RequestResult class and Pass*InfoForDecl fixes

2025-12-14 20:36:38 +01:00 · 2019-05-03 15:17:40 -04:00
parent a3a4d2d22b
commit 00d771ca6b
10 changed files with 352 additions and 285 deletions
--- a/tools/SourceKit/lib/SwiftLang/SwiftSourceDocInfo.cpp
+++ b/tools/SourceKit/lib/SwiftLang/SwiftSourceDocInfo.cpp
@@ -604,7 +604,7 @@ tryRemappingLocToLatestSnapshot(SwiftLangSupport &Lang,
 static bool passCursorInfoForModule(ModuleEntity Mod,
                                    SwiftInterfaceGenMap &IFaceGenContexts,
                                    const CompilerInvocation &Invok,
-                       std::function<void(const CursorInfoData &, StringRef error)> Receiver) {
+                       std::function<void(const RequestResult<CursorInfoData> &)> Receiver) {
  std::string Name = Mod.getName();
  std::string FullName = Mod.getFullName();
  CursorInfoData Info;
@@ -619,7 +619,7 @@ static bool passCursorInfoForModule(ModuleEntity Mod,
    Info.ModuleGroupArray = ide::collectModuleGroups(const_cast<ModuleDecl*>(MD),
                                                     Groups);
  }
-  Receiver(Info, "");
+  Receiver(RequestResult<CursorInfoData>::fromResult(Info));
  return false;
 }

@@ -697,24 +697,26 @@ getParamParentNameOffset(const ValueDecl *VD, SourceLoc Cursor) {
  return SM.getLocOffsetInBuffer(Loc, SM.findBufferContainingLoc(Loc));
 }

-/// Returns a non-empty StringRef on error, representing an internal diagnostic.
-static StringRef passCursorInfoForDecl(SourceFile* SF,
-                                       const ValueDecl *VD,
-                                       const ModuleDecl *MainModule,
-                                       const Type ContainerTy,
-                                       bool IsRef,
-                                       bool RetrieveRefactoring,
-                                       ResolvedCursorInfo TheTok,
-                                       Optional<unsigned> OrigBufferID,
-                                       SourceLoc CursorLoc,
-                        ArrayRef<RefactoringInfo> KownRefactoringInfoFromRange,
-                                       SwiftLangSupport &Lang,
-                                       const CompilerInvocation &Invok,
-                            ArrayRef<ImmutableTextSnapshotRef> PreviousASTSnaps,
-                        std::function<void(const CursorInfoData &,
-                                           StringRef Error)> Receiver) {
-  if (AvailableAttr::isUnavailable(VD))
-    return "Unavailable in the current compilation context.";
+/// Returns true on success, false on error (and sets `Diagnostic` accordingly).
+static bool passCursorInfoForDecl(SourceFile* SF,
+                                  const ValueDecl *VD,
+                                  const ModuleDecl *MainModule,
+                                  const Type ContainerTy,
+                                  bool IsRef,
+                                  bool RetrieveRefactoring,
+                                  ResolvedCursorInfo TheTok,
+                                  Optional<unsigned> OrigBufferID,
+                                  SourceLoc CursorLoc,
+                  ArrayRef<RefactoringInfo> KownRefactoringInfoFromRange,
+                                  SwiftLangSupport &Lang,
+                                  const CompilerInvocation &Invok,
+                                  std::string &Diagnostic,
+                      ArrayRef<ImmutableTextSnapshotRef> PreviousASTSnaps,
+                  std::function<void(const RequestResult<CursorInfoData> &)> Receiver) {
+  if (AvailableAttr::isUnavailable(VD)) {
+    Diagnostic = "Unavailable in the current compilation context.";
+    return false;
+  }

  SmallString<64> SS;
  auto BaseType = findBaseTypeForReplacingArchetype(VD, ContainerTy);
@@ -920,8 +922,10 @@ static StringRef passCursorInfoForDecl(SourceFile* SF,
                                                     *DeclarationLoc,
                                                     Filename,
                                                     PreviousASTSnaps);
-    if (!DeclarationLoc.hasValue())
-      return "Failed to remap declaration to latest snapshot.";
+    if (!DeclarationLoc.hasValue()) {
+      Diagnostic = "Failed to remap declaration to latest snapshot.";
+      return false;
+    }
  }

  SmallVector<StringRef, 4> OverUSRs;
@@ -966,8 +970,8 @@ static StringRef passCursorInfoForDecl(SourceFile* SF,
  Info.TypeInterface = StringRef();
  Info.AvailableActions = llvm::makeArrayRef(RefactoringInfoBuffer);
  Info.ParentNameOffset = getParamParentNameOffset(VD, CursorLoc);
-  Receiver(Info, "");
-  return "";
+  Receiver(RequestResult<CursorInfoData>::fromResult(Info));
+  return true;
 }

 static clang::DeclarationName
@@ -1035,11 +1039,11 @@ static DeclName getSwiftDeclName(const ValueDecl *VD,
  return DeclName(Ctx, BaseName, llvm::makeArrayRef(Args));
 }

