Move eager translation to a method on Diag

This will allow us to eagerly translate messages on a top-level
diagnostic, such as a `LintDiagnostic`. As a bonus, we can remove the
awkward closure passed into Subdiagnostic and make better use of
`Into`.

Author: shepmaster

compiler/rustc_ast_passes/src/errors.rs

@@ -2,7 +2,7 @@
 
 use rustc_ast::ParamKindOrd;
 use rustc_errors::codes::*;
-use rustc_errors::{Applicability, Diag, EmissionGuarantee, SubdiagMessageOp, Subdiagnostic};
+use rustc_errors::{Applicability, Diag, EmissionGuarantee, Subdiagnostic};
 use rustc_macros::{Diagnostic, Subdiagnostic};
 use rustc_span::{Ident, Span, Symbol};
 
@@ -394,11 +394,7 @@ pub(crate) struct EmptyLabelManySpans(pub Vec<Span>);
 
 // The derive for `Vec<Span>` does multiple calls to `span_label`, adding commas between each
 impl Subdiagnostic for EmptyLabelManySpans {
-    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
-        self,
-        diag: &mut Diag<'_, G>,
-        _: &F,
-    ) {
+    fn add_to_diag<G: EmissionGuarantee>(self, diag: &mut Diag<'_, G>) {
         diag.span_labels(self.0, "");
     }
 }
@@ -749,11 +745,7 @@ pub(crate) struct StableFeature {
 }
 
 impl Subdiagnostic for StableFeature {
-    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
-        self,
-        diag: &mut Diag<'_, G>,
-        _: &F,
-    ) {
+    fn add_to_diag<G: EmissionGuarantee>(self, diag: &mut Diag<'_, G>) {
         diag.arg("name", self.name);
         diag.arg("since", self.since);
         diag.help(fluent::ast_passes_stable_since);

compiler/rustc_builtin_macros/src/errors.rs

@@ -1,7 +1,7 @@
 use rustc_errors::codes::*;
 use rustc_errors::{
     Diag, DiagCtxtHandle, Diagnostic, EmissionGuarantee, Level, MultiSpan, SingleLabelManySpans,
-    SubdiagMessageOp, Subdiagnostic,
+    Subdiagnostic,
 };
 use rustc_macros::{Diagnostic, Subdiagnostic};
 use rustc_span::{Ident, Span, Symbol};
@@ -683,13 +683,9 @@ pub(crate) struct FormatUnusedArg {
 // Allow the singular form to be a subdiagnostic of the multiple-unused
 // form of diagnostic.
 impl Subdiagnostic for FormatUnusedArg {
-    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
-        self,
-        diag: &mut Diag<'_, G>,
-        f: &F,
-    ) {
+    fn add_to_diag<G: EmissionGuarantee>(self, diag: &mut Diag<'_, G>) {
         diag.arg("named", self.named);
-        let msg = f(diag, crate::fluent_generated::builtin_macros_format_unused_arg.into());
+        let msg = diag.eagerly_translate(crate::fluent_generated::builtin_macros_format_unused_arg);
         diag.span_label(self.span, msg);
     }
 }

compiler/rustc_const_eval/src/errors.rs

@@ -6,7 +6,7 @@ use rustc_abi::WrappingRange;
 use rustc_errors::codes::*;
 use rustc_errors::{
     Diag, DiagArgValue, DiagCtxtHandle, DiagMessage, Diagnostic, EmissionGuarantee, Level,
-    MultiSpan, SubdiagMessageOp, Subdiagnostic,
+    MultiSpan, Subdiagnostic,
 };
 use rustc_hir::ConstContext;
 use rustc_macros::{Diagnostic, LintDiagnostic, Subdiagnostic};
@@ -290,19 +290,15 @@ pub struct FrameNote {
 }
 
 impl Subdiagnostic for FrameNote {
-    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
-        self,
-        diag: &mut Diag<'_, G>,
-        f: &F,
-    ) {
+    fn add_to_diag<G: EmissionGuarantee>(self, diag: &mut Diag<'_, G>) {
         diag.arg("times", self.times);
         diag.arg("where_", self.where_);
         diag.arg("instance", self.instance);
         let mut span: MultiSpan = self.span.into();
         if self.has_label && !self.span.is_dummy() {
             span.push_span_label(self.span, fluent::const_eval_frame_note_last);
         }
-        let msg = f(diag, fluent::const_eval_frame_note.into());
+        let msg = diag.eagerly_translate(fluent::const_eval_frame_note);
         diag.span_note(span, msg);
     }
 }

compiler/rustc_errors/src/diagnostic.rs

@@ -181,22 +181,9 @@ where
     Self: Sized,
 {
     /// Add a subdiagnostic to an existing diagnostic.
-    fn add_to_diag<G: EmissionGuarantee>(self, diag: &mut Diag<'_, G>) {
-        self.add_to_diag_with(diag, &|_, m| m);
-    }
-
-    /// Add a subdiagnostic to an existing diagnostic where `f` is invoked on every message used
-    /// (to optionally perform eager translation).
-    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
-        self,
-        diag: &mut Diag<'_, G>,
-        f: &F,
-    );
+    fn add_to_diag<G: EmissionGuarantee>(self, diag: &mut Diag<'_, G>);
 }
 
