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Rollup merge of rust-lang#125282 - WaffleLapkin:never-type-unsafe-imp…
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…rovements, r=compiler-errors

Never type unsafe lint improvements

- Move linting code to a separate method
- Remove mentions of `core::convert::absurd` (rust-lang#124311 was rejected)
- Make the lint into FCW

The last thing is a bit weird though. On one hand it should be `EditionSemanticsChange(2024)`, but on the other hand it shouldn't, because we also plan to break it on all editions some time later. _Also_, it's weird that we don't have `FutureReleaseSemanticsChangeReportInDeps`, IMO "this might cause UB in a future release" is important enough to be reported in deps...

IMO we ought to have three enums instead of [`FutureIncompatibilityReason`](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_lint_defs/enum.FutureIncompatibilityReason.html#):

```rust
enum IncompatibilityWhen {
     FutureRelease,
     Edition(Edition),
}

enum IncompatibilyWhat {
    Error,
    SemanticChange,
}

enum IncompatibilityReportInDeps {
    No,
    Yes,
}
```

Tracking:
- rust-lang#123748
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@matthiaskrgr
matthiaskrgr authored May 20, 2024
2 parents 7389416 + 434221b commit 8855261
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75 changes: 40 additions & 35 deletions compiler/rustc_hir_typeck/src/fallback.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -364,41 +364,11 @@ impl<'tcx> FnCtxt<'_, 'tcx> {
};

let mut fallback_to = |ty| {
let unsafe_infer_vars = unsafe_infer_vars.get_or_init(|| {
let unsafe_infer_vars = compute_unsafe_infer_vars(self.root_ctxt, self.body_id);
debug!(?unsafe_infer_vars);
unsafe_infer_vars
});

let affected_unsafe_infer_vars =
graph::depth_first_search_as_undirected(&coercion_graph, root_vid)
.filter_map(|x| unsafe_infer_vars.get(&x).copied())
.collect::<Vec<_>>();

for (hir_id, span, reason) in affected_unsafe_infer_vars {
self.tcx.emit_node_span_lint(
lint::builtin::NEVER_TYPE_FALLBACK_FLOWING_INTO_UNSAFE,
hir_id,
span,
match reason {
UnsafeUseReason::Call => {
errors::NeverTypeFallbackFlowingIntoUnsafe::Call
}
UnsafeUseReason::Method => {
errors::NeverTypeFallbackFlowingIntoUnsafe::Method
}
UnsafeUseReason::Path => {
errors::NeverTypeFallbackFlowingIntoUnsafe::Path
}
UnsafeUseReason::UnionField => {
errors::NeverTypeFallbackFlowingIntoUnsafe::UnionField
}
UnsafeUseReason::Deref => {
errors::NeverTypeFallbackFlowingIntoUnsafe::Deref
}
},
);
}
self.lint_never_type_fallback_flowing_into_unsafe_code(
&unsafe_infer_vars,
&coercion_graph,
root_vid,
);

diverging_fallback.insert(diverging_ty, ty);
};
Expand Down Expand Up @@ -464,6 +434,41 @@ impl<'tcx> FnCtxt<'_, 'tcx> {
diverging_fallback
}

fn lint_never_type_fallback_flowing_into_unsafe_code(
&self,
unsafe_infer_vars: &OnceCell<UnordMap<ty::TyVid, (HirId, Span, UnsafeUseReason)>>,
coercion_graph: &VecGraph<ty::TyVid, true>,
root_vid: ty::TyVid,
) {
let unsafe_infer_vars = unsafe_infer_vars.get_or_init(|| {
let unsafe_infer_vars = compute_unsafe_infer_vars(self.root_ctxt, self.body_id);
debug!(?unsafe_infer_vars);
unsafe_infer_vars
});

let affected_unsafe_infer_vars =
graph::depth_first_search_as_undirected(&coercion_graph, root_vid)
.filter_map(|x| unsafe_infer_vars.get(&x).copied())
.collect::<Vec<_>>();

for (hir_id, span, reason) in affected_unsafe_infer_vars {
self.tcx.emit_node_span_lint(
lint::builtin::NEVER_TYPE_FALLBACK_FLOWING_INTO_UNSAFE,
hir_id,
span,
match reason {
UnsafeUseReason::Call => errors::NeverTypeFallbackFlowingIntoUnsafe::Call,
UnsafeUseReason::Method => errors::NeverTypeFallbackFlowingIntoUnsafe::Method,
UnsafeUseReason::Path => errors::NeverTypeFallbackFlowingIntoUnsafe::Path,
UnsafeUseReason::UnionField => {
errors::NeverTypeFallbackFlowingIntoUnsafe::UnionField
}
UnsafeUseReason::Deref => errors::NeverTypeFallbackFlowingIntoUnsafe::Deref,
},
);
}
}

