From ab4891ce740ded668900102453149592f1b5e7d3 Mon Sep 17 00:00:00 2001
From: Jonathan Brouwer <jonathantbrouwer@gmail.com>
Date: Wed, 11 Feb 2026 19:45:04 +0100
Subject: [PATCH] Convert some `impl Subdiagnostic`s to derives

---
 compiler/rustc_ast_passes/src/errors.rs       | 14 +++++-------
 compiler/rustc_lint/src/lints.rs              | 22 +++++--------------
 compiler/rustc_pattern_analysis/src/errors.rs | 14 +++---------
 3 files changed, 14 insertions(+), 36 deletions(-)

diff --git a/compiler/rustc_ast_passes/src/errors.rs b/compiler/rustc_ast_passes/src/errors.rs
index bda04129e579..dd260aede489 100644
--- a/compiler/rustc_ast_passes/src/errors.rs
+++ b/compiler/rustc_ast_passes/src/errors.rs
@@ -3,7 +3,7 @@
 use rustc_abi::ExternAbi;
 use rustc_ast::ParamKindOrd;
 use rustc_errors::codes::*;
-use rustc_errors::{Applicability, Diag, EmissionGuarantee, Subdiagnostic, inline_fluent};
+use rustc_errors::{Applicability, Diag, EmissionGuarantee, Subdiagnostic};
 use rustc_macros::{Diagnostic, LintDiagnostic, Subdiagnostic};
 use rustc_span::{Ident, Span, Symbol};
 
@@ -927,19 +927,15 @@ pub(crate) struct FeatureOnNonNightly {
     pub sugg: Option<Span>,
 }
 
+#[derive(Subdiagnostic)]
+#[help(
+    "the feature `{$name}` has been stable since `{$since}` and no longer requires an attribute to enable"
+)]
 pub(crate) struct StableFeature {
     pub name: Symbol,
     pub since: Symbol,
 }
 
-impl Subdiagnostic for StableFeature {
-    fn add_to_diag<G: EmissionGuarantee>(self, diag: &mut Diag<'_, G>) {
-        diag.arg("name", self.name);
-        diag.arg("since", self.since);
-        diag.help(inline_fluent!("the feature `{$name}` has been stable since `{$since}` and no longer requires an attribute to enable"));
-    }
-}
-
 #[derive(Diagnostic)]
 #[diag("`{$f1}` and `{$f2}` are incompatible, using them at the same time is not allowed")]
 #[help("remove one of these features")]
diff --git a/compiler/rustc_lint/src/lints.rs b/compiler/rustc_lint/src/lints.rs
index 0aa5199cffc6..15414c287a85 100644
--- a/compiler/rustc_lint/src/lints.rs
+++ b/compiler/rustc_lint/src/lints.rs
@@ -1975,27 +1975,17 @@ pub(crate) struct OverflowingBinHex<'a> {
     pub sign_bit_sub: Option<OverflowingBinHexSignBitSub<'a>>,
 }
 
+#[derive(Subdiagnostic)]
 pub(crate) enum OverflowingBinHexSign {
+    #[note(
+        "the literal `{$lit}` (decimal `{$dec}`) does not fit into the type `{$ty}` and will become `{$actually}{$ty}`"
+    )]
     Positive,
+    #[note("the literal `{$lit}` (decimal `{$dec}`) does not fit into the type `{$ty}`")]
+    #[note("and the value `-{$lit}` will become `{$actually}{$ty}`")]
     Negative,
 }
 
-impl Subdiagnostic for OverflowingBinHexSign {
-    fn add_to_diag<G: EmissionGuarantee>(self, diag: &mut Diag<'_, G>) {
-        match self {
-            OverflowingBinHexSign::Positive => {
-                diag.note(inline_fluent!("the literal `{$lit}` (decimal `{$dec}`) does not fit into the type `{$ty}` and will become `{$actually}{$ty}`"));
-            }
-            OverflowingBinHexSign::Negative => {
-                diag.note(inline_fluent!(
-                    "the literal `{$lit}` (decimal `{$dec}`) does not fit into the type `{$ty}`"
-                ));
-                diag.note(inline_fluent!("and the value `-{$lit}` will become `{$actually}{$ty}`"));
-            }
-        }
-    }
-}
-
 #[derive(Subdiagnostic)]
 pub(crate) enum OverflowingBinHexSub<'a> {
     #[suggestion(
diff --git a/compiler/rustc_pattern_analysis/src/errors.rs b/compiler/rustc_pattern_analysis/src/errors.rs
index 64d4ff422043..e7448613cc14 100644
--- a/compiler/rustc_pattern_analysis/src/errors.rs
+++ b/compiler/rustc_pattern_analysis/src/errors.rs
@@ -56,22 +56,14 @@ pub struct OverlappingRangeEndpoints {
     pub overlap: Vec<Overlap>,
 }
 
+#[derive(Subdiagnostic)]
+#[label("this range overlaps on `{$range}`...")]
 pub struct Overlap {
+    #[primary_span]
     pub span: Span,
     pub range: String, // a printed pattern
 }
 
-impl Subdiagnostic for Overlap {
-    fn add_to_diag<G: EmissionGuarantee>(self, diag: &mut Diag<'_, G>) {
-        let Overlap { span, range } = self;
-
-        // FIXME(mejrs) unfortunately `#[derive(LintDiagnostic)]`
-        // does not support `#[subdiagnostic(eager)]`...
-        let message = format!("this range overlaps on `{range}`...");
-        diag.span_label(span, message);
-    }
-}
-
 #[derive(LintDiagnostic)]
 #[diag("exclusive range missing `{$max}`")]
 pub struct ExclusiveRangeMissingMax {