-pub trait SubdiagMessageOp<G: EmissionGuarantee> =
-    Fn(&mut Diag<'_, G>, SubdiagMessage) -> SubdiagMessage;
-
 /// Trait implemented by lint types. This should not be implemented manually. Instead, use
 /// `#[derive(LintDiagnostic)]` -- see [rustc_macros::LintDiagnostic].
 #[rustc_diagnostic_item = "LintDiagnostic"]
@@ -1225,15 +1212,16 @@ impl<'a, G: EmissionGuarantee> Diag<'a, G> {
     /// interpolated variables).
     #[rustc_lint_diagnostics]
     pub fn subdiagnostic(&mut self, subdiagnostic: impl Subdiagnostic) -> &mut Self {
-        let dcx = self.dcx;
-        subdiagnostic.add_to_diag_with(self, &|diag, msg| {
-            let args = diag.args.iter();
-            let msg = diag.subdiagnostic_message_to_diagnostic_message(msg);
-            dcx.eagerly_translate(msg, args)
-        });
+        subdiagnostic.add_to_diag(self);
         self
     }
 
+    pub fn eagerly_translate(&self, msg: impl Into<SubdiagMessage>) -> SubdiagMessage {
+        let args = self.args.iter();
+        let msg = self.subdiagnostic_message_to_diagnostic_message(msg.into());
+        self.dcx.eagerly_translate(msg, args)
+    }
+
     with_fn! { with_span,
     /// Add a span.
     #[rustc_lint_diagnostics]

compiler/rustc_errors/src/diagnostic_impls.rs

@@ -19,7 +19,7 @@ use {rustc_ast as ast, rustc_hir as hir};
 use crate::diagnostic::DiagLocation;
 use crate::{
     Diag, DiagArgValue, DiagCtxtHandle, Diagnostic, EmissionGuarantee, ErrCode, IntoDiagArg, Level,
-    SubdiagMessageOp, Subdiagnostic, fluent_generated as fluent,
+    Subdiagnostic, fluent_generated as fluent,
 };
 
 pub struct DiagArgFromDisplay<'a>(pub &'a dyn fmt::Display);
@@ -384,11 +384,7 @@ pub struct SingleLabelManySpans {
     pub label: &'static str,
 }
 impl Subdiagnostic for SingleLabelManySpans {
-    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
-        self,
-        diag: &mut Diag<'_, G>,
-        _: &F,
-    ) {
+    fn add_to_diag<G: EmissionGuarantee>(self, diag: &mut Diag<'_, G>) {
         diag.span_labels(self.spans, self.label);
     }
 }

compiler/rustc_errors/src/lib.rs

@@ -47,7 +47,7 @@ pub use codes::*;
 pub use diagnostic::{
     BugAbort, Diag, DiagArg, DiagArgMap, DiagArgName, DiagArgValue, DiagInner, DiagStyledString,
     Diagnostic, EmissionGuarantee, FatalAbort, IntoDiagArg, LintDiagnostic, StringPart, Subdiag,
-    SubdiagMessageOp, Subdiagnostic,
+    Subdiagnostic,
 };
 pub use diagnostic_impls::{
     DiagArgFromDisplay, DiagSymbolList, ElidedLifetimeInPathSubdiag, ExpectedLifetimeParameter,

compiler/rustc_hir_typeck/src/errors.rs

@@ -5,7 +5,7 @@ use std::borrow::Cow;
 use rustc_errors::codes::*;
 use rustc_errors::{
     Applicability, Diag, DiagArgValue, DiagSymbolList, EmissionGuarantee, IntoDiagArg, MultiSpan,
-    SubdiagMessageOp, Subdiagnostic,
+    Subdiagnostic,
 };
 use rustc_macros::{Diagnostic, LintDiagnostic, Subdiagnostic};
 use rustc_middle::ty::{self, Ty};
@@ -270,11 +270,7 @@ pub(crate) struct SuggestAnnotations {
     pub suggestions: Vec<SuggestAnnotation>,
 }
 impl Subdiagnostic for SuggestAnnotations {
-    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
-        self,
-        diag: &mut Diag<'_, G>,
-        _: &F,
-    ) {
+    fn add_to_diag<G: EmissionGuarantee>(self, diag: &mut Diag<'_, G>) {
         if self.suggestions.is_empty() {
             return;
         }
@@ -337,11 +333,7 @@ pub(crate) struct TypeMismatchFruTypo {
 }
 
 impl Subdiagnostic for TypeMismatchFruTypo {
-    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
-        self,
-        diag: &mut Diag<'_, G>,
-        _f: &F,
-    ) {
+    fn add_to_diag<G: EmissionGuarantee>(self, diag: &mut Diag<'_, G>) {
         diag.arg("expr", self.expr.as_deref().unwrap_or("NONE"));
 
