Rollup merge of #121382 - nnethercote:rework-untranslatable_diagnostic-lint, r=davidtwco

Rework `untranslatable_diagnostic` lint Currently it only checks calls to functions marked with `#[rustc_lint_diagnostics]`. This PR changes it to check calls to any function with an `impl Into<{D,Subd}iagnosticMessage>` parameter. This greatly improves its coverage and doesn't rely on people remembering to add `#[rustc_lint_diagnostics]`. It also lets us add `#[rustc_lint_diagnostics]` to a number of functions that don't have an `impl Into<{D,Subd}iagnosticMessage>`, such as `Diag::span`. r? ``@davidtwco``
2024-03-06 22:02:46 +01:00 · 2024-03-06 22:02:46 +01:00 · efe9deace8
parent c7fca03240 3591e77b35
commit efe9deace8
42 changed files with 305 additions and 89 deletions
--- a/compiler/rustc_abi/src/layout.rs
+++ b/compiler/rustc_abi/src/layout.rs
@ -1,6 +1,9 @@
+use std::borrow::{Borrow, Cow};
+use std::cmp;
 use std::fmt::{self, Write};
+use std::iter;
+use std::ops::Bound;
 use std::ops::Deref;
-use std::{borrow::Borrow, cmp, iter, ops::Bound};

 use rustc_index::Idx;
 use tracing::debug;
@ -32,7 +35,7 @@ where
 pub trait LayoutCalculator {
    type TargetDataLayoutRef: Borrow<TargetDataLayout>;

-    fn delayed_bug(&self, txt: String);
+    fn delayed_bug(&self, txt: impl Into<Cow<'static, str>>);
    fn current_data_layout(&self) -> Self::TargetDataLayoutRef;

    fn scalar_pair<FieldIdx: Idx, VariantIdx: Idx>(
--- a/compiler/rustc_ast_lowering/src/asm.rs
+++ b/compiler/rustc_ast_lowering/src/asm.rs
@ -22,6 +22,7 @@ use std::collections::hash_map::Entry;
 use std::fmt::Write;

 impl<'a, 'hir> LoweringContext<'a, 'hir> {
+    #[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
    pub(crate) fn lower_inline_asm(
        &mut self,
        sp: Span,
--- a/compiler/rustc_ast_lowering/src/expr.rs
+++ b/compiler/rustc_ast_lowering/src/expr.rs
@ -1513,6 +1513,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
        }
    }

+    #[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
    fn lower_expr_yield(&mut self, span: Span, opt_expr: Option<&Expr>) -> hir::ExprKind<'hir> {
        let yielded =
            opt_expr.as_ref().map(|x| self.lower_expr(x)).unwrap_or_else(|| self.expr_unit(span));
--- a/compiler/rustc_ast_lowering/src/lib.rs
+++ b/compiler/rustc_ast_lowering/src/lib.rs
@ -2272,6 +2272,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
        self.expr_block(block)
    }

+    #[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
    fn lower_array_length(&mut self, c: &AnonConst) -> hir::ArrayLen {
        match c.value.kind {
            ExprKind::Underscore => {
--- a/compiler/rustc_ast_passes/src/feature_gate.rs
+++ b/compiler/rustc_ast_passes/src/feature_gate.rs
@ -17,6 +17,7 @@ use crate::errors;
 macro_rules! gate {
    ($visitor:expr, $feature:ident, $span:expr, $explain:expr) => {{
        if !$visitor.features.$feature && !$span.allows_unstable(sym::$feature) {
+            #[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
            feature_err(&$visitor.sess, sym::$feature, $span, $explain).emit();
        }
    }};
@ -34,6 +35,7 @@ macro_rules! gate {
 macro_rules! gate_alt {
    ($visitor:expr, $has_feature:expr, $name:expr, $span:expr, $explain:expr) => {{
        if !$has_feature && !$span.allows_unstable($name) {
+            #[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
            feature_err(&$visitor.sess, $name, $span, $explain).emit();
        }
    }};
@ -73,6 +75,7 @@ struct PostExpansionVisitor<'a> {
 }

 impl<'a> PostExpansionVisitor<'a> {
+    #[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
    fn check_abi(&self, abi: ast::StrLit, constness: ast::Const) {
        let ast::StrLit { symbol_unescaped, span, .. } = abi;

@ -579,6 +582,7 @@ pub fn check_crate(krate: &ast::Crate, sess: &Session, features: &Features) {
                if let Ok(snippet) = sm.span_to_snippet(span)
                    && snippet == "!"
                {
+                    #[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
                    feature_err(sess, sym::never_patterns, span, "`!` patterns are experimental")
                        .emit();
                } else {
--- a/compiler/rustc_attr/src/builtin.rs
+++ b/compiler/rustc_attr/src/builtin.rs
@ -516,6 +516,7 @@ pub struct Condition {
 }

 /// Tests if a cfg-pattern matches the cfg set
+#[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
 pub fn cfg_matches(
    cfg: &ast::MetaItem,
    sess: &Session,
@ -566,6 +567,7 @@ fn try_gate_cfg(name: Symbol, span: Span, sess: &Session, features: Option<&Feat
    }
 }

+#[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
 fn gate_cfg(gated_cfg: &GatedCfg, cfg_span: Span, sess: &Session, features: &Features) {
    let (cfg, feature, has_feature) = gated_cfg;
    if !has_feature(features) && !cfg_span.allows_unstable(*feature) {
@ -592,6 +594,7 @@ fn parse_version(s: Symbol) -> Option<RustcVersion> {

 /// Evaluate a cfg-like condition (with `any` and `all`), using `eval` to
 /// evaluate individual items.
+#[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
 pub fn eval_condition(
    cfg: &ast::MetaItem,
    sess: &Session,
--- a/compiler/rustc_borrowck/src/diagnostics/mod.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/mod.rs
@ -76,6 +76,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
    /// LL |         for (key, value) in dict {
    ///    |                             ^^^^
    /// ```
+    #[allow(rustc::diagnostic_outside_of_impl)] // FIXME
    pub(super) fn add_moved_or_invoked_closure_note(
        &self,
        location: Location,
@ -585,6 +586,7 @@ impl UseSpans<'_> {
    }

    /// Add a span label to the arguments of the closure, if it exists.
+    #[allow(rustc::diagnostic_outside_of_impl)]
    pub(super) fn args_subdiag(
        self,
        dcx: &rustc_errors::DiagCtxt,
@ -598,6 +600,7 @@ impl UseSpans<'_> {

    /// Add a span label to the use of the captured variable, if it exists.
    /// only adds label to the `path_span`
+    #[allow(rustc::diagnostic_outside_of_impl)]
    pub(super) fn var_path_only_subdiag(
        self,
        dcx: &rustc_errors::DiagCtxt,
@ -635,6 +638,7 @@ impl UseSpans<'_> {
    }

    /// Add a subdiagnostic to the use of the captured variable, if it exists.
+    #[allow(rustc::diagnostic_outside_of_impl)]
    pub(super) fn var_subdiag(
        self,
        dcx: &rustc_errors::DiagCtxt,
@ -1008,6 +1012,8 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
        self.borrow_spans(span, borrow.reserve_location)
    }

