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use crate::Interner;
use rustc_data_structures::fx::FxHashMap;
use rustc_serialize::{Decoder, Encoder};
/// The shorthand encoding uses an enum's variant index `usize`
/// and is offset by this value so it never matches a real variant.
/// This offset is also chosen so that the first byte is never < 0x80.
pub const SHORTHAND_OFFSET: usize = 0x80;
/// Trait for decoding to a reference.
///
/// This is a separate trait from `Decodable` so that we can implement it for
/// upstream types, such as `FxHashSet`.
///
/// The `TyDecodable` derive macro will use this trait for fields that are
/// references (and don't use a type alias to hide that).
///
/// `Decodable` can still be implemented in cases where `Decodable` is required
/// by a trait bound.
pub trait RefDecodable<'tcx, D: TyDecoder> {
fn decode(d: &mut D) -> &'tcx Self;
}
pub trait TyEncoder: Encoder {
type I: Interner;
const CLEAR_CROSS_CRATE: bool;
fn position(&self) -> usize;
fn type_shorthands(&mut self) -> &mut FxHashMap<<Self::I as Interner>::Ty, usize>;
fn predicate_shorthands(
&mut self,
) -> &mut FxHashMap<<Self::I as Interner>::PredicateKind, usize>;
fn encode_alloc_id(&mut self, alloc_id: &<Self::I as Interner>::AllocId);
}
pub trait TyDecoder: Decoder {
type I: Interner;
const CLEAR_CROSS_CRATE: bool;
fn interner(&self) -> Self::I;
fn peek_byte(&self) -> u8;
fn position(&self) -> usize;
fn cached_ty_for_shorthand<F>(
&mut self,
shorthand: usize,
or_insert_with: F,
) -> <Self::I as Interner>::Ty
where
F: FnOnce(&mut Self) -> <Self::I as Interner>::Ty;
fn with_position<F, R>(&mut self, pos: usize, f: F) -> R
where
F: FnOnce(&mut Self) -> R;
fn positioned_at_shorthand(&self) -> bool {
(self.peek_byte() & (SHORTHAND_OFFSET as u8)) != 0
}
fn decode_alloc_id(&mut self) -> <Self::I as Interner>::AllocId;
}
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