-/// Returns a non-empty StringRef on error, representing an internal diagnostic.
-static StringRef passNameInfoForDecl(ResolvedCursorInfo CursorInfo,
-                                     NameTranslatingInfo &Info,
-                    std::function<void(const NameTranslatingInfo &,
-                                       StringRef Error)> Receiver) {
+/// Returns true on success, false on error (and sets `Diagnostic` accordingly).
+static bool passNameInfoForDecl(ResolvedCursorInfo CursorInfo,
+                                NameTranslatingInfo &Info,
+                                std::string &Diagnostic,
+                    std::function<void(const RequestResult<NameTranslatingInfo> &)> Receiver) {
  auto *VD = CursorInfo.ValueD;

  // If the given name is not a function name, and the cursor points to
@@ -1054,15 +1058,17 @@ static StringRef passNameInfoForDecl(ResolvedCursorInfo CursorInfo,
  case NameKind::Swift: {
    NameTranslatingInfo Result;
    auto DeclName = getSwiftDeclName(VD, Info);
-    if (!DeclName)
-      return "Unable to resolve Swift declaration name.";
+    if (!DeclName) {
+      Diagnostic = "Unable to resolve Swift declaration name.";
+      return false;
+    }
    auto ResultPair =
        swift::objc_translation::getObjCNameForSwiftDecl(VD, DeclName);
    Identifier Name = ResultPair.first;
    if (!Name.empty()) {
      Result.NameKind = SwiftLangSupport::getUIDForNameKind(NameKind::ObjC);
      Result.BaseName = Name.str();
-      Receiver(Result, "");
+      Receiver(RequestResult<NameTranslatingInfo>::fromResult(Result));
    } else if (ObjCSelector Selector = ResultPair.second) {
      Result.NameKind = SwiftLangSupport::getUIDForNameKind(NameKind::ObjC);
      SmallString<64> Buffer;
@@ -1076,11 +1082,12 @@ static StringRef passNameInfoForDecl(ResolvedCursorInfo CursorInfo,
        Result.IsZeroArgSelector = true;
      }
      Result.ArgNames.insert(Result.ArgNames.begin(), Pieces.begin(), Pieces.end());
-      Receiver(Result, "");
+      Receiver(RequestResult<NameTranslatingInfo>::fromResult(Result));
    } else {
-      return "Unable to resolve name info.";
+      Diagnostic = "Unable to resolve name info.";
+      return false;
    }
-    return "";
+    return true;
  }
  case NameKind::ObjC: {
    ClangImporter *Importer = static_cast<ClangImporter *>(VD->getDeclContext()->
@@ -1093,12 +1100,16 @@ static StringRef passNameInfoForDecl(ResolvedCursorInfo CursorInfo,
      Named = dyn_cast_or_null<clang::NamedDecl>(BaseDecl->getClangDecl());
      BaseDecl = BaseDecl->getOverriddenDecl();
    }
-    if (!Named)
-      return "Unable to resolve a named declaration.";
+    if (!Named) {
+      Diagnostic = "Unable to resolve a named declaration.";
+      return false;
+    }

    auto ObjCName = getClangDeclarationName(Named, Info);
-    if (!ObjCName)
-      return "Unable to resolve ObjC declaration name.";
+    if (!ObjCName) {
+      Diagnostic = "Unable to resolve ObjC declaration name.";
+      return false;
+    }

    DeclName Name = Importer->importName(Named, ObjCName);
    NameTranslatingInfo Result;
@@ -1108,8 +1119,8 @@ static StringRef passNameInfoForDecl(ResolvedCursorInfo CursorInfo,
                   Name.getArgumentNames().end(),
                   std::back_inserter(Result.ArgNames),
                   [](Identifier Id) { return Id.str(); });
-    Receiver(Result, "");
-    return "";
+    Receiver(RequestResult<NameTranslatingInfo>::fromResult(Result));
+    return true;
  }
  }
 }
@@ -1201,12 +1212,12 @@ static void resolveCursor(SwiftLangSupport &Lang,
                          SwiftInvocationRef Invok,
                          bool TryExistingAST,
                          bool CancelOnSubsequentRequest,
-                          std::function<void(const CursorInfoData &, StringRef)> Receiver) {
+                          std::function<void(const RequestResult<CursorInfoData> &)> Receiver) {
  assert(Invok);

  class CursorInfoConsumer : public CursorRangeInfoConsumer {
    bool Actionables;
-    std::function<void(const CursorInfoData &, StringRef)> Receiver;
+    std::function<void(const RequestResult<CursorInfoData> &)> Receiver;

