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Warn against redundant use<...>

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This commit is contained in:
Michael Goulet 2024-04-20 11:22:06 -04:00
parent f3fb727b08
commit 1529c661e4
10 changed files with 276 additions and 118 deletions
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15
compiler/rustc_ast_lowering/src/lib.rs
View File

@ -1407,7 +1407,7 @@ fn lower_ty_direct(&mut self, t: &Ty, itctx: ImplTraitContext) -> hir::Ty<'hir>
bounds,
fn_kind,
itctx,
precise_capturing.as_deref().map(|(args, _)| args.as_slice()),
precise_capturing.as_deref().map(|(args, span)| (args.as_slice(), *span)),
),
ImplTraitContext::Universal => {
if let Some(&(_, span)) = precise_capturing.as_deref() {
@ -1523,7 +1523,7 @@ fn lower_opaque_impl_trait(
bounds: &GenericBounds,
fn_kind: Option<FnDeclKind>,
itctx: ImplTraitContext,
precise_capturing_args: Option<&[PreciseCapturingArg]>,
precise_capturing_args: Option<(&[PreciseCapturingArg], Span)>,
) -> hir::TyKind<'hir> {
// Make sure we know that some funky desugaring has been going on here.
// This is a first: there is code in other places like for loop
@ -1533,7 +1533,7 @@ fn lower_opaque_impl_trait(
let opaque_ty_span = self.mark_span_with_reason(DesugaringKind::OpaqueTy, span, None);
let captured_lifetimes_to_duplicate =
if let Some(precise_capturing) = precise_capturing_args {
if let Some((precise_capturing, _)) = precise_capturing_args {
// We'll actually validate these later on; all we need is the list of
// lifetimes to duplicate during this portion of lowering.
precise_capturing
@ -1607,7 +1607,7 @@ fn lower_opaque_inner(
captured_lifetimes_to_duplicate: FxIndexSet<Lifetime>,
span: Span,
opaque_ty_span: Span,
precise_capturing_args: Option<&[PreciseCapturingArg]>,
precise_capturing_args: Option<(&[PreciseCapturingArg], Span)>,
lower_item_bounds: impl FnOnce(&mut Self) -> &'hir [hir::GenericBound<'hir>],
) -> hir::TyKind<'hir> {
let opaque_ty_def_id = self.create_def(
@ -1698,8 +1698,11 @@ fn lower_opaque_inner(
this.with_remapping(captured_to_synthesized_mapping, |this| {
(
lower_item_bounds(this),
precise_capturing_args.map(|precise_capturing| {
this.lower_precise_capturing_args(precise_capturing)
precise_capturing_args.map(|(precise_capturing, span)| {
(
this.lower_precise_capturing_args(precise_capturing),
this.lower_span(span),
)
}),
)
});

11
compiler/rustc_hir/src/hir.rs
View File

@ -2631,7 +2631,7 @@ pub struct OpaqueTy<'hir> {
/// lowered as an associated type.
pub in_trait: bool,
/// List of arguments captured via `impl use<'a, P, ...> Trait` syntax.
pub precise_capturing_args: Option<&'hir [PreciseCapturingArg<'hir>]>,
pub precise_capturing_args: Option<(&'hir [PreciseCapturingArg<'hir>], Span)>,
}
#[derive(Debug, Clone, Copy, HashStable_Generic)]
@ -2641,6 +2641,15 @@ pub enum PreciseCapturingArg<'hir> {
Param(PreciseCapturingNonLifetimeArg),
}
impl PreciseCapturingArg<'_> {
pub fn hir_id(self) -> HirId {
match self {
PreciseCapturingArg::Lifetime(lt) => lt.hir_id,
PreciseCapturingArg::Param(param) => param.hir_id,
}
}
}
/// We need to have a [`Node`] for the [`HirId`] that we attach the type/const param
/// resolution to. Lifetimes don't have this problem, and for them, it's actually
/// kind of detrimental to use a custom node type versus just using [`Lifetime`],

