"
  43 #include "clang/Basic/LLVM.h"
  44 #include "clang/Basic/SourceLocation.h"
  45 #include "clang/Basic/SourceManager.h"
  46 #include "clang/Basic/Specifiers.h"
  47 #include "clang/Basic/TokenKinds.h"
  48 #include "clang/Index/IndexSymbol.h"
  49 #include "clang/Tooling/Syntax/Tokens.h"
  50 #include "llvm/ADT/ArrayRef.h"
  51 #include "llvm/ADT/DenseSet.h"
  52 #include "llvm/ADT/STLExtras.h"
  53 #include "llvm/ADT/SmallVector.h"
  54 #include "llvm/ADT/StringExtras.h"
  55 #include "llvm/ADT/StringRef.h"
  56 #include "llvm/Support/Casting.h"
  57 #include "llvm/Support/Error.h"
  58 #include "llvm/Support/Format.h"
  59 #include "llvm/Support/ScopedPrinter.h"
  60 #include "llvm/Support/raw_ostream.h"
  61 #include <algorithm>
  62 #include <optional>
  63 #include <string>
  64 #include <vector>
  65
  66 namespace clang {
  67 namespace clangd {
  68 namespace {
  69
  70 PrintingPolicy getPrintingPolicy(PrintingPolicy Base) {
  71   Base.AnonymousTagLocations = false;
  72   Base.TerseOutput = true;
  73   Base.PolishForDeclaration = true;
  74   Base.ConstantsAsWritten = true;
  75   Base.SuppressTemplateArgsInCXXConstructors = true;
  76   return Base;
  77 }
  78
  79 /// Given a declaration \p D, return a human-readable string representing the
  80 /// local scope in which it is declared, i.e. class(es) and method name. Returns
  81 /// an empty string if it is not local.
  82 std::string getLocalScope(const Decl *D) {
  83   std::vector<std::string> Scopes;
  84   const DeclContext *DC = D->getDeclContext();
  85
  86   // ObjC scopes won't have multiple components for us to join, instead:
  87   // - Methods: "-[Class methodParam1:methodParam2]"
  88   // - Classes, categories, and protocols: "MyClass(Category)"
  89   if (const ObjCMethodDecl *MD = dyn_cast<ObjCMethodDecl>(DC))
  90     return printObjCMethod(*MD);
  91   if (const ObjCContainerDecl *CD = dyn_cast<ObjCContainerDecl>(DC))
  92     return printObjCContainer(*CD);
  93
  94   auto GetName = [](const TypeDecl *D) {
  95     if (!D->getDeclName().isEmpty()) {
  96       PrintingPolicy Policy = D->getASTContext().getPrintingPolicy();
  97       Policy.SuppressScope = true;
  98       return declaredType(D).getAsString(Policy);
  99     }
 100     if (auto *RD = dyn_cast<RecordDecl>(D))
 101       return ("(anonymous " + RD->getKindName() + ")").str();
 102     return std::string("");
 103   };
 104   while (DC) {
 105     if (const TypeDecl *TD = dyn_cast<TypeDecl>(DC))
 106       Scopes.push_back(GetName(TD));
 107     else if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(DC))
 108       Scopes.push_back(FD->getNameAsString());
 109     DC = DC->getParent();
 110   }
 111
 112   return llvm::join(llvm::reverse(Scopes), "::");
 113 }
 114
 115 /// Returns the human-readable representation for namespace containing the
 116 /// declaration \p D. Returns empty if it is contained global namespace.
 117 std::string getNamespaceScope(const Decl *D) {
 118   const DeclContext *DC = D->getDeclContext();
 119
 120   // ObjC does not have the concept of namespaces, so instead we support
 121   // local scopes.
 122   if (isa<ObjCMethodDecl, ObjCContainerDecl>(DC))
 123     return "";
 124
 125   if (const TagDecl *TD = dyn_cast<TagDecl>(DC))
 126     return getNamespaceScope(TD);
 127   if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(DC))
 128     return getNamespaceScope(FD);
 129   if (const NamespaceDecl *NSD = dyn_cast<NamespaceDecl>(DC)) {
 130     // Skip inline/anon namespaces.
 131     if (NSD->isInline() || NSD->isAnonymousNamespace())
 132       return getNamespaceScope(NSD);
 133   }
 134   if (const NamedDecl *ND = dyn_cast<NamedDecl>(DC))
 135     return printQualifiedName(*ND);
 136
 137   return "";
 138 }
 139
 140 std::string printDefinition(const Decl *D, PrintingPolicy PP,
 141                             const syntax::TokenBuffer &TB) {
 142   if (auto *VD = llvm::dyn_cast<VarDecl>(D)) {
 143     if (auto *IE = VD->getInit()) {
 144       // Initializers might be huge and result in lots of memory allocations in
 145       // some catostrophic cases. Such long lists are not useful in hover cards
 146       // anyway.
 147       if (200 < TB.expandedTokens(IE->getSourceRange()).size())
 148         PP.SuppressInitializers = true;
 149     }
 150   }
 151   std::string Definition;
 152   llvm::raw_string_ostream OS(Definition);
 153   D->print(OS, PP);
 154   OS.flush();
 155   return Definition;
 156 }
 157
 158 const char *getMarkdownLanguage(const ASTContext &Ctx) {
 159   const auto &LangOpts = Ctx.getLangOpts();
 160   if (LangOpts.ObjC && LangOpts.CPlusPlus)
 161     return "objective-cpp";
 162   return LangOpts.ObjC ? "objective-c" : "cpp";
 163 }
 164
 165 HoverInfo::PrintedType printType(QualType QT, ASTContext &ASTCtx,
 166                                  const PrintingPolicy &PP) {
 167   // TypePrinter doesn't resolve decltypes, so resolve them here.
 168   // FIXME: This doesn't handle composite types that contain a decltype in them.
 169   // We should rather have a printing policy for that.
 170   while (!QT.isNull() && QT->isDecltypeType())
 171     QT = QT->castAs<DecltypeType>()->getUnderlyingType();
 172   HoverInfo::PrintedType Result;
 173   llvm::raw_string_ostream OS(Result.Type);
 174   // Special case: if the outer type is a tag type without qualifiers, then
 175   // include the tag for extra clarity.
 176   // This isn't very idiomatic, so don't attempt it for complex cases, including
 177   // pointers/references, template specializations, etc.
 178   if (!QT.isNull() && !QT.hasQualifiers() && PP.SuppressTagKeyword) {
 179     if (auto *TT = llvm::dyn_cast<TagType>(QT.getTypePtr()))
 180       OS << TT->getDecl()->getKindName() << " ";
 181   }
 182   QT.print(OS, PP);
 183   OS.flush();
 184
 185   const Config &Cfg = Config::current();
 186   if (!QT.isNull() && Cfg.Hover.ShowAKA) {
 187     bool ShouldAKA = false;
 188     QualType DesugaredTy = clang::desugarForDiagnostic(ASTCtx, QT, ShouldAKA);
 189     if (ShouldAKA)
 190       Result.AKA = DesugaredTy.getAsString(PP);
 191   }
 192   return Result;
 193 }
 194
 195 HoverInfo::PrintedType printType(const TemplateTypeParmDecl *TTP) {
 196   HoverInfo::PrintedType Result;
 197   Result.Type = TTP->wasDeclaredWithTypename() ? "typename" : "class";
 198   if (TTP->isParameterPack())
 199     Result.Type += "...";
 200   return Result;
 201 }
 202
 203 HoverInfo::PrintedType printType(const NonTypeTemplateParmDecl *NTTP,
 204                                  const PrintingPolicy &PP) {
 205   auto PrintedType = printType(NTTP->getType(), NTTP->getASTContext(), PP);
 206   if (NTTP->isParameterPack()) {
 207     PrintedType.Type += "...";
 208     if (PrintedType.AKA)
 209       *PrintedType.AKA += "...";
 210   }
 211   return PrintedType;
 212 }
 213
 214 HoverInfo::PrintedType printType(const TemplateTemplateParmDecl *TTP,
 215                                  const PrintingPolicy &PP) {
 216   HoverInfo::PrintedType Result;
 217   llvm::raw_string_ostream OS(Result.Type);
 218   OS << "template <";
 219   llvm::StringRef Sep = "";
 220   for (const Decl *Param : *TTP->getTemplateParameters()) {
 221     OS << Sep;
 222     Sep = ", ";
 223     if (const auto *TTP = dyn_cast<TemplateTypeParmDecl>(Param))
 224       OS << printType(TTP).Type;
 225     else if (const auto *NTTP = dyn_cast<NonTypeTemplateParmDecl>(Param))
 226       OS << printType(NTTP, PP).Type;
 227     else if (const auto *TTPD = dyn_cast<TemplateTemplateParmDecl>(Param))
 228       OS << printType(TTPD, PP).Type;
 229   }
 230   // FIXME: TemplateTemplateParameter doesn't store the info on whether this
 231   // param was a "typename" or "class".
