[SourceKit] Mark functions on CancellableResult const

include/swift/IDE/CancellableResult.h

@@ -118,25 +118,25 @@ public:
 
   /// Return the result kind this \c CancellableResult represents: success,
   /// failure or cancelled.
-  CancellableResultKind getKind() { return Kind; }
+  CancellableResultKind getKind() const { return Kind; }
 
   /// Assuming that the result represents success, return the underlying result
   /// value.
-  ResultType &getResult() {
+  const ResultType &getResult() const {
     assert(getKind() == CancellableResultKind::Success);
     return Result;
   }
 
   /// Assuming that the result represents success, retrieve members of the
   /// underlying result value.
-  ResultType *operator->() { return &getResult(); }
+  const ResultType *operator->() { return &getResult(); }
 
   /// Assuming that the result represents success, return the underlying result
   /// value.
-  ResultType &operator*() { return getResult(); }
+  const ResultType &operator*() { return getResult(); }
 
   /// Assuming that the result represents a failure, return the error message.
-  std::string getError() {
+  std::string getError() const {
     assert(getKind() == CancellableResultKind::Failure);
     return Error;
   }
@@ -152,7 +152,7 @@ public:
   template <typename NewResultType>
   void
   mapAsync(llvm::function_ref<
-               void(ResultType &,
+               void(const ResultType &,
                     llvm::function_ref<void(CancellableResult<NewResultType>)>)>
                Transform,
            llvm::function_ref<void(CancellableResult<NewResultType>)> Handle) {
@@ -170,6 +170,24 @@ public:
       break;
     }
   }
+
+  /// If the result represents success, invoke \p Transform to create a success
+  /// result containing new backing data.
+  ///
+  /// If the result represents error or cancelled, propagate that kind without
+  /// modification.
+  template <typename NewResultType>
+  CancellableResult<NewResultType>
+  map(llvm::function_ref<NewResultType(const ResultType &)> Transform) {
+    switch (getKind()) {
+    case CancellableResultKind::Success:
+      return CancellableResult<NewResultType>::success(Transform(getResult()));
+    case CancellableResultKind::Failure:
+      return CancellableResult<NewResultType>::failure(getError());
+    case CancellableResultKind::Cancelled:
+      return CancellableResult<NewResultType>::cancelled();
+    }
+  }
 };
 
 } // namespace ide

tools/swift-ide-test/swift-ide-test.cpp

@@ -1147,8 +1147,9 @@ static bool performWithCompletionLikeOperationParams(
 }
 
 template <typename ResultType>
-static int printResult(CancellableResult<ResultType> Result,
-                       llvm::function_ref<int(ResultType &)> PrintSuccess) {
+static int
+printResult(CancellableResult<ResultType> Result,
+            llvm::function_ref<int(const ResultType &)> PrintSuccess) {
   switch (Result.getKind()) {
   case CancellableResultKind::Success: {
     return PrintSuccess(Result.getResult());
@@ -1166,7 +1167,7 @@ static int printResult(CancellableResult<ResultType> Result,
 static int printTypeContextInfo(
     CancellableResult<TypeContextInfoResult> CancellableResult) {
   return printResult<TypeContextInfoResult>(
-      CancellableResult, [](TypeContextInfoResult &Result) {
+      CancellableResult, [](const TypeContextInfoResult &Result) {
         llvm::outs() << "-----BEGIN TYPE CONTEXT INFO-----\n";
         for (auto resultItem : Result.Results) {
           llvm::outs() << "- TypeName: ";
@@ -1227,7 +1228,7 @@ static int doTypeContextInfo(const CompilerInvocation &InitInvok,
 static int printConformingMethodList(
     CancellableResult<ConformingMethodListResults> CancellableResult) {
   return printResult<ConformingMethodListResults>(
-      CancellableResult, [](ConformingMethodListResults &Results) {
+      CancellableResult, [](const ConformingMethodListResults &Results) {
         auto Result = Results.Result;
         if (!Result) {
           return 0;
@@ -1396,7 +1397,7 @@ static int printCodeCompletionResults(
     bool PrintAnnotatedDescription) {
   llvm::raw_fd_ostream &OS = llvm::outs();
   return printResult<CodeCompleteResult>(
-      CancellableResult, [&](CodeCompleteResult &Result) {
+      CancellableResult, [&](const CodeCompleteResult &Result) {
         printCodeCompletionResultsImpl(
             Result.ResultSink.Results, OS, IncludeKeywords, IncludeComments,
             IncludeSourceText, PrintAnnotatedDescription,