2
compiler/rustc_hir/src/intravisit.rs
View File

@ -533,7 +533,7 @@ pub fn walk_item<'v, V: Visitor<'v>>(visitor: &mut V, item: &'v Item<'v>) -> V::
try_visit!(visitor.visit_id(item.hir_id()));
try_visit!(walk_generics(visitor, generics));
walk_list!(visitor, visit_param_bound, bounds);
if let Some(precise_capturing_args) = precise_capturing_args {
if let Some((precise_capturing_args, _)) = precise_capturing_args {
for arg in precise_capturing_args {
try_visit!(visitor.visit_precise_capturing_arg(arg));
}

2
compiler/rustc_hir_analysis/src/check/check.rs
View File

@ -486,7 +486,7 @@ fn sanity_check_found_hidden_type<'tcx>(
fn check_opaque_precise_captures<'tcx>(tcx: TyCtxt<'tcx>, opaque_def_id: LocalDefId) {
let hir::OpaqueTy { precise_capturing_args, .. } =
*tcx.hir_node_by_def_id(opaque_def_id).expect_item().expect_opaque_ty();
let Some(precise_capturing_args) = precise_capturing_args else {
let Some((precise_capturing_args, _)) = precise_capturing_args else {
// No precise capturing args; nothing to validate
return;
};

19
compiler/rustc_lint/messages.ftl
View File

@ -9,14 +9,6 @@ lint_array_into_iter =
.use_explicit_into_iter_suggestion =
or use `IntoIterator::into_iter(..)` instead of `.into_iter()` to explicitly iterate by value
lint_impl_trait_overcaptures = `{$self_ty}` will capture more lifetimes than possibly intended in edition 2024
.note = specifically, {$num_captured ->
[one] this lifetime is
*[other] these lifetimes are
} in scope but not mentioned in the type's bounds
.note2 = all lifetimes in scope will be captured by `impl Trait`s in edition 2024
.suggestion = use the precise capturing `use<...>` syntax to make the captures explicit
lint_async_fn_in_trait = use of `async fn` in public traits is discouraged as auto trait bounds cannot be specified
.note = you can suppress this lint if you plan to use the trait only in your own code, or do not care about auto traits like `Send` on the `Future`
.suggestion = you can alternatively desugar to a normal `fn` that returns `impl Future` and add any desired bounds such as `Send`, but these cannot be relaxed without a breaking API change
@ -277,6 +269,17 @@ lint_identifier_uncommon_codepoints = identifier contains {$codepoints_len ->
lint_ignored_unless_crate_specified = {$level}({$name}) is ignored unless specified at crate level
lint_impl_trait_overcaptures = `{$self_ty}` will capture more lifetimes than possibly intended in edition 2024
.note = specifically, {$num_captured ->
[one] this lifetime is
*[other] these lifetimes are
} in scope but not mentioned in the type's bounds
.note2 = all lifetimes in scope will be captured by `impl Trait`s in edition 2024
.suggestion = use the precise capturing `use<...>` syntax to make the captures explicit
lint_impl_trait_redundant_captures = all possible in-scope parameters are already captured, so `use<...>` syntax is redundant
.suggestion = remove the `use<...>` syntax
lint_improper_ctypes = `extern` {$desc} uses type `{$ty}`, which is not FFI-safe
.label = not FFI-safe
.note = the type is defined here

