From 0ae0643a5353da7b79e53a11beca93ceeea067d5 Mon Sep 17 00:00:00 2001
From: Michael Goulet <michael@errs.io>
Date: Thu, 27 Jul 2023 22:04:19 +0000
Subject: [PATCH] Skip reporting item name when checking RPITIT GAT's
 associated type bounds hold

---
 .../src/infer/error_reporting/note.rs         | 18 +++++++----
 .../in-trait/bad-item-bound-within-rpitit.rs  | 25 ++++++++++++++++
 .../bad-item-bound-within-rpitit.stderr       | 30 +++++++++++++++++++
 3 files changed, 67 insertions(+), 6 deletions(-)
 create mode 100644 tests/ui/impl-trait/in-trait/bad-item-bound-within-rpitit.rs
 create mode 100644 tests/ui/impl-trait/in-trait/bad-item-bound-within-rpitit.stderr

diff --git a/compiler/rustc_infer/src/infer/error_reporting/note.rs b/compiler/rustc_infer/src/infer/error_reporting/note.rs
index 7144084c78eb..8cd1b82130b0 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/note.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/note.rs
@@ -243,12 +243,18 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
             }
             infer::CheckAssociatedTypeBounds { impl_item_def_id, trait_item_def_id, parent } => {
                 let mut err = self.report_concrete_failure(*parent, sub, sup);
-                let trait_item_span = self.tcx.def_span(trait_item_def_id);
-                let item_name = self.tcx.item_name(impl_item_def_id.to_def_id());
-                err.span_label(
-                    trait_item_span,
-                    format!("definition of `{}` from trait", item_name),
-                );
+
+                // Don't mention the item name if it's an RPITIT, since that'll just confuse
+                // folks.
+                if !self.tcx.is_impl_trait_in_trait(impl_item_def_id.to_def_id()) {
+                    let trait_item_span = self.tcx.def_span(trait_item_def_id);
+                    let item_name = self.tcx.item_name(impl_item_def_id.to_def_id());
+                    err.span_label(
+                        trait_item_span,
+                        format!("definition of `{}` from trait", item_name),
+                    );
+                }
+
                 self.suggest_copy_trait_method_bounds(
                     trait_item_def_id,
                     impl_item_def_id,
diff --git a/tests/ui/impl-trait/in-trait/bad-item-bound-within-rpitit.rs b/tests/ui/impl-trait/in-trait/bad-item-bound-within-rpitit.rs
new file mode 100644
index 000000000000..8b97336fe0c6
--- /dev/null
+++ b/tests/ui/impl-trait/in-trait/bad-item-bound-within-rpitit.rs
@@ -0,0 +1,25 @@
+// issue: 114145
+
+#![feature(return_position_impl_trait_in_trait)]
+
+trait Iterable {
+    type Item<'a>
+    where
+        Self: 'a;
+
+    fn iter(&self) -> impl '_ + Iterator<Item = Self::Item<'_>>;
+}
+
+impl<'a, I: 'a + Iterable> Iterable for &'a I {
+    type Item<'b> = I::Item<'a>
+    where
+        'b: 'a;
+    //~^ ERROR impl has stricter requirements than trait
+
+    fn iter(&self) -> impl 'a + Iterator<Item = I::Item<'a>> {
+        //~^ ERROR the type `&'a I` does not fulfill the required lifetime
+        (*self).iter()
+    }
+}
+
+fn main() {}
diff --git a/tests/ui/impl-trait/in-trait/bad-item-bound-within-rpitit.stderr b/tests/ui/impl-trait/in-trait/bad-item-bound-within-rpitit.stderr
new file mode 100644
index 000000000000..1e3363268f06
--- /dev/null
+++ b/tests/ui/impl-trait/in-trait/bad-item-bound-within-rpitit.stderr
@@ -0,0 +1,30 @@
+error[E0276]: impl has stricter requirements than trait
+  --> $DIR/bad-item-bound-within-rpitit.rs:16:13
+   |
+LL |     type Item<'a>
+   |     ------------- definition of `Item` from trait
+...
+LL |         'b: 'a;
+   |             ^^ impl has extra requirement `'b: 'a`
+   |
+help: copy the `where` clause predicates from the trait
+   |
+LL |     where Self: 'b;
+   |     ~~~~~~~~~~~~~~
+
+error[E0477]: the type `&'a I` does not fulfill the required lifetime
+  --> $DIR/bad-item-bound-within-rpitit.rs:19:5
+   |
+LL |     fn iter(&self) -> impl 'a + Iterator<Item = I::Item<'a>> {
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+note: type must outlive the anonymous lifetime as defined here
+  --> $DIR/bad-item-bound-within-rpitit.rs:10:28
+   |
+LL |     fn iter(&self) -> impl '_ + Iterator<Item = Self::Item<'_>>;
+   |                            ^^
+
+error: aborting due to 2 previous errors
+
+Some errors have detailed explanations: E0276, E0477.
+For more information about an error, try `rustc --explain E0276`.