lifetime defined here err

compiler/rustc_borrowck/src/diagnostics/region_name.rs

@@ -10,6 +10,7 @@ use rustc_middle::ty::{self, DefIdTree, RegionVid, Ty};
 use rustc_span::symbol::{kw, sym, Ident, Symbol};
 use rustc_span::{Span, DUMMY_SP};
 
+use crate::session_diagnostics::RegionNameLables;
 use crate::{nll::ToRegionVid, universal_regions::DefiningTy, MirBorrowckCtxt};
 
 /// A name for a particular region used in emitting diagnostics. This name could be a generated
@@ -106,7 +107,11 @@ impl RegionName {
         match &self.source {
             RegionNameSource::NamedFreeRegion(span)
             | RegionNameSource::NamedEarlyBoundRegion(span) => {
-                diag.span_label(*span, format!("lifetime `{self}` defined here"));
+                let name = format!("{self}");
+                diag.subdiagnostic(RegionNameLables::LifetimeDefinedHere {
+                    span: *span,
+                    rg_name: name,
+                });
             }
             RegionNameSource::SynthesizedFreeEnvRegion(span, note) => {
                 diag.span_label(*span, format!("lifetime `{self}` represents this closure's body"));

compiler/rustc_borrowck/src/session_diagnostics.rs

@@ -157,3 +157,13 @@ pub(crate) enum RequireStaticErr {
         multi_span: MultiSpan,
     },
 }
+
+#[derive(SessionSubdiagnostic)]
+pub(crate) enum RegionNameLables {
+    #[label(borrowck::lifetime_defined_here)]
+    LifetimeDefinedHere {
+        rg_name: String,
+        #[primary_span]
+        span: Span,
+    },
+}

compiler/rustc_error_messages/locales/en-US/borrowck.ftl

@@ -58,3 +58,6 @@ borrowck_returned_lifetime_short =
 
 borrowck_used_impl_require_static =
     the used `impl` has a `'static` requirement
+
+borrowck_lifetime_defined_here =
+    lifetime `{$rg_name}` defined here