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Auto merge of rust-lang#130050 - cjgillot:expect-attr-id, r=<try>
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Enumerate lint expectations using AttrId

This PR implements the idea I outlined in rust-lang#127884 (comment)

We can uniquely identify a lint expectation `#[expect(lint0, lint1...)]` using the `AttrId` and the index of the lint inside the attribute. This PR uses this property in `check_expectations`.

In addition, this PR stops stashing expected diagnostics to wait for the unstable -> stable `LintExpectationId` mapping: if the lint is emitted with an unstable attribute, it must have been emitted by an `eval_always` query (like inside the resolver), so won't be loaded from cache. Decoding an `AttrId` from the on-disk cache ICEs, so we have no risk of accidentally checking an expectation.

Fixes rust-lang#127884

cc `@xFrednet`
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bors committed Sep 6, 2024
2 parents 26b5599 + 94f8347 commit f42cfbb
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Showing 5 changed files with 73 additions and 167 deletions.
24 changes: 2 additions & 22 deletions compiler/rustc_errors/src/diagnostic.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -8,11 +8,11 @@ use std::thread::panicking;

use rustc_data_structures::fx::FxIndexMap;
use rustc_error_messages::{fluent_value_from_str_list_sep_by_and, FluentValue};
use rustc_lint_defs::{Applicability, LintExpectationId};
use rustc_lint_defs::Applicability;
use rustc_macros::{Decodable, Encodable};
use rustc_span::source_map::Spanned;
use rustc_span::symbol::Symbol;
use rustc_span::{AttrId, Span, DUMMY_SP};
use rustc_span::{Span, DUMMY_SP};
use tracing::debug;

use crate::snippet::Style;
Expand Down Expand Up @@ -354,26 +354,6 @@ impl DiagInner {
}
}

pub(crate) fn update_unstable_expectation_id(
&mut self,
unstable_to_stable: &FxIndexMap<AttrId, LintExpectationId>,
) {
if let Level::Expect(expectation_id) | Level::ForceWarning(Some(expectation_id)) =
&mut self.level
&& let LintExpectationId::Unstable { attr_id, lint_index } = *expectation_id
{
// The unstable to stable map only maps the unstable `AttrId` to a stable `HirId` with an attribute index.
// The lint index inside the attribute is manually transferred here.
let Some(stable_id) = unstable_to_stable.get(&attr_id) else {
panic!("{expectation_id:?} must have a matching stable id")
};

let mut stable_id = *stable_id;
stable_id.set_lint_index(lint_index);
*expectation_id = stable_id;
}
}

/// Indicates whether this diagnostic should show up in cargo's future breakage report.
pub(crate) fn has_future_breakage(&self) -> bool {
matches!(self.is_lint, Some(IsLint { has_future_breakage: true, .. }))
Expand Down
101 changes: 15 additions & 86 deletions compiler/rustc_errors/src/lib.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -69,7 +69,7 @@ use rustc_macros::{Decodable, Encodable};
pub use rustc_span::fatal_error::{FatalError, FatalErrorMarker};
use rustc_span::source_map::SourceMap;
pub use rustc_span::ErrorGuaranteed;
use rustc_span::{AttrId, Loc, Span, DUMMY_SP};
use rustc_span::{Loc, Span, DUMMY_SP};
pub use snippet::Style;
// Used by external projects such as `rust-gpu`.
// See https://github.com/rust-lang/rust/pull/115393.
Expand Down Expand Up @@ -497,28 +497,18 @@ struct DiagCtxtInner {

future_breakage_diagnostics: Vec<DiagInner>,

/// The [`Self::unstable_expect_diagnostics`] should be empty when this struct is
/// dropped. However, it can have values if the compilation is stopped early
/// or is only partially executed. To avoid ICEs, like in rust#94953 we only
/// check if [`Self::unstable_expect_diagnostics`] is empty, if the expectation ids
/// have been converted.
check_unstable_expect_diagnostics: bool,

/// Expected [`DiagInner`][struct@diagnostic::DiagInner]s store a [`LintExpectationId`] as part
/// of the lint level. [`LintExpectationId`]s created early during the compilation
/// (before `HirId`s have been defined) are not stable and can therefore not be
/// stored on disk. This buffer stores these diagnostics until the ID has been
/// replaced by a stable [`LintExpectationId`]. The [`DiagInner`][struct@diagnostic::DiagInner]s
/// are submitted for storage and added to the list of fulfilled expectations.
unstable_expect_diagnostics: Vec<DiagInner>,