  public:
    CursorInfoConsumer(StringRef InputFile, unsigned Offset,
@@ -1215,7 +1226,7 @@ static void resolveCursor(SwiftLangSupport &Lang,
                       SwiftInvocationRef ASTInvok,
                       bool TryExistingAST,
                       bool CancelOnSubsequentRequest,
-                       std::function<void(const CursorInfoData &, StringRef)> Receiver)
+                       std::function<void(const RequestResult<CursorInfoData> &)> Receiver)
    : CursorRangeInfoConsumer(InputFile, Offset, Length, Lang, ASTInvok,
                              TryExistingAST, CancelOnSubsequentRequest),
      Actionables(Actionables),
@@ -1229,7 +1240,8 @@ static void resolveCursor(SwiftLangSupport &Lang,
      SourceLoc Loc =
        Lexer::getLocForStartOfToken(SM, BufferID, Offset);
      if (Loc.isInvalid()) {
-        Receiver(CursorInfoData(), "Unable to resolve the start of the token.");
+        Receiver(RequestResult<CursorInfoData>::fromError(
+          "Unable to resolve the start of the token."));
        return;
      }

@@ -1273,7 +1285,7 @@ static void resolveCursor(SwiftLangSupport &Lang,

          // If Length is given, then the cursor-info request should only about
          // collecting available refactorings for the range.
-          Receiver(Info, "");
+          Receiver(RequestResult<CursorInfoData>::fromResult(Info));
          return;
        }
        // If the range start may need rename, we fall back to a regular cursor
@@ -1285,7 +1297,7 @@ static void resolveCursor(SwiftLangSupport &Lang,
      if (CursorInfo.isInvalid()) {
        CursorInfoData Info;
        Info.InternalDiagnostic = "Unable to resolve cursor info.";
-        Receiver(Info, "");
+        Receiver(RequestResult<CursorInfoData>::fromResult(Info));
        return;
      }
      CompilerInvocation CompInvok;
@@ -1305,18 +1317,19 @@ static void resolveCursor(SwiftLangSupport &Lang,
          VD = CursorInfo.CtorTyRef;
          ContainerType = Type();
        }
-        StringRef Diag = passCursorInfoForDecl(&AstUnit->getPrimarySourceFile(),
-                                               VD, MainModule,
-                                               ContainerType,
-                                               CursorInfo.IsRef,
-                                               Actionables,
-                                               CursorInfo,
-                                               BufferID, Loc,
-                                               AvailableRefactorings,
-                                               Lang, CompInvok,
-                                               getPreviousASTSnaps(),
-                                               Receiver);
-        if (!Diag.empty()) {
+        std::string Diagnostic;
+        bool Success = passCursorInfoForDecl(&AstUnit->getPrimarySourceFile(),
+                                             VD, MainModule,
+                                             ContainerType,
+                                             CursorInfo.IsRef,
+                                             Actionables,
+                                             CursorInfo,
+                                             BufferID, Loc,
+                                             AvailableRefactorings,
+                                             Lang, CompInvok, Diagnostic,
+                                             getPreviousASTSnaps(),
+                                             Receiver);
+        if (!Success) {
          if (!getPreviousASTSnaps().empty()) {
            // Attempt again using the up-to-date AST.
            resolveCursor(Lang, InputFile, Offset, Length, Actionables, ASTInvok,
@@ -1324,8 +1337,8 @@ static void resolveCursor(SwiftLangSupport &Lang,
                          Receiver);
          } else {
            CursorInfoData Info;
-            Info.InternalDiagnostic = Diag;
-            Receiver(Info, "");
+            Info.InternalDiagnostic = Diagnostic;
+            Receiver(RequestResult<CursorInfoData>::fromResult(Info));
          }
        }
        return;
@@ -1350,7 +1363,7 @@ static void resolveCursor(SwiftLangSupport &Lang,
                NameRetriever[I], ReasonRetriever[I]});
            }
            Info.AvailableActions = llvm::makeArrayRef(AvailableRefactorings);
-            Receiver(Info, "");
+            Receiver(RequestResult<CursorInfoData>::fromResult(Info));
            return;
          }
        }
@@ -1358,7 +1371,7 @@ static void resolveCursor(SwiftLangSupport &Lang,
        CursorInfoData Info;
        Info.InternalDiagnostic =
            "Resolved to incomplete expression or statement.";
-        Receiver(Info, "");
+        Receiver(RequestResult<CursorInfoData>::fromResult(Info));
        return;
      }
      case CursorInfoKind::Invalid: {
@@ -1368,14 +1381,12 @@ static void resolveCursor(SwiftLangSupport &Lang,
    }

    void cancelled() override {
-      CursorInfoData Info;
-      Info.IsCancelled = true;
-      Receiver(Info, "Cancelled.");
+      Receiver(RequestResult<CursorInfoData>::cancelled());
    }

    void failed(StringRef Error) override {
      LOG_WARN_FUNC("cursor info failed: " << Error);
-      Receiver(CursorInfoData(), Error);
+      Receiver(RequestResult<CursorInfoData>::fromError(Error));
    }
  };

