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When deduplicating diagnostics, look at how it is rendered instead of its internal state #153794

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When deduplicating diagnostics, look at how it is rendered instead of its internal state #153794

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1 change: 1 addition & 0 deletions compiler/rustc_const_eval/src/errors.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -332,6 +332,7 @@ pub struct LongRunning {

#[derive(Diagnostic)]
#[diag("constant evaluation is taking a long time")]
#[note("number of steps elapsed: {$force_duplicate}")]
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@RalfJung RalfJung Mar 12, 2026 •
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This number was not meant to be user-visible. Now that it is, we have to worry about what it represents. It counts how many ConstEvalCounter there have been... I don't actually know when and how those get emitted, and whether it is appropriate to call each of them one "step".

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@oli-obk oli-obk Mar 15, 2026

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I'm fine showing it to users, but we need to filter it in UI tests, otherwise a lot of random changes will keep changing these tests

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@estebank estebank Mar 16, 2026

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An option would be to add an explicit disambiguation field to Diag independent of the message variables.

pub struct LongRunningWarn {
#[primary_span]
#[label("the const evaluator is currently interpreting this expression")]
Expand Down
39 changes: 37 additions & 2 deletions compiler/rustc_errors/src/diagnostic.rs
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Expand Up @@ -9,6 +9,7 @@ use std::thread::panicking;

use rustc_data_structures::sync::DynSend;
use rustc_error_messages::{DiagArgMap, DiagArgName, DiagArgValue, IntoDiagArg};
use rustc_errors::formatting::{format_diag_message, format_diag_messages};
use rustc_lint_defs::{Applicability, LintExpectationId};
use rustc_macros::{Decodable, Encodable};
use rustc_span::source_map::Spanned;
Expand Down Expand Up @@ -350,7 +351,7 @@ impl DiagInner {
}
}

/// Fields used for Hash, and PartialEq trait.
/// Fields used for PartialEq trait.
fn keys(
&self,
) -> (
Expand Down Expand Up @@ -383,7 +384,41 @@ impl Hash for DiagInner {
where
H: Hasher,
{
self.keys().hash(state);
// Instead of using `Self::keys`, we compute the hash for every field because we want to
// ensure that two independent diagnostics that are built from different structured errors
// or through the `Diag` API are equivalent if their *rendered output* is the same, which
// means we have to format the diagnostic messages (and labels) before computing the hash.
self.level.hash(state);
format_diag_messages(&self.messages, &self.args).hash(state);
self.code.hash(state);
for span in self.span.primary_spans() {
span.hash(state);
}
for span_label in self.span.span_labels() {
span_label.span.hash(state);
span_label.is_primary.hash(state);
if let Some(label) = span_label.label {
format_diag_message(&label, &self.args).hash(state);
}
}
for c in &self.children {
c.level.hash(state);
format_diag_messages(&c.messages, &self.args).hash(state);
for span_label in c.span.span_labels() {
span_label.span.hash(state);
span_label.is_primary.hash(state);
if let Some(label) = span_label.label {
format_diag_message(&label, &self.args).hash(state);
}
}
}
for s in self.suggestions.borrow_tag() {
s.style.hash(state);
s.substitutions.hash(state);
format_diag_message(&s.msg, &self.args).hash(state);
s.applicability.hash(state);
}
self.is_lint.hash(state);
}
}

Expand Down
12 changes: 12 additions & 0 deletions compiler/rustc_errors/src/lib.rs
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Expand Up @@ -138,6 +138,14 @@ impl Suggestions {
Suggestions::Disabled => Vec::new(),
}
}

pub fn borrow_tag(&self) -> &[CodeSuggestion] {
match self {
Suggestions::Enabled(suggestions) => &suggestions,
Suggestions::Sealed(suggestions) => &suggestions,
Suggestions::Disabled => &[],
}
}
}

impl Default for Suggestions {
Expand Down Expand Up @@ -1285,8 +1293,12 @@ impl DiagCtxtInner {
let mut hasher = StableHasher::new();
diagnostic.hash(&mut hasher);
let diagnostic_hash = hasher.finish();
tracing::info!(?diagnostic.messages);
tracing::info!(?diagnostic.span);
tracing::info!(?diagnostic_hash);
!self.emitted_diagnostics.insert(diagnostic_hash)
};
tracing::info!(?already_emitted);

let is_error = diagnostic.is_error();
let is_lint = diagnostic.is_lint.is_some();
Expand Down
2 changes: 2 additions & 0 deletions tests/ui/cfg/cfg-stmt-recovery.stderr
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Expand Up @@ -15,6 +15,8 @@ error: removing an expression is not supported in this position
|
LL | let _ = #[cfg(false)] 0;
| ^^^^^^^^^^^^^
|
= note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`