 232   OS << "> class";
 233   OS.flush();
 234   return Result;
 235 }
 236
 237 std::vector<HoverInfo::Param>
 238 fetchTemplateParameters(const TemplateParameterList *Params,
 239                         const PrintingPolicy &PP) {
 240   assert(Params);
 241   std::vector<HoverInfo::Param> TempParameters;
 242
 243   for (const Decl *Param : *Params) {
 244     HoverInfo::Param P;
 245     if (const auto *TTP = dyn_cast<TemplateTypeParmDecl>(Param)) {
 246       P.Type = printType(TTP);
 247
 248       if (!TTP->getName().empty())
 249         P.Name = TTP->getNameAsString();
 250
 251       if (TTP->hasDefaultArgument())
 252         P.Default = TTP->getDefaultArgument().getAsString(PP);
 253     } else if (const auto *NTTP = dyn_cast<NonTypeTemplateParmDecl>(Param)) {
 254       P.Type = printType(NTTP, PP);
 255
 256       if (IdentifierInfo *II = NTTP->getIdentifier())
 257         P.Name = II->getName().str();
 258
 259       if (NTTP->hasDefaultArgument()) {
 260         P.Default.emplace();
 261         llvm::raw_string_ostream Out(*P.Default);
 262         NTTP->getDefaultArgument()->printPretty(Out, nullptr, PP);
 263       }
 264     } else if (const auto *TTPD = dyn_cast<TemplateTemplateParmDecl>(Param)) {
 265       P.Type = printType(TTPD, PP);
 266
 267       if (!TTPD->getName().empty())
 268         P.Name = TTPD->getNameAsString();
 269
 270       if (TTPD->hasDefaultArgument()) {
 271         P.Default.emplace();
 272         llvm::raw_string_ostream Out(*P.Default);
 273         TTPD->getDefaultArgument().getArgument().print(PP, Out,
 274                                                        /*IncludeType*/ false);
 275       }
 276     }
 277     TempParameters.push_back(std::move(P));
 278   }
 279
 280   return TempParameters;
 281 }
 282
 283 const FunctionDecl *getUnderlyingFunction(const Decl *D) {
 284   // Extract lambda from variables.
 285   if (const VarDecl *VD = llvm::dyn_cast<VarDecl>(D)) {
 286     auto QT = VD->getType();
 287     if (!QT.isNull()) {
 288       while (!QT->getPointeeType().isNull())
 289         QT = QT->getPointeeType();
 290
 291       if (const auto *CD = QT->getAsCXXRecordDecl())
 292         return CD->getLambdaCallOperator();
 293     }
 294   }
 295
 296   // Non-lambda functions.
 297   return D->getAsFunction();
 298 }
 299
 300 // Returns the decl that should be used for querying comments, either from index
 301 // or AST.
 302 const NamedDecl *getDeclForComment(const NamedDecl *D) {
 303   const NamedDecl *DeclForComment = D;
 304   if (const auto *TSD = llvm::dyn_cast<ClassTemplateSpecializationDecl>(D)) {
 305     // Template may not be instantiated e.g. if the type didn't need to be
 306     // complete; fallback to primary template.
 307     if (TSD->getTemplateSpecializationKind() == TSK_Undeclared)
 308       DeclForComment = TSD->getSpecializedTemplate();
 309     else if (const auto *TIP = TSD->getTemplateInstantiationPattern())
 310       DeclForComment = TIP;
 311   } else if (const auto *TSD =
 312                  llvm::dyn_cast<VarTemplateSpecializationDecl>(D)) {
 313     if (TSD->getTemplateSpecializationKind() == TSK_Undeclared)
 314       DeclForComment = TSD->getSpecializedTemplate();
 315     else if (const auto *TIP = TSD->getTemplateInstantiationPattern())
 316       DeclForComment = TIP;
 317   } else if (const auto *FD = D->getAsFunction())
 318     if (const auto *TIP = FD->getTemplateInstantiationPattern())
 319       DeclForComment = TIP;
 320   // Ensure that getDeclForComment(getDeclForComment(X)) = getDeclForComment(X).
 321   // This is usually not needed, but in strange cases of comparision operators
 322   // being instantiated from spasceship operater, which itself is a template
 323   // instantiation the recursrive call is necessary.
 324   if (D != DeclForComment)
 325     DeclForComment = getDeclForComment(DeclForComment);
 326   return DeclForComment;
 327 }
 328
 329 // Look up information about D from the index, and add it to Hover.
 330 void enhanceFromIndex(HoverInfo &Hover, const NamedDecl &ND,
 331                       const SymbolIndex *Index) {
 332   assert(&ND == getDeclForComment(&ND));
 333   // We only add documentation, so don't bother if we already have some.
 334   if (!Hover.Documentation.empty() || !Index)
 335     return;
 336
 337   // Skip querying for non-indexable symbols, there's no point.
 338   // We're searching for symbols that might be indexed outside this main file.
 339   if (!SymbolCollector::shouldCollectSymbol(ND, ND.getASTContext(),
 340                                             SymbolCollector::Options(),
 341                                             /*IsMainFileOnly=*/false))
 342     return;
 343   auto ID = getSymbolID(&ND);
 344   if (!ID)
 345     return;
 346   LookupRequest Req;
 347   Req.IDs.insert(ID);
 348   Index->lookup(Req, [&](const Symbol &S) {
 349     Hover.Documentation = std::string(S.Documentation);
 350   });
 351 }
 352
 353 // Default argument might exist but be unavailable, in the case of unparsed
 354 // arguments for example. This function returns the default argument if it is
 355 // available.
 356 const Expr *getDefaultArg(const ParmVarDecl *PVD) {
 357   // Default argument can be unparsed or uninstantiated. For the former we
 358   // can't do much, as token information is only stored in Sema and not
 359   // attached to the AST node. For the latter though, it is safe to proceed as
 360   // the expression is still valid.
 361   if (!PVD->hasDefaultArg() || PVD->hasUnparsedDefaultArg())
 362     return nullptr;
 363   return PVD->hasUninstantiatedDefaultArg() ? PVD->getUninstantiatedDefaultArg()
 364                                             : PVD->getDefaultArg();
 365 }
 366
 367 HoverInfo::Param toHoverInfoParam(const ParmVarDecl *PVD,
 368                                   const PrintingPolicy &PP) {
 369   HoverInfo::Param Out;
 370   Out.Type = printType(PVD->getType(), PVD->getASTContext(), PP);
 371   if (!PVD->getName().empty())
 372     Out.Name = PVD->getNameAsString();
 373   if (const Expr *DefArg = getDefaultArg(PVD)) {
 374     Out.Default.emplace();
 375     llvm::raw_string_ostream OS(*Out.Default);
 376     DefArg->printPretty(OS, nullptr, PP);
 377   }
 378   return Out;
 379 }
 380
 381 // Populates Type, ReturnType, and Parameters for function-like decls.
 382 void fillFunctionTypeAndParams(HoverInfo &HI, const Decl *D,
 383                                const FunctionDecl *FD,
 384                                const PrintingPolicy &PP) {
 385   HI.Parameters.emplace();
 386   for (const ParmVarDecl *PVD : FD->parameters())
 387     HI.Parameters->emplace_back(toHoverInfoParam(PVD, PP));
 388
 389   // We don't want any type info, if name already contains it. This is true for
 390   // constructors/destructors and conversion operators.
 391   const auto NK = FD->getDeclName().getNameKind();
 392   if (NK == DeclarationName::CXXConstructorName ||
 393       NK == DeclarationName::CXXDestructorName ||
 394       NK == DeclarationName::CXXConversionFunctionName)
 395     return;
 396
 397   HI.ReturnType = printType(FD->getReturnType(), FD->getASTContext(), PP);
 398   QualType QT = FD->getType();
 399   if (const VarDecl *VD = llvm::dyn_cast<VarDecl>(D)) // Lambdas
 400     QT = VD->getType().getDesugaredType(D->getASTContext());
 401   HI.Type = printType(QT, D->getASTContext(), PP);
 402   // FIXME: handle variadics.
 403 }
 404
 405 // Non-negative numbers are printed using min digits
 406 // 0     => 0x0
 407 // 100   => 0x64
 408 // Negative numbers are sign-extended to 32/64 bits
 409 // -2    => 0xfffffffe
 410 // -2^32 => 0xffffffff00000000
 411 static llvm::FormattedNumber printHex(const llvm::APSInt &V) {
 412   uint64_t Bits = V.getZExtValue();
 413   if (V.isNegative() && V.getSignificantBits() <= 32)
 414     return llvm::format_hex(uint32_t(Bits), 0);
 415   return llvm::format_hex(Bits, 0);
 416 }
 417
 418 std::optional<std::string> printExprValue(const Expr *E,
 419                                           const ASTContext &Ctx) {
 420   // InitListExpr has two forms, syntactic and semantic. They are the same thing
 421   // (refer to a same AST node) in most cases.
 422   // When they are different, RAV returns the syntactic form, and we should feed
 423   // the semantic form to EvaluateAsRValue.
 424   if (const auto *ILE = llvm::dyn_cast<InitListExpr>(E)) {
 425     if (!ILE->isSemanticForm())
 426       E = ILE->getSemanticForm();
 427   }
 428
 429   // Evaluating [[foo]]() as "&foo" isn't useful, and prevents us walking up
 430   // to the enclosing call. Evaluating an expression of void type doesn't
 431   // produce a meaningful result.
 432   QualType T = E->getType();
 433   if (T.isNull() || T->isFunctionType() || T->isFunctionPointerType() ||
 434       T->isFunctionReferenceType() || T->isVoidType())
 435     return std::nullopt;
 436
 437   Expr::EvalResult Constant;
 438   // Attempt to evaluate. If expr is dependent, evaluation crashes!
 439   if (E->isValueDependent() || !E->EvaluateAsRValue(Constant, Ctx) ||
 440       // Disable printing for record-types, as they are usually confusing and
 441       // might make clang crash while printing the expressions.
 442       Constant.Val.isStruct() || Constant.Val.isUnion())
 443     return std::nullopt;
 444
 445   // Show enums symbolically, not numerically like APValue::printPretty().
 446   if (T->isEnumeralType() && Constant.Val.isInt() &&
 447       Constant.Val.getInt().getSignificantBits() <= 64) {
 448     // Compare to int64_t to avoid bit-width match requirements.