@@ -1397,20 +1408,18 @@ static void resolveName(SwiftLangSupport &Lang, StringRef InputFile,
                        unsigned Offset, SwiftInvocationRef Invok,
                        bool TryExistingAST,
                        NameTranslatingInfo &Input,
-                        std::function<void(const NameTranslatingInfo &,
-                                           StringRef Error)> Receiver) {
+                        std::function<void(const RequestResult<NameTranslatingInfo> &)> Receiver) {
  assert(Invok);

  class NameInfoConsumer : public CursorRangeInfoConsumer {
    NameTranslatingInfo Input;
-    std::function<void(const NameTranslatingInfo &, StringRef Error)> Receiver;
+    std::function<void(const RequestResult<NameTranslatingInfo> &)> Receiver;

  public:
    NameInfoConsumer(StringRef InputFile, unsigned Offset,
                     SwiftLangSupport &Lang, SwiftInvocationRef ASTInvok,
                     bool TryExistingAST, NameTranslatingInfo Input,
-                     std::function<void(const NameTranslatingInfo &,
-                                        StringRef Error)> Receiver)
+                     std::function<void(const RequestResult<NameTranslatingInfo> &)> Receiver)
    : CursorRangeInfoConsumer(InputFile, Offset, 0, Lang, ASTInvok,
                              TryExistingAST,
                              /*CancelOnSubsequentRequest=*/false),
@@ -1423,7 +1432,8 @@ static void resolveName(SwiftLangSupport &Lang, StringRef InputFile,
      SourceLoc Loc =
        Lexer::getLocForStartOfToken(CompIns.getSourceMgr(), BufferID, Offset);
      if (Loc.isInvalid()) {
-        Receiver({}, "Unable to resolve the start of the token.");
+        Receiver(RequestResult<NameTranslatingInfo>::fromError(
+          "Unable to resolve the start of the token."));
        return;
      }

@@ -1432,7 +1442,7 @@ static void resolveName(SwiftLangSupport &Lang, StringRef InputFile,
      if (CursorInfo.isInvalid()) {
        NameTranslatingInfo Info;
        Info.InternalDiagnostic = "Unable to resolve cursor info.";
-        Receiver(Info, "");
+        Receiver(RequestResult<NameTranslatingInfo>::fromResult(Info));
        return;
      }

@@ -1444,8 +1454,10 @@ static void resolveName(SwiftLangSupport &Lang, StringRef InputFile,
        return;

      case CursorInfoKind::ValueRef: {
-        StringRef Diagnostic = passNameInfoForDecl(CursorInfo, Input, Receiver);
-        if (!Diagnostic.empty()) {
+        std::string Diagnostic;
+        bool Success = passNameInfoForDecl(CursorInfo, Input, Diagnostic,
+                                           Receiver);
+        if (!Success) {
          if (!getPreviousASTSnaps().empty()) {
            // Attempt again using the up-to-date AST.
            resolveName(Lang, InputFile, Offset, ASTInvok,
@@ -1453,7 +1465,7 @@ static void resolveName(SwiftLangSupport &Lang, StringRef InputFile,
          } else {
            NameTranslatingInfo Info;
            Info.InternalDiagnostic = Diagnostic;
-            Receiver(Info, "");
+            Receiver(RequestResult<NameTranslatingInfo>::fromResult(Info));
          }
        }
        return;
@@ -1463,7 +1475,7 @@ static void resolveName(SwiftLangSupport &Lang, StringRef InputFile,
        NameTranslatingInfo Info;
        Info.InternalDiagnostic =
            "Resolved to incomplete expression or statement.";
-        Receiver(Info, "");
+        Receiver(RequestResult<NameTranslatingInfo>::fromResult(Info));
        return;
      }
      case CursorInfoKind::Invalid:
@@ -1472,14 +1484,12 @@ static void resolveName(SwiftLangSupport &Lang, StringRef InputFile,
    }

    void cancelled() override {
-      NameTranslatingInfo Info;
-      Info.IsCancelled = true;
-      Receiver(Info, "Cancelled.");
+      Receiver(RequestResult<NameTranslatingInfo>::cancelled());
    }

    void failed(StringRef Error) override {
      LOG_WARN_FUNC("name info failed: " << Error);
-      Receiver({}, Error);
+      Receiver(RequestResult<NameTranslatingInfo>::fromError(Error));
    }
  };

