ices/80409.rs: fixed with no errors

[github-actions]

Issue: rust-lang/rust#80409

use std::marker::PhantomData;

struct FsmBuilder<TFsm> {
    _fsm: PhantomData<TFsm>,
}

impl<TFsm> FsmBuilder<TFsm> {
    fn state(&mut self) -> FsmStateBuilder<TFsm> {
        todo!()
    }
}

struct FsmStateBuilder<TFsm> {
    _state: PhantomData<TFsm>,
}

impl<TFsm> FsmStateBuilder<TFsm> {
    fn on_entry<TAction: Fn(&mut StateContext<'_, TFsm>)>(&self, _action: TAction) {}
}

trait Fsm {
    type Context;
}

struct StateContext<'a, TFsm: Fsm> {
    context: &'a mut TFsm::Context,
}

fn main() {
    let mut builder: FsmBuilder<usize> = todo!();
    builder.state().on_entry(|_| {});
}

=== stdout ===
=== stderr ===
warning: unreachable statement
  --> /home/runner/work/glacier/glacier/ices/80409.rs:31:5
   |
30 |     let mut builder: FsmBuilder<usize> = todo!();
   |                                          ------- any code following this expression is unreachable
31 |     builder.state().on_entry(|_| {});
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ unreachable statement
   |
   = note: `#[warn(unreachable_code)]` on by default

warning: unused variable: `builder`
  --> /home/runner/work/glacier/glacier/ices/80409.rs:30:13
   |
30 |     let mut builder: FsmBuilder<usize> = todo!();
   |             ^^^^^^^ help: if this is intentional, prefix it with an underscore: `_builder`
   |
   = note: `#[warn(unused_variables)]` on by default

warning: field `context` is never read
  --> /home/runner/work/glacier/glacier/ices/80409.rs:26:5
   |
25 | struct StateContext<'a, TFsm: Fsm> {
   |        ------------ field in this struct
26 |     context: &'a mut TFsm::Context,
   |     ^^^^^^^
   |
   = note: `#[warn(dead_code)]` on by default

warning: 3 warnings emitted

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