 449     int64_t Val = Constant.Val.getInt().getExtValue();
 450     for (const EnumConstantDecl *ECD :
 451          T->castAs<EnumType>()->getDecl()->enumerators())
 452       if (ECD->getInitVal() == Val)
 453         return llvm::formatv("{0} ({1})", ECD->getNameAsString(),
 454                              printHex(Constant.Val.getInt()))
 455             .str();
 456   }
 457   // Show hex value of integers if they're at least 10 (or negative!)
 458   if (T->isIntegralOrEnumerationType() && Constant.Val.isInt() &&
 459       Constant.Val.getInt().getSignificantBits() <= 64 &&
 460       Constant.Val.getInt().uge(10))
 461     return llvm::formatv("{0} ({1})", Constant.Val.getAsString(Ctx, T),
 462                          printHex(Constant.Val.getInt()))
 463         .str();
 464   return Constant.Val.getAsString(Ctx, T);
 465 }
 466
 467 struct PrintExprResult {
 468   /// The evaluation result on expression `Expr`.
 469   std::optional<std::string> PrintedValue;
 470   /// The Expr object that represents the closest evaluable
 471   /// expression.
 472   const clang::Expr *TheExpr;
 473   /// The node of selection tree where the traversal stops.
 474   const SelectionTree::Node *TheNode;
 475 };
 476
 477 // Seek the closest evaluable expression along the ancestors of node N
 478 // in a selection tree. If a node in the path can be converted to an evaluable
 479 // Expr, a possible evaluation would happen and the associated context
 480 // is returned.
 481 // If evaluation couldn't be done, return the node where the traversal ends.
 482 PrintExprResult printExprValue(const SelectionTree::Node *N,
 483                                const ASTContext &Ctx) {
 484   for (; N; N = N->Parent) {
 485     // Try to evaluate the first evaluatable enclosing expression.
 486     if (const Expr *E = N->ASTNode.get<Expr>()) {
 487       // Once we cross an expression of type 'cv void', the evaluated result
 488       // has nothing to do with our original cursor position.
 489       if (!E->getType().isNull() && E->getType()->isVoidType())
 490         break;
 491       if (auto Val = printExprValue(E, Ctx))
 492         return PrintExprResult{/*PrintedValue=*/std::move(Val), /*Expr=*/E,
 493                                /*Node=*/N};
 494     } else if (N->ASTNode.get<Decl>() || N->ASTNode.get<Stmt>()) {
 495       // Refuse to cross certain non-exprs. (TypeLoc are OK as part of Exprs).
 496       // This tries to ensure we're showing a value related to the cursor.
 497       break;
 498     }
 499   }
 500   return PrintExprResult{/*PrintedValue=*/std::nullopt, /*Expr=*/nullptr,
 501                          /*Node=*/N};
 502 }
 503
 504 std::optional<StringRef> fieldName(const Expr *E) {
 505   const auto *ME = llvm::dyn_cast<MemberExpr>(E->IgnoreCasts());
 506   if (!ME || !llvm::isa<CXXThisExpr>(ME->getBase()->IgnoreCasts()))
 507     return std::nullopt;
 508   const auto *Field = llvm::dyn_cast<FieldDecl>(ME->getMemberDecl());
 509   if (!Field || !Field->getDeclName().isIdentifier())
 510     return std::nullopt;
 511   return Field->getDeclName().getAsIdentifierInfo()->getName();
 512 }
 513
 514 // If CMD is of the form T foo() { return FieldName; } then returns "FieldName".
 515 std::optional<StringRef> getterVariableName(const CXXMethodDecl *CMD) {
 516   assert(CMD->hasBody());
 517   if (CMD->getNumParams() != 0 || CMD->isVariadic())
 518     return std::nullopt;
 519   const auto *Body = llvm::dyn_cast<CompoundStmt>(CMD->getBody());
 520   const auto *OnlyReturn = (Body && Body->size() == 1)
 521                                ? llvm::dyn_cast<ReturnStmt>(Body->body_front())
 522                                : nullptr;
 523   if (!OnlyReturn || !OnlyReturn->getRetValue())
 524     return std::nullopt;
 525   return fieldName(OnlyReturn->getRetValue());
 526 }
 527
 528 // If CMD is one of the forms:
 529 //   void foo(T arg) { FieldName = arg; }
 530 //   R foo(T arg) { FieldName = arg; return *this; }
 531 //   void foo(T arg) { FieldName = std::move(arg); }
 532 //   R foo(T arg) { FieldName = std::move(arg); return *this; }
 533 // then returns "FieldName"
 534 std::optional<StringRef> setterVariableName(const CXXMethodDecl *CMD) {
 535   assert(CMD->hasBody());
 536   if (CMD->isConst() || CMD->getNumParams() != 1 || CMD->isVariadic())
 537     return std::nullopt;
 538   const ParmVarDecl *Arg = CMD->getParamDecl(0);
 539   if (Arg->isParameterPack())
 540     return std::nullopt;
 541
 542   const auto *Body = llvm::dyn_cast<CompoundStmt>(CMD->getBody());
 543   if (!Body || Body->size() == 0 || Body->size() > 2)
 544     return std::nullopt;
 545   // If the second statement exists, it must be `return this` or `return *this`.
 546   if (Body->size() == 2) {
 547     auto *Ret = llvm::dyn_cast<ReturnStmt>(Body->body_back());
 548     if (!Ret || !Ret->getRetValue())
 549       return std::nullopt;
 550     const Expr *RetVal = Ret->getRetValue()->IgnoreCasts();
 551     if (const auto *UO = llvm::dyn_cast<UnaryOperator>(RetVal)) {
 552       if (UO->getOpcode() != UO_Deref)
 553         return std::nullopt;
 554       RetVal = UO->getSubExpr()->IgnoreCasts();
 555     }
 556     if (!llvm::isa<CXXThisExpr>(RetVal))
 557       return std::nullopt;
 558   }
 559   // The first statement must be an assignment of the arg to a field.
 560   const Expr *LHS, *RHS;
 561   if (const auto *BO = llvm::dyn_cast<BinaryOperator>(Body->body_front())) {
 562     if (BO->getOpcode() != BO_Assign)
 563       return std::nullopt;
 564     LHS = BO->getLHS();
 565     RHS = BO->getRHS();
 566   } else if (const auto *COCE =
 567                  llvm::dyn_cast<CXXOperatorCallExpr>(Body->body_front())) {
 568     if (COCE->getOperator() != OO_Equal || COCE->getNumArgs() != 2)
 569       return std::nullopt;
 570     LHS = COCE->getArg(0);
 571     RHS = COCE->getArg(1);
 572   } else {
 573     return std::nullopt;
 574   }
 575
 576   // Detect the case when the item is moved into the field.
 577   if (auto *CE = llvm::dyn_cast<CallExpr>(RHS->IgnoreCasts())) {
 578     if (CE->getNumArgs() != 1)
 579       return std::nullopt;
 580     auto *ND = llvm::dyn_cast_or_null<NamedDecl>(CE->getCalleeDecl());
 581     if (!ND || !ND->getIdentifier() || ND->getName() != "move" ||
 582         !ND->isInStdNamespace())
 583       return std::nullopt;
 584     RHS = CE->getArg(0);
 585   }
 586
 587   auto *DRE = llvm::dyn_cast<DeclRefExpr>(RHS->IgnoreCasts());
 588   if (!DRE || DRE->getDecl() != Arg)
 589     return std::nullopt;
 590   return fieldName(LHS);
 591 }
 592
 593 std::string synthesizeDocumentation(const NamedDecl *ND) {
 594   if (const auto *CMD = llvm::dyn_cast<CXXMethodDecl>(ND)) {
 595     // Is this an ordinary, non-static method whose definition is visible?
 596     if (CMD->getDeclName().isIdentifier() && !CMD->isStatic() &&
 597         (CMD = llvm::dyn_cast_or_null<CXXMethodDecl>(CMD->getDefinition())) &&
 598         CMD->hasBody()) {
 599       if (const auto GetterField = getterVariableName(CMD))
 600         return llvm::formatv("Trivial accessor for `{0}`.", *GetterField);
 601       if (const auto SetterField = setterVariableName(CMD))
 602         return llvm::formatv("Trivial setter for `{0}`.", *SetterField);
 603     }
 604   }
 605   return "";
 606 }
 607
 608 /// Generate a \p Hover object given the declaration \p D.
 609 HoverInfo getHoverContents(const NamedDecl *D, const PrintingPolicy &PP,
 610                            const SymbolIndex *Index,
 611                            const syntax::TokenBuffer &TB) {
 612   HoverInfo HI;
 613   auto &Ctx = D->getASTContext();
 614
 615   HI.AccessSpecifier = getAccessSpelling(D->getAccess()).str();
 616   HI.NamespaceScope = getNamespaceScope(D);
 617   if (!HI.NamespaceScope->empty())
 618     HI.NamespaceScope->append("::");
 619   HI.LocalScope = getLocalScope(D);
 620   if (!HI.LocalScope.empty())
 621     HI.LocalScope.append("::");
 622
 623   HI.Name = printName(Ctx, *D);
 624   const auto *CommentD = getDeclForComment(D);
 625   HI.Documentation = getDeclComment(Ctx, *CommentD);
 626   enhanceFromIndex(HI, *CommentD, Index);
 627   if (HI.Documentation.empty())
 628     HI.Documentation = synthesizeDocumentation(D);
 629
 630   HI.Kind = index::getSymbolInfo(D).Kind;
 631
 632   // Fill in template params.
