error: expected identifier, found `1`
  --> $DIR/issue-79099.rs:3:65
   |
LL |         let f: impl core::future::Future<Output = u8> = async { 1 };
   |                                                         -----   ^ expected identifier
   |                                                         |
   |                                                         `async` blocks are only allowed in Rust 2018 or later
   |
   = help: pass `--edition 2021` to `rustc`
   = note: for more on editions, read https://doc.rust-lang.org/edition-guide

error[E0562]: `impl Trait` only allowed in function and inherent method return types, not in variable binding
  --> $DIR/issue-79099.rs:3:16
   |
LL |         let f: impl core::future::Future<Output = u8> = async { 1 };
   |                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0562`.