After editing #include, Qt Creator clangd hangs in onHighlighterResultAvailable

Steps:

• Clone my sample project (link).
• Open src/test.cpp. (Copying the contents into a header works as well.)
  • The line before the #include is necessary to reproduce the hang. It can be a comment, a #pragma once, a #define, etc. but cannot be empty.

// test
#include <QtQml/qqml.h
class Type {
    QML_SINGLETON
};

• Add a > to the end of the #include line, and wait for the errors to disappear.

Instead Qt Creator will hang.

If it doesn't hang, undo, wait for the errors to appear, then type > again. Sometimes it hangs on the first try, sometimes it takes several tries.

In gdb, qtcreator is stuck within "CppEditor::SemanticHighlighter::onHighlighterResultAvailable(int, int) (), from /home/nyanpasu64/Qt/Tools/Preview/Qt Creator 6.0.0-beta1/lib/qtcreator/plugins/libCppEditor.so".

This function never returns (telling gdb to finish hangs). However it does call child functions (gdb doesn't know the name of the child, but it calls TextEditor::TextDocumentLayout::parentheses(QTextBlock const&)) which return (telling gdb to finish returns).