error: functions cannot be both `const` and `gen`
  --> $DIR/const_gen_fn.rs:6:1
   |
LL | const gen fn a() {}
   | ^^^^^-^^^----------
   | |     |
   | |     `gen` because of this
   | `const` because of this

error: functions cannot be both `const` and `async gen`
  --> $DIR/const_gen_fn.rs:9:1
   |
LL | const async gen fn b() {}
   | ^^^^^-^^^^^^^^^----------
   | |     |
   | |     `async gen` because of this
   | `const` because of this

error: aborting due to 2 previous errors