+    #[allow(rustc::diagnostic_outside_of_impl)]
+    #[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
    fn explain_captures(
        &mut self,
        err: &mut Diag<'_>,
--- a/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
@ -201,6 +201,8 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
    // For generic associated types (GATs) which implied 'static requirement
    // from higher-ranked trait bounds (HRTB). Try to locate span of the trait
    // and the span which bounded to the trait for adding 'static lifetime suggestion
+    #[allow(rustc::diagnostic_outside_of_impl)]
+    #[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
    fn suggest_static_lifetime_for_gat_from_hrtb(
        &self,
        diag: &mut Diag<'_>,
@ -254,9 +256,6 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {

        hrtb_bounds.iter().for_each(|bound| {
            let Trait(PolyTraitRef { trait_ref, span: trait_span, .. }, _) = bound else { return; };
-            // FIXME: make this translatable
-            #[allow(rustc::diagnostic_outside_of_impl)]
-            #[allow(rustc::untranslatable_diagnostic)]
            diag.span_note(
                *trait_span,
                "due to current limitations in the borrow checker, this implies a `'static` lifetime"
@ -580,6 +579,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
    ///            executing...
    ///    = note: ...therefore, returned references to captured variables will escape the closure
    /// ```
+    #[allow(rustc::diagnostic_outside_of_impl)] // FIXME
    fn report_fnmut_error(
        &self,
        errci: &ErrorConstraintInfo<'tcx>,
@ -761,6 +761,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
    ///    |     ^^^^^^^^^^^^^^ function was supposed to return data with lifetime `'a` but it
    ///    |                    is returning data with lifetime `'b`
    /// ```
+    #[allow(rustc::diagnostic_outside_of_impl)] // FIXME
    fn report_general_error(&self, errci: &ErrorConstraintInfo<'tcx>) -> Diag<'tcx> {
        let ErrorConstraintInfo {
            fr,
@ -822,6 +823,8 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
    /// LL |     fn iter_values_anon(&self) -> impl Iterator<Item=u32> + 'a {
    ///    |                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    /// ```
+    #[allow(rustc::diagnostic_outside_of_impl)]
+    #[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
    fn add_static_impl_trait_suggestion(
        &self,
        diag: &mut Diag<'_>,
@ -972,6 +975,8 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
        self.suggest_constrain_dyn_trait_in_impl(diag, &visitor.0, ident, self_ty);
    }

+    #[allow(rustc::diagnostic_outside_of_impl)]
+    #[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
    #[instrument(skip(self, err), level = "debug")]
    fn suggest_constrain_dyn_trait_in_impl(
        &self,
@ -1034,6 +1039,8 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
        suggest_adding_lifetime_params(self.infcx.tcx, sub, ty_sup, ty_sub, diag);
    }

+    #[allow(rustc::diagnostic_outside_of_impl)]
+    #[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
    fn suggest_move_on_borrowing_closure(&self, diag: &mut Diag<'_>) {
        let map = self.infcx.tcx.hir();
        let body_id = map.body_owned_by(self.mir_def_id());
--- a/compiler/rustc_const_eval/src/transform/check_consts/ops.rs
+++ b/compiler/rustc_const_eval/src/transform/check_consts/ops.rs
@ -62,6 +62,7 @@ impl<'tcx> NonConstOp<'tcx> for FloatingPointOp {
        }
    }

+    #[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
    fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> Diag<'tcx> {
        feature_err(
            &ccx.tcx.sess,
@ -556,6 +557,7 @@ impl<'tcx> NonConstOp<'tcx> for RawMutPtrDeref {
        Status::Unstable(sym::const_mut_refs)
    }

+    #[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
    fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> Diag<'tcx> {
        feature_err(
            &ccx.tcx.sess,
@ -589,6 +591,7 @@ impl<'tcx> NonConstOp<'tcx> for StaticAccess {
        }
    }

+    #[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
    fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> Diag<'tcx> {
        let mut err = feature_err(
            &ccx.tcx.sess,
@ -632,6 +635,7 @@ pub mod ty {
            }
        }

+        #[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
        fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> Diag<'tcx> {
            feature_err(
                &ccx.tcx.sess,
--- a/compiler/rustc_driver_impl/src/args.rs
+++ b/compiler/rustc_driver_impl/src/args.rs
@ -97,6 +97,7 @@ impl Expander {
 /// **Note:** This function doesn't interpret argument 0 in any special way.
 /// If this function is intended to be used with command line arguments,
 /// `argv[0]` must be removed prior to calling it manually.
+#[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
 pub fn arg_expand_all(early_dcx: &EarlyDiagCtxt, at_args: &[String]) -> Vec<String> {
    let mut expander = Expander::default();
    for arg in at_args {
--- a/compiler/rustc_driver_impl/src/lib.rs
+++ b/compiler/rustc_driver_impl/src/lib.rs
@ -4,6 +4,7 @@
 //!
 //! This API is completely unstable and subject to change.

+#![allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
 #![doc(rust_logo)]
 #![feature(rustdoc_internals)]
--- a/compiler/rustc_errors/src/diagnostic.rs
+++ b/compiler/rustc_errors/src/diagnostic.rs
@ -598,6 +598,7 @@ impl<'a, G: EmissionGuarantee> Diag<'a, G> {
    ///
    /// In the meantime, though, callsites are required to deal with the "bug"
    /// locally in whichever way makes the most sense.
+    #[rustc_lint_diagnostics]
    #[track_caller]
    pub fn downgrade_to_delayed_bug(&mut self) {
        assert!(
@ -631,6 +632,7 @@ impl<'a, G: EmissionGuarantee> Diag<'a, G> {
    with_fn! { with_span_labels,
    /// Labels all the given spans with the provided label.
    /// See [`Self::span_label()`] for more information.
+    #[rustc_lint_diagnostics]
    pub fn span_labels(&mut self, spans: impl IntoIterator<Item = Span>, label: &str) -> &mut Self {
        for span in spans {
            self.span_label(span, label.to_string());
@ -638,6 +640,7 @@ impl<'a, G: EmissionGuarantee> Diag<'a, G> {
        self
    } }

+    #[rustc_lint_diagnostics]
    pub fn replace_span_with(&mut self, after: Span, keep_label: bool) -> &mut Self {
        let before = self.span.clone();
        self.span(after);
@ -653,6 +656,7 @@ impl<'a, G: EmissionGuarantee> Diag<'a, G> {
        self
    }

+    #[rustc_lint_diagnostics]
    pub fn note_expected_found(
        &mut self,
        expected_label: &dyn fmt::Display,
@ -663,6 +667,7 @@ impl<'a, G: EmissionGuarantee> Diag<'a, G> {
        self.note_expected_found_extra(expected_label, expected, found_label, found, &"", &"")
    }

+    #[rustc_lint_diagnostics]
    pub fn note_expected_found_extra(
        &mut self,
        expected_label: &dyn fmt::Display,
@ -705,6 +710,7 @@ impl<'a, G: EmissionGuarantee> Diag<'a, G> {
        self
    }

+    #[rustc_lint_diagnostics]
    pub fn note_trait_signature(&mut self, name: Symbol, signature: String) -> &mut Self {
        self.highlighted_note(vec![
            StringPart::normal(format!("`{name}` from trait: `")),
@ -722,12 +728,14 @@ impl<'a, G: EmissionGuarantee> Diag<'a, G> {
        self
    } }

+    #[rustc_lint_diagnostics]
    fn highlighted_note(&mut self, msg: Vec<StringPart>) -> &mut Self {
        self.sub_with_highlights(Level::Note, msg, MultiSpan::new());
        self
    }

    /// This is like [`Diag::note()`], but it's only printed once.
+    #[rustc_lint_diagnostics]
    pub fn note_once(&mut self, msg: impl Into<SubdiagMessage>) -> &mut Self {
        self.sub(Level::OnceNote, msg, MultiSpan::new());
        self
@ -748,6 +756,7 @@ impl<'a, G: EmissionGuarantee> Diag<'a, G> {

    /// Prints the span with a note above it.
    /// This is like [`Diag::note_once()`], but it gets its own span.
+    #[rustc_lint_diagnostics]
    pub fn span_note_once<S: Into<MultiSpan>>(
        &mut self,
        sp: S,
@ -786,12 +795,14 @@ impl<'a, G: EmissionGuarantee> Diag<'a, G> {
    } }

    /// This is like [`Diag::help()`], but it's only printed once.
+    #[rustc_lint_diagnostics]
    pub fn help_once(&mut self, msg: impl Into<SubdiagMessage>) -> &mut Self {
        self.sub(Level::OnceHelp, msg, MultiSpan::new());
        self
    }

