rustc_middle/lint.rs
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use std::cmp;
use rustc_data_structures::fx::FxIndexMap;
use rustc_data_structures::sorted_map::SortedMap;
use rustc_errors::{Diag, MultiSpan};
use rustc_hir::{HirId, ItemLocalId};
use rustc_macros::HashStable;
use rustc_session::Session;
use rustc_session::lint::builtin::{self, FORBIDDEN_LINT_GROUPS};
use rustc_session::lint::{FutureIncompatibilityReason, Level, Lint, LintExpectationId, LintId};
use rustc_span::hygiene::{ExpnKind, MacroKind};
use rustc_span::{DUMMY_SP, DesugaringKind, Span, Symbol, symbol};
use tracing::instrument;
use crate::ty::TyCtxt;
/// How a lint level was set.
#[derive(Clone, Copy, PartialEq, Eq, HashStable, Debug)]
pub enum LintLevelSource {
/// Lint is at the default level as declared in rustc.
Default,
/// Lint level was set by an attribute.
Node {
name: Symbol,
span: Span,
/// RFC 2383 reason
reason: Option<Symbol>,
},
/// Lint level was set by a command-line flag.
/// The provided `Level` is the level specified on the command line.
/// (The actual level may be lower due to `--cap-lints`.)
CommandLine(Symbol, Level),
}
impl LintLevelSource {
pub fn name(&self) -> Symbol {
match *self {
LintLevelSource::Default => symbol::kw::Default,
LintLevelSource::Node { name, .. } => name,
LintLevelSource::CommandLine(name, _) => name,
}
}
pub fn span(&self) -> Span {
match *self {
LintLevelSource::Default => DUMMY_SP,
LintLevelSource::Node { span, .. } => span,
LintLevelSource::CommandLine(_, _) => DUMMY_SP,
}
}
}
/// A tuple of a lint level and its source.
pub type LevelAndSource = (Level, LintLevelSource);
/// Return type for the `shallow_lint_levels_on` query.
///
/// This map represents the set of allowed lints and allowance levels given
/// by the attributes for *a single HirId*.
#[derive(Default, Debug, HashStable)]
pub struct ShallowLintLevelMap {
pub expectations: Vec<(LintExpectationId, LintExpectation)>,
pub specs: SortedMap<ItemLocalId, FxIndexMap<LintId, LevelAndSource>>,
}
/// From an initial level and source, verify the effect of special annotations:
/// `warnings` lint level and lint caps.
///
/// The return of this function is suitable for diagnostics.
pub fn reveal_actual_level(
level: Option<Level>,
src: &mut LintLevelSource,
sess: &Session,
lint: LintId,
probe_for_lint_level: impl FnOnce(LintId) -> (Option<Level>, LintLevelSource),
) -> Level {
// If `level` is none then we actually assume the default level for this lint.
let mut level = level.unwrap_or_else(|| lint.lint.default_level(sess.edition()));
// If we're about to issue a warning, check at the last minute for any
// directives against the warnings "lint". If, for example, there's an
// `allow(warnings)` in scope then we want to respect that instead.
//
// We exempt `FORBIDDEN_LINT_GROUPS` from this because it specifically
// triggers in cases (like #80988) where you have `forbid(warnings)`,
// and so if we turned that into an error, it'd defeat the purpose of the
// future compatibility warning.
if level == Level::Warn && lint != LintId::of(FORBIDDEN_LINT_GROUPS) {
let (warnings_level, warnings_src) = probe_for_lint_level(LintId::of(builtin::WARNINGS));
if let Some(configured_warning_level) = warnings_level {
if configured_warning_level != Level::Warn {
level = configured_warning_level;
*src = warnings_src;
}
}
}
// Ensure that we never exceed the `--cap-lints` argument unless the source is a --force-warn
level = if let LintLevelSource::CommandLine(_, Level::ForceWarn(_)) = src {
level
} else {
cmp::min(level, sess.opts.lint_cap.unwrap_or(Level::Forbid))
};
if let Some(driver_level) = sess.driver_lint_caps.get(&lint) {
// Ensure that we never exceed driver level.
level = cmp::min(*driver_level, level);
}
level
}
impl ShallowLintLevelMap {
/// Perform a deep probe in the HIR tree looking for the actual level for the lint.