 633   if (const TemplateDecl *TD = D->getDescribedTemplate()) {
 634     HI.TemplateParameters =
 635         fetchTemplateParameters(TD->getTemplateParameters(), PP);
 636     D = TD;
 637   } else if (const FunctionDecl *FD = D->getAsFunction()) {
 638     if (const auto *FTD = FD->getDescribedTemplate()) {
 639       HI.TemplateParameters =
 640           fetchTemplateParameters(FTD->getTemplateParameters(), PP);
 641       D = FTD;
 642     }
 643   }
 644
 645   // Fill in types and params.
 646   if (const FunctionDecl *FD = getUnderlyingFunction(D))
 647     fillFunctionTypeAndParams(HI, D, FD, PP);
 648   else if (const auto *VD = dyn_cast<ValueDecl>(D))
 649     HI.Type = printType(VD->getType(), Ctx, PP);
 650   else if (const auto *TTP = dyn_cast<TemplateTypeParmDecl>(D))
 651     HI.Type = TTP->wasDeclaredWithTypename() ? "typename" : "class";
 652   else if (const auto *TTP = dyn_cast<TemplateTemplateParmDecl>(D))
 653     HI.Type = printType(TTP, PP);
 654   else if (const auto *VT = dyn_cast<VarTemplateDecl>(D))
 655     HI.Type = printType(VT->getTemplatedDecl()->getType(), Ctx, PP);
 656   else if (const auto *TN = dyn_cast<TypedefNameDecl>(D))
 657     HI.Type = printType(TN->getUnderlyingType().getDesugaredType(Ctx), Ctx, PP);
 658   else if (const auto *TAT = dyn_cast<TypeAliasTemplateDecl>(D))
 659     HI.Type = printType(TAT->getTemplatedDecl()->getUnderlyingType(), Ctx, PP);
 660
 661   // Fill in value with evaluated initializer if possible.
 662   if (const auto *Var = dyn_cast<VarDecl>(D); Var && !Var->isInvalidDecl()) {
 663     if (const Expr *Init = Var->getInit())
 664       HI.Value = printExprValue(Init, Ctx);
 665   } else if (const auto *ECD = dyn_cast<EnumConstantDecl>(D)) {
 666     // Dependent enums (e.g. nested in template classes) don't have values yet.
 667     if (!ECD->getType()->isDependentType())
 668       HI.Value = toString(ECD->getInitVal(), 10);
 669   }
 670
 671   HI.Definition = printDefinition(D, PP, TB);
 672   return HI;
 673 }
 674
 675 /// The standard defines __func__ as a "predefined variable".
 676 std::optional<HoverInfo>
 677 getPredefinedExprHoverContents(const PredefinedExpr &PE, ASTContext &Ctx,
 678                                const PrintingPolicy &PP) {
 679   HoverInfo HI;
 680   HI.Name = PE.getIdentKindName();
 681   HI.Kind = index::SymbolKind::Variable;
 682   HI.Documentation = "Name of the current function (predefined variable)";
 683   if (const StringLiteral *Name = PE.getFunctionName()) {
 684     HI.Value.emplace();
 685     llvm::raw_string_ostream OS(*HI.Value);
 686     Name->outputString(OS);
 687     HI.Type = printType(Name->getType(), Ctx, PP);
 688   } else {
 689     // Inside templates, the approximate type `const char[]` is still useful.
 690     QualType StringType = Ctx.getIncompleteArrayType(
 691         Ctx.CharTy.withConst(), ArrayType::ArraySizeModifier::Normal,
 692         /*IndexTypeQuals=*/0);
 693     HI.Type = printType(StringType, Ctx, PP);
 694   }
 695   return HI;
 696 }
 697
 698 HoverInfo evaluateMacroExpansion(unsigned int SpellingBeginOffset,
 699                                  unsigned int SpellingEndOffset,
 700                                  llvm::ArrayRef<syntax::Token> Expanded,
 701                                  ParsedAST &AST) {
 702   auto &Context = AST.getASTContext();
 703   auto &Tokens = AST.getTokens();
 704   auto PP = getPrintingPolicy(Context.getPrintingPolicy());
 705   auto Tree = SelectionTree::createRight(Context, Tokens, SpellingBeginOffset,
 706                                          SpellingEndOffset);
 707
 708   // If macro expands to one single token, rule out punctuator or digraph.
 709   // E.g., for the case `array L_BRACKET 42 R_BRACKET;` where L_BRACKET and
 710   // R_BRACKET expand to
 711   // '[' and ']' respectively, we don't want the type of
 712   // 'array[42]' when user hovers on L_BRACKET.
 713   if (Expanded.size() == 1)
 714     if (tok::getPunctuatorSpelling(Expanded[0].kind()))
 715       return {};
 716
 717   auto *StartNode = Tree.commonAncestor();
 718   if (!StartNode)
 719     return {};
 720   // If the common ancestor is partially selected, do evaluate if it has no
 721   // children, thus we can disallow evaluation on incomplete expression.
 722   // For example,
 723   // #define PLUS_2 +2
 724   // 40 PL^US_2
 725   // In this case we don't want to present 'value: 2' as PLUS_2 actually expands
 726   // to a non-value rather than a binary operand.
 727   if (StartNode->Selected == SelectionTree::Selection::Partial)
 728     if (!StartNode->Children.empty())
 729       return {};
 730
 731   HoverInfo HI;
 732   // Attempt to evaluate it from Expr first.
 733   auto ExprResult = printExprValue(StartNode, Context);
 734   HI.Value = std::move(ExprResult.PrintedValue);
 735   if (auto *E = ExprResult.TheExpr)
 736     HI.Type = printType(E->getType(), Context, PP);
 737
 738   // If failed, extract the type from Decl if possible.
 739   if (!HI.Value && !HI.Type && ExprResult.TheNode)
 740     if (auto *VD = ExprResult.TheNode->ASTNode.get<VarDecl>())
 741       HI.Type = printType(VD->getType(), Context, PP);
 742
 743   return HI;
 744 }
 745
 746 /// Generate a \p Hover object given the macro \p MacroDecl.
 747 HoverInfo getHoverContents(const DefinedMacro &Macro, const syntax::Token &Tok,
 748                            ParsedAST &AST) {
 749   HoverInfo HI;
 750   SourceManager &SM = AST.getSourceManager();
 751   HI.Name = std::string(Macro.Name);
 752   HI.Kind = index::SymbolKind::Macro;
 753   // FIXME: Populate documentation
 754   // FIXME: Populate parameters
 755
 756   // Try to get the full definition, not just the name
 757   SourceLocation StartLoc = Macro.Info->getDefinitionLoc();
 758   SourceLocation EndLoc = Macro.Info->getDefinitionEndLoc();
 759   // Ensure that EndLoc is a valid offset. For example it might come from
 760   // preamble, and source file might've changed, in such a scenario EndLoc still
 761   // stays valid, but getLocForEndOfToken will fail as it is no longer a valid
 762   // offset.
 763   // Note that this check is just to ensure there's text data inside the range.
 764   // It will still succeed even when the data inside the range is irrelevant to
 765   // macro definition.
 766   if (SM.getPresumedLoc(EndLoc, /*UseLineDirectives=*/false).isValid()) {
 767     EndLoc = Lexer::getLocForEndOfToken(EndLoc, 0, SM, AST.getLangOpts());
 768     bool Invalid;
 769     StringRef Buffer = SM.getBufferData(SM.getFileID(StartLoc), &Invalid);
 770     if (!Invalid) {
 771       unsigned StartOffset = SM.getFileOffset(StartLoc);
 772       unsigned EndOffset = SM.getFileOffset(EndLoc);
 773       if (EndOffset <= Buffer.size() && StartOffset < EndOffset)
 774         HI.Definition =
 775             ("#define " + Buffer.substr(StartOffset, EndOffset - StartOffset))
 776                 .str();
 777     }
 778   }
 779
 780   if (auto Expansion = AST.getTokens().expansionStartingAt(&Tok)) {
 781     // We drop expansion that's longer than the threshold.
 782     // For extremely long expansion text, it's not readable from hover card
 783     // anyway.
 784     std::string ExpansionText;
 785     for (const auto &ExpandedTok : Expansion->Expanded) {
 786       ExpansionText += ExpandedTok.text(SM);
 787       ExpansionText += " ";
 788       if (ExpansionText.size() > 2048) {
 789         ExpansionText.clear();
 790         break;
 791       }
 792     }
 793
 794     if (!ExpansionText.empty()) {
 795       if (!HI.Definition.empty()) {
 796         HI.Definition += "\n\n";
 797       }
 798       HI.Definition += "// Expands to\n";
 799       HI.Definition += ExpansionText;
 800     }
 801
 802     auto Evaluated = evaluateMacroExpansion(
 803         /*SpellingBeginOffset=*/SM.getFileOffset(Tok.location()),
 804         /*SpellingEndOffset=*/SM.getFileOffset(Tok.endLocation()),
 805         /*Expanded=*/Expansion->Expanded, AST);
 806     HI.Value = std::move(Evaluated.Value);
 807     HI.Type = std::move(Evaluated.Type);
 808   }
 809   return HI;
 810 }
 811
 812 std::string typeAsDefinition(const HoverInfo::PrintedType &PType) {
 813   std::string Result;
 814   llvm::raw_string_ostream OS(Result);
 815   OS << PType.Type;
 816   if (PType.AKA)
 817     OS << " // aka: " << *PType.AKA;
 818   OS.flush();
 819   return Result;
 820 }
 821
 822 std::optional<HoverInfo> getThisExprHoverContents(const CXXThisExpr *CTE,
 823                                                   ASTContext &ASTCtx,
 824                                                   const PrintingPolicy &PP) {
 825   QualType OriginThisType = CTE->getType()->getPointeeType();
 826   QualType ClassType = declaredType(OriginThisType->getAsTagDecl());
 827   // For partial specialization class, origin `this` pointee type will be
 828   // parsed as `InjectedClassNameType`, which will ouput template arguments
 829   // like "type-parameter-0-0". So we retrieve user written class type in this
 830   // case.