    /// Add a help message attached to this diagnostic with a customizable highlighted message.
+    #[rustc_lint_diagnostics]
    pub fn highlighted_help(&mut self, msg: Vec<StringPart>) -> &mut Self {
        self.sub_with_highlights(Level::Help, msg, MultiSpan::new());
        self
@ -812,12 +823,14 @@ impl<'a, G: EmissionGuarantee> Diag<'a, G> {
    /// Disallow attaching suggestions this diagnostic.
    /// Any suggestions attached e.g. with the `span_suggestion_*` methods
    /// (before and after the call to `disable_suggestions`) will be ignored.
+    #[rustc_lint_diagnostics]
    pub fn disable_suggestions(&mut self) -> &mut Self {
        self.suggestions = Err(SuggestionsDisabled);
        self
    }

    /// Helper for pushing to `self.suggestions`, if available (not disable).
+    #[rustc_lint_diagnostics]
    fn push_suggestion(&mut self, suggestion: CodeSuggestion) {
        for subst in &suggestion.substitutions {
            for part in &subst.parts {
@ -838,6 +851,7 @@ impl<'a, G: EmissionGuarantee> Diag<'a, G> {
    with_fn! { with_multipart_suggestion,
    /// Show a suggestion that has multiple parts to it.
    /// In other words, multiple changes need to be applied as part of this suggestion.
+    #[rustc_lint_diagnostics]
    pub fn multipart_suggestion(
        &mut self,
        msg: impl Into<SubdiagMessage>,
@ -854,6 +868,7 @@ impl<'a, G: EmissionGuarantee> Diag<'a, G> {

    /// Show a suggestion that has multiple parts to it, always as it's own subdiagnostic.
    /// In other words, multiple changes need to be applied as part of this suggestion.
+    #[rustc_lint_diagnostics]
    pub fn multipart_suggestion_verbose(
        &mut self,
        msg: impl Into<SubdiagMessage>,
@ -869,6 +884,7 @@ impl<'a, G: EmissionGuarantee> Diag<'a, G> {
    }

    /// [`Diag::multipart_suggestion()`] but you can set the [`SuggestionStyle`].
+    #[rustc_lint_diagnostics]
    pub fn multipart_suggestion_with_style(
        &mut self,
        msg: impl Into<SubdiagMessage>,
@ -911,6 +927,7 @@ impl<'a, G: EmissionGuarantee> Diag<'a, G> {
    /// be from the message, showing the span label inline would be visually unpleasant
    /// (marginally overlapping spans or multiline spans) and showing the snippet window wouldn't
    /// improve understandability.
+    #[rustc_lint_diagnostics]
    pub fn tool_only_multipart_suggestion(
        &mut self,
        msg: impl Into<SubdiagMessage>,
@ -943,6 +960,7 @@ impl<'a, G: EmissionGuarantee> Diag<'a, G> {
    /// * may contain a name of a function, variable, or type, but not whole expressions
    ///
    /// See `CodeSuggestion` for more information.
+    #[rustc_lint_diagnostics]
    pub fn span_suggestion(
        &mut self,
        sp: Span,
@ -961,6 +979,7 @@ impl<'a, G: EmissionGuarantee> Diag<'a, G> {
    } }

    /// [`Diag::span_suggestion()`] but you can set the [`SuggestionStyle`].
+    #[rustc_lint_diagnostics]
    pub fn span_suggestion_with_style(
        &mut self,
        sp: Span,
@ -986,6 +1005,7 @@ impl<'a, G: EmissionGuarantee> Diag<'a, G> {

    with_fn! { with_span_suggestion_verbose,
    /// Always show the suggested change.
+    #[rustc_lint_diagnostics]
    pub fn span_suggestion_verbose(
        &mut self,
        sp: Span,
@ -1006,6 +1026,7 @@ impl<'a, G: EmissionGuarantee> Diag<'a, G> {
    with_fn! { with_span_suggestions,
    /// Prints out a message with multiple suggested edits of the code.
    /// See also [`Diag::span_suggestion()`].
+    #[rustc_lint_diagnostics]
    pub fn span_suggestions(
        &mut self,
        sp: Span,
@ -1022,6 +1043,7 @@ impl<'a, G: EmissionGuarantee> Diag<'a, G> {
        )
    } }

+    #[rustc_lint_diagnostics]
    pub fn span_suggestions_with_style(
        &mut self,
        sp: Span,
@ -1052,6 +1074,7 @@ impl<'a, G: EmissionGuarantee> Diag<'a, G> {
    /// Prints out a message with multiple suggested edits of the code, where each edit consists of
    /// multiple parts.
    /// See also [`Diag::multipart_suggestion()`].
+    #[rustc_lint_diagnostics]
    pub fn multipart_suggestions(
        &mut self,
        msg: impl Into<SubdiagMessage>,
@ -1098,6 +1121,7 @@ impl<'a, G: EmissionGuarantee> Diag<'a, G> {
    /// inline, it will only show the message and not the suggestion.
    ///
    /// See `CodeSuggestion` for more information.
+    #[rustc_lint_diagnostics]
    pub fn span_suggestion_short(
        &mut self,
        sp: Span,
@ -1121,6 +1145,7 @@ impl<'a, G: EmissionGuarantee> Diag<'a, G> {
    /// be from the message, showing the span label inline would be visually unpleasant
    /// (marginally overlapping spans or multiline spans) and showing the snippet window wouldn't
    /// improve understandability.
+    #[rustc_lint_diagnostics]
    pub fn span_suggestion_hidden(
        &mut self,
        sp: Span,
@ -1165,6 +1190,7 @@ impl<'a, G: EmissionGuarantee> Diag<'a, G> {
    /// [rustc_macros::Subdiagnostic]). Performs eager translation of any translatable messages
    /// used in the subdiagnostic, so suitable for use with repeated messages (i.e. re-use of
    /// interpolated variables).
+    #[rustc_lint_diagnostics]
    pub fn subdiagnostic(
        &mut self,
        dcx: &crate::DiagCtxt,
@ -1180,6 +1206,7 @@ impl<'a, G: EmissionGuarantee> Diag<'a, G> {

    with_fn! { with_span,
    /// Add a span.
+    #[rustc_lint_diagnostics]
    pub fn span(&mut self, sp: impl Into<MultiSpan>) -> &mut Self {
        self.span = sp.into();
        if let Some(span) = self.span.primary_span() {
@ -1188,6 +1215,7 @@ impl<'a, G: EmissionGuarantee> Diag<'a, G> {
        self
    } }

+    #[rustc_lint_diagnostics]
    pub fn is_lint(&mut self, name: String, has_future_breakage: bool) -> &mut Self {
        self.is_lint = Some(IsLint { name, has_future_breakage });
        self
@ -1195,6 +1223,7 @@ impl<'a, G: EmissionGuarantee> Diag<'a, G> {

    with_fn! { with_code,
    /// Add an error code.
+    #[rustc_lint_diagnostics]
    pub fn code(&mut self, code: ErrCode) -> &mut Self {
        self.code = Some(code);
        self
@ -1202,6 +1231,7 @@ impl<'a, G: EmissionGuarantee> Diag<'a, G> {

    with_fn! { with_primary_message,
    /// Add a primary message.
+    #[rustc_lint_diagnostics]
    pub fn primary_message(&mut self, msg: impl Into<DiagMessage>) -> &mut Self {
        self.messages[0] = (msg.into(), Style::NoStyle);
        self
@ -1209,6 +1239,7 @@ impl<'a, G: EmissionGuarantee> Diag<'a, G> {

    with_fn! { with_arg,
    /// Add an argument.
+    #[rustc_lint_diagnostics]
    pub fn arg(
        &mut self,
        name: impl Into<DiagArgName>,
--- a/compiler/rustc_errors/src/lib.rs
+++ b/compiler/rustc_errors/src/lib.rs
@ -1101,32 +1101,36 @@ impl DiagCtxt {
 // Functions beginning with `struct_`/`create_` create a diagnostic. Other
 // functions create and emit a diagnostic all in one go.
 impl DiagCtxt {
-    // No `#[rustc_lint_diagnostics]` because bug messages aren't user-facing.
+    // No `#[rustc_lint_diagnostics]` and no `impl Into<DiagMessage>` because bug messages aren't
+    // user-facing.
    #[track_caller]
-    pub fn struct_bug(&self, msg: impl Into<DiagMessage>) -> Diag<'_, BugAbort> {
-        Diag::new(self, Bug, msg)
+    pub fn struct_bug(&self, msg: impl Into<Cow<'static, str>>) -> Diag<'_, BugAbort> {
+        Diag::new(self, Bug, msg.into())
    }

-    // No `#[rustc_lint_diagnostics]` because bug messages aren't user-facing.
+    // No `#[rustc_lint_diagnostics]` and no `impl Into<DiagMessage>` because bug messages aren't
+    // user-facing.
    #[track_caller]
-    pub fn bug(&self, msg: impl Into<DiagMessage>) -> ! {
+    pub fn bug(&self, msg: impl Into<Cow<'static, str>>) -> ! {
        self.struct_bug(msg).emit()
    }

-    // No `#[rustc_lint_diagnostics]` because bug messages aren't user-facing.
+    // No `#[rustc_lint_diagnostics]` and no `impl Into<DiagMessage>` because bug messages aren't
+    // user-facing.
    #[track_caller]
    pub fn struct_span_bug(
        &self,
        span: impl Into<MultiSpan>,
-        msg: impl Into<DiagMessage>,
+        msg: impl Into<Cow<'static, str>>,
    ) -> Diag<'_, BugAbort> {
        self.struct_bug(msg).with_span(span)
    }

-    // No `#[rustc_lint_diagnostics]` because bug messages aren't user-facing.
+    // No `#[rustc_lint_diagnostics]` and no `impl Into<DiagMessage>` because bug messages aren't
+    // user-facing.
    #[track_caller]
-    pub fn span_bug(&self, span: impl Into<MultiSpan>, msg: impl Into<DiagMessage>) -> ! {
-        self.struct_span_bug(span, msg).emit()
+    pub fn span_bug(&self, span: impl Into<MultiSpan>, msg: impl Into<Cow<'static, str>>) -> ! {
+        self.struct_span_bug(span, msg.into()).emit()
    }

    #[track_caller]
@ -1240,24 +1244,28 @@ impl DiagCtxt {
    }

    /// Ensures that an error is printed. See `Level::DelayedBug`.
-    // No `#[rustc_lint_diagnostics]` because bug messages aren't user-facing.
+    //
+    // No `#[rustc_lint_diagnostics]` and no `impl Into<DiagMessage>` because bug messages aren't
+    // user-facing.
    #[track_caller]
-    pub fn delayed_bug(&self, msg: impl Into<DiagMessage>) -> ErrorGuaranteed {
-        Diag::<ErrorGuaranteed>::new(self, DelayedBug, msg).emit()
+    pub fn delayed_bug(&self, msg: impl Into<Cow<'static, str>>) -> ErrorGuaranteed {
+        Diag::<ErrorGuaranteed>::new(self, DelayedBug, msg.into()).emit()
    }

    /// Ensures that an error is printed. See `Level::DelayedBug`.
    ///
    /// Note: this function used to be called `delay_span_bug`. It was renamed
    /// to match similar functions like `span_err`, `span_warn`, etc.
-    // No `#[rustc_lint_diagnostics]` because bug messages aren't user-facing.
+    //
+    // No `#[rustc_lint_diagnostics]` and no `impl Into<DiagMessage>` because bug messages aren't
+    // user-facing.
    #[track_caller]
    pub fn span_delayed_bug(
        &self,
        sp: impl Into<MultiSpan>,
-        msg: impl Into<DiagMessage>,
+        msg: impl Into<Cow<'static, str>>,
    ) -> ErrorGuaranteed {
-        Diag::<ErrorGuaranteed>::new(self, DelayedBug, msg).with_span(sp).emit()
+        Diag::<ErrorGuaranteed>::new(self, DelayedBug, msg.into()).with_span(sp).emit()
    }

    #[rustc_lint_diagnostics]
--- a/compiler/rustc_expand/src/base.rs
+++ b/compiler/rustc_expand/src/base.rs
@ -1493,6 +1493,8 @@ fn pretty_printing_compatibility_hack(item: &Item, sess: &Session) -> bool {
                            };

                            if crate_matches {
+                                // FIXME: make this translatable
+                                #[allow(rustc::untranslatable_diagnostic)]
                                sess.psess.buffer_lint_with_diagnostic(
                                        PROC_MACRO_BACK_COMPAT,
                                        item.ident.span,
--- a/compiler/rustc_expand/src/config.rs
+++ b/compiler/rustc_expand/src/config.rs
@ -239,6 +239,7 @@ impl<'a> StripUnconfigured<'a> {
    /// Gives a compiler warning when the `cfg_attr` contains no attributes and
    /// is in the original source file. Gives a compiler error if the syntax of
    /// the attribute is incorrect.
+    #[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
    pub(crate) fn expand_cfg_attr(&self, attr: &Attribute, recursive: bool) -> Vec<Attribute> {
        let Some((cfg_predicate, expanded_attrs)) =
            rustc_parse::parse_cfg_attr(attr, &self.sess.psess)
@ -273,6 +274,7 @@ impl<'a> StripUnconfigured<'a> {
        }
    }

+    #[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
    fn expand_cfg_attr_item(
        &self,
        attr: &Attribute,
@ -371,6 +373,7 @@ impl<'a> StripUnconfigured<'a> {
    }

    /// If attributes are not allowed on expressions, emit an error for `attr`
+    #[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
    #[instrument(level = "trace", skip(self))]
    pub(crate) fn maybe_emit_expr_attr_err(&self, attr: &Attribute) {
        if self.features.is_some_and(|features| !features.stmt_expr_attributes)
@ -384,7 +387,6 @@ impl<'a> StripUnconfigured<'a> {
            );

            if attr.is_doc_comment() {
-                #[allow(rustc::untranslatable_diagnostic)]
                err.help("`///` is for documentation comments. For a plain comment, use `//`.");
            }

--- a/compiler/rustc_expand/src/expand.rs
+++ b/compiler/rustc_expand/src/expand.rs
@ -783,6 +783,7 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
        })
    }

+    #[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
    fn gate_proc_macro_attr_item(&self, span: Span, item: &Annotatable) {
        let kind = match item {
            Annotatable::Item(_)
@ -825,6 +826,7 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
        }

        impl<'ast, 'a> Visitor<'ast> for GateProcMacroInput<'a> {
+            #[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
            fn visit_item(&mut self, item: &'ast ast::Item) {
                match &item.kind {
                    ItemKind::Mod(_, mod_kind)
@ -1689,6 +1691,7 @@ impl<'a, 'b> InvocationCollector<'a, 'b> {

    // Detect use of feature-gated or invalid attributes on macro invocations
    // since they will not be detected after macro expansion.
+    #[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
    fn check_attributes(&self, attrs: &[ast::Attribute], call: &ast::MacCall) {
        let features = self.cx.ecfg.features;
        let mut attrs = attrs.iter().peekable();
--- a/compiler/rustc_expand/src/lib.rs
+++ b/compiler/rustc_expand/src/lib.rs
@ -5,6 +5,7 @@
 #![feature(associated_type_defaults)]
 #![feature(if_let_guard)]
 #![feature(let_chains)]
+#![feature(lint_reasons)]
 #![feature(macro_metavar_expr)]
 #![feature(map_try_insert)]
 #![feature(proc_macro_diagnostic)]
--- a/compiler/rustc_expand/src/proc_macro_server.rs
+++ b/compiler/rustc_expand/src/proc_macro_server.rs
@ -517,6 +517,9 @@ impl server::FreeFunctions for Rustc<'_, '_> {
            Diag::new(&self.psess().dcx, diagnostic.level.to_internal(), message);
        diag.span(MultiSpan::from_spans(diagnostic.spans));
        for child in diagnostic.children {
+            // This message comes from another diagnostic, and we are just reconstructing the
+            // diagnostic, so there's no need for translation.
+            #[allow(rustc::untranslatable_diagnostic)]
            diag.sub(child.level.to_internal(), child.message, MultiSpan::from_spans(child.spans));
        }
        diag.emit();
--- a/compiler/rustc_expand/src/tests.rs
+++ b/compiler/rustc_expand/src/tests.rs
@ -178,6 +178,7 @@ impl<T: Write> Write for Shared<T> {
    }
 }