/// This lint level is not usable for diagnostics, it needs to be corrected by
/// `reveal_actual_level` beforehand.
#[instrument(level = "trace", skip(self, tcx), ret)]
fn probe_for_lint_level(
&self,
tcx: TyCtxt<'_>,
id: LintId,
start: HirId,
) -> (Option<Level>, LintLevelSource) {
if let Some(map) = self.specs.get(&start.local_id)
&& let Some(&(level, src)) = map.get(&id)
{
return (Some(level), src);
}
let mut owner = start.owner;
let mut specs = &self.specs;
for parent in tcx.hir().parent_id_iter(start) {
if parent.owner != owner {
owner = parent.owner;
specs = &tcx.shallow_lint_levels_on(owner).specs;
}
if let Some(map) = specs.get(&parent.local_id)
&& let Some(&(level, src)) = map.get(&id)
{
return (Some(level), src);
}
}
(None, LintLevelSource::Default)
}
/// Fetch and return the user-visible lint level for the given lint at the given HirId.
#[instrument(level = "trace", skip(self, tcx), ret)]
pub fn lint_level_id_at_node(
&self,
tcx: TyCtxt<'_>,
lint: LintId,
cur: HirId,
) -> (Level, LintLevelSource) {
let (level, mut src) = self.probe_for_lint_level(tcx, lint, cur);
let level = reveal_actual_level(level, &mut src, tcx.sess, lint, |lint| {
self.probe_for_lint_level(tcx, lint, cur)
});
(level, src)
}
}
impl TyCtxt<'_> {
/// Fetch and return the user-visible lint level for the given lint at the given HirId.
pub fn lint_level_at_node(self, lint: &'static Lint, id: HirId) -> (Level, LintLevelSource) {
self.shallow_lint_levels_on(id.owner).lint_level_id_at_node(self, LintId::of(lint), id)
}
}
/// This struct represents a lint expectation and holds all required information
/// to emit the `unfulfilled_lint_expectations` lint if it is unfulfilled after
/// the `LateLintPass` has completed.
#[derive(Clone, Debug, HashStable)]
pub struct LintExpectation {
/// The reason for this expectation that can optionally be added as part of
/// the attribute. It will be displayed as part of the lint message.
pub reason: Option<Symbol>,
/// The [`Span`] of the attribute that this expectation originated from.
pub emission_span: Span,
/// Lint messages for the `unfulfilled_lint_expectations` lint will be
/// adjusted to include an additional note. Therefore, we have to track if
/// the expectation is for the lint.
pub is_unfulfilled_lint_expectations: bool,
/// This will hold the name of the tool that this lint belongs to. For
/// the lint `clippy::some_lint` the tool would be `clippy`, the same
/// goes for `rustdoc`. This will be `None` for rustc lints
pub lint_tool: Option<Symbol>,
}
impl LintExpectation {
pub fn new(
reason: Option<Symbol>,
emission_span: Span,
is_unfulfilled_lint_expectations: bool,
lint_tool: Option<Symbol>,
) -> Self {
Self { reason, emission_span, is_unfulfilled_lint_expectations, lint_tool }
}
}
pub fn explain_lint_level_source(
lint: &'static Lint,
level: Level,
src: LintLevelSource,
err: &mut Diag<'_, ()>,
) {
let name = lint.name_lower();
if let Level::Allow = level {
// Do not point at `#[allow(compat_lint)]` as the reason for a compatibility lint
// triggering. (#121009)
return;
}
match src {
LintLevelSource::Default => {
err.note_once(format!("`#[{}({})]` on by default", level.as_str(), name));
}
LintLevelSource::CommandLine(lint_flag_val, orig_level) => {
let flag = orig_level.to_cmd_flag();
let hyphen_case_lint_name = name.replace('_', "-");
if lint_flag_val.as_str() == name {
err.note_once(format!(
"requested on the command line with `{flag} {hyphen_case_lint_name}`"
));
} else {
let hyphen_case_flag_val = lint_flag_val.as_str().replace('_', "-");
err.note_once(format!(
"`{flag} {hyphen_case_lint_name}` implied by `{flag} {hyphen_case_flag_val}`"
));
if matches!(orig_level, Level::Warn | Level::Deny) {
err.help_once(format!(
"to override `{flag} {hyphen_case_flag_val}` add `#[allow({name})]`"
));
}
}
}
LintLevelSource::Node { name: lint_attr_name, span, reason, .. } => {
if let Some(rationale) = reason {
err.note(rationale.to_string());
}
err.span_note_once(span, "the lint level is defined here");
if lint_attr_name.as_str() != name {
let level_str = level.as_str();
err.note_once(format!(
"`#[{level_str}({name})]` implied by `#[{level_str}({lint_attr_name})]`"
));
}
}
}
}
/// The innermost function for emitting lints.