 831   QualType PrettyThisType = ASTCtx.getPointerType(
 832       QualType(ClassType.getTypePtr(), OriginThisType.getCVRQualifiers()));
 833
 834   HoverInfo HI;
 835   HI.Name = "this";
 836   HI.Definition = typeAsDefinition(printType(PrettyThisType, ASTCtx, PP));
 837   return HI;
 838 }
 839
 840 /// Generate a HoverInfo object given the deduced type \p QT
 841 HoverInfo getDeducedTypeHoverContents(QualType QT, const syntax::Token &Tok,
 842                                       ASTContext &ASTCtx,
 843                                       const PrintingPolicy &PP,
 844                                       const SymbolIndex *Index) {
 845   HoverInfo HI;
 846   // FIXME: distinguish decltype(auto) vs decltype(expr)
 847   HI.Name = tok::getTokenName(Tok.kind());
 848   HI.Kind = index::SymbolKind::TypeAlias;
 849
 850   if (QT->isUndeducedAutoType()) {
 851     HI.Definition = "/* not deduced */";
 852   } else {
 853     HI.Definition = typeAsDefinition(printType(QT, ASTCtx, PP));
 854
 855     if (const auto *D = QT->getAsTagDecl()) {
 856       const auto *CommentD = getDeclForComment(D);
 857       HI.Documentation = getDeclComment(ASTCtx, *CommentD);
 858       enhanceFromIndex(HI, *CommentD, Index);
 859     }
 860   }
 861
 862   return HI;
 863 }
 864
 865 HoverInfo getStringLiteralContents(const StringLiteral *SL,
 866                                    const PrintingPolicy &PP) {
 867   HoverInfo HI;
 868
 869   HI.Name = "string-literal";
 870   HI.Size = (SL->getLength() + 1) * SL->getCharByteWidth() * 8;
 871   HI.Type = SL->getType().getAsString(PP).c_str();
 872
 873   return HI;
 874 }
 875
 876 bool isLiteral(const Expr *E) {
 877   // Unfortunately there's no common base Literal classes inherits from
 878   // (apart from Expr), therefore these exclusions.
 879   return llvm::isa<CompoundLiteralExpr>(E) ||
 880          llvm::isa<CXXBoolLiteralExpr>(E) ||
 881          llvm::isa<CXXNullPtrLiteralExpr>(E) ||
 882          llvm::isa<FixedPointLiteral>(E) || llvm::isa<FloatingLiteral>(E) ||
 883          llvm::isa<ImaginaryLiteral>(E) || llvm::isa<IntegerLiteral>(E) ||
 884          llvm::isa<StringLiteral>(E) || llvm::isa<UserDefinedLiteral>(E);
 885 }
 886
 887 llvm::StringLiteral getNameForExpr(const Expr *E) {
 888   // FIXME: Come up with names for `special` expressions.
 889   //
 890   // It's an known issue for GCC5, https://godbolt.org/z/Z_tbgi. Work around
 891   // that by using explicit conversion constructor.
 892   //
 893   // TODO: Once GCC5 is fully retired and not the minimal requirement as stated
 894   // in `GettingStarted`, please remove the explicit conversion constructor.
 895   return llvm::StringLiteral("expression");
 896 }
 897
 898 void maybeAddCalleeArgInfo(const SelectionTree::Node *N, HoverInfo &HI,
 899                            const PrintingPolicy &PP);
 900
 901 // Generates hover info for `this` and evaluatable expressions.
 902 // FIXME: Support hover for literals (esp user-defined)
 903 std::optional<HoverInfo> getHoverContents(const SelectionTree::Node *N,
 904                                           const Expr *E, ParsedAST &AST,
 905                                           const PrintingPolicy &PP,
 906                                           const SymbolIndex *Index) {
 907   std::optional<HoverInfo> HI;
 908
 909   if (const StringLiteral *SL = dyn_cast<StringLiteral>(E)) {
 910     // Print the type and the size for string literals
 911     HI = getStringLiteralContents(SL, PP);
 912   } else if (isLiteral(E)) {
 913     // There's not much value in hovering over "42" and getting a hover card
 914     // saying "42 is an int", similar for most other literals.
 915     // However, if we have CalleeArgInfo, it's still useful to show it.
 916     maybeAddCalleeArgInfo(N, HI.emplace(), PP);
 917     if (HI->CalleeArgInfo) {
 918       // FIXME Might want to show the expression's value here instead?
 919       // E.g. if the literal is in hex it might be useful to show the decimal
 920       // value here.
 921       HI->Name = "literal";
 922       return HI;
 923     }
 924     return std::nullopt;
 925   }
 926
 927   // For `this` expr we currently generate hover with pointee type.
 928   if (const CXXThisExpr *CTE = dyn_cast<CXXThisExpr>(E))
 929     HI = getThisExprHoverContents(CTE, AST.getASTContext(), PP);
 930   if (const PredefinedExpr *PE = dyn_cast<PredefinedExpr>(E))
 931     HI = getPredefinedExprHoverContents(*PE, AST.getASTContext(), PP);
 932   // For expressions we currently print the type and the value, iff it is
 933   // evaluatable.
 934   if (auto Val = printExprValue(E, AST.getASTContext())) {
 935     HI.emplace();
 936     HI->Type = printType(E->getType(), AST.getASTContext(), PP);
 937     HI->Value = *Val;
 938     HI->Name = std::string(getNameForExpr(E));
 939   }
 940
 941   if (HI)
 942     maybeAddCalleeArgInfo(N, *HI, PP);
 943
 944   return HI;
 945 }
 946
 947 // Generates hover info for attributes.
 948 std::optional<HoverInfo> getHoverContents(const Attr *A, ParsedAST &AST) {
 949   HoverInfo HI;
 950   HI.Name = A->getSpelling();
 951   if (A->hasScope())
 952     HI.LocalScope = A->getScopeName()->getName().str();
 953   {
 954     llvm::raw_string_ostream OS(HI.Definition);
 955     A->printPretty(OS, AST.getASTContext().getPrintingPolicy());
 956   }
 957   HI.Documentation = Attr::getDocumentation(A->getKind()).str();
 958   return HI;
 959 }
 960
 961 bool isParagraphBreak(llvm::StringRef Rest) {
 962   return Rest.ltrim(" \t").startswith("\n");
 963 }
 964
 965 bool punctuationIndicatesLineBreak(llvm::StringRef Line) {
 966   constexpr llvm::StringLiteral Punctuation = R"txt(.:,;!?)txt";
 967
 968   Line = Line.rtrim();
 969   return !Line.empty() && Punctuation.contains(Line.back());
 970 }
 971
 972 bool isHardLineBreakIndicator(llvm::StringRef Rest) {
 973   // '-'/'*' md list, '@'/'\' documentation command, '>' md blockquote,
 974   // '#' headings, '`' code blocks
 975   constexpr llvm::StringLiteral LinebreakIndicators = R"txt(-*@\>#`)txt";
 976
 977   Rest = Rest.ltrim(" \t");
 978   if (Rest.empty())
 979     return false;
 980
 981   if (LinebreakIndicators.contains(Rest.front()))
 982     return true;
 983
 984   if (llvm::isDigit(Rest.front())) {
 985     llvm::StringRef AfterDigit = Rest.drop_while(llvm::isDigit);
 986     if (AfterDigit.startswith(".") || AfterDigit.startswith(")"))
 987       return true;
 988   }
 989   return false;
 990 }
 991
 992 bool isHardLineBreakAfter(llvm::StringRef Line, llvm::StringRef Rest) {
 993   // Should we also consider whether Line is short?
 994   return punctuationIndicatesLineBreak(Line) || isHardLineBreakIndicator(Rest);
 995 }
 996
 997 void addLayoutInfo(const NamedDecl &ND, HoverInfo &HI) {
 998   if (ND.isInvalidDecl())
 999     return;
1000
1001   const auto &Ctx = ND.getASTContext();
1002   if (auto *RD = llvm::dyn_cast<RecordDecl>(&ND)) {
1003     if (auto Size = Ctx.getTypeSizeInCharsIfKnown(RD->getTypeForDecl()))
1004       HI.Size = Size->getQuantity() * 8;
1005     return;
1006   }
1007
1008   if (const auto *FD = llvm::dyn_cast<FieldDecl>(&ND)) {
1009     const auto *Record = FD->getParent();
1010     if (Record)
1011       Record = Record->getDefinition();
1012     if (Record && !Record->isInvalidDecl() && !Record->isDependentType()) {
1013       const ASTRecordLayout &Layout = Ctx.getASTRecordLayout(Record);
1014       HI.Offset = Layout.getFieldOffset(FD->getFieldIndex());
1015       if (FD->isBitField())
1016         HI.Size = FD->getBitWidthValue(Ctx);
1017       else if (auto Size = Ctx.getTypeSizeInCharsIfKnown(FD->getType()))
1018         HI.Size = FD->isZeroSize(Ctx) ? 0 : Size->getQuantity() * 8;
1019       if (HI.Size) {
1020         unsigned EndOfField = *HI.Offset + *HI.Size;
1021
1022         // Calculate padding following the field.
1023         if (!Record->isUnion() &&
1024             FD->getFieldIndex() + 1 < Layout.getFieldCount()) {
1025           // Measure padding up to the next class field.