+#[allow(rustc::untranslatable_diagnostic)] // no translation needed for tests
 fn test_harness(file_text: &str, span_labels: Vec<SpanLabel>, expected_output: &str) {
    create_default_session_globals_then(|| {
        let (handler, source_map, output) = create_test_handler();
@ -192,7 +193,6 @@ fn test_harness(file_text: &str, span_labels: Vec<SpanLabel>, expected_output: &
            println!("text: {:?}", source_map.span_to_snippet(span));
        }

-        #[allow(rustc::untranslatable_diagnostic)]
        handler.span_err(msp, "foo");

        assert!(
--- a/compiler/rustc_feature/src/builtin_attrs.rs
+++ b/compiler/rustc_feature/src/builtin_attrs.rs
@ -695,8 +695,8 @@ pub const BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
    // Used by the `rustc::potential_query_instability` lint to warn methods which
    // might not be stable during incremental compilation.
    rustc_attr!(rustc_lint_query_instability, Normal, template!(Word), WarnFollowing, INTERNAL_UNSTABLE),
-    // Used by the `rustc::untranslatable_diagnostic` and `rustc::diagnostic_outside_of_impl` lints
-    // to assist in changes to diagnostic APIs.
+    // Used by the `rustc::diagnostic_outside_of_impl` lints to assist in changes to diagnostic
+    // APIs. Any function with this attribute will be checked by that lint.
    rustc_attr!(rustc_lint_diagnostics, Normal, template!(Word), WarnFollowing, INTERNAL_UNSTABLE),
    // Used by the `rustc::bad_opt_access` lint to identify `DebuggingOptions` and `CodegenOptions`
    // types (as well as any others in future).
--- a/compiler/rustc_interface/src/interface.rs
+++ b/compiler/rustc_interface/src/interface.rs
@ -320,6 +320,7 @@ pub struct Config {

 // JUSTIFICATION: before session exists, only config
 #[allow(rustc::bad_opt_access)]
+#[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
 pub fn run_compiler<R: Send>(config: Config, f: impl FnOnce(&Compiler) -> R + Send) -> R {
    trace!("run_compiler");

--- a/compiler/rustc_interface/src/util.rs
+++ b/compiler/rustc_interface/src/util.rs
@ -160,6 +160,7 @@ pub(crate) fn run_in_thread_pool_with_globals<F: FnOnce() -> R + Send, R: Send>(
    })
 }

+#[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
 fn load_backend_from_dylib(early_dcx: &EarlyDiagCtxt, path: &Path) -> MakeBackendFn {
    match unsafe { load_symbol_from_dylib::<MakeBackendFn>(path, "__rustc_codegen_backend") } {
        Ok(backend_sym) => backend_sym,
@ -227,6 +228,7 @@ fn get_rustc_path_inner(bin_path: &str) -> Option<PathBuf> {
    })
 }

+#[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
 fn get_codegen_sysroot(
    early_dcx: &EarlyDiagCtxt,
    maybe_sysroot: &Option<PathBuf>,
@ -319,6 +321,7 @@ fn get_codegen_sysroot(
    }
 }

+#[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
 pub(crate) fn check_attr_crate_type(
    sess: &Session,
    attrs: &[ast::Attribute],
--- a/compiler/rustc_lint/src/context.rs
+++ b/compiler/rustc_lint/src/context.rs
@ -621,12 +621,13 @@ pub trait LintContext {
    /// Note that this function should only be called for [`LintExpectationId`]s
    /// retrieved from the current lint pass. Buffered or manually created ids can
    /// cause ICEs.
-    #[rustc_lint_diagnostics]
    fn fulfill_expectation(&self, expectation: LintExpectationId) {
        // We need to make sure that submitted expectation ids are correctly fulfilled suppressed
        // and stored between compilation sessions. To not manually do these steps, we simply create
-        // a dummy diagnostic and emit is as usual, which will be suppressed and stored like a normal
-        // expected lint diagnostic.
+        // a dummy diagnostic and emit it as usual, which will be suppressed and stored like a
+        // normal expected lint diagnostic.
+        #[allow(rustc::diagnostic_outside_of_impl)]
+        #[allow(rustc::untranslatable_diagnostic)]
        self.sess()
            .dcx()
            .struct_expect(
--- a/compiler/rustc_lint/src/internal.rs
+++ b/compiler/rustc_lint/src/internal.rs
@ -10,7 +10,7 @@ use rustc_ast as ast;
 use rustc_hir::def::Res;
 use rustc_hir::{def_id::DefId, Expr, ExprKind, GenericArg, PatKind, Path, PathSegment, QPath};
 use rustc_hir::{BinOp, BinOpKind, HirId, Impl, Item, ItemKind, Node, Pat, Ty, TyKind};
-use rustc_middle::ty;
+use rustc_middle::ty::{self, Ty as MiddleTy};
 use rustc_session::{declare_lint_pass, declare_tool_lint};
 use rustc_span::hygiene::{ExpnKind, MacroKind};
 use rustc_span::symbol::{kw, sym, Symbol};
@ -338,10 +338,11 @@ impl<'tcx> LateLintPass<'tcx> for ExistingDocKeyword {
 }

 declare_tool_lint! {
-    /// The `untranslatable_diagnostic` lint detects diagnostics created
-    /// without using translatable Fluent strings.
+    /// The `untranslatable_diagnostic` lint detects messages passed to functions with `impl
+    /// Into<{D,Subd}iagMessage` parameters without using translatable Fluent strings.
    ///
-    /// More details on translatable diagnostics can be found [here](https://rustc-dev-guide.rust-lang.org/diagnostics/translation.html).
+    /// More details on translatable diagnostics can be found
+    /// [here](https://rustc-dev-guide.rust-lang.org/diagnostics/translation.html).
    pub rustc::UNTRANSLATABLE_DIAGNOSTIC,
    Deny,
    "prevent creation of diagnostics which cannot be translated",
@ -349,11 +350,13 @@ declare_tool_lint! {
 }

 declare_tool_lint! {
-    /// The `diagnostic_outside_of_impl` lint detects diagnostics created manually,
-    /// and inside an `IntoDiagnostic`/`AddToDiagnostic` implementation,
-    /// or a `#[derive(Diagnostic)]`/`#[derive(Subdiagnostic)]` expansion.
+    /// The `diagnostic_outside_of_impl` lint detects calls to functions annotated with
+    /// `#[rustc_lint_diagnostics]` that are outside an `IntoDiagnostic`, `AddToDiagnostic`, or
+    /// `DecorateLint` impl, or a `#[derive(Diagnostic)]`, `#[derive(Subdiagnostic)]`,
+    /// `#[derive(DecorateLint)]` expansion.
    ///
-    /// More details on diagnostics implementations can be found [here](https://rustc-dev-guide.rust-lang.org/diagnostics/diagnostic-structs.html).
+    /// More details on diagnostics implementations can be found
+    /// [here](https://rustc-dev-guide.rust-lang.org/diagnostics/diagnostic-structs.html).
    pub rustc::DIAGNOSTIC_OUTSIDE_OF_IMPL,
    Deny,
    "prevent creation of diagnostics outside of `IntoDiagnostic`/`AddToDiagnostic` impls",
@ -364,54 +367,130 @@ declare_lint_pass!(Diagnostics => [UNTRANSLATABLE_DIAGNOSTIC, DIAGNOSTIC_OUTSIDE

