Rollup merge of #124218 - Xiretza:subsubdiagnostics, r=davidtwco

Allow nesting subdiagnostics in #[derive(Subdiagnostic)]

3 files changed, 55 insertions, 50 deletions

diff --git a/compiler/rustc_errors/src/diagnostic.rs b/compiler/rustc_errors/src/diagnostic.rs
index a17e0da47a5..6c84eeaf888 100644
--- a/compiler/rustc_errors/src/diagnostic.rs
+++ b/compiler/rustc_errors/src/diagnostic.rs
@@ -177,7 +177,7 @@ where
 {
     /// 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);
+        self.add_to_diag_with(diag, &|_, m| m);
     }
 
     /// Add a subdiagnostic to an existing diagnostic where `f` is invoked on every message used
@@ -185,7 +185,7 @@ where
     fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
         self,
         diag: &mut Diag<'_, G>,
-        f: F,
+        f: &F,
     );
 }
 
@@ -1197,7 +1197,7 @@ impl<'a, G: EmissionGuarantee> Diag<'a, G> {
         dcx: &crate::DiagCtxt,
         subdiagnostic: impl Subdiagnostic,
     ) -> &mut Self {
-        subdiagnostic.add_to_diag_with(self, |diag, msg| {
+        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)
diff --git a/compiler/rustc_errors/src/diagnostic_impls.rs b/compiler/rustc_errors/src/diagnostic_impls.rs
index 6c0551848d6..2b10fcd8d6a 100644
--- a/compiler/rustc_errors/src/diagnostic_impls.rs
+++ b/compiler/rustc_errors/src/diagnostic_impls.rs
@@ -227,6 +227,36 @@ impl IntoDiagArg for rustc_lint_defs::Level {
     }
 }
 
+impl<Id> IntoDiagArg for hir::def::Res<Id> {
+    fn into_diag_arg(self) -> DiagArgValue {
+        DiagArgValue::Str(Cow::Borrowed(self.descr()))
+    }
+}
+
+impl IntoDiagArg for DiagLocation {
+    fn into_diag_arg(self) -> DiagArgValue {
+        DiagArgValue::Str(Cow::from(self.to_string()))
+    }
+}
+
+impl IntoDiagArg for Backtrace {
+    fn into_diag_arg(self) -> DiagArgValue {
+        DiagArgValue::Str(Cow::from(self.to_string()))
+    }
+}
+
+impl IntoDiagArg for Level {
+    fn into_diag_arg(self) -> DiagArgValue {
+        DiagArgValue::Str(Cow::from(self.to_string()))
+    }
+}
+
+impl IntoDiagArg for type_ir::ClosureKind {
+    fn into_diag_arg(self) -> DiagArgValue {
+        DiagArgValue::Str(self.as_str().into())
+    }
+}
+
 #[derive(Clone)]
 pub struct DiagSymbolList(Vec<Symbol>);
 
@@ -244,12 +274,6 @@ impl IntoDiagArg for DiagSymbolList {
     }
 }
 
-impl<Id> IntoDiagArg for hir::def::Res<Id> {
-    fn into_diag_arg(self) -> DiagArgValue {
-        DiagArgValue::Str(Cow::Borrowed(self.descr()))
-    }
-}
-
 impl<G: EmissionGuarantee> Diagnostic<'_, G> for TargetDataLayoutErrors<'_> {
     fn into_diag(self, dcx: &DiagCtxt, level: Level) -> Diag<'_, G> {
         match self {
@@ -302,7 +326,7 @@ impl Subdiagnostic for SingleLabelManySpans {
     fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
         self,
         diag: &mut Diag<'_, G>,
-        _: F,
+        _: &F,
     ) {
         diag.span_labels(self.spans, self.label);
     }
@@ -316,24 +340,6 @@ pub struct ExpectedLifetimeParameter {
     pub count: usize,
 }
 