1026           unsigned NextOffset = Layout.getFieldOffset(FD->getFieldIndex() + 1);
1027           if (NextOffset >= EndOfField) // next field could be a bitfield!
1028             HI.Padding = NextOffset - EndOfField;
1029         } else {
1030           // Measure padding up to the end of the object.
1031           HI.Padding = Layout.getSize().getQuantity() * 8 - EndOfField;
1032         }
1033       }
1034       // Offset in a union is always zero, so not really useful to report.
1035       if (Record->isUnion())
1036         HI.Offset.reset();
1037     }
1038     return;
1039   }
1040 }
1041
1042 HoverInfo::PassType::PassMode getPassMode(QualType ParmType) {
1043   if (ParmType->isReferenceType()) {
1044     if (ParmType->getPointeeType().isConstQualified())
1045       return HoverInfo::PassType::ConstRef;
1046     return HoverInfo::PassType::Ref;
1047   }
1048   return HoverInfo::PassType::Value;
1049 }
1050
1051 // If N is passed as argument to a function, fill HI.CalleeArgInfo with
1052 // information about that argument.
1053 void maybeAddCalleeArgInfo(const SelectionTree::Node *N, HoverInfo &HI,
1054                            const PrintingPolicy &PP) {
1055   const auto &OuterNode = N->outerImplicit();
1056   if (!OuterNode.Parent)
1057     return;
1058
1059   const FunctionDecl *FD = nullptr;
1060   llvm::ArrayRef<const Expr *> Args;
1061
1062   if (const auto *CE = OuterNode.Parent->ASTNode.get<CallExpr>()) {
1063     FD = CE->getDirectCallee();
1064     Args = {CE->getArgs(), CE->getNumArgs()};
1065   } else if (const auto *CE =
1066                  OuterNode.Parent->ASTNode.get<CXXConstructExpr>()) {
1067     FD = CE->getConstructor();
1068     Args = {CE->getArgs(), CE->getNumArgs()};
1069   }
1070   if (!FD)
1071     return;
1072
1073   // For non-function-call-like operators (e.g. operator+, operator<<) it's
1074   // not immediately obvious what the "passed as" would refer to and, given
1075   // fixed function signature, the value would be very low anyway, so we choose
1076   // to not support that.
1077   // Both variadic functions and operator() (especially relevant for lambdas)
1078   // should be supported in the future.
1079   if (!FD || FD->isOverloadedOperator() || FD->isVariadic())
1080     return;
1081
1082   HoverInfo::PassType PassType;
1083
1084   auto Parameters = resolveForwardingParameters(FD);
1085
1086   // Find argument index for N.
1087   for (unsigned I = 0; I < Args.size() && I < Parameters.size(); ++I) {
1088     if (Args[I] != OuterNode.ASTNode.get<Expr>())
1089       continue;
1090
1091     // Extract matching argument from function declaration.
1092     if (const ParmVarDecl *PVD = Parameters[I]) {
1093       HI.CalleeArgInfo.emplace(toHoverInfoParam(PVD, PP));
1094       if (N == &OuterNode)
1095         PassType.PassBy = getPassMode(PVD->getType());
1096     }
1097     break;
1098   }
1099   if (!HI.CalleeArgInfo)
1100     return;
1101
1102   // If we found a matching argument, also figure out if it's a
1103   // [const-]reference. For this we need to walk up the AST from the arg itself
1104   // to CallExpr and check all implicit casts, constructor calls, etc.
1105   if (const auto *E = N->ASTNode.get<Expr>()) {
1106     if (E->getType().isConstQualified())
1107       PassType.PassBy = HoverInfo::PassType::ConstRef;
1108   }
1109
1110   for (auto *CastNode = N->Parent;
1111        CastNode != OuterNode.Parent && !PassType.Converted;
1112        CastNode = CastNode->Parent) {
1113     if (const auto *ImplicitCast = CastNode->ASTNode.get<ImplicitCastExpr>()) {
1114       switch (ImplicitCast->getCastKind()) {
1115       case CK_NoOp:
1116       case CK_DerivedToBase:
1117       case CK_UncheckedDerivedToBase:
1118         // If it was a reference before, it's still a reference.
1119         if (PassType.PassBy != HoverInfo::PassType::Value)
1120           PassType.PassBy = ImplicitCast->getType().isConstQualified()
1121                                 ? HoverInfo::PassType::ConstRef
1122                                 : HoverInfo::PassType::Ref;
1123         break;
1124       case CK_LValueToRValue:
1125       case CK_ArrayToPointerDecay:
1126       case CK_FunctionToPointerDecay:
1127       case CK_NullToPointer:
1128       case CK_NullToMemberPointer:
1129         // No longer a reference, but we do not show this as type conversion.
1130         PassType.PassBy = HoverInfo::PassType::Value;
1131         break;
1132       default:
1133         PassType.PassBy = HoverInfo::PassType::Value;
1134         PassType.Converted = true;
1135         break;
1136       }
1137     } else if (const auto *CtorCall =
1138                    CastNode->ASTNode.get<CXXConstructExpr>()) {
1139       // We want to be smart about copy constructors. They should not show up as
1140       // type conversion, but instead as passing by value.
1141       if (CtorCall->getConstructor()->isCopyConstructor())
1142         PassType.PassBy = HoverInfo::PassType::Value;
1143       else
1144         PassType.Converted = true;
1145     } else if (CastNode->ASTNode.get<MaterializeTemporaryExpr>()) {
1146       // Can't bind a non-const-ref to a temporary, so has to be const-ref
1147       PassType.PassBy = HoverInfo::PassType::ConstRef;
1148     } else { // Unknown implicit node, assume type conversion.
1149       PassType.PassBy = HoverInfo::PassType::Value;
1150       PassType.Converted = true;
1151     }
1152   }
1153
1154   HI.CallPassType.emplace(PassType);
1155 }
1156
1157 const NamedDecl *pickDeclToUse(llvm::ArrayRef<const NamedDecl *> Candidates) {
1158   if (Candidates.empty())
1159     return nullptr;
1160
1161   // This is e.g the case for
1162   //     namespace ns { void foo(); }
1163   //     void bar() { using ns::foo; f^oo(); }
1164   // One declaration in Candidates will refer to the using declaration,
1165   // which isn't really useful for Hover. So use the other one,
1166   // which in this example would be the actual declaration of foo.
1167   if (Candidates.size() <= 2) {
1168     if (llvm::isa<UsingDecl>(Candidates.front()))
1169       return Candidates.back();
1170     return Candidates.front();
1171   }
1172
1173   // For something like
1174   //     namespace ns { void foo(int); void foo(char); }
1175   //     using ns::foo;
1176   //     template <typename T> void bar() { fo^o(T{}); }
1177   // we actually want to show the using declaration,
1178   // it's not clear which declaration to pick otherwise.
1179   auto BaseDecls = llvm::make_filter_range(
1180       Candidates, [](const NamedDecl *D) { return llvm::isa<UsingDecl>(D); });
1181   if (std::distance(BaseDecls.begin(), BaseDecls.end()) == 1)
1182     return *BaseDecls.begin();
1183
1184   return Candidates.front();
1185 }
1186
1187 void maybeAddSymbolProviders(ParsedAST &AST, HoverInfo &HI,
1188                              include_cleaner::Symbol Sym) {
1189   trace::Span Tracer("Hover::maybeAddSymbolProviders");
1190
1191   const SourceManager &SM = AST.getSourceManager();
1192   llvm::SmallVector<include_cleaner::Header> RankedProviders =
1193       include_cleaner::headersForSymbol(Sym, SM, AST.getPragmaIncludes());
1194   if (RankedProviders.empty())
1195     return;
1196
1197   std::string Result;
1198   include_cleaner::Includes ConvertedIncludes =
1199       convertIncludes(SM, AST.getIncludeStructure().MainFileIncludes);
1200   for (const auto &P : RankedProviders) {
1201     if (P.kind() == include_cleaner::Header::Physical &&
1202         P.physical() == SM.getFileEntryForID(SM.getMainFileID()))
1203       // Main file ranked higher than any #include'd file
1204       break;
1205
1206     // Pick the best-ranked #include'd provider
1207     auto Matches = ConvertedIncludes.match(P);
1208     if (!Matches.empty()) {
1209       Result = Matches[0]->quote();
1210       break;
1211     }
1212   }
1213
1214   if (!Result.empty()) {
1215     HI.Provider = std::move(Result);
1216     return;
1217   }
1218
1219   // Pick the best-ranked non-#include'd provider
1220   const auto &H = RankedProviders.front();
1221   if (H.kind() == include_cleaner::Header::Physical &&
1222       H.physical() == SM.getFileEntryForID(SM.getMainFileID()))
1223     // Do not show main file as provider, otherwise we'll show provider info
1224     // on local variables, etc.
1225     return;
1226
1227   HI.Provider = include_cleaner::spellHeader(
1228       {H, AST.getPreprocessor().getHeaderSearchInfo(),
1229        SM.getFileEntryForID(SM.getMainFileID())});
1230 }
1231
1232 // FIXME: similar functions are present in FindHeaders.cpp (symbolName)
1233 // and IncludeCleaner.cpp (getSymbolName). Introduce a name() method into
1234 // include_cleaner::Symbol instead.
