Since GHC 9.6, `OverloadedLabels` has not been restricted to identifiers but permits expressions like `#"a b c"` where the hash sign is immediately followed by a double-quoted string, number or various other characters. See the proposal (https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0170-unrestricted-overloadedlabels.rst) and implementation (https://gitlab.haskell.org/ghc/ghc/-/merge_requests/8966). However the GHC user's guide section (https://ghc.gitlab.haskell.org/ghc/doc/users_guide/exts/overloaded_labels.html) doesn't appear to have been updated along with the implementation. The documentation should point out the additional syntactic flexibility that is now available.