///
/// If you are looking to implement a lint, look for higher level functions,
/// for example:
/// - [`TyCtxt::emit_node_span_lint`]
/// - [`TyCtxt::node_span_lint`]
/// - [`TyCtxt::emit_node_lint`]
/// - [`TyCtxt::node_lint`]
/// - `LintContext::opt_span_lint`
///
/// ## `decorate`
///
/// It is not intended to call `emit`/`cancel` on the `Diag` passed in the `decorate` callback.
#[track_caller]
pub fn lint_level(
sess: &Session,
lint: &'static Lint,
level: Level,
src: LintLevelSource,
span: Option<MultiSpan>,
decorate: impl for<'a, 'b> FnOnce(&'b mut Diag<'a, ()>),
) {
// Avoid codegen bloat from monomorphization by immediately doing dyn dispatch of `decorate` to
// the "real" work.
#[track_caller]
fn lint_level_impl(
sess: &Session,
lint: &'static Lint,
level: Level,
src: LintLevelSource,
span: Option<MultiSpan>,
decorate: Box<dyn '_ + for<'a, 'b> FnOnce(&'b mut Diag<'a, ()>)>,
) {
// Check for future incompatibility lints and issue a stronger warning.
let future_incompatible = lint.future_incompatible;
let has_future_breakage = future_incompatible.map_or(
// Default allow lints trigger too often for testing.
sess.opts.unstable_opts.future_incompat_test && lint.default_level != Level::Allow,
|incompat| {
matches!(
incompat.reason,
FutureIncompatibilityReason::FutureReleaseErrorReportInDeps
)
},
);
// Convert lint level to error level.
let err_level = match level {
Level::Allow => {
if has_future_breakage {
rustc_errors::Level::Allow
} else {
return;
}
}
Level::Expect(expect_id) => {
// This case is special as we actually allow the lint itself in this context, but
// we can't return early like in the case for `Level::Allow` because we still
// need the lint diagnostic to be emitted to `rustc_error::DiagCtxtInner`.
//
// We can also not mark the lint expectation as fulfilled here right away, as it
// can still be cancelled in the decorate function. All of this means that we simply
// create a `Diag` and continue as we would for warnings.
rustc_errors::Level::Expect(expect_id)
}
Level::ForceWarn(Some(expect_id)) => rustc_errors::Level::ForceWarning(Some(expect_id)),
Level::ForceWarn(None) => rustc_errors::Level::ForceWarning(None),
Level::Warn => rustc_errors::Level::Warning,
Level::Deny | Level::Forbid => rustc_errors::Level::Error,
};
let mut err = Diag::new(sess.dcx(), err_level, "");
if let Some(span) = span {
err.span(span);
}
// If this code originates in a foreign macro, aka something that this crate
// did not itself author, then it's likely that there's nothing this crate
// can do about it. We probably want to skip the lint entirely.
if err.span.primary_spans().iter().any(|s| in_external_macro(sess, *s)) {
// Any suggestions made here are likely to be incorrect, so anything we
// emit shouldn't be automatically fixed by rustfix.
err.disable_suggestions();
// If this is a future incompatible that is not an edition fixing lint
// it'll become a hard error, so we have to emit *something*. Also,
// if this lint occurs in the expansion of a macro from an external crate,
// allow individual lints to opt-out from being reported.
let incompatible = future_incompatible.is_some_and(|f| f.reason.edition().is_none());
if !incompatible && !lint.report_in_external_macro {
err.cancel();
// Don't continue further, since we don't want to have
// `diag_span_note_once` called for a diagnostic that isn't emitted.
return;
}
}
err.is_lint(lint.name_lower(), has_future_breakage);
// Lint diagnostics that are covered by the expect level will not be emitted outside
// the compiler. It is therefore not necessary to add any information for the user.