@@ -1493,19 +1503,17 @@ static void resolveRange(SwiftLangSupport &Lang,
                          StringRef InputFile, unsigned Offset, unsigned Length,
                          SwiftInvocationRef Invok,
                          bool TryExistingAST, bool CancelOnSubsequentRequest,
-                          std::function<void(const RangeInfo&,
-                                             StringRef Error)> Receiver) {
+                          std::function<void(const RequestResult<RangeInfo> &)> Receiver) {
  assert(Invok);

  class RangeInfoConsumer : public CursorRangeInfoConsumer {
-    std::function<void(const RangeInfo&, StringRef Error)> Receiver;
+    std::function<void(const RequestResult<RangeInfo> &)> Receiver;

  public:
    RangeInfoConsumer(StringRef InputFile, unsigned Offset, unsigned Length,
                       SwiftLangSupport &Lang, SwiftInvocationRef ASTInvok,
                       bool TryExistingAST, bool CancelOnSubsequentRequest,
-                       std::function<void(const RangeInfo&,
-                                          StringRef Error)> Receiver)
+                       std::function<void(const RequestResult<RangeInfo> &)> Receiver)
    : CursorRangeInfoConsumer(InputFile, Offset, Length, Lang, ASTInvok,
                              TryExistingAST, CancelOnSubsequentRequest),
      Receiver(std::move(Receiver)){ }
@@ -1533,14 +1541,14 @@ static void resolveRange(SwiftLangSupport &Lang,
        llvm::raw_svector_ostream OS(SS);
        Info.ExitInfo.ReturnType->print(OS);
        Result.ExprType = OS.str();
-        Receiver(Result, "");
+        Receiver(RequestResult<RangeInfo>::fromResult(Result));
        return;
      }
      case RangeKind::SingleDecl:
      case RangeKind::MultiTypeMemberDecl:
      case RangeKind::MultiStatement:
      case RangeKind::SingleStatement: {
-        Receiver(Result, "");
+        Receiver(RequestResult<RangeInfo>::fromResult(Result));
        return;
      }
      case RangeKind::PartOfExpression:
@@ -1551,21 +1559,19 @@ static void resolveRange(SwiftLangSupport &Lang,
                      /*TryExistingAST=*/false, CancelOnSubsequentRequest,
                      Receiver);
        } else {
-          Receiver(Result, "");
+          Receiver(RequestResult<RangeInfo>::fromResult(Result));
        }
        return;
      }
    }

    void cancelled() override {
-      RangeInfo Info;
-      Info.IsCancelled = true;
-      Receiver(Info, "Cancelled.");
+      Receiver(RequestResult<RangeInfo>::cancelled());
    }

    void failed(StringRef Error) override {
      LOG_WARN_FUNC("range info failed: " << Error);
-      Receiver({}, Error);
+      Receiver(RequestResult<RangeInfo>::fromError(Error));
    }
  };

@@ -1582,7 +1588,7 @@ static void resolveRange(SwiftLangSupport &Lang,
 void SwiftLangSupport::getCursorInfo(
    StringRef InputFile, unsigned Offset, unsigned Length, bool Actionables,
    bool CancelOnSubsequentRequest, ArrayRef<const char *> Args,
-    std::function<void(const CursorInfoData &, StringRef error)> Receiver) {
+    std::function<void(const RequestResult<CursorInfoData> &)> Receiver) {

  if (auto IFaceGenRef = IFaceGenContexts.get(InputFile)) {
    IFaceGenRef->accessASTAsync([this, IFaceGenRef, Offset, Actionables, Receiver] {
@@ -1595,19 +1601,20 @@ void SwiftLangSupport::getCursorInfo(
          passCursorInfoForModule(Entity.Mod, IFaceGenContexts, Invok,
                                  Receiver);
        } else {
+          std::string Diagnostic;  // Unused.
          // FIXME: Should pass the main module for the interface but currently
          // it's not necessary.
          passCursorInfoForDecl(
              /*SourceFile*/nullptr, Entity.Dcl, /*MainModule*/ nullptr,
              Type(), Entity.IsRef, Actionables, ResolvedCursorInfo(),
              /*OrigBufferID=*/None, SourceLoc(),
-              {}, *this, Invok, {}, Receiver);
+              {}, *this, Invok, Diagnostic, {}, Receiver);
        }
      } else {
        CursorInfoData Info;
        Info.InternalDiagnostic =
            "Unable to resolve entity from generated interface.";
-        Receiver(Info, "");
+        Receiver(RequestResult<CursorInfoData>::fromResult(Info));
      }
    });
    return;
@@ -1617,7 +1624,7 @@ void SwiftLangSupport::getCursorInfo(
  SwiftInvocationRef Invok = ASTMgr->getInvocation(Args, InputFile, Error);
  if (!Invok) {
    LOG_WARN_FUNC("failed to create an ASTInvocation: " << Error);
-    Receiver(CursorInfoData(), Error);
+    Receiver(RequestResult<CursorInfoData>::fromError(Error));
    return;
  }

