[clangd] Fix error message with incorrect TextDocumentcontentChangeEvent.rangeLength

git-svn-id: https://llvm.org/svn/llvm-project/clang-tools-extra/trunk@367811 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/clangd/DraftStore.cpp b/clangd/DraftStore.cpp
index 16d7dde..dcf4813 100644
--- a/clangd/DraftStore.cpp
+++ b/clangd/DraftStore.cpp
@@ -90,7 +90,7 @@
       return llvm::make_error<llvm::StringError>(
           llvm::formatv("Change's rangeLength ({0}) doesn't match the "
                         "computed range length ({1}).",
-                        *Change.rangeLength, *EndIndex - *StartIndex),
+                        *Change.rangeLength, ComputedRangeLength),
           llvm::errc::invalid_argument);
 
     std::string NewContents;