fidl_next_codec/
never.rs

1// Copyright 2025 The Fuchsia Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5//! Helper types for encoding and decoding.
6
7use core::hint::unreachable_unchecked;
8use core::mem::MaybeUninit;
9
10use crate::{Constrained, Encode, EncodeError, Slot, ValidationError, Wire};
11
12/// A type which cannot be constructed.
13pub enum Never {}
14
15impl Constrained for Never {
16    type Constraint = ();
17
18    fn validate(_: Slot<'_, Self>, _: Self::Constraint) -> Result<(), ValidationError> {
19        Ok(())
20    }
21}
22
23// SAFETY: `Never` cannot exist, so this code can never be reached.
24unsafe impl<W: Wire, E: ?Sized> Encode<W, E> for Never {
25    fn encode(
26        self,
27        _: &mut E,
28        _: &mut MaybeUninit<W>,
29        _: W::Constraint,
30    ) -> Result<(), EncodeError> {
31        // SAFETY: `Never` cannot be constructed, so this code is unreachable.
32        unsafe { unreachable_unchecked() }
33    }
34}
fidl_next_codec/never.rs

fidl_next_codec/
never.rs
