I think that this should not need fixing, since an undefined requires clause is just bottom, but the LLVM backend complains about it, so whatever:
[Warn#booster] LLVM backend error detected: [hook_BYTES_substr]: Invalid string slice for string: Requested end index 6 is greater than string length 3 For more details, enable context logging '--log-context "*>abort,detail"'
I think that this should not need fixing, since an undefined requires clause is just bottom, but the LLVM backend complains about it, so whatever: