error: expected one of `!`, `.`, `::`, `;`, `?`, `{`, `}`, or an operator, found `gen`
  --> $DIR/feature-gate-gen_blocks.rs:12:11
   |
LL |     async gen {};
   |           ^^^ expected one of 8 possible tokens

error: expected one of `!`, `.`, `::`, `;`, `?`, `{`, `}`, or an operator, found `gen`
  --> $DIR/feature-gate-gen_blocks.rs:25:11
   |
LL |     async gen {};
   |           ^^^ expected one of 8 possible tokens

error[E0422]: cannot find struct, variant or union type `gen` in this scope
  --> $DIR/feature-gate-gen_blocks.rs:5:5
   |
LL |     gen {};
   |     ^^^ not found in this scope

error: aborting due to 3 previous errors

For more information about this error, try `rustc --explain E0422`.