/// expected diagnostic will have the level `Expect` which additionally
/// carries the [`LintExpectationId`] of the expectation that can be
/// marked as fulfilled. This is a collection of all [`LintExpectationId`]s
/// that have been marked as fulfilled this way.
///
/// [RFC-2383]: https://rust-lang.github.io/rfcs/2383-lint-reasons.html
fulfilled_expectations: FxHashSet<LintExpectationId>,
fulfilled_expectations: FxIndexSet<LintExpectationId>,

/// Whether `fulfilled_expectations` has been stolen. This is used to ICE in case we emit
/// an expectation diagnostic after stealing it, which means that expectation would not be
/// correctly handled.
stolen_fulfilled_expectations: bool,

/// The file where the ICE information is stored. This allows delayed_span_bug backtraces to be
/// stored along side the main panic backtrace.
Expand Down Expand Up @@ -605,13 +595,6 @@ impl Drop for DiagCtxtInner {
);
}
}

if self.check_unstable_expect_diagnostics {
assert!(
self.unstable_expect_diagnostics.is_empty(),
"all diagnostics with unstable expectations should have been converted",
);
}
}
}

Expand Down Expand Up @@ -740,9 +723,8 @@ impl DiagCtxt {
emitted_diagnostics,
stashed_diagnostics,
future_breakage_diagnostics,
check_unstable_expect_diagnostics,
unstable_expect_diagnostics,
fulfilled_expectations,
stolen_fulfilled_expectations: _,
ice_file: _,
} = inner.deref_mut();

Expand All @@ -761,8 +743,6 @@ impl DiagCtxt {
*emitted_diagnostics = Default::default();
*stashed_diagnostics = Default::default();
*future_breakage_diagnostics = Default::default();
*check_unstable_expect_diagnostics = false;
*unstable_expect_diagnostics = Default::default();
*fulfilled_expectations = Default::default();
}

Expand Down Expand Up @@ -1094,44 +1074,11 @@ impl<'a> DiagCtxtHandle<'a> {
inner.emitter.emit_unused_externs(lint_level, unused_externs)
}

pub fn update_unstable_expectation_id(
&self,
unstable_to_stable: FxIndexMap<AttrId, LintExpectationId>,
) {
let mut inner = self.inner.borrow_mut();
let diags = std::mem::take(&mut inner.unstable_expect_diagnostics);
inner.check_unstable_expect_diagnostics = true;

if !diags.is_empty() {
inner.suppressed_expected_diag = true;
for mut diag in diags.into_iter() {
diag.update_unstable_expectation_id(&unstable_to_stable);

// Here the diagnostic is given back to `emit_diagnostic` where it was first
// intercepted. Now it should be processed as usual, since the unstable expectation
// id is now stable.
inner.emit_diagnostic(diag, self.tainted_with_errors);
}
}

inner
.stashed_diagnostics
.values_mut()
.for_each(|(diag, _guar)| diag.update_unstable_expectation_id(&unstable_to_stable));
inner
.future_breakage_diagnostics
.iter_mut()
.for_each(|diag| diag.update_unstable_expectation_id(&unstable_to_stable));
}

/// This methods steals all [`LintExpectationId`]s that are stored inside
/// [`DiagCtxtInner`] and indicate that the linked expectation has been fulfilled.
#[must_use]
pub fn steal_fulfilled_expectation_ids(&self) -> FxHashSet<LintExpectationId> {
assert!(
self.inner.borrow().unstable_expect_diagnostics.is_empty(),
"`DiagCtxtInner::unstable_expect_diagnostics` should be empty at this point",
);
pub fn steal_fulfilled_expectation_ids(&self) -> FxIndexSet<LintExpectationId> {
self.inner.borrow_mut().stolen_fulfilled_expectations = true;
std::mem::take(&mut self.inner.borrow_mut().fulfilled_expectations)
}