// This will therefore directly call the decorate function which will in turn emit
// the diagnostic.
if let Level::Expect(_) = level {
decorate(&mut err);
err.emit();
return;
}
if let Some(future_incompatible) = future_incompatible {
let explanation = match future_incompatible.reason {
FutureIncompatibilityReason::FutureReleaseErrorDontReportInDeps
| FutureIncompatibilityReason::FutureReleaseErrorReportInDeps => {
"this was previously accepted by the compiler but is being phased out; \
it will become a hard error in a future release!"
.to_owned()
}
FutureIncompatibilityReason::FutureReleaseSemanticsChange => {
"this will change its meaning in a future release!".to_owned()
}
FutureIncompatibilityReason::EditionError(edition) => {
let current_edition = sess.edition();
format!(
"this is accepted in the current edition (Rust {current_edition}) but is a hard error in Rust {edition}!"
)
}
FutureIncompatibilityReason::EditionSemanticsChange(edition) => {
format!("this changes meaning in Rust {edition}")
}
FutureIncompatibilityReason::Custom(reason) => reason.to_owned(),
};
if future_incompatible.explain_reason {
err.warn(explanation);
}
if !future_incompatible.reference.is_empty() {
let citation =
format!("for more information, see {}", future_incompatible.reference);
err.note(citation);
}
}
// Finally, run `decorate`. `decorate` can call `trimmed_path_str` (directly or indirectly),
// so we need to make sure when we do call `decorate` that the diagnostic is eventually
// emitted or we'll get a `must_produce_diag` ICE.
//
// When is a diagnostic *eventually* emitted? Well, that is determined by 2 factors:
// 1. If the corresponding `rustc_errors::Level` is beyond warning, i.e. `ForceWarning(_)`
// or `Error`, then the diagnostic will be emitted regardless of CLI options.
// 2. If the corresponding `rustc_errors::Level` is warning, then that can be affected by
// `-A warnings` or `--cap-lints=xxx` on the command line. In which case, the diagnostic
// will be emitted if `can_emit_warnings` is true.
let skip = err_level == rustc_errors::Level::Warning && !sess.dcx().can_emit_warnings();
if !skip {
decorate(&mut err);
}
explain_lint_level_source(lint, level, src, &mut err);
err.emit()
}
lint_level_impl(sess, lint, level, src, span, Box::new(decorate))
}
/// Returns whether `span` originates in a foreign crate's external macro.
///
/// This is used to test whether a lint should not even begin to figure out whether it should
/// be reported on the current node.
pub fn in_external_macro(sess: &Session, span: Span) -> bool {
let expn_data = span.ctxt().outer_expn_data();
match expn_data.kind {
ExpnKind::Root
| ExpnKind::Desugaring(
DesugaringKind::ForLoop
| DesugaringKind::WhileLoop
| DesugaringKind::OpaqueTy
| DesugaringKind::Async
| DesugaringKind::Await,
) => false,
ExpnKind::AstPass(_) | ExpnKind::Desugaring(_) => true, // well, it's "external"
ExpnKind::Macro(MacroKind::Bang, _) => {
// Dummy span for the `def_site` means it's an external macro.
expn_data.def_site.is_dummy() || sess.source_map().is_imported(expn_data.def_site)
}
ExpnKind::Macro { .. } => true, // definitely a plugin
}
}
/// Return whether `span` is generated by `async` or `await`.
pub fn is_from_async_await(span: Span) -> bool {
let expn_data = span.ctxt().outer_expn_data();
match expn_data.kind {
ExpnKind::Desugaring(DesugaringKind::Async | DesugaringKind::Await) => true,
_ => false,
}
}