177
compiler/rustc_lint/src/impl_trait_overcaptures.rs
View File

@ -1,9 +1,11 @@
use rustc_data_structures::fx::FxIndexSet;
use rustc_data_structures::unord::UnordSet;
use rustc_errors::{Applicability, LintDiagnostic};
use rustc_hir as hir;
use rustc_hir::def::DefKind;
use rustc_hir::def_id::{DefId, LocalDefId};
use rustc_hir::intravisit;
use rustc_macros::LintDiagnostic;
use rustc_middle::middle::resolve_bound_vars::ResolvedArg;
use rustc_middle::ty::{
self, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable, TypeVisitableExt, TypeVisitor,
};
@ -14,10 +16,12 @@
use crate::fluent_generated as fluent;
use crate::{LateContext, LateLintPass};
// TODO: feature gate these too
declare_lint! {
/// UwU
pub IMPL_TRAIT_OVERCAPTURES,
Warn,
Allow,
"will capture more lifetimes than possibly intended in edition 2024",
@future_incompatible = FutureIncompatibleInfo {
reason: FutureIncompatibilityReason::EditionSemanticsChange(Edition::Edition2024),
@ -25,52 +29,51 @@
};
}
declare_lint! {
/// UwU
pub IMPL_TRAIT_REDUNDANT_CAPTURES,
Warn,
"uwu 2"
}
declare_lint_pass!(
/// Lint for opaque types that will begin capturing in-scope but unmentioned lifetimes
/// in edition 2024.
ImplTraitOvercaptures => [IMPL_TRAIT_OVERCAPTURES]
ImplTraitOvercaptures => [IMPL_TRAIT_OVERCAPTURES, IMPL_TRAIT_REDUNDANT_CAPTURES]
);
impl<'tcx> LateLintPass<'tcx> for ImplTraitOvercaptures {
fn check_fn(
&mut self,
cx: &LateContext<'tcx>,
_: intravisit::FnKind<'tcx>,
_: &'tcx hir::FnDecl<'tcx>,
_: &'tcx hir::Body<'tcx>,
_: Span,
parent_def_id: LocalDefId,
) {
match cx.tcx.def_kind(parent_def_id) {
DefKind::AssocFn => {
// RPITITs already capture all lifetimes in scope, so skip them.
if matches!(
cx.tcx.def_kind(cx.tcx.local_parent(parent_def_id)),
DefKind::Trait | DefKind::Impl { of_trait: true }
) {
return;
}
}
DefKind::Fn => {
// All free functions need to check for overcaptures.
}
DefKind::Closure => return,
kind => {
unreachable!(
"expected function item, found {}",
kind.descr(parent_def_id.to_def_id())
)
fn check_item(&mut self, cx: &LateContext<'tcx>, it: &'tcx hir::Item<'tcx>) {
match &it.kind {
hir::ItemKind::Fn(..) => check_fn(cx.tcx, it.owner_id.def_id),
_ => {}
}
}
let sig = cx.tcx.fn_sig(parent_def_id).instantiate_identity();
fn check_impl_item(&mut self, cx: &LateContext<'tcx>, it: &'tcx hir::ImplItem<'tcx>) {
match &it.kind {
hir::ImplItemKind::Fn(_, _) => check_fn(cx.tcx, it.owner_id.def_id),
_ => {}
}
}
fn check_trait_item(&mut self, cx: &LateContext<'tcx>, it: &'tcx hir::TraitItem<'tcx>) {
match &it.kind {
hir::TraitItemKind::Fn(_, _) => check_fn(cx.tcx, it.owner_id.def_id),
_ => {}
}
}
}
fn check_fn(tcx: TyCtxt<'_>, parent_def_id: LocalDefId) {
let sig = tcx.fn_sig(parent_def_id).instantiate_identity();
let mut in_scope_parameters = FxIndexSet::default();
// Populate the in_scope_parameters list first with all of the generics in scope
let mut current_def_id = Some(parent_def_id.to_def_id());
while let Some(def_id) = current_def_id {