Expand Down Expand Up @@ -1440,9 +1387,8 @@ impl DiagCtxtInner {
emitted_diagnostics: Default::default(),
stashed_diagnostics: Default::default(),
future_breakage_diagnostics: Vec::new(),
check_unstable_expect_diagnostics: false,
unstable_expect_diagnostics: Vec::new(),
fulfilled_expectations: Default::default(),
stolen_fulfilled_expectations: false,
ice_file: None,
}
}
Expand Down Expand Up @@ -1471,24 +1417,6 @@ impl DiagCtxtInner {
mut diagnostic: DiagInner,
taint: Option<&Cell<Option<ErrorGuaranteed>>>,
) -> Option<ErrorGuaranteed> {
match diagnostic.level {
Expect(expect_id) | ForceWarning(Some(expect_id)) => {
// The `LintExpectationId` can be stable or unstable depending on when it was
// created. Diagnostics created before the definition of `HirId`s are unstable and
// can not yet be stored. Instead, they are buffered until the `LintExpectationId`
// is replaced by a stable one by the `LintLevelsBuilder`.
if let LintExpectationId::Unstable { .. } = expect_id {
// We don't call TRACK_DIAGNOSTIC because we wait for the
// unstable ID to be updated, whereupon the diagnostic will be
// passed into this method again.
self.unstable_expect_diagnostics.push(diagnostic);
return None;
}
// Continue through to the `Expect`/`ForceWarning` case below.
}
_ => {}
}

if diagnostic.has_future_breakage() {
// Future breakages aren't emitted if they're `Level::Allow` or
// `Level::Expect`, but they still need to be constructed and
Expand Down Expand Up @@ -1564,9 +1492,10 @@ impl DiagCtxtInner {
return None;
}
Expect(expect_id) | ForceWarning(Some(expect_id)) => {
if let LintExpectationId::Unstable { .. } = expect_id {
unreachable!(); // this case was handled at the top of this function
}
assert!(
!self.stolen_fulfilled_expectations,
"Attempting to emit an expected diagnostic after `check_expectations`.",
);
self.fulfilled_expectations.insert(expect_id);
if let Expect(_) = diagnostic.level {
// Nothing emitted here for expected lints.
Expand Down
90 changes: 39 additions & 51 deletions compiler/rustc_lint/src/expect.rs
View file
Original file line number Diff line number Diff line change
@@ -1,10 +1,10 @@
use rustc_data_structures::fx::FxIndexMap;
use rustc_hir::{HirId, CRATE_OWNER_ID};
use rustc_data_structures::fx::FxHashSet;
use rustc_hir::CRATE_OWNER_ID;
use rustc_middle::lint::LintExpectation;
use rustc_middle::query::Providers;
use rustc_middle::ty::TyCtxt;
use rustc_session::lint::builtin::UNFULFILLED_LINT_EXPECTATIONS;
use rustc_session::lint::{Level, LintExpectationId};
use rustc_session::lint::LintExpectationId;
use rustc_span::Symbol;

use crate::lints::{Expectation, ExpectationNote};
Expand All @@ -17,68 +17,56 @@ fn lint_expectations(tcx: TyCtxt<'_>, (): ()) -> Vec<(LintExpectationId, LintExp
let krate = tcx.hir_crate_items(());

let mut expectations = Vec::new();
let mut unstable_to_stable_ids = FxIndexMap::default();

let mut record_stable = |attr_id, hir_id, attr_index| {
let expect_id = LintExpectationId::Stable { hir_id, attr_index, lint_index: None };
unstable_to_stable_ids.entry(attr_id).or_insert(expect_id);
};
let mut push_expectations = |owner| {
for owner in std::iter::once(CRATE_OWNER_ID).chain(krate.owners()) {
let lints = tcx.shallow_lint_levels_on(owner);
if lints.expectations.is_empty() {
return;
}

expectations.extend_from_slice(&lints.expectations);

let attrs = tcx.hir_attrs(owner);
for &(local_id, attrs) in attrs.map.iter() {
// Some attributes appear multiple times in HIR, to ensure they are correctly taken
// into account where they matter. This means we cannot just associate the AttrId to
// the first HirId where we see it, but need to check it actually appears in a lint
// level.
// FIXME(cjgillot): Can this cause an attribute to appear in multiple expectation ids?
if !lints.specs.contains_key(&local_id) {
continue;
}
for (attr_index, attr) in attrs.iter().enumerate() {
let Some(Level::Expect(_)) = Level::from_attr(attr) else { continue };
record_stable(attr.id, HirId { owner, local_id }, attr_index.try_into().unwrap());
}
}
};

