Index: clang-tools-extra/trunk/clangd/ClangdLSPServer.cpp
===================================================================
--- clang-tools-extra/trunk/clangd/ClangdLSPServer.cpp
+++ clang-tools-extra/trunk/clangd/ClangdLSPServer.cpp
@@ -1045,7 +1045,7 @@
         if (!Path)
           return Reply(Path.takeError());
         if (*Path)
-          Reply(URIForFile::canonicalize(**Path, Params.uri.file()));
+          return Reply(URIForFile::canonicalize(**Path, Params.uri.file()));
         return Reply(llvm::None);
       });
 }
Index: clang-tools-extra/trunk/clangd/ClangdServer.cpp
===================================================================
--- clang-tools-extra/trunk/clangd/ClangdServer.cpp
+++ clang-tools-extra/trunk/clangd/ClangdServer.cpp
@@ -460,7 +460,7 @@
   if (auto CorrespondingFile =
           getCorrespondingHeaderOrSource(Path, FSProvider.getFileSystem()))
     return CB(std::move(CorrespondingFile));
-  auto Action = [Path, CB = std::move(CB),
+  auto Action = [Path = Path.str(), CB = std::move(CB),
                  this](llvm::Expected<InputsAndAST> InpAST) mutable {
     if (!InpAST)
       return CB(InpAST.takeError());
Index: clang-tools-extra/trunk/clangd/HeaderSourceSwitch.cpp
===================================================================
--- clang-tools-extra/trunk/clangd/HeaderSourceSwitch.cpp
+++ clang-tools-extra/trunk/clangd/HeaderSourceSwitch.cpp
@@ -86,7 +86,9 @@
     if (auto TargetPath = URI::resolve(TargetURI, OriginalFile)) {
       if (*TargetPath != OriginalFile) // exclude the original file.
         ++Candidates[*TargetPath];
-    };
+    } else {
+      elog("Failed to resolve URI {0}: {1}", TargetURI, TargetPath.takeError());
+    }
   };
   // If we switch from a header, we are looking for the implementation
   // file, so we use the definition loc; otherwise we look for the header file,
Index: clang-tools-extra/trunk/clangd/unittests/HeaderSourceSwitchTests.cpp
===================================================================
--- clang-tools-extra/trunk/clangd/unittests/HeaderSourceSwitchTests.cpp
+++ clang-tools-extra/trunk/clangd/unittests/HeaderSourceSwitchTests.cpp
@@ -125,6 +125,7 @@
   Testing.HeaderCode = R"cpp(
   void B_Sym1();
   void B_Sym2();
+  void B_Sym3_NoDef();
   )cpp";
   Testing.Filename = "b.cpp";
   Testing.Code = R"cpp(
@@ -163,6 +164,12 @@
          void B_Sym1();
        )cpp",
        testPath("a.cpp")},
+
+       {R"cpp(
+          // We don't have definition in the index, so stay in the header.
+          void B_Sym3_NoDef();
+       )cpp",
+       None},
   };
   for (const auto &Case : TestCases) {
     TestTU TU = TestTU::withCode(Case.HeaderCode);