@@ -1628,22 +1635,22 @@ void SwiftLangSupport::getCursorInfo(
 void SwiftLangSupport::
 getRangeInfo(StringRef InputFile, unsigned Offset, unsigned Length,
             bool CancelOnSubsequentRequest, ArrayRef<const char *> Args,
-             std::function<void(const RangeInfo&, StringRef error)> Receiver) {
+             std::function<void(const RequestResult<RangeInfo> &)> Receiver) {
  if (IFaceGenContexts.get(InputFile)) {
    // FIXME: return range info for generated interfaces.
-    Receiver(RangeInfo(),
-             "Range info for generated interfaces is not implemented.");
+    Receiver(RequestResult<RangeInfo>::fromError(
+        "Range info for generated interfaces is not implemented."));
    return;
  }
  std::string Error;
  SwiftInvocationRef Invok = ASTMgr->getInvocation(Args, InputFile, Error);
  if (!Invok) {
    LOG_WARN_FUNC("failed to create an ASTInvocation: " << Error);
-    Receiver(RangeInfo(), Error);
+    Receiver(RequestResult<RangeInfo>::fromError(Error));
    return;
  }
  if (Length == 0) {
-    Receiver(RangeInfo(), "Invalid range length.");
+    Receiver(RequestResult<RangeInfo>::fromError("Invalid range length."));
    return;
  }
  resolveRange(*this, InputFile, Offset, Length, Invok, /*TryExistingAST=*/true,
@@ -1653,7 +1660,7 @@ getRangeInfo(StringRef InputFile, unsigned Offset, unsigned Length,
 void SwiftLangSupport::
 getNameInfo(StringRef InputFile, unsigned Offset, NameTranslatingInfo &Input,
            ArrayRef<const char *> Args,
-            std::function<void(const NameTranslatingInfo &, StringRef error)> Receiver) {
+            std::function<void(const RequestResult<NameTranslatingInfo> &)> Receiver) {

  if (auto IFaceGenRef = IFaceGenContexts.get(InputFile)) {
    IFaceGenRef->accessASTAsync([IFaceGenRef, Offset, Input, Receiver] {
@@ -1672,7 +1679,7 @@ getNameInfo(StringRef InputFile, unsigned Offset, NameTranslatingInfo &Input,
        NameTranslatingInfo Info;
        Info.InternalDiagnostic =
            "Unable to resolve entity from generated interface.";
-        Receiver(Info, "");
+        Receiver(RequestResult<NameTranslatingInfo>::fromResult(Info));
      }
    });
    return;
@@ -1682,7 +1689,7 @@ getNameInfo(StringRef InputFile, unsigned Offset, NameTranslatingInfo &Input,
  SwiftInvocationRef Invok = ASTMgr->getInvocation(Args, InputFile, Error);
  if (!Invok) {
    LOG_WARN_FUNC("failed to create an ASTInvocation: " << Error);
-    Receiver({}, Error);
+    Receiver(RequestResult<NameTranslatingInfo>::fromError(Error));
    return;
  }

@@ -1694,7 +1701,7 @@ static void
 resolveCursorFromUSR(SwiftLangSupport &Lang, StringRef InputFile, StringRef USR,
                     SwiftInvocationRef Invok, bool TryExistingAST,
                     bool CancelOnSubsequentRequest,
-                     std::function<void(const CursorInfoData &, StringRef error)> Receiver) {
+                     std::function<void(const RequestResult<CursorInfoData> &)> Receiver) {
  assert(Invok);

  class CursorInfoConsumer : public SwiftASTConsumer {
@@ -1704,15 +1711,14 @@ resolveCursorFromUSR(SwiftLangSupport &Lang, StringRef InputFile, StringRef USR,
    SwiftInvocationRef ASTInvok;
    const bool TryExistingAST;
    bool CancelOnSubsequentRequest;
-    std::function<void(const CursorInfoData &, StringRef Error)> Receiver;
+    std::function<void(const RequestResult<CursorInfoData> &)> Receiver;
    SmallVector<ImmutableTextSnapshotRef, 4> PreviousASTSnaps;

  public:
    CursorInfoConsumer(StringRef InputFile, StringRef USR,
                       SwiftLangSupport &Lang, SwiftInvocationRef ASTInvok,
                       bool TryExistingAST, bool CancelOnSubsequentRequest,
-                       std::function<void(const CursorInfoData &,
-                                          StringRef Error)> Receiver)
+                       std::function<void(const RequestResult<CursorInfoData> &)> Receiver)
        : InputFile(InputFile), USR(USR), Lang(Lang),
          ASTInvok(std::move(ASTInvok)), TryExistingAST(TryExistingAST),
          CancelOnSubsequentRequest(CancelOnSubsequentRequest),
@@ -1746,7 +1752,7 @@ resolveCursorFromUSR(SwiftLangSupport &Lang, StringRef InputFile, StringRef USR,
        LOG_WARN_FUNC("lookup for C/C++/ObjC USRs not implemented");
        CursorInfoData Info;
        Info.InternalDiagnostic = "Lookup for C/C++/ObjC USRs not implemented.";
-        Receiver(Info, "");
+        Receiver(RequestResult<CursorInfoData>::fromResult(Info));
        return;
      }