let generics = cx.tcx.generics_of(def_id);
for param in &generics.params {
let generics = tcx.generics_of(def_id);
for param in &generics.own_params {
in_scope_parameters.insert(param.def_id);
}
current_def_id = generics.parent;
@ -79,13 +82,12 @@ fn check_fn(
// Then visit the signature to walk through all the binders (incl. the late-bound
// vars on the function itself, which we need to count too).
sig.visit_with(&mut VisitOpaqueTypes {
tcx: cx.tcx,
tcx,
parent_def_id,
in_scope_parameters,
seen: Default::default(),
});
}
}
struct VisitOpaqueTypes<'tcx> {
tcx: TyCtxt<'tcx>,
@ -109,14 +111,11 @@ fn visit_binder<T: TypeVisitable<TyCtxt<'tcx>>>(
let unique = self.in_scope_parameters.insert(def_id);
assert!(unique);
}
ty::BoundVariableKind::Ty(_) => {
todo!("we don't support late-bound type params in `impl Trait`")
}
ty::BoundVariableKind::Region(..) => {
unreachable!("all AST-derived bound regions should have a name")
}
ty::BoundVariableKind::Const => {
unreachable!("non-lifetime binder consts are not allowed")
_ => {
self.tcx.dcx().span_delayed_bug(
self.tcx.def_span(self.parent_def_id),
format!("unsupported bound variable kind: {arg:?}"),
);
}
}
}
@ -131,11 +130,19 @@ fn visit_binder<T: TypeVisitable<TyCtxt<'tcx>>>(
}
fn visit_ty(&mut self, t: Ty<'tcx>) -> Self::Result {
if !t.has_opaque_types() {
if !t.has_aliases() {
return;
}
if let ty::Alias(ty::Opaque, opaque_ty) = *t.kind()
if let ty::Alias(ty::Projection, opaque_ty) = *t.kind()
&& self.tcx.is_impl_trait_in_trait(opaque_ty.def_id)
{
// visit the opaque of the RPITIT
self.tcx
.type_of(opaque_ty.def_id)
.instantiate(self.tcx, opaque_ty.args)
.visit_with(self)
} else if let ty::Alias(ty::Opaque, opaque_ty) = *t.kind()
&& let Some(opaque_def_id) = opaque_ty.def_id.as_local()
// Don't recurse infinitely on an opaque
&& self.seen.insert(opaque_def_id)
@ -144,8 +151,6 @@ fn visit_ty(&mut self, t: Ty<'tcx>) -> Self::Result {
self.tcx.hir_node_by_def_id(opaque_def_id).expect_item().expect_opaque_ty()
&& let hir::OpaqueTyOrigin::FnReturn(parent_def_id) = opaque.origin
&& parent_def_id == self.parent_def_id
// And if the opaque doesn't already have `use<>` syntax on it...
&& opaque.precise_capturing_args.is_none()
{
// Compute the set of args that are captured by the opaque...
let mut captured = FxIndexSet::default();
@ -178,9 +183,16 @@ fn visit_ty(&mut self, t: Ty<'tcx>) -> Self::Result {
.map(|def_id| self.tcx.def_span(def_id))
.collect();
if !uncaptured_spans.is_empty() {
let opaque_span = self.tcx.def_span(opaque_def_id);
let new_capture_rules =
opaque_span.at_least_rust_2024() || self.tcx.features().lifetime_capture_rules_2024;
// If we have uncaptured args, and if the opaque doesn't already have
// `use<>` syntax on it, and we're < edition 2024, then warn the user.
if !new_capture_rules
&& opaque.precise_capturing_args.is_none()
&& !uncaptured_spans.is_empty()
{
let suggestion = if let Ok(snippet) =
self.tcx.sess.source_map().span_to_snippet(opaque_span)
