From 48fe89f9941ba0b79618e44e0176909ad85decb7 Mon Sep 17 00:00:00 2001
From: mejrs <59372212+mejrs@users.noreply.github.com>
Date: Sun, 26 Apr 2026 14:23:53 +0200
Subject: [PATCH] add default field values to diagnostic FormatArgs

---
 .../src/diagnostics/conflict_errors.rs              |  9 +--------
 compiler/rustc_expand/src/lib.rs                    |  1 +
 compiler/rustc_expand/src/mbe/diagnostics.rs        | 13 +------------
 compiler/rustc_hir/src/attrs/diagnostic.rs          |  7 ++++---
 compiler/rustc_hir/src/lib.rs                       |  1 +
 compiler/rustc_resolve/src/imports.rs               |  7 +------
 6 files changed, 9 insertions(+), 29 deletions(-)

diff --git a/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs b/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
index 2735c800c4a3..f7d35f3ff3b4 100644
--- a/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
@@ -156,14 +156,7 @@ pub(crate) fn report_use_of_moved_or_uninitialized(
                     .collect();
                 generic_args.push((kw::SelfUpper, this.clone()));
 
-                let args = FormatArgs {
-                    this,
-                    // Unused
-                    this_sugared: String::new(),
-                    // Unused
-                    item_context: "",
-                    generic_args,
-                };
+                let args = FormatArgs { this, generic_args, .. };
                 let CustomDiagnostic { message, label, notes, parent_label: _ } =
                     directive.eval(None, &args);
 
diff --git a/compiler/rustc_expand/src/lib.rs b/compiler/rustc_expand/src/lib.rs
index d2ac7103bccb..5068501a0e2d 100644
--- a/compiler/rustc_expand/src/lib.rs
+++ b/compiler/rustc_expand/src/lib.rs
@@ -1,6 +1,7 @@
 // tidy-alphabetical-start
 #![allow(internal_features)]
 #![feature(associated_type_defaults)]
+#![feature(default_field_values)]
 #![feature(macro_metavar_expr)]
 #![feature(proc_macro_diagnostic)]
 #![feature(proc_macro_internals)]
diff --git a/compiler/rustc_expand/src/mbe/diagnostics.rs b/compiler/rustc_expand/src/mbe/diagnostics.rs
index 4e7e51c0a43c..16b21b062cce 100644
--- a/compiler/rustc_expand/src/mbe/diagnostics.rs
+++ b/compiler/rustc_expand/src/mbe/diagnostics.rs
@@ -77,19 +77,8 @@ pub(super) fn failed_to_match_macro(
     let CustomDiagnostic {
         message: custom_message, label: custom_label, notes: custom_notes, ..
     } = {
-        let macro_name = name.to_string();
         on_unmatch_args
-            .map(|directive| {
-                directive.eval(
-                    None,
-                    &FormatArgs {
-                        this: macro_name.clone(),
-                        this_sugared: macro_name,
-                        item_context: "macro invocation",
-                        generic_args: Vec::new(),
-                    },
-                )
-            })
+            .map(|directive| directive.eval(None, &FormatArgs { this: name.to_string(), .. }))
             .unwrap_or_default()
     };
 
diff --git a/compiler/rustc_hir/src/attrs/diagnostic.rs b/compiler/rustc_hir/src/attrs/diagnostic.rs
index 66cdf2be8fc4..2beafee54541 100644
--- a/compiler/rustc_hir/src/attrs/diagnostic.rs
+++ b/compiler/rustc_hir/src/attrs/diagnostic.rs
@@ -218,10 +218,11 @@ fn visit_params(&self, visit: &mut impl FnMut(Symbol, Span)) {
 /// ```
 #[derive(Debug)]
 pub struct FormatArgs {
+    /// The name of the item the attribute is on.
     pub this: String,
-    pub this_sugared: String,
-    pub item_context: &'static str,
-    pub generic_args: Vec<(Symbol, String)>,
+    pub this_sugared: String = String::new(),
+    pub item_context: &'static str = "",
+    pub generic_args: Vec<(Symbol, String)> = Vec::new(),
 }
 
 #[derive(Clone, Debug, HashStable_Generic, Encodable, Decodable, PrintAttribute)]
diff --git a/compiler/rustc_hir/src/lib.rs b/compiler/rustc_hir/src/lib.rs
index c2d9f879cd60..7c2bf3c5b279 100644
--- a/compiler/rustc_hir/src/lib.rs
+++ b/compiler/rustc_hir/src/lib.rs
@@ -7,6 +7,7 @@
 #![feature(closure_track_caller)]
 #![feature(const_default)]
 #![feature(const_trait_impl)]
+#![feature(default_field_values)]
 #![feature(derive_const)]
 #![feature(exhaustive_patterns)]
 #![feature(never_type)]
diff --git a/compiler/rustc_resolve/src/imports.rs b/compiler/rustc_resolve/src/imports.rs
index 198ec4080816..b6ba35f0f3db 100644
--- a/compiler/rustc_resolve/src/imports.rs
+++ b/compiler/rustc_resolve/src/imports.rs
@@ -886,12 +886,7 @@ fn throw_unresolved_import_error(
 
                 let args = FormatArgs {
                     this,
-                    // Unused
-                    this_sugared: String::new(),
-                    // Unused
-                    item_context: "",
-                    // Unused
-                    generic_args: Vec::new(),
+                    ..
                 };
                 let CustomDiagnostic { message, label, notes, .. } = directive.eval(None, &args);