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transmutability: Refactor tests for simplicity #139932

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Apr 17, 2025
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transmutability: Refactor tests for simplicity #139932

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140 changes: 74 additions & 66 deletions compiler/rustc_transmute/src/maybe_transmutable/tests.rs
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Original file line number Diff line number Diff line change
@@ -1,93 +1,115 @@
use itertools::Itertools;

use super::query_context::test::{Def, UltraMinimal};
use crate::maybe_transmutable::MaybeTransmutableQuery;
use crate::{Reason, layout};
use crate::{Answer, Assume, Reason, layout};

mod safety {
use super::*;
use crate::Answer;
type Tree = layout::Tree<Def, !>;
type Dfa = layout::Dfa<!>;

type Tree = layout::Tree<Def, !>;
trait Representation {
fn is_transmutable(src: Self, dst: Self, assume: Assume) -> Answer<!>;
}

const DST_HAS_SAFETY_INVARIANTS: Answer<!> =
Answer::No(crate::Reason::DstMayHaveSafetyInvariants);
impl Representation for Tree {
fn is_transmutable(src: Self, dst: Self, assume: Assume) -> Answer<!> {
crate::maybe_transmutable::MaybeTransmutableQuery::new(src, dst, assume, UltraMinimal)
.answer()
}
}

fn is_transmutable(src: &Tree, dst: &Tree, assume_safety: bool) -> crate::Answer<!> {
let src = src.clone();
let dst = dst.clone();
// The only dimension of the transmutability analysis we want to test
// here is the safety analysis. To ensure this, we disable all other
// toggleable aspects of the transmutability analysis.
let assume = crate::Assume {
alignment: true,
lifetimes: true,
validity: true,
safety: assume_safety,
};
impl Representation for Dfa {
fn is_transmutable(src: Self, dst: Self, assume: Assume) -> Answer<!> {
crate::maybe_transmutable::MaybeTransmutableQuery::new(src, dst, assume, UltraMinimal)
.answer()
}
}

fn is_transmutable<R: Representation + Clone>(
src: &R,
dst: &R,
assume: Assume,
) -> crate::Answer<!> {
let src = src.clone();
let dst = dst.clone();
// The only dimension of the transmutability analysis we want to test
// here is the safety analysis. To ensure this, we disable all other
// toggleable aspects of the transmutability analysis.
R::is_transmutable(src, dst, assume)
}

mod safety {
use super::*;
use crate::Answer;

const DST_HAS_SAFETY_INVARIANTS: Answer<!> =
Answer::No(crate::Reason::DstMayHaveSafetyInvariants);

#[test]
fn src_safe_dst_safe() {
let src = Tree::Def(Def::NoSafetyInvariants).then(Tree::u8());
let dst = Tree::Def(Def::NoSafetyInvariants).then(Tree::u8());
assert_eq!(is_transmutable(&src, &dst, false), Answer::Yes);
assert_eq!(is_transmutable(&src, &dst, true), Answer::Yes);
assert_eq!(is_transmutable(&src, &dst, Assume::default()), Answer::Yes);
assert_eq!(
is_transmutable(&src, &dst, Assume { safety: true, ..Assume::default() }),
Answer::Yes
);
}

#[test]
fn src_safe_dst_unsafe() {
let src = Tree::Def(Def::NoSafetyInvariants).then(Tree::u8());
let dst = Tree::Def(Def::HasSafetyInvariants).then(Tree::u8());
assert_eq!(is_transmutable(&src, &dst, false), DST_HAS_SAFETY_INVARIANTS);
assert_eq!(is_transmutable(&src, &dst, true), Answer::Yes);
assert_eq!(is_transmutable(&src, &dst, Assume::default()), DST_HAS_SAFETY_INVARIANTS);
assert_eq!(
is_transmutable(&src, &dst, Assume { safety: true, ..Assume::default() }),
Answer::Yes
);
}

