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Gate access_kind_for_place_use AccessKind::Move rule on !prove_ty_is_copy #448

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88c9974
Specfically gate AccessKind::move on not prove_ty_is_copy
jackh726 Aug 7, 2026
c04a5e0
Make cargo fmt in to_rust check status
jackh726 Aug 7, 2026
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3 changes: 2 additions & 1 deletion crates/formality-rust/src/check/borrow_check/nll.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -947,8 +947,9 @@ judgment_fn! {
)

(
(if !prove_ty_is_copy(env, assumptions, state, &place.ty).is_proven())!

@nikomatsakis nikomatsakis Aug 12, 2026 •
edited by rustbot
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Yeah I feel like this should not be needed, I want to look into this more closely.

View changes since the review

------------------------------------------------------------ ("move")
(access_kind_for_place_use(_env, _assumptions, state, _place) => (AccessKind::Move, state))
(access_kind_for_place_use(env, assumptions, state, place) => (AccessKind::Move, state))
)
}
}
Expand Down
2 changes: 1 addition & 1 deletion crates/formality-rust/src/to_rust/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -94,7 +94,7 @@ pub fn create_workspace(crates: &Crates, root_directory: &std::path::Path) -> Fa

std::process::Command::new("cargo")
.args(["fmt", "--all", "--manifest-path", location])
.spawn()?;
.status()?;

Ok(location.to_string())
}
Expand Down
251 changes: 99 additions & 152 deletions tests/borrowck.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -41,23 +41,14 @@ fn use_of_uninitialized_variable() {
.borrowck_err(
BorrowCheckFailure::All,
expect_test::expect![[r#"
the rule "access_permitted" at (nll.rs) failed because
condition evaluated to false: `match access.kind
{
AccessKind::Write =>
check_place_writable(&state, &access.place.to_place_expression()),
AccessKind::Read | AccessKind::Move =>
check_place_initialized(&state, &access.place.to_place_expression()),
}`

the rule "access_permitted" at (nll.rs) failed because
condition evaluated to false: `match access.kind
{
AccessKind::Write =>
check_place_writable(&state, &access.place.to_place_expression()),
AccessKind::Read | AccessKind::Move =>
check_place_initialized(&state, &access.place.to_place_expression()),
}`"#]],
the rule "access_permitted" at (nll.rs) failed because
condition evaluated to false: `match access.kind
{
AccessKind::Write =>
check_place_writable(&state, &access.place.to_place_expression()),
AccessKind::Read | AccessKind::Move =>
check_place_initialized(&state, &access.place.to_place_expression()),
}`"#]],
)
}

Expand Down Expand Up @@ -157,23 +148,14 @@ fn conditional_init_one_branch() {
.borrowck_err(
BorrowCheckFailure::All,
expect_test::expect![[r#"
the rule "access_permitted" at (nll.rs) failed because
condition evaluated to false: `match access.kind
{
AccessKind::Write =>
check_place_writable(&state, &access.place.to_place_expression()),
AccessKind::Read | AccessKind::Move =>
check_place_initialized(&state, &access.place.to_place_expression()),
}`

the rule "access_permitted" at (nll.rs) failed because
condition evaluated to false: `match access.kind
{
AccessKind::Write =>
check_place_writable(&state, &access.place.to_place_expression()),
AccessKind::Read | AccessKind::Move =>
check_place_initialized(&state, &access.place.to_place_expression()),
}`"#]],
the rule "access_permitted" at (nll.rs) failed because
condition evaluated to false: `match access.kind
{
AccessKind::Write =>
check_place_writable(&state, &access.place.to_place_expression()),
AccessKind::Read | AccessKind::Move =>
check_place_initialized(&state, &access.place.to_place_expression()),
}`"#]],
)
}