/// Returns a graph whose nodes are (unresolved) inference variables and where
/// an edge `?A -> ?B` indicates that the variable `?A` is coerced to `?B`.
fn create_coercion_graph(&self) -> VecGraph<ty::TyVid, true> {
Expand Down
10 changes: 7 additions & 3 deletions compiler/rustc_lint_defs/src/builtin.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -4263,8 +4263,7 @@ declare_lint! {
///
/// // where absurd is a function with the following signature
/// // (it's sound, because `!` always marks unreachable code):
/// fn absurd<T>(_: !) -> T { ... }
// FIXME: use `core::convert::absurd` here instead, once it's merged
/// fn absurd<T>(never: !) -> T { ... }
/// ```
///
/// While it's convenient to be able to use non-diverging code in one of the branches (like
Expand Down Expand Up @@ -4321,7 +4320,12 @@ declare_lint! {
/// [`()`]: https://doc.rust-lang.org/core/primitive.unit.html
pub NEVER_TYPE_FALLBACK_FLOWING_INTO_UNSAFE,
Warn,
"never type fallback affecting unsafe function calls"
"never type fallback affecting unsafe function calls",
@future_incompatible = FutureIncompatibleInfo {
reason: FutureIncompatibilityReason::FutureReleaseSemanticsChange,
reference: "issue #123748 <https://github.com/rust-lang/rust/issues/123748>",
};
report_in_external_macro
}

declare_lint! {
Expand Down
10 changes: 10 additions & 0 deletions tests/ui/never_type/lint-never-type-fallback-flowing-into-unsafe.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,7 @@ fn _zero() {
if false {
unsafe { mem::zeroed() }
//~^ warn: never type fallback affects this call to an `unsafe` function
//~| warn: this will change its meaning in a future release!
} else {
return;
};
Expand All @@ -21,6 +22,7 @@ fn _trans() {
struct Zst;
core::mem::transmute(Zst)
//~^ warn: never type fallback affects this call to an `unsafe` function
//~| warn: this will change its meaning in a future release!
}
} else {
return;
Expand All @@ -36,6 +38,7 @@ fn _union() {

unsafe { Union { a: () }.b }
//~^ warn: never type fallback affects this union access
//~| warn: this will change its meaning in a future release!
} else {
return;
};
Expand All @@ -45,6 +48,7 @@ fn _deref() {
if false {
unsafe { *ptr::from_ref(&()).cast() }
//~^ warn: never type fallback affects this raw pointer dereference
//~| warn: this will change its meaning in a future release!
} else {
return;
};
Expand All @@ -62,6 +66,7 @@ fn _only_generics() {

unsafe { internally_create(x) }
//~^ warn: never type fallback affects this call to an `unsafe` function
//~| warn: this will change its meaning in a future release!

x.unwrap()
} else {
Expand All @@ -73,9 +78,11 @@ fn _stored_function() {
if false {
let zeroed = mem::zeroed;
//~^ warn: never type fallback affects this `unsafe` function
//~| warn: this will change its meaning in a future release!

unsafe { zeroed() }
//~^ warn: never type fallback affects this call to an `unsafe` function
//~| warn: this will change its meaning in a future release!
} else {
return;
};
Expand All @@ -90,6 +97,7 @@ fn _only_generics_stored_function() {
let x = None;
let f = internally_create;
//~^ warn: never type fallback affects this `unsafe` function
//~| warn: this will change its meaning in a future release!

unsafe { f(x) }

Expand All @@ -113,6 +121,7 @@ fn _method() {
unsafe {
S(marker::PhantomData).create_out_of_thin_air()
//~^ warn: never type fallback affects this call to an `unsafe` method
//~| warn: this will change its meaning in a future release!
}
} else {
return;
Expand All @@ -129,6 +138,7 @@ fn _objc() {
() => {
match send_message::<_ /* ?0 */>() {
//~^ warn: never type fallback affects this call to an `unsafe` function
//~| warn: this will change its meaning in a future release!
Ok(x) => x,
Err(_) => loop {},
}
Expand Down
38 changes: 29 additions & 9 deletions tests/ui/never_type/lint-never-type-fallback-flowing-into-unsafe.stderr
View file
Original file line number Diff line number Diff line change
Expand Up @@ -4,82 +4,102 @@ warning: never type fallback affects this call to an `unsafe` function
LL | unsafe { mem::zeroed() }
| ^^^^^^^^^^^^^
|
= warning: this will change its meaning in a future release!
= note: for more information, see issue #123748 <https://github.com/rust-lang/rust/issues/123748>
= help: specify the type explicitly
= note: `#[warn(never_type_fallback_flowing_into_unsafe)]` on by default

