Qt 5.9.1 expands Q_REQUIRED_RESULT to the [[nodiscard]] attribute (see
commit d254d8c19 in qtbase). This breaks the build with clang compilers
because [[nodiscard]] cannot be used at the end of a function
declaration:
error: 'nodiscard' attribute cannot be applied to types
For the record, GCC just issues a 'attribute ignored' warning when
[[nodiscard]] is used at the end of a declaration.