         // Only explain that `a ..b` is a range if it's split up
@@ -599,11 +591,7 @@ pub(crate) struct RemoveSemiForCoerce {
 }
 
 impl Subdiagnostic for RemoveSemiForCoerce {
-    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
-        self,
-        diag: &mut Diag<'_, G>,
-        _f: &F,
-    ) {
+    fn add_to_diag<G: EmissionGuarantee>(self, diag: &mut Diag<'_, G>) {
         let mut multispan: MultiSpan = self.semi.into();
         multispan.push_span_label(self.expr, fluent::hir_typeck_remove_semi_for_coerce_expr);
         multispan.push_span_label(self.ret, fluent::hir_typeck_remove_semi_for_coerce_ret);
@@ -778,20 +766,16 @@ pub(crate) enum CastUnknownPointerSub {
 }
 
 impl rustc_errors::Subdiagnostic for CastUnknownPointerSub {
-    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
-        self,
-        diag: &mut Diag<'_, G>,
-        f: &F,
-    ) {
+    fn add_to_diag<G: EmissionGuarantee>(self, diag: &mut Diag<'_, G>) {
         match self {
             CastUnknownPointerSub::To(span) => {
-                let msg = f(diag, crate::fluent_generated::hir_typeck_label_to);
+                let msg = diag.eagerly_translate(fluent::hir_typeck_label_to);
                 diag.span_label(span, msg);
-                let msg = f(diag, crate::fluent_generated::hir_typeck_note);
+                let msg = diag.eagerly_translate(fluent::hir_typeck_note);
                 diag.note(msg);
             }
             CastUnknownPointerSub::From(span) => {
-                let msg = f(diag, crate::fluent_generated::hir_typeck_label_from);
+                let msg = diag.eagerly_translate(fluent::hir_typeck_label_from);
                 diag.span_label(span, msg);
             }
         }

compiler/rustc_lint/src/errors.rs

@@ -1,5 +1,5 @@
 use rustc_errors::codes::*;
-use rustc_errors::{Diag, EmissionGuarantee, SubdiagMessageOp, Subdiagnostic};
+use rustc_errors::{Diag, EmissionGuarantee, Subdiagnostic};
 use rustc_macros::{Diagnostic, Subdiagnostic};
 use rustc_session::lint::Level;
 use rustc_span::{Span, Symbol};
@@ -26,11 +26,7 @@ pub(crate) enum OverruledAttributeSub {
 }
 
 impl Subdiagnostic for OverruledAttributeSub {
-    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
-        self,
-        diag: &mut Diag<'_, G>,
-        _f: &F,
-    ) {
+    fn add_to_diag<G: EmissionGuarantee>(self, diag: &mut Diag<'_, G>) {
         match self {
             OverruledAttributeSub::DefaultSource { id } => {
                 diag.note(fluent::lint_default_source);

compiler/rustc_lint/src/if_let_rescope.rs

@@ -3,9 +3,7 @@ use std::ops::ControlFlow;
 
 use hir::intravisit::{self, Visitor};
 use rustc_ast::Recovered;
-use rustc_errors::{
-    Applicability, Diag, EmissionGuarantee, SubdiagMessageOp, Subdiagnostic, SuggestionStyle,
-};
+use rustc_errors::{Applicability, Diag, EmissionGuarantee, Subdiagnostic, SuggestionStyle};
 use rustc_hir::{self as hir, HirIdSet};
 use rustc_macros::{LintDiagnostic, Subdiagnostic};
 use rustc_middle::ty::adjustment::Adjust;
@@ -327,11 +325,7 @@ struct IfLetRescopeRewrite {
 }
 
 impl Subdiagnostic for IfLetRescopeRewrite {
-    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
-        self,
-        diag: &mut Diag<'_, G>,
-        f: &F,
-    ) {
+    fn add_to_diag<G: EmissionGuarantee>(self, diag: &mut Diag<'_, G>) {
         let mut suggestions = vec![];
         for match_head in self.match_heads {
             match match_head {
@@ -360,7 +354,7 @@ impl Subdiagnostic for IfLetRescopeRewrite {
                 .chain(repeat('}').take(closing_brackets.count))
                 .collect(),
         ));
-        let msg = f(diag, crate::fluent_generated::lint_suggestion);
+        let msg = diag.eagerly_translate(crate::fluent_generated::lint_suggestion);
         diag.multipart_suggestion_with_style(
             msg,
             suggestions,