@@ -1756,7 +1762,7 @@ resolveCursorFromUSR(SwiftLangSupport &Lang, StringRef InputFile, StringRef USR,
      if (!D) {
        CursorInfoData Info;
        Info.InternalDiagnostic = "Unable to resolve type from USR.";
-        Receiver(Info, "");
+        Receiver(RequestResult<CursorInfoData>::fromResult(Info));
        return;
      }

@@ -1773,12 +1779,13 @@ resolveCursorFromUSR(SwiftLangSupport &Lang, StringRef InputFile, StringRef USR,
          selfTy = DC->getSelfInterfaceType();
          selfTy = D->getInnermostDeclContext()->mapTypeIntoContext(selfTy);
        }
-        StringRef Diagnostic =
+        std::string Diagnostic;
+        bool Success =
            passCursorInfoForDecl(/*SourceFile*/nullptr, D, MainModule, selfTy,
                                  /*IsRef=*/false, false, ResolvedCursorInfo(),
                                  BufferID, SourceLoc(), {}, Lang, CompInvok,
-                                  PreviousASTSnaps, Receiver);
-        if (!Diagnostic.empty()) {
+                                  Diagnostic, PreviousASTSnaps, Receiver);
+        if (!Success) {
          if (!PreviousASTSnaps.empty()) {
            // Attempt again using the up-to-date AST.
            resolveCursorFromUSR(Lang, InputFile, USR, ASTInvok,
@@ -1787,21 +1794,19 @@ resolveCursorFromUSR(SwiftLangSupport &Lang, StringRef InputFile, StringRef USR,
          } else {
            CursorInfoData Info;
            Info.InternalDiagnostic = Diagnostic;
-            Receiver(Info, "");
+            Receiver(RequestResult<CursorInfoData>::fromResult(Info));
          }
        }
      }
    }

    void cancelled() override {
-      CursorInfoData Info;
-      Info.IsCancelled = true;
-      Receiver(Info, "Cancelled.");
+      Receiver(RequestResult<CursorInfoData>::cancelled());
    }

    void failed(StringRef Error) override {
      LOG_WARN_FUNC("cursor info failed: " << Error);
-      Receiver(CursorInfoData(), Error);
+      Receiver(RequestResult<CursorInfoData>::fromError(Error));
    }
  };

@@ -1817,26 +1822,26 @@ resolveCursorFromUSR(SwiftLangSupport &Lang, StringRef InputFile, StringRef USR,

 void SwiftLangSupport::getCursorInfoFromUSR(
    StringRef filename, StringRef USR, bool CancelOnSubsequentRequest,
-    ArrayRef<const char *> args,
-    std::function<void(const CursorInfoData &, StringRef Error)> receiver) {
+    ArrayRef<const char *> Args,
+    std::function<void(const RequestResult<CursorInfoData> &)> Receiver) {
  if (auto IFaceGenRef = IFaceGenContexts.get(filename)) {
    LOG_WARN_FUNC("Info from usr for generated interface not implemented yet.");
    CursorInfoData Info;
    Info.InternalDiagnostic = "Info for generated interfaces not implemented.";
-    receiver(Info, "");
+    Receiver(RequestResult<CursorInfoData>::fromResult(Info));
    return;
  }

  std::string Error;
-  SwiftInvocationRef Invok = ASTMgr->getInvocation(args, filename, Error);
+  SwiftInvocationRef Invok = ASTMgr->getInvocation(Args, filename, Error);
  if (!Invok) {
    LOG_WARN_FUNC("failed to create an ASTInvocation: " << Error);
-    receiver(CursorInfoData(), Error);
+    Receiver(RequestResult<CursorInfoData>::fromError(Error));
    return;
  }

  resolveCursorFromUSR(*this, filename, USR, Invok, /*TryExistingAST=*/true,
-                       CancelOnSubsequentRequest, receiver);
+                       CancelOnSubsequentRequest, Receiver);
 }

 //===----------------------------------------------------------------------===//
@@ -1923,25 +1928,24 @@ void SwiftLangSupport::findRelatedIdentifiersInFile(
    StringRef InputFile, unsigned Offset,
    bool CancelOnSubsequentRequest,
    ArrayRef<const char *> Args,
-    std::function<void(const RelatedIdentsInfo &, StringRef error)> Receiver) {
+    std::function<void(const RequestResult<RelatedIdentsInfo> &)> Receiver) {

  std::string Error;
  SwiftInvocationRef Invok = ASTMgr->getInvocation(Args, InputFile, Error);
  if (!Invok) {
    LOG_WARN_FUNC("failed to create an ASTInvocation: " << Error);
-    Receiver({}, Error);
+    Receiver(RequestResult<RelatedIdentsInfo>::fromError(Error));
    return;
  }

  class RelatedIdConsumer : public SwiftASTConsumer {
    unsigned Offset;
-    std::function<void(const RelatedIdentsInfo &, StringRef Error)> Receiver;
+    std::function<void(const RequestResult<RelatedIdentsInfo> &)> Receiver;
    SwiftInvocationRef Invok;

  public:
    RelatedIdConsumer(unsigned Offset,
-                      std::function<void(const RelatedIdentsInfo &,
-                                         StringRef Error)> Receiver,
+                      std::function<void(const RequestResult<RelatedIdentsInfo> &)> Receiver,
                      SwiftInvocationRef Invok)
      : Offset(Offset), Receiver(std::move(Receiver)), Invok(Invok) { }