 impl LateLintPass<'_> for Diagnostics {
    fn check_expr(&mut self, cx: &LateContext<'_>, expr: &Expr<'_>) {
-        let Some((span, def_id, args)) = typeck_results_of_method_fn(cx, expr) else { return };
-        debug!(?span, ?def_id, ?args);
-        let has_attr = ty::Instance::resolve(cx.tcx, cx.param_env, def_id, args)
+        // Only check function calls and method calls.
+        let (span, def_id, fn_gen_args, call_tys) = match expr.kind {
+            ExprKind::Call(callee, args) => {
+                match cx.typeck_results().node_type(callee.hir_id).kind() {
+                    &ty::FnDef(def_id, fn_gen_args) => {
+                        let call_tys: Vec<_> =
+                            args.iter().map(|arg| cx.typeck_results().expr_ty(arg)).collect();
+                        (callee.span, def_id, fn_gen_args, call_tys)
+                    }
+                    _ => return, // occurs for fns passed as args
+                }
+            }
+            ExprKind::MethodCall(segment, _recv, args, _span) => {
+                let def_id = cx.typeck_results().type_dependent_def_id(expr.hir_id).unwrap();
+                let fn_gen_args = cx.typeck_results().node_args(expr.hir_id);
+                let mut call_tys: Vec<_> =
+                    args.iter().map(|arg| cx.typeck_results().expr_ty(arg)).collect();
+                call_tys.insert(0, cx.tcx.types.self_param); // dummy inserted for `self`
+                (segment.ident.span, def_id, fn_gen_args, call_tys)
+            }
+            _ => return,
+        };
+
+        // Is the callee marked with `#[rustc_lint_diagnostics]`?
+        let has_attr = ty::Instance::resolve(cx.tcx, cx.param_env, def_id, fn_gen_args)
            .ok()
            .flatten()
            .is_some_and(|inst| cx.tcx.has_attr(inst.def_id(), sym::rustc_lint_diagnostics));
-        if !has_attr {
-            return;
-        }

-        let mut found_parent_with_attr = false;
-        let mut found_impl = false;
-        for (hir_id, parent) in cx.tcx.hir().parent_iter(expr.hir_id) {
-            if let Some(owner_did) = hir_id.as_owner() {
-                found_parent_with_attr = found_parent_with_attr
-                    || cx.tcx.has_attr(owner_did, sym::rustc_lint_diagnostics);
-            }
-
-            debug!(?parent);
-            if let Node::Item(Item { kind: ItemKind::Impl(impl_), .. }) = parent
-                && let Impl { of_trait: Some(of_trait), .. } = impl_
-                && let Some(def_id) = of_trait.trait_def_id()
-                && let Some(name) = cx.tcx.get_diagnostic_name(def_id)
-                && matches!(name, sym::IntoDiagnostic | sym::AddToDiagnostic | sym::DecorateLint)
-            {
-                found_impl = true;
-                break;
-            }
-        }
-        debug!(?found_impl);
-        if !found_parent_with_attr && !found_impl {
-            cx.emit_span_lint(DIAGNOSTIC_OUTSIDE_OF_IMPL, span, DiagOutOfImpl);
-        }
-
-        let mut found_diagnostic_message = false;
-        for ty in args.types() {
-            debug!(?ty);
+        // Closure: is the type `{D,Subd}iagMessage`?
+        let is_diag_message = |ty: MiddleTy<'_>| {
            if let Some(adt_def) = ty.ty_adt_def()
                && let Some(name) = cx.tcx.get_diagnostic_name(adt_def.did())
                && matches!(name, sym::DiagMessage | sym::SubdiagMessage)
            {
-                found_diagnostic_message = true;
+                true
+            } else {
+                false
+            }
+        };
+
+        // Does the callee have a `impl Into<{D,Subd}iagMessage>` parameter? (There should be at
+        // most one.)
+        let mut impl_into_diagnostic_message_param = None;
+        let fn_sig = cx.tcx.fn_sig(def_id).instantiate_identity().skip_binder();
+        let predicates = cx.tcx.predicates_of(def_id).instantiate_identity(cx.tcx).predicates;
+        for (i, &param_ty) in fn_sig.inputs().iter().enumerate() {
+            if let ty::Param(p) = param_ty.kind() {
+                // It is a type parameter. Check if it is `impl Into<{D,Subd}iagMessage>`.
+                for pred in predicates.iter() {
+                    if let Some(trait_pred) = pred.as_trait_clause()
+                        && let trait_ref = trait_pred.skip_binder().trait_ref
+                        && trait_ref.self_ty() == param_ty // correct predicate for the param?
+                        && cx.tcx.is_diagnostic_item(sym::Into, trait_ref.def_id)
+                        && let ty1 = trait_ref.args.type_at(1)
+                        && is_diag_message(ty1)
+                    {
+                        if impl_into_diagnostic_message_param.is_some() {
+                            cx.tcx.dcx().span_bug(
+                                span,
+                                "can't handle multiple `impl Into<{D,Sub}iagMessage>` params",
+                            );
+                        }
+                        impl_into_diagnostic_message_param = Some((i, p.name));
+                    }
+                }
+            }
+        }
+
+        // Is the callee interesting?
+        if !has_attr && impl_into_diagnostic_message_param.is_none() {
+            return;
+        }
+
+        // Is the parent method marked with `#[rustc_lint_diagnostics]`?
+        let mut parent_has_attr = false;
+        for (hir_id, _parent) in cx.tcx.hir().parent_iter(expr.hir_id) {
+            if let Some(owner_did) = hir_id.as_owner()
+                && cx.tcx.has_attr(owner_did, sym::rustc_lint_diagnostics)
+            {
+                parent_has_attr = true;
                break;
            }
        }
-        debug!(?found_diagnostic_message);
-        if !found_parent_with_attr && !found_diagnostic_message {
-            cx.emit_span_lint(UNTRANSLATABLE_DIAGNOSTIC, span, UntranslatableDiag);
+
+        // Calls to `#[rustc_lint_diagnostics]`-marked functions should only occur:
+        // - inside an impl of `IntoDiagnostic`, `AddToDiagnostic`, or `DecorateLint`, or
+        // - inside a parent function that is itself marked with `#[rustc_lint_diagnostics]`.
+        //
+        // Otherwise, emit a `DIAGNOSTIC_OUTSIDE_OF_IMPL` lint.
+        if has_attr && !parent_has_attr {
+            let mut is_inside_appropriate_impl = false;
+            for (_hir_id, parent) in cx.tcx.hir().parent_iter(expr.hir_id) {
+                debug!(?parent);
+                if let Node::Item(Item { kind: ItemKind::Impl(impl_), .. }) = parent
+                    && let Impl { of_trait: Some(of_trait), .. } = impl_
+                    && let Some(def_id) = of_trait.trait_def_id()
+                    && let Some(name) = cx.tcx.get_diagnostic_name(def_id)
+                    && matches!(
+                        name,
+                        sym::IntoDiagnostic | sym::AddToDiagnostic | sym::DecorateLint
+                    )
+                {
+                    is_inside_appropriate_impl = true;
+                    break;
+                }
+            }
+            debug!(?is_inside_appropriate_impl);
+            if !is_inside_appropriate_impl {
+                cx.emit_span_lint(DIAGNOSTIC_OUTSIDE_OF_IMPL, span, DiagOutOfImpl);
+            }
+        }
+
+        // Calls to methods with an `impl Into<{D,Subd}iagMessage>` parameter must be passed an arg
+        // with type `{D,Subd}iagMessage` or `impl Into<{D,Subd}iagMessage>`. Otherwise, emit an
+        // `UNTRANSLATABLE_DIAGNOSTIC` lint.
+        if let Some((param_i, param_i_p_name)) = impl_into_diagnostic_message_param {
+            // Is the arg type `{Sub,D}iagMessage`or `impl Into<{Sub,D}iagMessage>`?
+            let arg_ty = call_tys[param_i];
+            let is_translatable = is_diag_message(arg_ty)
+                || matches!(arg_ty.kind(), ty::Param(p) if p.name == param_i_p_name);
+            if !is_translatable {
+                cx.emit_span_lint(UNTRANSLATABLE_DIAGNOSTIC, span, UntranslatableDiag);
+            }
        }
    }
 }
@ -425,7 +504,7 @@ declare_tool_lint! {
    report_in_external_macro: true
 }