warning: never type fallback affects this call to an `unsafe` function
--> $DIR/lint-never-type-fallback-flowing-into-unsafe.rs:22:13
--> $DIR/lint-never-type-fallback-flowing-into-unsafe.rs:23:13
|
LL | core::mem::transmute(Zst)
| ^^^^^^^^^^^^^^^^^^^^^^^^^
|
= warning: this will change its meaning in a future release!
= note: for more information, see issue #123748 <https://github.com/rust-lang/rust/issues/123748>
= help: specify the type explicitly

warning: never type fallback affects this union access
--> $DIR/lint-never-type-fallback-flowing-into-unsafe.rs:37:18
--> $DIR/lint-never-type-fallback-flowing-into-unsafe.rs:39:18
|
LL | unsafe { Union { a: () }.b }
| ^^^^^^^^^^^^^^^^^
|
= warning: this will change its meaning in a future release!
= note: for more information, see issue #123748 <https://github.com/rust-lang/rust/issues/123748>
= help: specify the type explicitly

warning: never type fallback affects this raw pointer dereference
--> $DIR/lint-never-type-fallback-flowing-into-unsafe.rs:46:18
--> $DIR/lint-never-type-fallback-flowing-into-unsafe.rs:49:18
|
LL | unsafe { *ptr::from_ref(&()).cast() }
| ^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= warning: this will change its meaning in a future release!
= note: for more information, see issue #123748 <https://github.com/rust-lang/rust/issues/123748>
= help: specify the type explicitly

warning: never type fallback affects this call to an `unsafe` function
--> $DIR/lint-never-type-fallback-flowing-into-unsafe.rs:63:18
--> $DIR/lint-never-type-fallback-flowing-into-unsafe.rs:67:18
|
LL | unsafe { internally_create(x) }
| ^^^^^^^^^^^^^^^^^^^^
|
= warning: this will change its meaning in a future release!
= note: for more information, see issue #123748 <https://github.com/rust-lang/rust/issues/123748>
= help: specify the type explicitly

warning: never type fallback affects this call to an `unsafe` function
--> $DIR/lint-never-type-fallback-flowing-into-unsafe.rs:77:18
--> $DIR/lint-never-type-fallback-flowing-into-unsafe.rs:83:18
|
LL | unsafe { zeroed() }
| ^^^^^^^^
|
= warning: this will change its meaning in a future release!
= note: for more information, see issue #123748 <https://github.com/rust-lang/rust/issues/123748>
= help: specify the type explicitly

warning: never type fallback affects this `unsafe` function
--> $DIR/lint-never-type-fallback-flowing-into-unsafe.rs:74:22
--> $DIR/lint-never-type-fallback-flowing-into-unsafe.rs:79:22
|
LL | let zeroed = mem::zeroed;
| ^^^^^^^^^^^
|
= warning: this will change its meaning in a future release!
= note: for more information, see issue #123748 <https://github.com/rust-lang/rust/issues/123748>
= help: specify the type explicitly

warning: never type fallback affects this `unsafe` function
--> $DIR/lint-never-type-fallback-flowing-into-unsafe.rs:91:17
--> $DIR/lint-never-type-fallback-flowing-into-unsafe.rs:98:17
|
LL | let f = internally_create;
| ^^^^^^^^^^^^^^^^^
|
= warning: this will change its meaning in a future release!
= note: for more information, see issue #123748 <https://github.com/rust-lang/rust/issues/123748>
= help: specify the type explicitly

warning: never type fallback affects this call to an `unsafe` method
--> $DIR/lint-never-type-fallback-flowing-into-unsafe.rs:114:13
--> $DIR/lint-never-type-fallback-flowing-into-unsafe.rs:122:13
|
LL | S(marker::PhantomData).create_out_of_thin_air()
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= warning: this will change its meaning in a future release!
= note: for more information, see issue #123748 <https://github.com/rust-lang/rust/issues/123748>
= help: specify the type explicitly

warning: never type fallback affects this call to an `unsafe` function
--> $DIR/lint-never-type-fallback-flowing-into-unsafe.rs:130:19
--> $DIR/lint-never-type-fallback-flowing-into-unsafe.rs:139:19
|
LL | match send_message::<_ /* ?0 */>() {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
...
LL | msg_send!();
| ----------- in this macro invocation
|
= warning: this will change its meaning in a future release!
= note: for more information, see issue #123748 <https://github.com/rust-lang/rust/issues/123748>
= help: specify the type explicitly
= note: this warning originates in the macro `msg_send` (in Nightly builds, run with -Z macro-backtrace for more info)

Expand Down

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