-impl IntoDiagArg for DiagLocation {
-    fn into_diag_arg(self) -> DiagArgValue {
-        DiagArgValue::Str(Cow::from(self.to_string()))
-    }
-}
-
-impl IntoDiagArg for Backtrace {
-    fn into_diag_arg(self) -> DiagArgValue {
-        DiagArgValue::Str(Cow::from(self.to_string()))
-    }
-}
-
-impl IntoDiagArg for Level {
-    fn into_diag_arg(self) -> DiagArgValue {
-        DiagArgValue::Str(Cow::from(self.to_string()))
-    }
-}
-
 #[derive(Subdiagnostic)]
 #[suggestion(errors_indicate_anonymous_lifetime, code = "{suggestion}", style = "verbose")]
 pub struct IndicateAnonymousLifetime {
@@ -343,8 +349,10 @@ pub struct IndicateAnonymousLifetime {
     pub suggestion: String,
 }
 
-impl IntoDiagArg for type_ir::ClosureKind {
-    fn into_diag_arg(self) -> DiagArgValue {
-        DiagArgValue::Str(self.as_str().into())
-    }
+#[derive(Subdiagnostic)]
+pub struct ElidedLifetimeInPathSubdiag {
+    #[subdiagnostic]
+    pub expected: ExpectedLifetimeParameter,
+    #[subdiagnostic]
+    pub indicate: Option<IndicateAnonymousLifetime>,
 }
diff --git a/compiler/rustc_errors/src/lib.rs b/compiler/rustc_errors/src/lib.rs
index e3363e89594..b3c1c6c8515 100644
--- a/compiler/rustc_errors/src/lib.rs
+++ b/compiler/rustc_errors/src/lib.rs
@@ -40,8 +40,8 @@ pub use diagnostic::{
     SubdiagMessageOp, Subdiagnostic,
 };
 pub use diagnostic_impls::{
-    DiagArgFromDisplay, DiagSymbolList, ExpectedLifetimeParameter, IndicateAnonymousLifetime,
-    SingleLabelManySpans,
+    DiagArgFromDisplay, DiagSymbolList, ElidedLifetimeInPathSubdiag, ExpectedLifetimeParameter,
+    IndicateAnonymousLifetime, SingleLabelManySpans,
 };
 pub use emitter::ColorConfig;
 pub use rustc_error_messages::{
@@ -1911,27 +1911,24 @@ impl Level {
 }
 
 // FIXME(eddyb) this doesn't belong here AFAICT, should be moved to callsite.
-pub fn add_elided_lifetime_in_path_suggestion<G: EmissionGuarantee>(
+pub fn elided_lifetime_in_path_suggestion(
     source_map: &SourceMap,
-    diag: &mut Diag<'_, G>,
     n: usize,
     path_span: Span,
     incl_angl_brckt: bool,
     insertion_span: Span,
-) {
-    diag.subdiagnostic(diag.dcx, ExpectedLifetimeParameter { span: path_span, count: n });
-    if !source_map.is_span_accessible(insertion_span) {
-        // Do not try to suggest anything if generated by a proc-macro.
-        return;
-    }
-    let anon_lts = vec!["'_"; n].join(", ");
-    let suggestion =
-        if incl_angl_brckt { format!("<{anon_lts}>") } else { format!("{anon_lts}, ") };
-
-    diag.subdiagnostic(
-        diag.dcx,
-        IndicateAnonymousLifetime { span: insertion_span.shrink_to_hi(), count: n, suggestion },
-    );
+) -> ElidedLifetimeInPathSubdiag {
+    let expected = ExpectedLifetimeParameter { span: path_span, count: n };
+    // Do not try to suggest anything if generated by a proc-macro.
+    let indicate = source_map.is_span_accessible(insertion_span).then(|| {
+        let anon_lts = vec!["'_"; n].join(", ");
+        let suggestion =
+            if incl_angl_brckt { format!("<{anon_lts}>") } else { format!("{anon_lts}, ") };
+
+        IndicateAnonymousLifetime { span: insertion_span.shrink_to_hi(), count: n, suggestion }
+    });
+
+    ElidedLifetimeInPathSubdiag { expected, indicate }
 }
 
 pub fn report_ambiguity_error<'a, G: EmissionGuarantee>(