error: aborting due to 3 previous errors

1 change: 1 addition & 0 deletions tests/ui/consts/const-eval/stable-metric/ctfe-simple-loop.allow.stderr
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Expand Up @@ -6,6 +6,7 @@ LL | / while index < n {
LL | | }
| |_____^ the const evaluator is currently interpreting this expression
|
= note: number of steps elapsed: 32
help: the constant being evaluated
--> $DIR/ctfe-simple-loop.rs:20:1
|
Expand Down
1 change: 1 addition & 0 deletions tests/ui/consts/const-eval/stable-metric/ctfe-simple-loop.warn.stderr
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Expand Up @@ -43,6 +43,7 @@ LL | / while index < n {
LL | | }
| |_____^ the const evaluator is currently interpreting this expression
|
= note: number of steps elapsed: 32
help: the constant being evaluated
--> $DIR/ctfe-simple-loop.rs:20:1
|
Expand Down
5 changes: 5 additions & 0 deletions tests/ui/consts/const-eval/stable-metric/evade-deduplication-issue-118612.stderr
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Expand Up @@ -6,6 +6,7 @@ LL | / loop {
LL | | }
| |_____^ the const evaluator is currently interpreting this expression
|
= note: number of steps elapsed: 32
help: the constant being evaluated
--> $DIR/evade-deduplication-issue-118612.rs:6:1
|
Expand All @@ -20,6 +21,7 @@ LL | / loop {
LL | | }
| |_____^ the const evaluator is currently interpreting this expression
|
= note: number of steps elapsed: 64
help: the constant being evaluated
--> $DIR/evade-deduplication-issue-118612.rs:6:1
|
Expand All @@ -34,6 +36,7 @@ LL | / loop {
LL | | }
| |_____^ the const evaluator is currently interpreting this expression
|
= note: number of steps elapsed: 128
help: the constant being evaluated
--> $DIR/evade-deduplication-issue-118612.rs:6:1
|
Expand All @@ -48,6 +51,7 @@ LL | / loop {
LL | | }
| |_____^ the const evaluator is currently interpreting this expression
|
= note: number of steps elapsed: 256
help: the constant being evaluated
--> $DIR/evade-deduplication-issue-118612.rs:6:1
|
Expand All @@ -62,6 +66,7 @@ LL | / loop {
LL | | }
| |_____^ the const evaluator is currently interpreting this expression
|
= note: number of steps elapsed: 512
help: the constant being evaluated
--> $DIR/evade-deduplication-issue-118612.rs:6:1
|
Expand Down
2 changes: 2 additions & 0 deletions tests/ui/coroutine/gen_block.none.stderr
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Expand Up @@ -73,6 +73,7 @@ LL | let _ = || yield true;
= note: see issue #43122 <https://github.com/rust-lang/rust/issues/43122> for more information
= help: add `#![feature(yield_expr)]` to the crate attributes to enable
= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
= note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`

error: `yield` can only be used in `#[coroutine]` closures, or `gen` blocks
--> $DIR/gen_block.rs:16:16
Expand All @@ -94,6 +95,7 @@ LL | let _ = #[coroutine] || yield true;
= note: see issue #43122 <https://github.com/rust-lang/rust/issues/43122> for more information
= help: add `#![feature(yield_expr)]` to the crate attributes to enable
= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
= note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`

error: aborting due to 11 previous errors

Expand Down
2 changes: 2 additions & 0 deletions tests/ui/feature-gates/feature-gate-coroutines.e2024.stderr
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Expand Up @@ -47,6 +47,7 @@ LL | yield true;
= note: see issue #43122 <https://github.com/rust-lang/rust/issues/43122> for more information
= help: add `#![feature(yield_expr)]` to the crate attributes to enable
= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
= note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`

error: `yield` can only be used in `#[coroutine]` closures, or `gen` blocks
--> $DIR/feature-gate-coroutines.rs:5:5
Expand All @@ -68,6 +69,7 @@ LL | let _ = || yield true;
= note: see issue #43122 <https://github.com/rust-lang/rust/issues/43122> for more information
= help: add `#![feature(yield_expr)]` to the crate attributes to enable
= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
= note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`

error: `yield` can only be used in `#[coroutine]` closures, or `gen` blocks
--> $DIR/feature-gate-coroutines.rs:10:16
Expand Down
2 changes: 2 additions & 0 deletions tests/ui/feature-gates/feature-gate-coroutines.none.stderr
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Expand Up @@ -47,6 +47,7 @@ LL | yield true;
= note: see issue #43122 <https://github.com/rust-lang/rust/issues/43122> for more information
= help: add `#![feature(yield_expr)]` to the crate attributes to enable
= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
= note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`

error: `yield` can only be used in `#[coroutine]` closures, or `gen` blocks
--> $DIR/feature-gate-coroutines.rs:5:5
Expand All @@ -68,6 +69,7 @@ LL | let _ = || yield true;
= note: see issue #43122 <https://github.com/rust-lang/rust/issues/43122> for more information
= help: add `#![feature(yield_expr)]` to the crate attributes to enable
= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
= note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`

error: `yield` can only be used in `#[coroutine]` closures, or `gen` blocks
--> $DIR/feature-gate-coroutines.rs:10:16
Expand Down
1 change: 1 addition & 0 deletions tests/ui/feature-gates/feature-gate-yield-expr.stderr
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Expand Up @@ -17,6 +17,7 @@ LL | yield ();
= note: see issue #43122 <https://github.com/rust-lang/rust/issues/43122> for more information
= help: add `#![feature(yield_expr)]` to the crate attributes to enable
= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
= note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`

error: `yield` can only be used in `#[coroutine]` closures, or `gen` blocks
--> $DIR/feature-gate-yield-expr.rs:5:5
Expand Down
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