push_expectations(CRATE_OWNER_ID);
for owner in krate.owners() {
push_expectations(owner);
}

tcx.dcx().update_unstable_expectation_id(unstable_to_stable_ids);
expectations
}

fn check_expectations(tcx: TyCtxt<'_>, tool_filter: Option<Symbol>) {
let lint_expectations = tcx.lint_expectations(());
let fulfilled_expectations = tcx.dcx().steal_fulfilled_expectation_ids();

for (id, expectation) in lint_expectations {
// This check will always be true, since `lint_expectations` only
// holds stable ids
if let LintExpectationId::Stable { hir_id, .. } = id {
if !fulfilled_expectations.contains(id)
&& tool_filter.map_or(true, |filter| expectation.lint_tool == Some(filter))
{
let rationale = expectation.reason.map(|rationale| ExpectationNote { rationale });
let note = expectation.is_unfulfilled_lint_expectations;
tcx.emit_node_span_lint(
UNFULFILLED_LINT_EXPECTATIONS,
*hir_id,
expectation.emission_span,
Expectation { rationale, note },
);
// Turn a `LintExpectationId` into a `(AttrId, lint_index)` pair.
let canonicalize_id = |expect_id: &LintExpectationId| {
match *expect_id {
LintExpectationId::Unstable { attr_id, lint_index: Some(lint_index) } => {
(attr_id, lint_index)
}
LintExpectationId::Stable { hir_id, attr_index, lint_index: Some(lint_index) } => {
// We are an `eval_always` query, so looking at the attribute's `AttrId` is ok.
let attr_id = tcx.hir().attrs(hir_id)[attr_index as usize].id;
(attr_id, lint_index)
}
} else {
_ => panic!("fulfilled expectations must have a lint index"),
}
};

let fulfilled_expectations: FxHashSet<_> =
fulfilled_expectations.iter().map(canonicalize_id).collect();

for (expect_id, expectation) in lint_expectations {
// This check will always be true, since `lint_expectations` only holds stable ids
let LintExpectationId::Stable { hir_id, .. } = expect_id else {
unreachable!("at this stage all `LintExpectationId`s are stable");
};

let expect_id = canonicalize_id(expect_id);

if !fulfilled_expectations.contains(&expect_id)
&& tool_filter.map_or(true, |filter| expectation.lint_tool == Some(filter))
{
let rationale = expectation.reason.map(|rationale| ExpectationNote { rationale });
let note = expectation.is_unfulfilled_lint_expectations;
tcx.emit_node_span_lint(
UNFULFILLED_LINT_EXPECTATIONS,
*hir_id,
expectation.emission_span,
Expectation { rationale, note },
);
}
}
}
9 changes: 9 additions & 0 deletions tests/ui/lint/expect-unused-imports.rs
View file
Original file line number Diff line number Diff line change
@@ -0,0 +1,9 @@
//@ check-pass

#![deny(unused_imports)]
#![deny(unfulfilled_lint_expectations)]

#[expect(unused_imports)]
use std::{io, fs};

fn main() {}
16 changes: 8 additions & 8 deletions tests/ui/lint/rfc-2383-lint-reason/force_warn_expected_lints_fulfilled.stderr
View file
Original file line number Diff line number Diff line change
@@ -1,3 +1,11 @@
warning: denote infinite loops with `loop { ... }`
--> $DIR/force_warn_expected_lints_fulfilled.rs:8:5
|
LL | while true {
| ^^^^^^^^^^ help: use `loop`
|
= note: requested on the command line with `--force-warn while-true`

warning: unused variable: `x`
--> $DIR/force_warn_expected_lints_fulfilled.rs:18:9
|
Expand Down Expand Up @@ -28,13 +36,5 @@ warning: unused variable: `this_should_fulfill_the_expectation`
LL | let this_should_fulfill_the_expectation = "The `#[allow]` has no power here";
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: if this is intentional, prefix it with an underscore: `_this_should_fulfill_the_expectation`

warning: denote infinite loops with `loop { ... }`
--> $DIR/force_warn_expected_lints_fulfilled.rs:8:5
|
LL | while true {
| ^^^^^^^^^^ help: use `loop`
|
= note: requested on the command line with `--force-warn while-true`

warning: 5 warnings emitted

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