Expand Down Expand Up @@ -257,15 +239,6 @@ fn conditional_init_no_else() {
}
}])
.err(expect_test::expect![[r#"
the rule "access_permitted" at (nll.rs) failed because
condition evaluated to false: `match access.kind
{
AccessKind::Write =>
check_place_writable(&state, &access.place.to_place_expression()),
AccessKind::Read | AccessKind::Move =>
check_place_initialized(&state, &access.place.to_place_expression()),
}`

the rule "access_permitted" at (nll.rs) failed because
condition evaluated to false: `match access.kind
{
Expand Down Expand Up @@ -589,23 +562,14 @@ fn move_parent_then_access_child() {
.borrowck_err(
BorrowCheckFailure::All,
expect_test::expect![[r#"
the rule "access_permitted" at (nll.rs) failed because
condition evaluated to false: `match access.kind
{
AccessKind::Write =>
check_place_writable(&state, &access.place.to_place_expression()),
AccessKind::Read | AccessKind::Move =>
check_place_initialized(&state, &access.place.to_place_expression()),
}`

the rule "access_permitted" at (nll.rs) failed because
condition evaluated to false: `match access.kind
{
AccessKind::Write =>
check_place_writable(&state, &access.place.to_place_expression()),
AccessKind::Read | AccessKind::Move =>
check_place_initialized(&state, &access.place.to_place_expression()),
}`"#]],
the rule "access_permitted" at (nll.rs) failed because
condition evaluated to false: `match access.kind
{
AccessKind::Write =>
check_place_writable(&state, &access.place.to_place_expression()),
AccessKind::Read | AccessKind::Move =>
check_place_initialized(&state, &access.place.to_place_expression()),
}`"#]],
)
}

Expand Down Expand Up @@ -2026,23 +1990,14 @@ fn uninitialized_return() {
.borrowck_err(
BorrowCheckFailure::All,
expect_test::expect![[r#"
the rule "access_permitted" at (nll.rs) failed because
condition evaluated to false: `match access.kind
{
AccessKind::Write =>
check_place_writable(&state, &access.place.to_place_expression()),
AccessKind::Read | AccessKind::Move =>
check_place_initialized(&state, &access.place.to_place_expression()),
}`

the rule "access_permitted" at (nll.rs) failed because
condition evaluated to false: `match access.kind
{
AccessKind::Write =>
check_place_writable(&state, &access.place.to_place_expression()),
AccessKind::Read | AccessKind::Move =>
check_place_initialized(&state, &access.place.to_place_expression()),
}`"#]],
the rule "access_permitted" at (nll.rs) failed because
condition evaluated to false: `match access.kind
{
AccessKind::Write =>
check_place_writable(&state, &access.place.to_place_expression()),
AccessKind::Read | AccessKind::Move =>
check_place_initialized(&state, &access.place.to_place_expression()),
}`"#]],
)
}
/// Test the holding a shared reference to a local
Expand Down Expand Up @@ -2390,13 +2345,9 @@ fn undeclared_universal_region_relationship() {
}
}
}]).borrowck_err(BorrowCheckFailure::All, expect_test::expect![[r#"
crates/formality-rust/src/prove/prove_via.rs:8:1: no applicable rules for prove_via { goal: !lt_1 : !lt_2, via: @ wf(?lt_0), assumptions: {@ wf(?lt_0)}, env: Env { variables: [!lt_1, !lt_2, ?lt_0], bias: Soundness, pending: [], allow_pending_outlives: false } }

crates/formality-rust/src/prove/prove_outlives.rs:8:1: no applicable rules for prove_outlives { a: !lt_1, b: !lt_2, assumptions: {@ wf(?lt_0)}, env: Env { variables: [!lt_1, !lt_2, ?lt_0], bias: Soundness, pending: [], allow_pending_outlives: false } }
crates/formality-rust/src/prove/prove_via.rs:8:1: no applicable rules for prove_via { goal: !lt_1 : !lt_2, via: @ wf(?lt_0), assumptions: {@ wf(?lt_0)}, env: Env { variables: [!lt_1, !lt_2, ?lt_0], bias: Soundness, pending: [], allow_pending_outlives: false } }

