warning: unknown lint: `multiple_supertrait_upcastable`
  --> $DIR/feature-gate-multiple_supertrait_upcastable.rs:3:1
   |
LL | #![deny(multiple_supertrait_upcastable)]
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: the `multiple_supertrait_upcastable` lint is unstable
   = help: add `#![feature(multiple_supertrait_upcastable)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
   = note: `#[warn(unknown_lints)]` on by default

warning: unknown lint: `multiple_supertrait_upcastable`
  --> $DIR/feature-gate-multiple_supertrait_upcastable.rs:5:1
   |
LL | #![warn(multiple_supertrait_upcastable)]
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: the `multiple_supertrait_upcastable` lint is unstable
   = help: add `#![feature(multiple_supertrait_upcastable)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

warning: 2 warnings emitted