@@ -1997,18 +2001,16 @@ void SwiftLangSupport::findRelatedIdentifiersInFile(

      RelatedIdentsInfo Info;
      Info.Ranges = Ranges;
-      Receiver(Info, "");
+      Receiver(RequestResult<RelatedIdentsInfo>::fromResult(Info));
    }

    void cancelled() override {
-      RelatedIdentsInfo Info;
-      Info.IsCancelled = true;
-      Receiver(Info, "Cancelled.");
+      Receiver(RequestResult<RelatedIdentsInfo>::cancelled());
    }

    void failed(StringRef Error) override {
      LOG_WARN_FUNC("related idents failed: " << Error);
-      Receiver({}, Error);
+      Receiver(RequestResult<RelatedIdentsInfo>::fromError(Error));
    }

    static CaseStmt *getCaseStmtOfCanonicalVar(Decl *D) {
@@ -2051,7 +2053,7 @@ semanticRefactoring(StringRef Filename, SemanticRefactoringInfo Info,
  SwiftInvocationRef Invok = ASTMgr->getInvocation(Args, Filename, Error);
  if (!Invok) {
    LOG_WARN_FUNC("failed to create an ASTInvocation: " << Error);
-    Receiver({}, Error);
+    Receiver(RequestResult<ArrayRef<CategorizedEdits>>::fromError(Error));
    return;
  }
  assert(Invok);
@@ -2081,12 +2083,11 @@ semanticRefactoring(StringRef Filename, SemanticRefactoringInfo Info,
    }

    void cancelled() override {
-      // FIXME: inform the receiver of cancellation instead of an error.
-      Receiver({}, "Cancelled.");
+      Receiver(RequestResult<ArrayRef<CategorizedEdits>>::cancelled());
    }

    void failed(StringRef Error) override {
-      Receiver({}, Error);
+      Receiver(RequestResult<ArrayRef<CategorizedEdits>>::fromError(Error));
    }
  };

@@ -2100,23 +2101,21 @@ semanticRefactoring(StringRef Filename, SemanticRefactoringInfo Info,
 void SwiftLangSupport::collectExpressionTypes(StringRef FileName,
                                              ArrayRef<const char *> Args,
                                    ArrayRef<const char *> ExpectedProtocols,
-                  std::function<void(const ExpressionTypesInFile&,
-                                     StringRef Error)> Receiver) {
+                  std::function<void(const RequestResult<ExpressionTypesInFile> &)> Receiver) {
  std::string Error;
  SwiftInvocationRef Invok = ASTMgr->getInvocation(Args, FileName, Error);
  if (!Invok) {
    LOG_WARN_FUNC("failed to create an ASTInvocation: " << Error);
-    Receiver({}, Error);
+    Receiver(RequestResult<ExpressionTypesInFile>::fromError(Error));
    return;
  }
  assert(Invok);
  class ExpressionTypeCollector: public SwiftASTConsumer {
-    std::function<void(const ExpressionTypesInFile&, StringRef Error)> Receiver;
+    std::function<void(const RequestResult<ExpressionTypesInFile> &)> Receiver;
    std::vector<const char *> ExpectedProtocols;
  public:
    ExpressionTypeCollector(
-        std::function<void(const ExpressionTypesInFile&,
-                           StringRef Error)> Receiver,
+        std::function<void(const RequestResult<ExpressionTypesInFile> &)> Receiver,
        ArrayRef<const char *> ExpectedProtocols): Receiver(std::move(Receiver)),
          ExpectedProtocols(ExpectedProtocols.vec()) {}
    void handlePrimaryAST(ASTUnitRef AstUnit) override {
@@ -2132,16 +2131,15 @@ void SwiftLangSupport::collectExpressionTypes(StringRef FileName,
        }
      }
      Result.TypeBuffer = OS.str();
-      Receiver(Result, "");
+      Receiver(RequestResult<ExpressionTypesInFile>::fromResult(Result));
    }

    void cancelled() override {
-      // FIXME: inform the receiver of cancellation instead of an error.
-      Receiver({}, "Cancelled.");
+      Receiver(RequestResult<ExpressionTypesInFile>::cancelled());
    }

    void failed(StringRef Error) override {
-      Receiver({}, Error);
+      Receiver(RequestResult<ExpressionTypesInFile>::fromError(Error));
    }
  };
  auto Collector = std::make_shared<ExpressionTypeCollector>(Receiver,