crates/formality-rust/src/prove/prove_via.rs:8:1: no applicable rules for prove_via { goal: !lt_1 : !lt_2, via: @ wf(?lt_0), assumptions: {@ wf(?lt_0)}, env: Env { variables: [!lt_1, !lt_2, ?lt_0], bias: Soundness, pending: [], allow_pending_outlives: false } }

crates/formality-rust/src/prove/prove_outlives.rs:8:1: no applicable rules for prove_outlives { a: !lt_1, b: !lt_2, assumptions: {@ wf(?lt_0)}, env: Env { variables: [!lt_1, !lt_2, ?lt_0], bias: Soundness, pending: [], allow_pending_outlives: false } }"#]])
crates/formality-rust/src/prove/prove_outlives.rs:8:1: no applicable rules for prove_outlives { a: !lt_1, b: !lt_2, assumptions: {@ wf(?lt_0)}, env: Env { variables: [!lt_1, !lt_2, ?lt_0], bias: Soundness, pending: [], allow_pending_outlives: false } }"#]])
}

/// Same as `undeclared_universal_region_relationship`, but the function
Expand All @@ -2412,13 +2363,9 @@ fn undeclared_universal_region_relationship_no_return() {
}
}
}]).borrowck_err(BorrowCheckFailure::All, expect_test::expect![[r#"
crates/formality-rust/src/prove/prove_outlives.rs:8:1: no applicable rules for prove_outlives { a: !lt_0, b: !lt_1, assumptions: {}, env: Env { variables: [!lt_0, !lt_1], bias: Soundness, pending: [], allow_pending_outlives: false } }

crates/formality-rust/src/prove/prove_outlives.rs:8:1: no applicable rules for prove_outlives { a: !lt_0, b: !lt_1, assumptions: {}, env: Env { variables: [!lt_0, !lt_1], bias: Soundness, pending: [], allow_pending_outlives: false } }
crates/formality-rust/src/prove/prove_outlives.rs:8:1: no applicable rules for prove_outlives { a: !lt_0, b: !lt_1, assumptions: {}, env: Env { variables: [!lt_0, !lt_1], bias: Soundness, pending: [], allow_pending_outlives: false } }

crates/formality-rust/src/prove/prove_outlives.rs:8:1: no applicable rules for prove_outlives { a: !lt_0, b: !lt_1, assumptions: {}, env: Env { variables: [!lt_0, !lt_1], bias: Soundness, pending: [], allow_pending_outlives: false } }

crates/formality-rust/src/prove/prove_outlives.rs:8:1: no applicable rules for prove_outlives { a: !lt_0, b: !lt_1, assumptions: {}, env: Env { variables: [!lt_0, !lt_1], bias: Soundness, pending: [], allow_pending_outlives: false } }"#]])
crates/formality-rust/src/prove/prove_outlives.rs:8:1: no applicable rules for prove_outlives { a: !lt_0, b: !lt_1, assumptions: {}, env: Env { variables: [!lt_0, !lt_1], bias: Soundness, pending: [], allow_pending_outlives: false } }"#]])
}

/// Upcasting from `'a` to `'b` is allowed because
Expand Down Expand Up @@ -2469,13 +2416,9 @@ fn undeclared_transitive_universal_region_relationship() {
return v1;
}
}]).borrowck_err(BorrowCheckFailure::All, expect_test::expect![[r#"
crates/formality-rust/src/prove/prove_via.rs:8:1: no applicable rules for prove_via { goal: !lt_0 : !lt_2, via: !lt_0 : !lt_1, assumptions: {!lt_0 : !lt_1}, env: Env { variables: [!lt_0, !lt_1, !lt_2], bias: Soundness, pending: [], allow_pending_outlives: false } }