-declare_lint_pass!(BadOptAccess => [ BAD_OPT_ACCESS ]);
+declare_lint_pass!(BadOptAccess => [BAD_OPT_ACCESS]);

 impl LateLintPass<'_> for BadOptAccess {
    fn check_expr(&mut self, cx: &LateContext<'_>, expr: &Expr<'_>) {
--- a/compiler/rustc_lint/src/let_underscore.rs
+++ b/compiler/rustc_lint/src/let_underscore.rs
@ -104,6 +104,7 @@ const SYNC_GUARD_SYMBOLS: [Symbol; 3] = [
 ];

 impl<'tcx> LateLintPass<'tcx> for LetUnderscore {
+    #[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
    fn check_local(&mut self, cx: &LateContext<'_>, local: &hir::Local<'_>) {
        if matches!(local.source, rustc_hir::LocalSource::AsyncFn) {
            return;
--- a/compiler/rustc_lint/src/levels.rs
+++ b/compiler/rustc_lint/src/levels.rs
@ -724,6 +724,7 @@ impl<'s, P: LintLevelsProvider> LintLevelsBuilder<'s, P> {
        };
    }

+    #[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
    fn add(&mut self, attrs: &[ast::Attribute], is_crate_node: bool, source_hir_id: Option<HirId>) {
        let sess = self.sess;
        for (attr_index, attr) in attrs.iter().enumerate() {
--- a/compiler/rustc_metadata/src/creader.rs
+++ b/compiler/rustc_metadata/src/creader.rs
@ -947,6 +947,7 @@ impl<'a, 'tcx> CrateLoader<'a, 'tcx> {
        }
    }

+    #[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
    fn report_unused_deps(&mut self, krate: &ast::Crate) {
        // Make a point span rather than covering the whole file
        let span = krate.spans.inner_span.shrink_to_lo();
--- a/compiler/rustc_metadata/src/native_libs.rs
+++ b/compiler/rustc_metadata/src/native_libs.rs
@ -93,6 +93,7 @@ struct Collector<'tcx> {
 }

 impl<'tcx> Collector<'tcx> {
+    #[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
    fn process_module(&mut self, module: &ForeignModule) {
        let ForeignModule { def_id, abi, ref foreign_items } = *module;
        let def_id = def_id.expect_local();
--- a/compiler/rustc_middle/src/ty/layout.rs
+++ b/compiler/rustc_middle/src/ty/layout.rs
@ -17,6 +17,7 @@ use rustc_target::abi::call::FnAbi;
 use rustc_target::abi::*;
 use rustc_target::spec::{abi::Abi as SpecAbi, HasTargetSpec, PanicStrategy, Target};

+use std::borrow::Cow;
 use std::cmp;
 use std::fmt;
 use std::num::NonZero;
@ -268,7 +269,7 @@ pub struct LayoutCx<'tcx, C> {
 impl<'tcx> LayoutCalculator for LayoutCx<'tcx, TyCtxt<'tcx>> {
    type TargetDataLayoutRef = &'tcx TargetDataLayout;

-    fn delayed_bug(&self, txt: String) {
+    fn delayed_bug(&self, txt: impl Into<Cow<'static, str>>) {
        self.tcx.dcx().delayed_bug(txt);
    }

--- a/compiler/rustc_middle/src/ty/sty.rs
+++ b/compiler/rustc_middle/src/ty/sty.rs
@ -13,7 +13,7 @@ use crate::ty::{GenericArg, GenericArgs, GenericArgsRef};
 use crate::ty::{List, ParamEnv};
 use hir::def::DefKind;
 use rustc_data_structures::captures::Captures;
-use rustc_errors::{DiagArgValue, DiagMessage, ErrorGuaranteed, IntoDiagnosticArg, MultiSpan};
+use rustc_errors::{DiagArgValue, ErrorGuaranteed, IntoDiagnosticArg, MultiSpan};
 use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
 use rustc_hir::LangItem;
@ -1543,7 +1543,7 @@ impl<'tcx> Ty<'tcx> {
    pub fn new_error_with_message<S: Into<MultiSpan>>(
        tcx: TyCtxt<'tcx>,
        span: S,
-        msg: impl Into<DiagMessage>,
+        msg: impl Into<Cow<'static, str>>,
    ) -> Ty<'tcx> {
        let reported = tcx.dcx().span_delayed_bug(span, msg);
        Ty::new(tcx, Error(reported))
--- a/compiler/rustc_passes/src/check_attr.rs
+++ b/compiler/rustc_passes/src/check_attr.rs
@ -1074,6 +1074,7 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
    /// of one item. Read the documentation of [`check_doc_inline`] for more information.
    ///
    /// [`check_doc_inline`]: Self::check_doc_inline
+    #[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
    fn check_doc_attrs(
        &self,
        attr: &Attribute,
@ -1756,6 +1757,7 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
    }

    /// Checks if the `#[repr]` attributes on `item` are valid.
+    #[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
    fn check_repr(
        &self,
        attrs: &[Attribute],
@ -2328,6 +2330,7 @@ impl<'tcx> CheckAttrVisitor<'tcx> {

            let hir_sig = tcx.hir().fn_sig_by_hir_id(hir_id);
            if let Some(hir_sig) = hir_sig {
+                #[allow(rustc::diagnostic_outside_of_impl)] // FIXME
                match terr {
                    TypeError::ArgumentMutability(idx) | TypeError::ArgumentSorts(_, idx) => {
                        if let Some(ty) = hir_sig.decl.inputs.get(idx) {
--- a/compiler/rustc_passes/src/check_const.rs
+++ b/compiler/rustc_passes/src/check_const.rs
@ -77,6 +77,7 @@ impl<'tcx> CheckConstVisitor<'tcx> {
    }

    /// Emits an error when an unsupported expression is found in a const context.
+    #[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
    fn const_check_violated(&self, expr: NonConstExpr, span: Span) {
        let Self { tcx, def_id, const_kind } = *self;

--- a/compiler/rustc_passes/src/entry.rs
+++ b/compiler/rustc_passes/src/entry.rs
@ -114,6 +114,7 @@ fn find_item(id: ItemId, ctxt: &mut EntryContext<'_>) {
    }
 }

+#[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
 fn configure_main(tcx: TyCtxt<'_>, visitor: &EntryContext<'_>) -> Option<(DefId, EntryFnType)> {
    if let Some((def_id, _)) = visitor.start_fn {
        Some((def_id.to_def_id(), EntryFnType::Start))
--- a/compiler/rustc_session/src/config.rs
+++ b/compiler/rustc_session/src/config.rs
@ -1,6 +1,8 @@
 //! Contains infrastructure for configuring the compiler, including parsing
 //! command-line options.