1235 std::string getSymbolName(include_cleaner::Symbol Sym) {
1236   std::string Name;
1237   switch (Sym.kind()) {
1238   case include_cleaner::Symbol::Declaration:
1239     if (const auto *ND = llvm::dyn_cast<NamedDecl>(&Sym.declaration()))
1240       Name = ND->getDeclName().getAsString();
1241     break;
1242   case include_cleaner::Symbol::Macro:
1243     Name = Sym.macro().Name->getName();
1244     break;
1245   }
1246   return Name;
1247 }
1248
1249 void maybeAddUsedSymbols(ParsedAST &AST, HoverInfo &HI, const Inclusion &Inc) {
1250   const SourceManager &SM = AST.getSourceManager();
1251   const auto &ConvertedMainFileIncludes =
1252       convertIncludes(SM, AST.getIncludeStructure().MainFileIncludes);
1253   const auto &HoveredInclude = convertIncludes(SM, llvm::ArrayRef{Inc});
1254   llvm::DenseSet<include_cleaner::Symbol> UsedSymbols;
1255   include_cleaner::walkUsed(
1256       AST.getLocalTopLevelDecls(), collectMacroReferences(AST),
1257       AST.getPragmaIncludes(), SM,
1258       [&](const include_cleaner::SymbolReference &Ref,
1259           llvm::ArrayRef<include_cleaner::Header> Providers) {
1260         if (Ref.RT != include_cleaner::RefType::Explicit ||
1261             UsedSymbols.contains(Ref.Target))
1262           return;
1263
1264         auto Provider =
1265             firstMatchedProvider(ConvertedMainFileIncludes, Providers);
1266         if (!Provider || HoveredInclude.match(*Provider).empty())
1267           return;
1268
1269         UsedSymbols.insert(Ref.Target);
1270       });
1271
1272   for (const auto &UsedSymbolDecl : UsedSymbols)
1273     HI.UsedSymbolNames.push_back(getSymbolName(UsedSymbolDecl));
1274   llvm::sort(HI.UsedSymbolNames);
1275   HI.UsedSymbolNames.erase(
1276       std::unique(HI.UsedSymbolNames.begin(), HI.UsedSymbolNames.end()),
1277       HI.UsedSymbolNames.end());
1278 }
1279
1280 } // namespace
1281
1282 std::optional<HoverInfo> getHover(ParsedAST &AST, Position Pos,
1283                                   const format::FormatStyle &Style,
1284                                   const SymbolIndex *Index) {
1285   static constexpr trace::Metric HoverCountMetric(
1286       "hover", trace::Metric::Counter, "case");
1287   PrintingPolicy PP =
1288       getPrintingPolicy(AST.getASTContext().getPrintingPolicy());
1289   const SourceManager &SM = AST.getSourceManager();
1290   auto CurLoc = sourceLocationInMainFile(SM, Pos);
1291   if (!CurLoc) {
1292     llvm::consumeError(CurLoc.takeError());
1293     return std::nullopt;
1294   }
1295   const auto &TB = AST.getTokens();
1296   auto TokensTouchingCursor = syntax::spelledTokensTouching(*CurLoc, TB);
1297   // Early exit if there were no tokens around the cursor.
1298   if (TokensTouchingCursor.empty())
1299     return std::nullopt;
1300
1301   // Show full header file path if cursor is on include directive.
1302   for (const auto &Inc : AST.getIncludeStructure().MainFileIncludes) {
1303     if (Inc.Resolved.empty() || Inc.HashLine != Pos.line)
1304       continue;
1305     HoverCountMetric.record(1, "include");
1306     HoverInfo HI;
1307     HI.Name = std::string(llvm::sys::path::filename(Inc.Resolved));
1308     // FIXME: We don't have a fitting value for Kind.
1309     HI.Definition =
1310         URIForFile::canonicalize(Inc.Resolved, AST.tuPath()).file().str();
1311     HI.DefinitionLanguage = "";
1312     maybeAddUsedSymbols(AST, HI, Inc);
1313     return HI;
1314   }
1315
1316   // To be used as a backup for highlighting the selected token, we use back as
1317   // it aligns better with biases elsewhere (editors tend to send the position
1318   // for the left of the hovered token).
1319   CharSourceRange HighlightRange =
1320       TokensTouchingCursor.back().range(SM).toCharRange(SM);
1321   std::optional<HoverInfo> HI;
1322   // Macros and deducedtype only works on identifiers and auto/decltype keywords
1323   // respectively. Therefore they are only trggered on whichever works for them,
1324   // similar to SelectionTree::create().
1325   for (const auto &Tok : TokensTouchingCursor) {
1326     if (Tok.kind() == tok::identifier) {
1327       // Prefer the identifier token as a fallback highlighting range.
1328       HighlightRange = Tok.range(SM).toCharRange(SM);
1329       if (auto M = locateMacroAt(Tok, AST.getPreprocessor())) {
1330         HoverCountMetric.record(1, "macro");
1331         HI = getHoverContents(*M, Tok, AST);
1332         if (auto DefLoc = M->Info->getDefinitionLoc(); DefLoc.isValid()) {
1333           include_cleaner::Macro IncludeCleanerMacro{
1334               AST.getPreprocessor().getIdentifierInfo(Tok.text(SM)), DefLoc};
1335           maybeAddSymbolProviders(AST, *HI,
1336                                   include_cleaner::Symbol{IncludeCleanerMacro});
1337         }
1338         break;
1339       }
1340     } else if (Tok.kind() == tok::kw_auto || Tok.kind() == tok::kw_decltype) {
1341       HoverCountMetric.record(1, "keyword");
1342       if (auto Deduced = getDeducedType(AST.getASTContext(), Tok.location())) {
1343         HI = getDeducedTypeHoverContents(*Deduced, Tok, AST.getASTContext(), PP,
1344                                          Index);
1345         HighlightRange = Tok.range(SM).toCharRange(SM);
1346         break;
1347       }
1348
1349       // If we can't find interesting hover information for this
1350       // auto/decltype keyword, return nothing to avoid showing
1351       // irrelevant or incorrect informations.
1352       return std::nullopt;
1353     }
1354   }
1355
1356   // If it wasn't auto/decltype or macro, look for decls and expressions.
1357   if (!HI) {
1358     auto Offset = SM.getFileOffset(*CurLoc);
1359     // Editors send the position on the left of the hovered character.
1360     // So our selection tree should be biased right. (Tested with VSCode).
1361     SelectionTree ST =
1362         SelectionTree::createRight(AST.getASTContext(), TB, Offset, Offset);
1363     if (const SelectionTree::Node *N = ST.commonAncestor()) {
1364       // FIXME: Fill in HighlightRange with range coming from N->ASTNode.
1365       auto Decls = explicitReferenceTargets(N->ASTNode, DeclRelation::Alias,
1366                                             AST.getHeuristicResolver());
1367       if (const auto *DeclToUse = pickDeclToUse(Decls)) {
1368         HoverCountMetric.record(1, "decl");
1369         HI = getHoverContents(DeclToUse, PP, Index, TB);
1370         // Layout info only shown when hovering on the field/class itself.
1371         if (DeclToUse == N->ASTNode.get<Decl>())
1372           addLayoutInfo(*DeclToUse, *HI);
1373         // Look for a close enclosing expression to show the value of.
1374         if (!HI->Value)
1375           HI->Value = printExprValue(N, AST.getASTContext()).PrintedValue;
1376         maybeAddCalleeArgInfo(N, *HI, PP);
1377
1378         if (!isa<NamespaceDecl>(DeclToUse))
1379           maybeAddSymbolProviders(AST, *HI,
1380                                   include_cleaner::Symbol{*DeclToUse});
1381       } else if (const Expr *E = N->ASTNode.get<Expr>()) {
1382         HoverCountMetric.record(1, "expr");
1383         HI = getHoverContents(N, E, AST, PP, Index);
1384       } else if (const Attr *A = N->ASTNode.get<Attr>()) {
1385         HoverCountMetric.record(1, "attribute");
1386         HI = getHoverContents(A, AST);
1387       }
1388       // FIXME: support hovers for other nodes?
1389       //  - built-in types
1390     }
1391   }
1392
1393   if (!HI)
1394     return std::nullopt;
1395
1396   // Reformat Definition
1397   if (!HI->Definition.empty()) {
1398     auto Replacements = format::reformat(
1399         Style, HI->Definition, tooling::Range(0, HI->Definition.size()));
1400     if (auto Formatted =
1401             tooling::applyAllReplacements(HI->Definition, Replacements))
1402       HI->Definition = *Formatted;
1403   }
1404
1405   HI->DefinitionLanguage = getMarkdownLanguage(AST.getASTContext());
1406   HI->SymRange = halfOpenToRange(SM, HighlightRange);
1407
1408   return HI;
1409 }
1410
1411 // Sizes (and padding) are shown in bytes if possible, otherwise in bits.
1412 static std::string formatSize(uint64_t SizeInBits) {
1413   uint64_t Value = SizeInBits % 8 == 0 ? SizeInBits / 8 : SizeInBits;
1414   const char *Unit = Value != 0 && Value == SizeInBits ? "bit" : "byte";
1415   return llvm::formatv("{0} {1}{2}", Value, Unit, Value == 1 ? "" : "s").str();
1416 }
1417
1418 // Offsets are shown in bytes + bits, so offsets of different fields
1419 // can always be easily compared.
1420 static std::string formatOffset(uint64_t OffsetInBits) {
1421   const auto Bytes = OffsetInBits / 8;
1422   const auto Bits = OffsetInBits % 8;
1423   auto Offset = formatSize(Bytes * 8);
1424   if (Bits != 0)
1425     Offset += " and " + formatSize(Bits);
1426   return Offset;
1427 }
1428
1429 markup::Document HoverInfo::present() const {
1430   markup::Document Output;
1431
1432   // Header contains a text of the form:
1433   // variable `var`
1434   //
1435   // class `X`
1436   //
1437   // function `foo`
1438   //
1439   // expression
1440   //
1441   // Note that we are making use of a level-3 heading because VSCode renders
1442   // level 1 and 2 headers in a huge font, see
1443   // https://github.com/microsoft/vscode/issues/88417 for details.