compiler/rustc_lint/src/lints.rs

@@ -6,7 +6,7 @@ use rustc_abi::ExternAbi;
 use rustc_errors::codes::*;
 use rustc_errors::{
     Applicability, Diag, DiagArgValue, DiagMessage, DiagStyledString, ElidedLifetimeInPathSubdiag,
-    EmissionGuarantee, LintDiagnostic, MultiSpan, SubdiagMessageOp, Subdiagnostic, SuggestionStyle,
+    EmissionGuarantee, LintDiagnostic, MultiSpan, Subdiagnostic, SuggestionStyle,
 };
 use rustc_hir::def::Namespace;
 use rustc_hir::def_id::DefId;
@@ -449,11 +449,7 @@ pub(crate) struct BuiltinUnpermittedTypeInitSub {
 }
 
 impl Subdiagnostic for BuiltinUnpermittedTypeInitSub {
-    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
-        self,
-        diag: &mut Diag<'_, G>,
-        _f: &F,
-    ) {
+    fn add_to_diag<G: EmissionGuarantee>(self, diag: &mut Diag<'_, G>) {
         let mut err = self.err;
         loop {
             if let Some(span) = err.span {
@@ -504,11 +500,7 @@ pub(crate) struct BuiltinClashingExternSub<'a> {
 }
 
 impl Subdiagnostic for BuiltinClashingExternSub<'_> {
-    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
-        self,
-        diag: &mut Diag<'_, G>,
-        _f: &F,
-    ) {
+    fn add_to_diag<G: EmissionGuarantee>(self, diag: &mut Diag<'_, G>) {
         let mut expected_str = DiagStyledString::new();
         expected_str.push(self.expected.fn_sig(self.tcx).to_string(), false);
         let mut found_str = DiagStyledString::new();
@@ -808,11 +800,7 @@ pub(crate) struct HiddenUnicodeCodepointsDiagLabels {
 }
 
 impl Subdiagnostic for HiddenUnicodeCodepointsDiagLabels {
-    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
-        self,
-        diag: &mut Diag<'_, G>,
-        _f: &F,
-    ) {
+    fn add_to_diag<G: EmissionGuarantee>(self, diag: &mut Diag<'_, G>) {
         for (c, span) in self.spans {
             diag.span_label(span, format!("{c:?}"));
         }
@@ -826,11 +814,7 @@ pub(crate) enum HiddenUnicodeCodepointsDiagSub {
 
 // Used because of multiple multipart_suggestion and note
 impl Subdiagnostic for HiddenUnicodeCodepointsDiagSub {
-    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
-        self,
-        diag: &mut Diag<'_, G>,
-        _f: &F,
-    ) {
+    fn add_to_diag<G: EmissionGuarantee>(self, diag: &mut Diag<'_, G>) {
         match self {
             HiddenUnicodeCodepointsDiagSub::Escape { spans } => {
                 diag.multipart_suggestion_with_style(
@@ -999,11 +983,7 @@ pub(crate) struct NonBindingLetSub {
 }
 
 impl Subdiagnostic for NonBindingLetSub {
-    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
-        self,
-        diag: &mut Diag<'_, G>,
-        _f: &F,
-    ) {
+    fn add_to_diag<G: EmissionGuarantee>(self, diag: &mut Diag<'_, G>) {
         let can_suggest_binding = self.drop_fn_start_end.is_some() || !self.is_assign_desugar;
 
         if can_suggest_binding {
@@ -1287,11 +1267,7 @@ pub(crate) enum NonSnakeCaseDiagSub {
 }
 
 impl Subdiagnostic for NonSnakeCaseDiagSub {
-    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
-        self,
-        diag: &mut Diag<'_, G>,
-        _f: &F,
-    ) {
+    fn add_to_diag<G: EmissionGuarantee>(self, diag: &mut Diag<'_, G>) {
         match self {
             NonSnakeCaseDiagSub::Label { span } => {
                 diag.span_label(span, fluent::lint_label);
@@ -1613,11 +1589,7 @@ pub(crate) enum OverflowingBinHexSign {
 }
 
 impl Subdiagnostic for OverflowingBinHexSign {
-    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
-        self,
-        diag: &mut Diag<'_, G>,
-        _f: &F,
-    ) {
+    fn add_to_diag<G: EmissionGuarantee>(self, diag: &mut Diag<'_, G>) {
         match self {
             OverflowingBinHexSign::Positive => {
                 diag.note(fluent::lint_positive_note);