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Handle stashing of delayed bugs.
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By just emitting them immediately, because it does happen in practice,
when errors are downgraded to delayed bugs.

We already had one case in `lint.rs` where we handled this at the
callsite. This commit changes things so it's handled within
`stash_diagnostic` instead, because #121812 identified a second case,
and it's possible there are more.

Fixes #121812.
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nnethercote committed Feb 29, 2024
1 parent 721c741 commit 5607da0
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Showing 2 changed files with 27 additions and 21 deletions.
36 changes: 25 additions & 11 deletions compiler/rustc_errors/src/lib.rs
Original file line number Diff line number Diff line change
Expand Up @@ -712,33 +712,47 @@ impl DiagCtxt {
/// Stashes a diagnostic for possible later improvement in a different,
/// later stage of the compiler. Possible actions depend on the diagnostic
/// level:
/// - Level::Bug, Level:Fatal: not allowed, will trigger a panic.
/// - Level::Error: immediately counted as an error that has occurred, because it
/// is guaranteed to be emitted eventually. Can be later accessed with the
/// provided `span` and `key` through
/// [`DiagCtxt::try_steal_modify_and_emit_err`] or
/// [`DiagCtxt::try_steal_replace_and_emit_err`]. These do not allow
/// cancellation or downgrading of the error. Returns
/// `Some(ErrorGuaranteed)`.
/// - Level::DelayedBug: this does happen occasionally with errors that are
/// downgraded to delayed bugs. It is not stashed, but immediately
/// emitted as a delayed bug. This is because stashing it would cause it
/// to be counted by `err_count` which we don't want. It doesn't matter
/// that we cannot steal and improve it later, because it's not a
/// user-facing error. Returns `Some(ErrorGuaranteed)` as is normal for
/// delayed bugs.
/// - Level::Warning and lower (i.e. !is_error()): can be accessed with the
/// provided `span` and `key` through [`DiagCtxt::steal_non_err()`]. This
/// allows cancelling and downgrading of the diagnostic. Returns `None`.
/// - Others: not allowed, will trigger a panic.
pub fn stash_diagnostic(
&self,
span: Span,
key: StashKey,
diag: DiagInner,
) -> Option<ErrorGuaranteed> {
let guar = if diag.level() == Level::Error {
// This `unchecked_error_guaranteed` is valid. It is where the
// `ErrorGuaranteed` for stashed errors originates. See
// `DiagCtxtInner::drop`.
#[allow(deprecated)]
Some(ErrorGuaranteed::unchecked_error_guaranteed())
} else if !diag.is_error() {
None
} else {
self.span_bug(span, format!("invalid level in `stash_diagnostic`: {}", diag.level));
let guar = match diag.level {
Bug | Fatal => {
self.span_bug(
span,
format!("invalid level in `stash_diagnostic`: {:?}", diag.level),
);
}
Error => {
// This `unchecked_error_guaranteed` is valid. It is where the
// `ErrorGuaranteed` for stashed errors originates. See
// `DiagCtxtInner::drop`.
#[allow(deprecated)]
Some(ErrorGuaranteed::unchecked_error_guaranteed())
}
DelayedBug => return self.inner.borrow_mut().emit_diagnostic(diag),
ForceWarning(_) | Warning | Note | OnceNote | Help | OnceHelp | FailureNote | Allow
| Expect(_) => None,
};

// FIXME(Centril, #69537): Consider reintroducing panic on overwriting a stashed diagnostic
Expand Down
12 changes: 2 additions & 10 deletions compiler/rustc_hir_analysis/src/astconv/lint.rs
Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
use rustc_ast::TraitObjectSyntax;
use rustc_errors::{codes::*, Diag, EmissionGuarantee, Level, StashKey};
use rustc_errors::{codes::*, Diag, EmissionGuarantee, StashKey};
use rustc_hir as hir;
use rustc_hir::def::{DefKind, Res};
use rustc_lint_defs::{builtin::BARE_TRAIT_OBJECTS, Applicability};
Expand Down Expand Up @@ -237,15 +237,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
}
// check if the impl trait that we are considering is a impl of a local trait
self.maybe_lint_blanket_trait_impl(self_ty, &mut diag);
match diag.level() {
Level::Error => {
diag.stash(self_ty.span, StashKey::TraitMissingMethod);
}
Level::DelayedBug => {
diag.emit();
}
_ => unreachable!(),
}
diag.stash(self_ty.span, StashKey::TraitMissingMethod);
} else {
let msg = "trait objects without an explicit `dyn` are deprecated";
tcx.node_span_lint(BARE_TRAIT_OBJECTS, self_ty.hir_id, self_ty.span, msg, |lint| {
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