crates/formality-rust/src/prove/prove_outlives.rs:8:1: no applicable rules for prove_outlives { a: !lt_0, b: !lt_2, assumptions: {!lt_0 : !lt_1}, env: Env { variables: [!lt_0, !lt_1, !lt_2], bias: Soundness, pending: [], allow_pending_outlives: false } }

crates/formality-rust/src/prove/prove_via.rs:8:1: no applicable rules for prove_via { goal: !lt_0 : !lt_2, via: !lt_0 : !lt_1, assumptions: {!lt_0 : !lt_1}, env: Env { variables: [!lt_0, !lt_1, !lt_2], bias: Soundness, pending: [], allow_pending_outlives: false } }
crates/formality-rust/src/prove/prove_via.rs:8:1: no applicable rules for prove_via { goal: !lt_0 : !lt_2, via: !lt_0 : !lt_1, assumptions: {!lt_0 : !lt_1}, env: Env { variables: [!lt_0, !lt_1, !lt_2], bias: Soundness, pending: [], allow_pending_outlives: false } }

crates/formality-rust/src/prove/prove_outlives.rs:8:1: no applicable rules for prove_outlives { a: !lt_0, b: !lt_2, assumptions: {!lt_0 : !lt_1}, env: Env { variables: [!lt_0, !lt_1, !lt_2], bias: Soundness, pending: [], allow_pending_outlives: false } }"#]])
crates/formality-rust/src/prove/prove_outlives.rs:8:1: no applicable rules for prove_outlives { a: !lt_0, b: !lt_2, assumptions: {!lt_0 : !lt_1}, env: Env { variables: [!lt_0, !lt_1, !lt_2], bias: Soundness, pending: [], allow_pending_outlives: false } }"#]])
}

// For `list: &mut Map`, borrow `&mut (*list).value` then assign to `list`.
Expand Down Expand Up @@ -2702,41 +2645,23 @@ fn continue_drops_borrowed_local_loop_carried() {
.borrowck_err(
BorrowCheckFailure::All,
expect_test::expect![[r#"
the rule "access_permitted" at (nll.rs) failed because
condition evaluated to false: `match access.kind
{
AccessKind::Write =>
check_place_writable(&state, &access.place.to_place_expression()),
AccessKind::Read | AccessKind::Move =>
check_place_initialized(&state, &access.place.to_place_expression()),
}`

the rule "access_permitted" at (nll.rs) failed because
condition evaluated to false: `match access.kind
{
AccessKind::Write =>
check_place_writable(&state, &access.place.to_place_expression()),
AccessKind::Read | AccessKind::Move =>
check_place_initialized(&state, &access.place.to_place_expression()),
}`

the rule "access_permitted" at (nll.rs) failed because
condition evaluated to false: `match access.kind
{
AccessKind::Write =>
check_place_writable(&state, &access.place.to_place_expression()),
AccessKind::Read | AccessKind::Move =>
check_place_initialized(&state, &access.place.to_place_expression()),
}`

the rule "access_permitted" at (nll.rs) failed because
condition evaluated to false: `match access.kind
{
AccessKind::Write =>
check_place_writable(&state, &access.place.to_place_expression()),
AccessKind::Read | AccessKind::Move =>
check_place_initialized(&state, &access.place.to_place_expression()),
}`"#]],
the rule "access_permitted" at (nll.rs) failed because
condition evaluated to false: `match access.kind
{
AccessKind::Write =>
check_place_writable(&state, &access.place.to_place_expression()),
AccessKind::Read | AccessKind::Move =>
check_place_initialized(&state, &access.place.to_place_expression()),
}`

the rule "access_permitted" at (nll.rs) failed because
condition evaluated to false: `match access.kind
{
AccessKind::Write =>
check_place_writable(&state, &access.place.to_place_expression()),
AccessKind::Read | AccessKind::Move =>
check_place_initialized(&state, &access.place.to_place_expression()),
}`"#]],
)
}

