error: invalid format string: tuple index access isn't supported
  --> $DIR/format-args-non-identifier-diagnostics.rs:8:16
   |
LL |     println!("{x.0}");
   |                ^^^ not supported in format string
   |
help: consider using a positional formatting argument instead
   |
LL |     println!("{0}", x.0);
   |                ~  +++++

error: aborting due to 1 previous error