1444   markup::Paragraph &Header = Output.addHeading(3);
1445   if (Kind != index::SymbolKind::Unknown)
1446     Header.appendText(index::getSymbolKindString(Kind)).appendSpace();
1447   assert(!Name.empty() && "hover triggered on a nameless symbol");
1448   Header.appendCode(Name);
1449
1450   if (!Provider.empty()) {
1451     markup::Paragraph &DI = Output.addParagraph();
1452     DI.appendText("provided by");
1453     DI.appendSpace();
1454     DI.appendCode(Provider);
1455     Output.addRuler();
1456   }
1457
1458   // Put a linebreak after header to increase readability.
1459   Output.addRuler();
1460   // Print Types on their own lines to reduce chances of getting line-wrapped by
1461   // editor, as they might be long.
1462   if (ReturnType) {
1463     // For functions we display signature in a list form, e.g.:
1464     // → `x`
1465     // Parameters:
1466     // - `bool param1`
1467     // - `int param2 = 5`
1468     Output.addParagraph().appendText("→ ").appendCode(
1469         llvm::to_string(*ReturnType));
1470   }
1471
1472   if (Parameters && !Parameters->empty()) {
1473     Output.addParagraph().appendText("Parameters: ");
1474     markup::BulletList &L = Output.addBulletList();
1475     for (const auto &Param : *Parameters)
1476       L.addItem().addParagraph().appendCode(llvm::to_string(Param));
1477   }
1478
1479   // Don't print Type after Parameters or ReturnType as this will just duplicate
1480   // the information
1481   if (Type && !ReturnType && !Parameters)
1482     Output.addParagraph().appendText("Type: ").appendCode(
1483         llvm::to_string(*Type));
1484
1485   if (Value) {
1486     markup::Paragraph &P = Output.addParagraph();
1487     P.appendText("Value = ");
1488     P.appendCode(*Value);
1489   }
1490
1491   if (Offset)
1492     Output.addParagraph().appendText("Offset: " + formatOffset(*Offset));
1493   if (Size) {
1494     auto &P = Output.addParagraph().appendText("Size: " + formatSize(*Size));
1495     if (Padding && *Padding != 0) {
1496       P.appendText(
1497           llvm::formatv(" (+{0} padding)", formatSize(*Padding)).str());
1498     }
1499   }
1500
1501   if (CalleeArgInfo) {
1502     assert(CallPassType);
1503     std::string Buffer;
1504     llvm::raw_string_ostream OS(Buffer);
1505     OS << "Passed ";
1506     if (CallPassType->PassBy != HoverInfo::PassType::Value) {
1507       OS << "by ";
1508       if (CallPassType->PassBy == HoverInfo::PassType::ConstRef)
1509         OS << "const ";
1510       OS << "reference ";
1511     }
1512     if (CalleeArgInfo->Name)
1513       OS << "as " << CalleeArgInfo->Name;
1514     else if (CallPassType->PassBy == HoverInfo::PassType::Value)
1515       OS << "by value";
1516     if (CallPassType->Converted && CalleeArgInfo->Type)
1517       OS << " (converted to " << CalleeArgInfo->Type->Type << ")";
1518     Output.addParagraph().appendText(OS.str());
1519   }
1520
1521   if (!Documentation.empty())
1522     parseDocumentation(Documentation, Output);
1523
1524   if (!Definition.empty()) {
1525     Output.addRuler();
1526     std::string Buffer;
1527
1528     if (!Definition.empty()) {
1529       // Append scope comment, dropping trailing "::".
1530       // Note that we don't print anything for global namespace, to not annoy
1531       // non-c++ projects or projects that are not making use of namespaces.
1532       if (!LocalScope.empty()) {
1533         // Container name, e.g. class, method, function.
1534         // We might want to propagate some info about container type to print
1535         // function foo, class X, method X::bar, etc.
1536         Buffer +=
1537             "// In " + llvm::StringRef(LocalScope).rtrim(':').str() + '\n';
1538       } else if (NamespaceScope && !NamespaceScope->empty()) {
1539         Buffer += "// In namespace " +
1540                   llvm::StringRef(*NamespaceScope).rtrim(':').str() + '\n';
1541       }
1542
1543       if (!AccessSpecifier.empty()) {
1544         Buffer += AccessSpecifier + ": ";
1545       }
1546
1547       Buffer += Definition;
1548     }
1549
1550     Output.addCodeBlock(Buffer, DefinitionLanguage);
1551   }
1552
1553   if (!UsedSymbolNames.empty()) {
1554     Output.addRuler();
1555     markup::Paragraph &P = Output.addParagraph();
1556     P.appendText("provides ");
1557
1558     const std::vector<std::string>::size_type SymbolNamesLimit = 5;
1559     auto Front = llvm::ArrayRef(UsedSymbolNames).take_front(SymbolNamesLimit);
1560
1561     llvm::interleave(
1562         Front, [&](llvm::StringRef Sym) { P.appendCode(Sym); },
1563         [&] { P.appendText(", "); });
1564     if (UsedSymbolNames.size() > Front.size()) {
1565       P.appendText(" and ");
1566       P.appendText(std::to_string(UsedSymbolNames.size() - Front.size()));
1567       P.appendText(" more");
1568     }
1569   }
1570
1571   return Output;
1572 }
1573
1574 // If the backtick at `Offset` starts a probable quoted range, return the range
1575 // (including the quotes).
1576 std::optional<llvm::StringRef> getBacktickQuoteRange(llvm::StringRef Line,
1577                                                      unsigned Offset) {
1578   assert(Line[Offset] == '`');
1579
1580   // The open-quote is usually preceded by whitespace.
1581   llvm::StringRef Prefix = Line.substr(0, Offset);
1582   constexpr llvm::StringLiteral BeforeStartChars = " \t(=";
1583   if (!Prefix.empty() && !BeforeStartChars.contains(Prefix.back()))
1584     return std::nullopt;
1585
1586   // The quoted string must be nonempty and usually has no leading/trailing ws.
1587   auto Next = Line.find('`', Offset + 1);
1588   if (Next == llvm::StringRef::npos)
1589     return std::nullopt;
1590   llvm::StringRef Contents = Line.slice(Offset + 1, Next);
1591   if (Contents.empty() || isWhitespace(Contents.front()) ||
1592       isWhitespace(Contents.back()))
1593     return std::nullopt;
1594
1595   // The close-quote is usually followed by whitespace or punctuation.
1596   llvm::StringRef Suffix = Line.substr(Next + 1);
1597   constexpr llvm::StringLiteral AfterEndChars = " \t)=.,;:";
1598   if (!Suffix.empty() && !AfterEndChars.contains(Suffix.front()))
1599     return std::nullopt;
1600
1601   return Line.slice(Offset, Next + 1);
1602 }
1603
1604 void parseDocumentationLine(llvm::StringRef Line, markup::Paragraph &Out) {
1605   // Probably this is appendText(Line), but scan for something interesting.
1606   for (unsigned I = 0; I < Line.size(); ++I) {
1607     switch (Line[I]) {
1608     case '`':
1609       if (auto Range = getBacktickQuoteRange(Line, I)) {
1610         Out.appendText(Line.substr(0, I));
1611         Out.appendCode(Range->trim("`"), /*Preserve=*/true);
1612         return parseDocumentationLine(Line.substr(I + Range->size()), Out);
1613       }
1614       break;
1615     }
1616   }
1617   Out.appendText(Line).appendSpace();
1618 }
1619
1620 void parseDocumentation(llvm::StringRef Input, markup::Document &Output) {
1621   std::vector<llvm::StringRef> ParagraphLines;
1622   auto FlushParagraph = [&] {
1623     if (ParagraphLines.empty())
1624       return;
1625     auto &P = Output.addParagraph();
1626     for (llvm::StringRef Line : ParagraphLines)
1627       parseDocumentationLine(Line, P);
1628     ParagraphLines.clear();
1629   };
1630
1631   llvm::StringRef Line, Rest;
1632   for (std::tie(Line, Rest) = Input.split('\n');
1633        !(Line.empty() && Rest.empty());
1634        std::tie(Line, Rest) = Rest.split('\n')) {
1635
1636     // After a linebreak remove spaces to avoid 4 space markdown code blocks.
1637     // FIXME: make FlushParagraph handle this.
1638     Line = Line.ltrim();
1639     if (!Line.empty())
1640       ParagraphLines.push_back(Line);
1641
1642     if (isParagraphBreak(Rest) || isHardLineBreakAfter(Line, Rest)) {
1643       FlushParagraph();
1644     }
1645   }
1646   FlushParagraph();
1647 }
1648
1649 llvm::raw_ostream &operator<<(llvm::raw_ostream &OS,
1650                               const HoverInfo::PrintedType &T) {
1651   OS << T.Type;
1652   if (T.AKA)
1653     OS << " (aka " << *T.AKA << ")";
1654   return OS;
1655 }
1656
1657 llvm::raw_ostream &operator<<(llvm::raw_ostream &OS,
1658                               const HoverInfo::Param &P) {
1659   if (P.Type)
1660     OS << P.Type->Type;
1661   if (P.Name)
1662     OS << " " << *P.Name;
1663   if (P.Default)
1664     OS << " = " << *P.Default;
1665   if (P.Type && P.Type->AKA)
1666     OS << " (aka " << *P.Type->AKA << ")";
1667   return OS;
1668 }
1669
1670 } // namespace clangd
1671 } // namespace clang