1 files changed, 79 insertions, 0 deletions
diff --git a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/placeholder_relation.rs b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/placeholder_relation.rs
new file mode 100644
index 000000000..c42240f21
--- /dev/null
+++ b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/placeholder_relation.rs
@@ -0,0 +1,79 @@
+use crate::infer::{
+    error_reporting::nice_region_error::NiceRegionError, RegionResolutionError, SubregionOrigin,
+};
+use rustc_data_structures::intern::Interned;
+use rustc_errors::{DiagnosticBuilder, ErrorGuaranteed};
+use rustc_middle::ty::{self, RePlaceholder, Region};
+
+impl<'tcx> NiceRegionError<'_, 'tcx> {
+    /// Emitted wwhen given a `ConcreteFailure` when relating two placeholders.
+    pub(super) fn try_report_placeholder_relation(
+        &self,
+    ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
+        match &self.error {
+            Some(RegionResolutionError::ConcreteFailure(
+                SubregionOrigin::RelateRegionParamBound(span),
+                Region(Interned(RePlaceholder(ty::Placeholder { name: sub_name, .. }), _)),
+                Region(Interned(RePlaceholder(ty::Placeholder { name: sup_name, .. }), _)),
+            )) => {
+                let msg = "lifetime bound not satisfied";
+                let mut err = self.tcx().sess.struct_span_err(*span, msg);
+                let (sub_span, sub_symbol) = match sub_name {
+                    ty::BrNamed(def_id, symbol) => {
+                        (Some(self.tcx().def_span(def_id)), Some(symbol))
+                    }
+                    ty::BrAnon(_, span) => (*span, None),
+                    ty::BrEnv => (None, None),
+                };
+                let (sup_span, sup_symbol) = match sup_name {
+                    ty::BrNamed(def_id, symbol) => {
+                        (Some(self.tcx().def_span(def_id)), Some(symbol))
+                    }
+                    ty::BrAnon(_, span) => (*span, None),
+                    ty::BrEnv => (None, None),
+                };
+                match (sub_span, sup_span, sub_symbol, sup_symbol) {
+                    (Some(sub_span), Some(sup_span), Some(sub_symbol), Some(sup_symbol)) => {
+                        err.span_note(
+                            sub_span,
+                            format!("the lifetime `{sub_symbol}` defined here..."),
+                        );
+                        err.span_note(
+                            sup_span,
+                            format!("...must outlive the lifetime `{sup_symbol}` defined here"),
+                        );
+                    }
+                    (Some(sub_span), Some(sup_span), _, Some(sup_symbol)) => {
+                        err.span_note(sub_span, format!("the lifetime defined here..."));
+                        err.span_note(
+                            sup_span,
+                            format!("...must outlive the lifetime `{sup_symbol}` defined here"),
+                        );
+                    }
+                    (Some(sub_span), Some(sup_span), Some(sub_symbol), _) => {
+                        err.span_note(
+                            sub_span,
+                            format!("the lifetime `{sub_symbol}` defined here..."),
+                        );
+                        err.span_note(
+                            sup_span,
+                            format!("...must outlive the lifetime defined here"),
+                        );
+                    }
+                    (Some(sub_span), Some(sup_span), _, _) => {
+                        err.span_note(sub_span, format!("the lifetime defined here..."));
+                        err.span_note(
+                            sup_span,
+                            format!("...must outlive the lifetime defined here"),
+                        );
+                    }
+                    _ => {}
+                }
+                err.note("this is a known limitation that will be removed in the future (see issue #100013 <https://github.com/rust-lang/rust/issues/100013> for more information)");
+                Some(err)
+            }
+
+            _ => None,
+        }
+    }
+}