Suggest adding lifetime to struct field

src/librustc/middle/resolve_lifetime.rs

@@ -2306,7 +2306,13 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
 
                 Scope::Root => break None,
 
-                Scope::Binder { s, .. } => {
+                Scope::Binder { s, ref lifetimes, .. } => {
+                    // collect named lifetimes for suggestions
+                    for name in lifetimes.keys() {
+                        if let hir::ParamName::Plain(name) = name {
+                            lifetime_names.insert(*name);
+                        }
+                    }
                     late_depth += 1;
                     scope = s;
                 }
@@ -2323,6 +2329,7 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
                         Elide::Exact(l) => l.shifted(late_depth),
                         Elide::Error(ref e) => {
                             if let Scope::Binder { ref lifetimes, .. } = s {
+                                // collect named lifetimes for suggestions
                                 for name in lifetimes.keys() {
                                     if let hir::ParamName::Plain(name) = name {
                                         lifetime_names.insert(*name);

src/test/ui/suggestions/return-without-lifetime.rs

@@ -1,4 +1,6 @@
 struct Thing<'a>(&'a ());
+struct Foo<'a>(&usize);
+//~^ ERROR missing lifetime specifier
 
 fn func1<'a>(_arg: &'a Thing) -> &() { unimplemented!() }
 //~^ ERROR missing lifetime specifier

src/test/ui/suggestions/return-without-lifetime.stderr

@@ -1,19 +1,25 @@
 error[E0106]: missing lifetime specifier
-  --> $DIR/return-without-lifetime.rs:3:34
+  --> $DIR/return-without-lifetime.rs:2:16
+   |
+LL | struct Foo<'a>(&usize);
+   |                ^ help: consider using the named lifetime: `&'a`
+
+error[E0106]: missing lifetime specifier
+  --> $DIR/return-without-lifetime.rs:5:34
    |
 LL | fn func1<'a>(_arg: &'a Thing) -> &() { unimplemented!() }
    |                                  ^ help: consider using the named lifetime: `&'a`
    |
    = help: this function's return type contains a borrowed value, but the signature does not say which one of `_arg`'s 2 lifetimes it is borrowed from
 
 error[E0106]: missing lifetime specifier
-  --> $DIR/return-without-lifetime.rs:5:35
+  --> $DIR/return-without-lifetime.rs:7:35
    |
 LL | fn func2<'a>(_arg: &Thing<'a>) -> &() { unimplemented!() }
    |                                   ^ help: consider using the named lifetime: `&'a`
    |
    = help: this function's return type contains a borrowed value, but the signature does not say which one of `_arg`'s 2 lifetimes it is borrowed from
 
-error: aborting due to 2 previous errors
+error: aborting due to 3 previous errors
 
 For more information about this error, try `rustc --explain E0106`.