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#![feature(alloc_layout_extra, control_flow_enum, decl_macro, iterator_try_reduce, never_type)]
#![allow(dead_code, unused_variables)]
#![deny(rustc::untranslatable_diagnostic)]
#![deny(rustc::diagnostic_outside_of_impl)]
#[macro_use]
extern crate tracing;
pub(crate) use rustc_data_structures::fx::{FxIndexMap as Map, FxIndexSet as Set};
pub(crate) mod layout;
pub(crate) mod maybe_transmutable;
#[derive(Default)]
pub struct Assume {
pub alignment: bool,
pub lifetimes: bool,
pub safety: bool,
pub validity: bool,
}
/// The type encodes answers to the question: "Are these types transmutable?"
#[derive(Debug, Hash, Eq, PartialEq, PartialOrd, Ord, Clone)]
pub enum Answer<R>
where
R: layout::Ref,
{
/// `Src` is transmutable into `Dst`.
Yes,
/// `Src` is NOT transmutable into `Dst`.
No(Reason),
/// `Src` is transmutable into `Dst`, if `src` is transmutable into `dst`.
IfTransmutable { src: R, dst: R },
/// `Src` is transmutable into `Dst`, if all of the enclosed requirements are met.
IfAll(Vec<Answer<R>>),
/// `Src` is transmutable into `Dst` if any of the enclosed requirements are met.
IfAny(Vec<Answer<R>>),
}
/// Answers: Why wasn't the source type transmutable into the destination type?
#[derive(Debug, Hash, Eq, PartialEq, PartialOrd, Ord, Clone)]
pub enum Reason {
/// The layout of the source type is unspecified.
SrcIsUnspecified,
/// The layout of the destination type is unspecified.
DstIsUnspecified,
/// The layout of the destination type is bit-incompatible with the source type.
DstIsBitIncompatible,
/// There aren't any public constructors for `Dst`.
DstIsPrivate,
/// `Dst` is larger than `Src`, and the excess bytes were not exclusively uninitialized.
DstIsTooBig,
}
#[cfg(feature = "rustc")]
mod rustc {
use super::*;
use rustc_hir::lang_items::LangItem;
use rustc_infer::infer::InferCtxt;
use rustc_macros::{TypeFoldable, TypeVisitable};
use rustc_middle::traits::ObligationCause;
use rustc_middle::ty::Binder;
use rustc_middle::ty::Const;
use rustc_middle::ty::ParamEnv;
use rustc_middle::ty::Ty;
use rustc_middle::ty::TyCtxt;
/// The source and destination types of a transmutation.
#[derive(TypeFoldable, TypeVisitable, Debug, Clone, Copy)]
pub struct Types<'tcx> {
/// The source type.
pub src: Ty<'tcx>,
/// The destination type.
pub dst: Ty<'tcx>,
}
pub struct TransmuteTypeEnv<'cx, 'tcx> {
infcx: &'cx InferCtxt<'tcx>,
}
impl<'cx, 'tcx> TransmuteTypeEnv<'cx, 'tcx> {
pub fn new(infcx: &'cx InferCtxt<'tcx>) -> Self {
Self { infcx }
}
#[allow(unused)]
pub fn is_transmutable(
&mut self,
cause: ObligationCause<'tcx>,
src_and_dst: Binder<'tcx, Types<'tcx>>,
scope: Ty<'tcx>,
assume: crate::Assume,
) -> crate::Answer<crate::layout::rustc::Ref<'tcx>> {
let src = src_and_dst.map_bound(|types| types.src).skip_binder();
let dst = src_and_dst.map_bound(|types| types.dst).skip_binder();
crate::maybe_transmutable::MaybeTransmutableQuery::new(
src,
dst,
scope,
assume,
self.infcx.tcx,
)
.answer()
}
}
impl Assume {
/// Constructs an `Assume` from a given const-`Assume`.
pub fn from_const<'tcx>(
tcx: TyCtxt<'tcx>,
param_env: ParamEnv<'tcx>,
c: Const<'tcx>,
) -> Option<Self> {
use rustc_middle::ty::ScalarInt;
use rustc_middle::ty::TypeVisitable;
use rustc_span::symbol::sym;
let c = c.eval(tcx, param_env);
if let Some(err) = c.error_reported() {
return Some(Self {
alignment: true,
lifetimes: true,
safety: true,
validity: true,
});
}
let adt_def = c.ty().ty_adt_def()?;
assert_eq!(
tcx.require_lang_item(LangItem::TransmuteOpts, None),
adt_def.did(),
"The given `Const` was not marked with the `{}` lang item.",
LangItem::TransmuteOpts.name(),
);
let variant = adt_def.non_enum_variant();
let fields = c.to_valtree().unwrap_branch();
let get_field = |name| {
let (field_idx, _) = variant
.fields
.iter()
.enumerate()
.find(|(_, field_def)| name == field_def.name)
.expect(&format!("There were no fields named `{name}`."));
fields[field_idx].unwrap_leaf() == ScalarInt::TRUE
};
Some(Self {
alignment: get_field(sym::alignment),
lifetimes: get_field(sym::lifetimes),
safety: get_field(sym::safety),
validity: get_field(sym::validity),
})
}
}
}
#[cfg(feature = "rustc")]
pub use rustc::*;
|
