Point at inner item on E0401 generated by hir_typeck

```
error[E0401]: can't reference `Self` constructor from outer item
  --> $DIR/do-not-ice-on-note_and_explain.rs:6:13
   |
LL | impl<B> A<B> {
   | ------------ the inner item doesn't inherit generics from this impl, so `Self` is invalid to reference
LL |     fn d() {
LL |         fn d() {
   |            - `Self` used in this inner item
LL |             Self(1)
   |             ^^^^ help: replace `Self` with the actual type: `A`
```

Author: estebank

compiler/rustc_hir_typeck/messages.ftl

@@ -262,6 +262,8 @@ hir_typeck_self_ctor_from_outer_item = can't reference `Self` constructor from o
     .label = the inner item doesn't inherit generics from this impl, so `Self` is invalid to reference
     .suggestion = replace `Self` with the actual type
 
+hir_typeck_self_ctor_from_outer_item_inner_item = `Self` used in this inner item
+
 hir_typeck_slicing_suggestion = consider slicing here
 
 hir_typeck_struct_expr_non_exhaustive =

compiler/rustc_hir_typeck/src/errors.rs

@@ -978,6 +978,15 @@ pub(crate) struct SelfCtorFromOuterItem {
     pub impl_span: Span,
     #[subdiagnostic]
     pub sugg: Option<ReplaceWithName>,
+    #[subdiagnostic]
+    pub item: Option<InnerItem>,
+}
+
+#[derive(Subdiagnostic)]
+#[label(hir_typeck_self_ctor_from_outer_item_inner_item)]
+pub(crate) struct InnerItem {
+    #[primary_span]
+    pub span: Span,
 }
 
 #[derive(LintDiagnostic)]
@@ -987,6 +996,8 @@ pub(crate) struct SelfCtorFromOuterItemLint {
     pub impl_span: Span,
     #[subdiagnostic]
     pub sugg: Option<ReplaceWithName>,
+    #[subdiagnostic]
+    pub item: Option<InnerItem>,
 }
 
 #[derive(Subdiagnostic)]

compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs

@@ -1094,11 +1094,21 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     span: path_span,
                     name: self.tcx.item_name(def.did()).to_ident_string(),
                 });
+                let item = match self
+                    .tcx
+                    .hir_node_by_def_id(self.tcx.hir_get_parent_item(hir_id).def_id)
+                {
+                    hir::Node::Item(item) => Some(errors::InnerItem {
+                        span: item.kind.ident().map(|i| i.span).unwrap_or(item.span),
+                    }),
+                    _ => None,
+                };
                 if ty.raw.has_param() {
                     let guar = self.dcx().emit_err(errors::SelfCtorFromOuterItem {
                         span: path_span,
                         impl_span: tcx.def_span(impl_def_id),
                         sugg,
+                        item,
                     });
                     return (Ty::new_error(self.tcx, guar), res);
                 } else {
@@ -1109,6 +1119,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         errors::SelfCtorFromOuterItemLint {
                             impl_span: tcx.def_span(impl_def_id),
                             sugg,
+                            item,
                         },
                     );
                 }

tests/ui/malformed/do-not-ice-on-note_and_explain.stderr

@@ -3,7 +3,9 @@ error[E0401]: can't reference `Self` constructor from outer item
    |
 LL | impl<B> A<B> {
    | ------------ the inner item doesn't inherit generics from this impl, so `Self` is invalid to reference
-...
+LL |     fn d() {
+LL |         fn d() {
+   |            - `Self` used in this inner item
 LL |             Self(1)
    |             ^^^^ help: replace `Self` with the actual type: `A`
 

tests/ui/self/self-ctor-nongeneric.stderr

@@ -5,7 +5,9 @@ LL | impl S0 {
    | ------- the inner item doesn't inherit generics from this impl, so `Self` is invalid to reference
 LL |     fn foo() {
 LL |         const C: S0 = Self(0);
-   |                       ^^^^ help: replace `Self` with the actual type: `S0`
+   |               -       ^^^^ help: replace `Self` with the actual type: `S0`
+   |               |
+   |               `Self` used in this inner item
    |
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #124186 <https://github.com/rust-lang/rust/issues/124186>
@@ -17,6 +19,8 @@ warning: can't reference `Self` constructor from outer item
 LL | impl S0 {
    | ------- the inner item doesn't inherit generics from this impl, so `Self` is invalid to reference
 ...
+LL |         fn bar() -> S0 {
+   |            --- `Self` used in this inner item
 LL |             Self(0)
    |             ^^^^ help: replace `Self` with the actual type: `S0`
    |

tests/ui/self/self-ctor.stderr

@@ -5,14 +5,18 @@ LL | impl<T> S0<T> {
    | ------------- the inner item doesn't inherit generics from this impl, so `Self` is invalid to reference
 LL |     fn foo() {
 LL |         const C: S0<i32> = Self(0);
-   |                            ^^^^ help: replace `Self` with the actual type: `S0`
+   |               -            ^^^^ help: replace `Self` with the actual type: `S0`
+   |               |
+   |               `Self` used in this inner item
 
 error[E0401]: can't reference `Self` constructor from outer item
   --> $DIR/self-ctor.rs:8:13
    |
 LL | impl<T> S0<T> {
    | ------------- the inner item doesn't inherit generics from this impl, so `Self` is invalid to reference
 ...
+LL |         fn bar() -> S0<i32> {
+   |            --- `Self` used in this inner item
 LL |             Self(0)
    |             ^^^^ help: replace `Self` with the actual type: `S0`
 

tests/ui/traits/ice-index-out-of-bounds-issue-117446.stderr

@@ -24,6 +24,9 @@ error[E0401]: can't reference `Self` constructor from outer item
 LL | impl<'a, T> Foo<'a> for Repeated<T> {
    | ----------------------------------- the inner item doesn't inherit generics from this impl, so `Self` is invalid to reference
 ...
+LL |         fn inner<Q>(value: Option<()>) -> Repeated<Q> {
+   |            ----- `Self` used in this inner item
+LL |             match value {
 LL |                 _ => Self(unimplemented!()),
    |                      ^^^^ help: replace `Self` with the actual type: `Repeated`