error[E0391]: cycle detected when computing layout of `S<S<()>>`
   |
   = note: ...which requires computing layout of `<S<()> as Tr>::I`...
   = note: ...which again requires computing layout of `S<S<()>>`, completing the cycle
   = note: see https://rustc-dev-guide.rust-lang.org/overview.html#queries and https://rustc-dev-guide.rust-lang.org/query.html for more information

error: failed to get layout for S<S<()>>: a cycle occurred during layout computation

error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0391`.