Tweak output of #[rustc_object_lifetime_default]

* Print `Empty` as it's called in code, otherwise it's unnecessarily confusing
* Go through the middle::ty Generics instead of the HIR ones, so we can dump the
  default for the implicit `Self` type parameter of traits, too.

Author: fmease

compiler/rustc_passes/src/check_attr.rs

@@ -710,20 +710,18 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
     /// Debugging aid for `object_lifetime_default` query.
     fn check_object_lifetime_default(&self, hir_id: HirId) {
         let tcx = self.tcx;
-        if let Some(owner_id) = hir_id.as_owner()
-            && let Some(generics) = tcx.hir_get_generics(owner_id.def_id)
-        {
-            for p in generics.params {
-                let hir::GenericParamKind::Type { .. } = p.kind else { continue };
-                let default = tcx.object_lifetime_default(p.def_id);
-                let repr = match default {
-                    ObjectLifetimeDefault::Empty => "BaseDefault".to_owned(),
-                    ObjectLifetimeDefault::Static => "'static".to_owned(),
-                    ObjectLifetimeDefault::Param(def_id) => tcx.item_name(def_id).to_string(),
-                    ObjectLifetimeDefault::Ambiguous => "Ambiguous".to_owned(),
-                };
-                tcx.dcx().emit_err(errors::ObjectLifetimeErr { span: p.span, repr });
-            }
+        let Some(owner_id) = hir_id.as_owner() else { return };
+        for param in &tcx.generics_of(owner_id.def_id).own_params {
+            let ty::GenericParamDefKind::Type { .. } = param.kind else { continue };
+            let default = tcx.object_lifetime_default(param.def_id);
+            let repr = match default {
+                ObjectLifetimeDefault::Empty => "Empty".to_owned(),
+                ObjectLifetimeDefault::Static => "'static".to_owned(),
+                ObjectLifetimeDefault::Param(def_id) => tcx.item_name(def_id).to_string(),
+                ObjectLifetimeDefault::Ambiguous => "Ambiguous".to_owned(),
+            };
+            tcx.dcx()
+                .emit_err(errors::ObjectLifetimeErr { span: tcx.def_span(param.def_id), repr });
         }
     }
 

tests/ui/object-lifetime/object-lifetime-default.rs

@@ -2,13 +2,13 @@
 
 #[rustc_object_lifetime_default]
 struct A<
-    T, //~ ERROR BaseDefault
+    T, //~ ERROR Empty
 >(T);
 
 #[rustc_object_lifetime_default]
 struct B<
     'a,
-    T, //~ ERROR BaseDefault
+    T, //~ ERROR Empty
 >(&'a (), T);
 
 #[rustc_object_lifetime_default]
@@ -47,4 +47,12 @@ struct G<
     U: 'a + 'b, //~ ERROR Ambiguous
 >(&'a T, &'b U);
 
+// Check that we also dump the default for the implicit `Self` type param of traits.
+#[rustc_object_lifetime_default]
+trait H< //~ ERROR 'a
+    'a,
+    'b,
+    T: 'b, //~ ERROR 'b
+>: 'a {}
+
 fn main() {}

tests/ui/object-lifetime/object-lifetime-default.stderr

@@ -1,10 +1,10 @@
-error: BaseDefault
+error: Empty
   --> $DIR/object-lifetime-default.rs:5:5
    |
 LL |     T,
    |     ^
 
-error: BaseDefault
+error: Empty
   --> $DIR/object-lifetime-default.rs:11:5
    |
 LL |     T,
@@ -52,5 +52,21 @@ error: Ambiguous
 LL |     U: 'a + 'b,
    |     ^
 
-error: aborting due to 9 previous errors
+error: 'a
+  --> $DIR/object-lifetime-default.rs:52:1
+   |
+LL | / trait H<
+LL | |     'a,
+LL | |     'b,
+LL | |     T: 'b,
+LL | | >: 'a {}
+   | |_____^
+
+error: 'b
+  --> $DIR/object-lifetime-default.rs:55:5
+   |
+LL |     T: 'b,
+   |     ^
+
+error: aborting due to 11 previous errors