do not suggest adding a bound to a opaque type

Author: TaKO8Ki

compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs

@@ -273,13 +273,17 @@ impl<'tcx> BorrowExplanation<'tcx> {
             _ => {}
         }
     }
-    pub(crate) fn add_lifetime_bound_suggestion_to_diagnostic(
+
+    fn add_lifetime_bound_suggestion_to_diagnostic(
         &self,
         err: &mut Diagnostic,
         category: &ConstraintCategory<'tcx>,
         span: Span,
         region_name: &RegionName,
     ) {
+        if !span.is_desugaring(DesugaringKind::OpaqueTy) {
+            return;
+        }
         if let ConstraintCategory::OpaqueType = category {
             let suggestable_name =
                 if region_name.was_named() { region_name.name } else { kw::UnderscoreLifetime };

src/test/ui/regions/do-not-suggest-adding-bound-to-opaque-type.rs

@@ -0,0 +1,29 @@
+#![feature(allocator_api)]
+
+use std::{
+    alloc::{AllocError, Allocator, Layout},
+    ptr::NonNull,
+};
+
+struct GhostBump;
+
+unsafe impl Allocator for &GhostBump {
+    fn allocate(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocError> {
+        todo!()
+    }
+
+    unsafe fn deallocate(&self, ptr: NonNull<u8>, layout: Layout) {
+        todo!()
+    }
+}
+
+fn foo() -> impl Iterator<Item = usize> {
+    let arena = GhostBump;
+    let mut vec = Vec::new_in(&arena); //~ ERROR `arena` does not live long enough
+    vec.push(1);
+    vec.push(2);
+    vec.push(3);
+    vec.into_iter()
+}
+
+fn main() {}

src/test/ui/regions/do-not-suggest-adding-bound-to-opaque-type.stderr

@@ -0,0 +1,14 @@
+error[E0597]: `arena` does not live long enough
+  --> $DIR/do-not-suggest-adding-bound-to-opaque-type.rs:22:31
+   |
+LL |     let mut vec = Vec::new_in(&arena);
+   |                               ^^^^^^ borrowed value does not live long enough
+...
+LL |     vec.into_iter()
+   |     --------------- opaque type requires that `arena` is borrowed for `'static`
+LL | }
+   | - `arena` dropped here while still borrowed
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0597`.