#[test]
fn src_unsafe_dst_safe() {
let src = Tree::Def(Def::HasSafetyInvariants).then(Tree::u8());
let dst = Tree::Def(Def::NoSafetyInvariants).then(Tree::u8());
assert_eq!(is_transmutable(&src, &dst, false), Answer::Yes);
assert_eq!(is_transmutable(&src, &dst, true), Answer::Yes);
assert_eq!(is_transmutable(&src, &dst, Assume::default()), Answer::Yes);
assert_eq!(
is_transmutable(&src, &dst, Assume { safety: true, ..Assume::default() }),
Answer::Yes
);
}

#[test]
fn src_unsafe_dst_unsafe() {
let src = Tree::Def(Def::HasSafetyInvariants).then(Tree::u8());
let dst = Tree::Def(Def::HasSafetyInvariants).then(Tree::u8());
assert_eq!(is_transmutable(&src, &dst, false), DST_HAS_SAFETY_INVARIANTS);
assert_eq!(is_transmutable(&src, &dst, true), Answer::Yes);
assert_eq!(is_transmutable(&src, &dst, Assume::default()), DST_HAS_SAFETY_INVARIANTS);
assert_eq!(
is_transmutable(&src, &dst, Assume { safety: true, ..Assume::default() }),
Answer::Yes
);
}
}

mod bool {
use super::*;
use crate::Answer;

#[test]
fn should_permit_identity_transmutation_tree() {
let answer = crate::maybe_transmutable::MaybeTransmutableQuery::new(
layout::Tree::<Def, !>::bool(),
layout::Tree::<Def, !>::bool(),
crate::Assume { alignment: false, lifetimes: false, validity: true, safety: false },
UltraMinimal,
)
.answer();
assert_eq!(answer, Answer::Yes);
let src = Tree::bool();
assert_eq!(is_transmutable(&src, &src, Assume::default()), Answer::Yes);
assert_eq!(
is_transmutable(&src, &src, Assume { validity: true, ..Assume::default() }),
Answer::Yes
);
}

#[test]
fn should_permit_identity_transmutation_dfa() {
let answer = crate::maybe_transmutable::MaybeTransmutableQuery::new(
layout::Dfa::<!>::bool(),
layout::Dfa::<!>::bool(),
crate::Assume { alignment: false, lifetimes: false, validity: true, safety: false },
UltraMinimal,
)
.answer();
assert_eq!(answer, Answer::Yes);
let src = Dfa::bool();
assert_eq!(is_transmutable(&src, &src, Assume::default()), Answer::Yes);
assert_eq!(
is_transmutable(&src, &src, Assume { validity: true, ..Assume::default() }),
Answer::Yes
);
}

#[test]
Expand Down Expand Up @@ -122,41 +144,27 @@ mod bool {
if src_set.is_subset(&dst_set) {
assert_eq!(
Answer::Yes,
MaybeTransmutableQuery::new(
src_layout.clone(),
dst_layout.clone(),
crate::Assume { validity: false, ..crate::Assume::default() },
UltraMinimal,
)
.answer(),
is_transmutable(&src_layout, &dst_layout, Assume::default()),
"{:?} SHOULD be transmutable into {:?}",
src_layout,
dst_layout
);
} else if !src_set.is_disjoint(&dst_set) {
assert_eq!(
Answer::Yes,
MaybeTransmutableQuery::new(
src_layout.clone(),
dst_layout.clone(),
crate::Assume { validity: true, ..crate::Assume::default() },
UltraMinimal,
)
.answer(),
is_transmutable(
&src_layout,
&dst_layout,
Assume { validity: true, ..Assume::default() }
),
"{:?} SHOULD be transmutable (assuming validity) into {:?}",
src_layout,
dst_layout
);
} else {
assert_eq!(
Answer::No(Reason::DstIsBitIncompatible),
MaybeTransmutableQuery::new(
src_layout.clone(),
dst_layout.clone(),
crate::Assume { validity: false, ..crate::Assume::default() },
UltraMinimal,
)
.answer(),
is_transmutable(&src_layout, &dst_layout, Assume::default()),
"{:?} should NOT be transmutable into {:?}",
src_layout,
dst_layout
Expand Down
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