Expand Down Expand Up @@ -3139,10 +3064,7 @@ fn call_generic_fn_with_turbofish_missing_relation_upcast() {
let r: &'b u32 = identity::<&'b u32>(a);
return r;
}
}]).borrowck_err(BorrowCheckFailure::All, expect_test::expect![[r#"
crates/formality-rust/src/prove/prove_outlives.rs:8:1: no applicable rules for prove_outlives { a: !lt_0, b: !lt_1, assumptions: {}, env: Env { variables: [!lt_0, !lt_1], bias: Soundness, pending: [], allow_pending_outlives: false } }

crates/formality-rust/src/prove/prove_outlives.rs:8:1: no applicable rules for prove_outlives { a: !lt_0, b: !lt_1, assumptions: {}, env: Env { variables: [!lt_0, !lt_1], bias: Soundness, pending: [], allow_pending_outlives: false } }"#]])
}]).borrowck_err(BorrowCheckFailure::All, expect_test::expect!["crates/formality-rust/src/prove/prove_outlives.rs:8:1: no applicable rules for prove_outlives { a: !lt_0, b: !lt_1, assumptions: {}, env: Env { variables: [!lt_0, !lt_1], bias: Soundness, pending: [], allow_pending_outlives: false } }"])
}

/// Test call to a generic function using turbofish syntax with lifetime and type.
Expand Down Expand Up @@ -3290,25 +3212,15 @@ fn struct_construction_with_borrowed_local() {
.borrowck_err(
BorrowCheckFailure::All,
expect_test::expect![[r#"
the rule "borrow of disjoint places" at (nll.rs) failed because
condition evaluated to false: `place_disjoint_from_place(&loan.place, &access.place)`
&loan.place = v1 : u32
&access.place = v1 : u32

the rule "loan_cannot_outlive" at (nll.rs) failed because
condition evaluated to false: `!outlived_by_loan.contains(&lifetime.upcast())`
outlived_by_loan = {?lt_1, ?lt_2}
&lifetime.upcast() = ?lt_1

the rule "borrow of disjoint places" at (nll.rs) failed because
condition evaluated to false: `place_disjoint_from_place(&loan.place, &access.place)`
&loan.place = v1 : u32
&access.place = v1 : u32
the rule "borrow of disjoint places" at (nll.rs) failed because
condition evaluated to false: `place_disjoint_from_place(&loan.place, &access.place)`
&loan.place = v1 : u32
&access.place = v1 : u32

the rule "loan_cannot_outlive" at (nll.rs) failed because
condition evaluated to false: `!outlived_by_loan.contains(&lifetime.upcast())`
outlived_by_loan = {?lt_1, ?lt_2}
&lifetime.upcast() = ?lt_1"#]],
the rule "loan_cannot_outlive" at (nll.rs) failed because
condition evaluated to false: `!outlived_by_loan.contains(&lifetime.upcast())`
outlived_by_loan = {?lt_1, ?lt_2}
&lifetime.upcast() = ?lt_1"#]],
)
}

Expand Down Expand Up @@ -4589,3 +4501,38 @@ fn issue_70044_location_insensitive_constraints() {
.skip_execute()
.borrowck_err(BorrowCheckFailure::Nll, expect_test::expect![[""]]);
}

/// Reading a `Copy` place does not move out of it, so it can be read twice.
#[test]
fn read_copy_place_twice() {
FormalityTest::new(crates![crate Foo {
fn foo() -> u32 {
let a: u32 = 0_u32;
a;
a;
return 0_u32;
}
}])
.skip_execute()
.borrowck_ok()
}

/// Shared references are also `Copy`, so we can create two separate shared
// references without issue.
#[test]
fn read_copy_reference_twice() {
FormalityTest::new(crates![crate Foo {
fn foo() -> u32 {
exists<'l0> {
let a: u32 = 0_u32;
let p: &'l0 u32 = &'l0 a;
let q: &'l0 u32 = p;
let r: &'l0 u32 = p;
p;
return 0_u32;
}
}
}])
.skip_execute()
.borrowck_ok();
}
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