+#![allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
+
 pub use crate::options::*;

 use crate::errors::FileWriteFail;
@ -2468,9 +2470,7 @@ pub fn parse_externs(
            ));
            let adjusted_name = name.replace('-', "_");
            if is_ascii_ident(&adjusted_name) {
-                // FIXME: make this translatable
-                #[allow(rustc::diagnostic_outside_of_impl)]
-                #[allow(rustc::untranslatable_diagnostic)]
+                #[allow(rustc::diagnostic_outside_of_impl)] // FIXME
                error.help(format!(
                    "consider replacing the dashes with underscores: `{adjusted_name}`"
                ));
--- a/compiler/rustc_session/src/options.rs
+++ b/compiler/rustc_session/src/options.rs
@ -320,6 +320,7 @@ macro_rules! redirect_field {
 type OptionSetter<O> = fn(&mut O, v: Option<&str>) -> bool;
 type OptionDescrs<O> = &'static [(&'static str, OptionSetter<O>, &'static str, &'static str)];

+#[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
 fn build_options<O: Default>(
    early_dcx: &EarlyDiagCtxt,
    matches: &getopts::Matches,
--- a/compiler/rustc_session/src/parse.rs
+++ b/compiler/rustc_session/src/parse.rs
@ -168,6 +168,7 @@ pub fn add_feature_diagnostics<G: EmissionGuarantee>(
 /// This variant allows you to control whether it is a library or language feature.
 /// Almost always, you want to use this for a language feature. If so, prefer
 /// `add_feature_diagnostics`.
+#[allow(rustc::diagnostic_outside_of_impl)] // FIXME
 pub fn add_feature_diagnostics_for_issue<G: EmissionGuarantee>(
    err: &mut Diag<'_, G>,
    sess: &Session,
--- a/compiler/rustc_session/src/search_paths.rs
+++ b/compiler/rustc_session/src/search_paths.rs
@ -61,6 +61,7 @@ impl SearchPath {
            (PathKind::All, path)
        };
        if path.is_empty() {
+            #[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
            early_dcx.early_fatal("empty search path given via `-L`");
        }

--- a/compiler/rustc_session/src/session.rs
+++ b/compiler/rustc_session/src/session.rs
@ -312,6 +312,7 @@ impl Session {
    ) -> Diag<'a> {
        let mut err = self.dcx().create_err(err);
        if err.code.is_none() {
+            #[allow(rustc::diagnostic_outside_of_impl)]
            err.code(E0658);
        }
        add_feature_diagnostics(&mut err, self, feature);
@ -1022,6 +1023,7 @@ fn default_emitter(

 // JUSTIFICATION: literally session construction
 #[allow(rustc::bad_opt_access)]
+#[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
 pub fn build_session(
    early_dcx: EarlyDiagCtxt,
    sopts: config::Options,
--- a/src/tools/rust-analyzer/crates/hir-ty/src/layout.rs
+++ b/src/tools/rust-analyzer/crates/hir-ty/src/layout.rs
@ -1,5 +1,6 @@
 //! Compute the binary representation of a type

+use std::borrow::Cow;
 use std::fmt;

 use base_db::salsa::Cycle;
@ -114,8 +115,8 @@ struct LayoutCx<'a> {
 impl<'a> LayoutCalculator for LayoutCx<'a> {
    type TargetDataLayoutRef = &'a TargetDataLayout;

-    fn delayed_bug(&self, txt: String) {
-        never!("{}", txt);
+    fn delayed_bug(&self, txt: impl Into<Cow<'static, str>>) {
+        never!("{}", txt.into());
    }

    fn current_data_layout(&self) -> &'a TargetDataLayout {
--- a/src/tools/rustfmt/src/parse/session.rs
+++ b/src/tools/rustfmt/src/parse/session.rs
@ -360,6 +360,7 @@ mod tests {
        }

        fn build_diagnostic(level: DiagnosticLevel, span: Option<MultiSpan>) -> DiagInner {
+            #[allow(rustc::untranslatable_diagnostic)] // no translation needed for empty string
            let mut diag = DiagInner::new(level, "");
            diag.messages.clear();
            if let Some(span) = span {
--- a/tests/ui-fulldeps/internal-lints/diagnostics.rs
+++ b/tests/ui-fulldeps/internal-lints/diagnostics.rs
@ -14,8 +14,8 @@ extern crate rustc_session;
 extern crate rustc_span;

 use rustc_errors::{
-    AddToDiagnostic, Diag, EmissionGuarantee, DiagCtxt, IntoDiagnostic, Level,
-    SubdiagMessageOp,
+    AddToDiagnostic, DecorateLint, Diag, DiagCtxt, DiagInner, DiagMessage, EmissionGuarantee,
+    IntoDiagnostic, Level, SubdiagMessageOp,
 };
 use rustc_macros::{Diagnostic, Subdiagnostic};
 use rustc_span::Span;
@ -78,6 +78,31 @@ impl AddToDiagnostic for TranslatableInAddToDiagnostic {
    }
 }

+pub struct UntranslatableInDecorateLint;
+
+impl<'a> DecorateLint<'a, ()> for UntranslatableInDecorateLint {
+    fn decorate_lint<'b, >(self, diag: &'b mut Diag<'a, ()>) {
+        diag.note("untranslatable diagnostic");
+        //~^ ERROR diagnostics should be created using translatable messages
+    }
+
+    fn msg(&self) -> DiagMessage {
+        unreachable!();
+    }
+}
+
+pub struct TranslatableInDecorateLint;
+
+impl<'a> DecorateLint<'a, ()> for TranslatableInDecorateLint {
+    fn decorate_lint<'b>(self, diag: &'b mut Diag<'a, ()>) {
+        diag.note(crate::fluent_generated::no_crate_note);
+    }
+
+    fn msg(&self) -> DiagMessage {
+        unreachable!();
+    }
+}
+
 pub fn make_diagnostics<'a>(dcx: &'a DiagCtxt) {
    let _diag = dcx.struct_err(crate::fluent_generated::no_crate_example);
    //~^ ERROR diagnostics should only be created in `IntoDiagnostic`/`AddToDiagnostic` impls
@ -87,9 +112,11 @@ pub fn make_diagnostics<'a>(dcx: &'a DiagCtxt) {
    //~^^ ERROR diagnostics should be created using translatable messages
 }

-// Check that `rustc_lint_diagnostics`-annotated functions aren't themselves linted.
+// Check that `rustc_lint_diagnostics`-annotated functions aren't themselves linted for
+// `diagnostic_outside_of_impl`.

 #[rustc_lint_diagnostics]
 pub fn skipped_because_of_annotation<'a>(dcx: &'a DiagCtxt) {
+    #[allow(rustc::untranslatable_diagnostic)]
    let _diag = dcx.struct_err("untranslatable diagnostic"); // okay!
 }
--- a/tests/ui-fulldeps/internal-lints/diagnostics.stderr
+++ b/tests/ui-fulldeps/internal-lints/diagnostics.stderr
@ -16,8 +16,14 @@ error: diagnostics should be created using translatable messages
 LL |         diag.note("untranslatable diagnostic");
   |              ^^^^

+error: diagnostics should be created using translatable messages
+  --> $DIR/diagnostics.rs:85:14
+   |
+LL |         diag.note("untranslatable diagnostic");
+   |              ^^^^
+
 error: diagnostics should only be created in `IntoDiagnostic`/`AddToDiagnostic` impls
-  --> $DIR/diagnostics.rs:82:21
+  --> $DIR/diagnostics.rs:107:21
   |
 LL |     let _diag = dcx.struct_err(crate::fluent_generated::no_crate_example);
   |                     ^^^^^^^^^^
@ -29,16 +35,16 @@ LL | #![deny(rustc::diagnostic_outside_of_impl)]
   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

 error: diagnostics should only be created in `IntoDiagnostic`/`AddToDiagnostic` impls
-  --> $DIR/diagnostics.rs:85:21
+  --> $DIR/diagnostics.rs:110:21
   |
 LL |     let _diag = dcx.struct_err("untranslatable diagnostic");
   |                     ^^^^^^^^^^

 error: diagnostics should be created using translatable messages
-  --> $DIR/diagnostics.rs:85:21
+  --> $DIR/diagnostics.rs:110:21
   |
 LL |     let _diag = dcx.struct_err("untranslatable diagnostic");
   |                     ^^^^^^^^^^

-error: aborting due to 5 previous errors
+error: aborting due to 6 previous errors