Index: include-fixer/IncludeFixer.h
===================================================================
--- include-fixer/IncludeFixer.h
+++ include-fixer/IncludeFixer.h
@@ -68,8 +68,9 @@
 /// \param Header The header being inserted.
 /// \param Style clang-format style being used.
 ///
-/// \return Replacements for inserting and sorting headers.
-tooling::Replacements createInsertHeaderReplacements(
+/// \return Replacements for inserting and sorting headers on success;
+/// otherwise, an llvm::Error carrying llvm::StringError is returned.
+llvm::Expected<tooling::Replacements> createInsertHeaderReplacements(
     StringRef Code, StringRef FilePath, StringRef Header,
     const clang::format::FormatStyle &Style = clang::format::getLLVMStyle());
 
Index: include-fixer/IncludeFixer.cpp
===================================================================
--- include-fixer/IncludeFixer.cpp
+++ include-fixer/IncludeFixer.cpp
@@ -306,7 +306,7 @@
   return !Compiler.getDiagnostics().hasFatalErrorOccurred();
 }
 
-tooling::Replacements
+llvm::Expected<tooling::Replacements>
 createInsertHeaderReplacements(StringRef Code, StringRef FilePath,
                                StringRef Header,
                                const clang::format::FormatStyle &Style) {
@@ -317,8 +317,11 @@
   clang::tooling::Replacements Insertions = {
       tooling::Replacement(FilePath, UINT_MAX, 0, IncludeName)};
 
-  return formatReplacements(
-      Code, cleanupAroundReplacements(Code, Insertions, Style), Style);
+  auto CleanReplaces = cleanupAroundReplacements(Code, Insertions, Style);
+  if (!CleanReplaces)
+    return CleanReplaces;
+  auto FormattedReplaces = formatReplacements(Code, *CleanReplaces, Style);
+  return FormattedReplaces;
 }
 
 } // namespace include_fixer
Index: include-fixer/tool/ClangIncludeFixer.cpp
===================================================================
--- include-fixer/tool/ClangIncludeFixer.cpp
+++ include-fixer/tool/ClangIncludeFixer.cpp
@@ -208,12 +208,21 @@
       return 1;
     }
 
-    tooling::Replacements Replacements =
+    auto Replacements =
         clang::include_fixer::createInsertHeaderReplacements(
             Code->getBuffer(), FilePath, Context.Headers[0], InsertStyle);
-    std::string ChangedCode =
-        tooling::applyAllReplacements(Code->getBuffer(), Replacements);
-    llvm::outs() << ChangedCode;
+    if (!Replacements) {
+      errs() << "Failed to create header insertion replacement: "
+             << llvm::toString(Replacements.takeError()) << "\n";
+      return 1;
+    }
+    auto ChangedCode =
+        tooling::applyAllReplacements(Code->getBuffer(), *Replacements);
+    if (!ChangedCode) {
+      llvm::errs() << llvm::toString(ChangedCode.takeError()) << "\n";
+      return 1;
+    }
+    llvm::outs() << *ChangedCode;
     return 0;
   }
 
@@ -249,10 +258,14 @@
   }
 
   // FIXME: Rank the results and pick the best one instead of the first one.
-  tooling::Replacements Replacements =
-      clang::include_fixer::createInsertHeaderReplacements(
-          /*Code=*/Buffer.get()->getBuffer(), FilePath, Context.Headers.front(),
-          InsertStyle);
+  auto Replacements = clang::include_fixer::createInsertHeaderReplacements(
+      /*Code=*/Buffer.get()->getBuffer(), FilePath, Context.Headers.front(),
+      InsertStyle);
+  if (!Replacements) {
+    errs() << "Failed to create header insertion replacement: "
+           << llvm::toString(Replacements.takeError()) << "\n";
+    return 1;
+  }
 
   if (!Quiet)
     llvm::errs() << "Added #include" << Context.Headers.front();
@@ -265,15 +278,19 @@
   Diagnostics.setClient(&DiagnosticPrinter, false);
 
   if (STDINMode) {
-    std::string ChangedCode =
-        tooling::applyAllReplacements(Code->getBuffer(), Replacements);
-    llvm::outs() << ChangedCode;
+    auto ChangedCode =
+        tooling::applyAllReplacements(Code->getBuffer(), *Replacements);
+    if (!ChangedCode) {
+      llvm::errs() << llvm::toString(ChangedCode.takeError()) << "\n";
+      return 1;
+    }
+    llvm::outs() << *ChangedCode;
     return 0;
   }
 
   // Write replacements to disk.
   Rewriter Rewrites(SM, LangOptions());
-  tooling::applyAllReplacements(Replacements, Rewrites);
+  tooling::applyAllReplacements(*Replacements, Rewrites);
   return Rewrites.overwriteChangedFiles();
 }
 
Index: unittests/clang-tidy/ClangTidyTest.h
===================================================================
--- unittests/clang-tidy/ClangTidyTest.h
+++ unittests/clang-tidy/ClangTidyTest.h
@@ -17,6 +17,7 @@
 #include "clang/Frontend/FrontendActions.h"
 #include "clang/Tooling/Refactoring.h"
 #include "clang/Tooling/Tooling.h"
+#include "llvm/ADT/Optional.h"
 #include <map>
 #include <memory>
 
@@ -121,7 +122,12 @@
     Fixes.insert(Error.Fix.begin(), Error.Fix.end());
   if (Errors)
     *Errors = Context.getErrors();
-  return tooling::applyAllReplacements(Code, Fixes);
+  auto Result = tooling::applyAllReplacements(Code, Fixes);
+  if (!Result) {
+    // FIXME: propogate the error.
+    return "";
+  }
+  return *Result;
 }
 
 #define EXPECT_NO_CHANGES(Check, Code)                                         \
Index: unittests/include-fixer/IncludeFixerTest.cpp
===================================================================
--- unittests/include-fixer/IncludeFixerTest.cpp
+++ unittests/include-fixer/IncludeFixerTest.cpp
@@ -85,12 +85,14 @@
   runOnCode(&Factory, Code, "input.cc", ExtraArgs);
   if (FixerContext.Headers.empty())
     return Code;
-  tooling::Replacements Replacements =
-      clang::include_fixer::createInsertHeaderReplacements(
-          Code, "input.cc", FixerContext.Headers.front());
+  auto Replaces = clang::include_fixer::createInsertHeaderReplacements(
+      Code, "input.cc", FixerContext.Headers.front());
+  EXPECT_TRUE((bool)Replaces) << llvm::toString(Replaces.takeError()) << "\n";
+  if (!Replaces)
+    return "";
   clang::RewriterTestContext Context;
   clang::FileID ID = Context.createInMemoryFile("input.cc", Code);
-  clang::tooling::applyAllReplacements(Replacements, Context.Rewrite);
+  clang::tooling::applyAllReplacements(*Replaces, Context.Rewrite);
   return Context.getRewrittenText(ID);
 }