&& snippet.starts_with("impl ")
@ -207,11 +219,11 @@ fn visit_ty(&mut self, t: Ty<'tcx>) -> Self::Result {
None
};
self.tcx.emit_node_lint(
self.tcx.emit_node_span_lint(
IMPL_TRAIT_OVERCAPTURES,
self.tcx.local_def_id_to_hir_id(opaque_def_id),
ImplTraitOvercapturesLint {
opaque_span,
ImplTraitOvercapturesLint {
self_ty: t,
num_captured: uncaptured_spans.len(),
uncaptured_spans,
@ -219,6 +231,60 @@ fn visit_ty(&mut self, t: Ty<'tcx>) -> Self::Result {
},
);
}
// Otherwise, if we are edition 2024, have `use<>` syntax, and
// have no uncaptured args, then we should warn to the user that
// it's redundant to capture all args explicitly.
else if new_capture_rules
&& let Some((captured_args, capturing_span)) = opaque.precise_capturing_args
{
let mut explicitly_captured = UnordSet::default();
for arg in captured_args {
match self.tcx.named_bound_var(arg.hir_id()) {
Some(
ResolvedArg::EarlyBound(def_id) | ResolvedArg::LateBound(_, _, def_id),
) => {
if self.tcx.def_kind(self.tcx.parent(def_id)) == DefKind::OpaqueTy {
let (ty::ReEarlyParam(ty::EarlyParamRegion { def_id, .. })
| ty::ReLateParam(ty::LateParamRegion {
bound_region: ty::BoundRegionKind::BrNamed(def_id, _),
..
})) = self
.tcx
.map_opaque_lifetime_to_parent_lifetime(def_id.expect_local())
.kind()
else {
span_bug!(
self.tcx.def_span(def_id),
"variable should have been duplicated from a parent"
);
};
explicitly_captured.insert(def_id);
} else {
explicitly_captured.insert(def_id);
}
}
_ => {
self.tcx.dcx().span_delayed_bug(
self.tcx().hir().span(arg.hir_id()),
"no valid for captured arg",
);
}
}
}
if self
.in_scope_parameters
.iter()
.all(|def_id| explicitly_captured.contains(def_id))
{
self.tcx.emit_node_span_lint(
IMPL_TRAIT_REDUNDANT_CAPTURES,
self.tcx.local_def_id_to_hir_id(opaque_def_id),
opaque_span,
ImplTraitRedundantCapturesLint { capturing_span },
);
}
}
// Walk into the bounds of the opaque, too, since we want to get nested opaques
// in this lint as well. Interestingly, one place that I expect this lint to fire
@ -236,7 +302,6 @@ fn visit_ty(&mut self, t: Ty<'tcx>) -> Self::Result {
}
struct ImplTraitOvercapturesLint<'tcx> {
opaque_span: Span,
uncaptured_spans: Vec<Span>,
self_ty: Ty<'tcx>,
num_captured: usize,
@ -247,7 +312,6 @@ impl<'a> LintDiagnostic<'a, ()> for ImplTraitOvercapturesLint<'_> {
fn decorate_lint<'b>(self, diag: &'b mut rustc_errors::Diag<'a, ()>) {
diag.arg("self_ty", self.self_ty.to_string())
.arg("num_captured", self.num_captured)
.span(self.opaque_span)
.span_note(self.uncaptured_spans, fluent::lint_note)
.note(fluent::lint_note2);
if let Some((suggestion, span)) = self.suggestion {
@ -265,6 +329,13 @@ fn msg(&self) -> rustc_errors::DiagMessage {
}
}
#[derive(LintDiagnostic)]
#[diag(lint_impl_trait_redundant_captures)]
struct ImplTraitRedundantCapturesLint {
#[suggestion(lint_suggestion, code = "", applicability = "machine-applicable")]
capturing_span: Span,
}
fn extract_def_id_from_arg<'tcx>(
tcx: TyCtxt<'tcx>,
generics: &'tcx ty::Generics,

16
compiler/rustc_parse/src/parser/ty.rs
View File

@ -675,8 +675,8 @@ fn parse_impl_ty(&mut self, impl_dyn_multi: &mut bool) -> PResult<'a, TyKind> {
let precise_capturing = if self.eat_keyword(kw::Use) {
let use_span = self.prev_token.span;
self.psess.gated_spans.gate(sym::precise_capturing, use_span);
let args = self.parse_precise_capturing_args()?;
Some(P((args, use_span)))
let (args, args_span) = self.parse_precise_capturing_args()?;
Some(P((args, use_span.to(args_span))))
} else {
None
};
@ -689,9 +689,11 @@ fn parse_impl_ty(&mut self, impl_dyn_multi: &mut bool) -> PResult<'a, TyKind> {
Ok(TyKind::ImplTrait(ast::DUMMY_NODE_ID, bounds, precise_capturing))
}
fn parse_precise_capturing_args(&mut self) -> PResult<'a, ThinVec<PreciseCapturingArg>> {
Ok(self
.parse_unspanned_seq(
fn parse_precise_capturing_args(
&mut self,
) -> PResult<'a, (ThinVec<PreciseCapturingArg>, Span)> {
let lo = self.token.span;
let (args, _) = self.parse_unspanned_seq(
&TokenKind::Lt,
&TokenKind::Gt,
SeqSep::trailing_allowed(token::Comma),
@ -713,8 +715,8 @@ fn parse_precise_capturing_args(&mut self) -> PResult<'a, ThinVec<PreciseCapturi
self_.unexpected_any()
}
},
)?
.0)
)?;
Ok((args, lo.to(self.prev_token.span)))
}
/// Is a `dyn B0 + ... + Bn` type allowed here?

2
tests/ui/impl-trait/precise-capturing/apit.stderr
View File

@ -11,7 +11,7 @@ error: `use<...>` precise capturing syntax not allowed on argument-position `imp
--> $DIR/apit.rs:4:18
|
LL | fn hello(_: impl use<> Sized) {}
| ^^^
| ^^^^^
error: aborting due to 1 previous error; 1 warning emitted

25
tests/ui/impl-trait/precise-capturing/redundant.rs Normal file
View File

@ -0,0 +1,25 @@
//@ compile-flags: -Zunstable-options --edition=2024
//@ check-pass
#![feature(precise_capturing)]
//~^ WARN the feature `precise_capturing` is incomplete
fn hello<'a>() -> impl use<'a> Sized {}
//~^ WARN all possible in-scope parameters are already captured
struct Inherent;
impl Inherent {
fn inherent(&self) -> impl use<'_> Sized {}
//~^ WARN all possible in-scope parameters are already captured
}
trait Test<'a> {
fn in_trait() -> impl use<'a, Self> Sized;
//~^ WARN all possible in-scope parameters are already captured
}
impl<'a> Test<'a> for () {
fn in_trait() -> impl use<'a> Sized {}
//~^ WARN all possible in-scope parameters are already captured
}
fn main() {}

45
tests/ui/impl-trait/precise-capturing/redundant.stderr Normal file
View File

@ -0,0 +1,45 @@
warning: the feature `precise_capturing` is incomplete and may not be safe to use and/or cause compiler crashes
--> $DIR/redundant.rs:4:12
|
LL | #![feature(precise_capturing)]
| ^^^^^^^^^^^^^^^^^
|
= note: see issue #123432 <https://github.com/rust-lang/rust/issues/123432> for more information
= note: `#[warn(incomplete_features)]` on by default
warning: all possible in-scope parameters are already captured, so `use<...>` syntax is redundant
--> $DIR/redundant.rs:7:19
|
LL | fn hello<'a>() -> impl use<'a> Sized {}
| ^^^^^-------^^^^^^
| |
| help: remove the `use<...>` syntax
|
= note: `#[warn(impl_trait_redundant_captures)]` on by default
warning: all possible in-scope parameters are already captured, so `use<...>` syntax is redundant
--> $DIR/redundant.rs:12:27
|
LL | fn inherent(&self) -> impl use<'_> Sized {}
| ^^^^^-------^^^^^^
| |
| help: remove the `use<...>` syntax
warning: all possible in-scope parameters are already captured, so `use<...>` syntax is redundant
--> $DIR/redundant.rs:17:22
|
LL | fn in_trait() -> impl use<'a, Self> Sized;
| ^^^^^-------------^^^^^^
| |
| help: remove the `use<...>` syntax
warning: all possible in-scope parameters are already captured, so `use<...>` syntax is redundant
--> $DIR/redundant.rs:21:22
|
LL | fn in_trait() -> impl use<'a> Sized {}
| ^^^^^-------^^^^^^
| |
| help: remove the `use<...>` syntax
warning: 5 warnings emitted