Rollup merge of #96409 - marmeladema:fix-nll-introduce-named-lifetime-suggestion, r=jackh726

Recover suggestions to introduce named lifetime under NLL

Fixes #96157

r? ```@jackh726```

Built on top of #96385 so only the second commit is relevant

16 files changed, 220 insertions, 0 deletions

diff --git a/src/test/ui/lifetimes/issue-90170-elision-mismatch.nll.stderr b/src/test/ui/lifetimes/issue-90170-elision-mismatch.nll.stderr
index a5bc7450bbf..48fb3fb4a22 100644
--- a/src/test/ui/lifetimes/issue-90170-elision-mismatch.nll.stderr
+++ b/src/test/ui/lifetimes/issue-90170-elision-mismatch.nll.stderr
@@ -6,6 +6,11 @@ LL | pub fn foo(x: &mut Vec<&u8>, y: &u8) { x.push(y); }
    |                        |        |
    |                        |        let's call the lifetime of this reference `'1`
    |                        let's call the lifetime of this reference `'2`
+   |
+help: consider introducing a named lifetime parameter
+   |
+LL | pub fn foo<'a>(x: &mut Vec<&'a u8>, y: &'a u8) { x.push(y); }
+   |           ++++              ++          ++
 
 error: lifetime may not live long enough
   --> $DIR/issue-90170-elision-mismatch.rs:5:44
@@ -15,6 +20,11 @@ LL | pub fn foo2(x: &mut Vec<&'_ u8>, y: &u8) { x.push(y); }
    |                         |           |
    |                         |           let's call the lifetime of this reference `'1`
    |                         let's call the lifetime of this reference `'2`
+   |
+help: consider introducing a named lifetime parameter
+   |
+LL | pub fn foo2<'a>(x: &mut Vec<&'a u8>, y: &'a u8) { x.push(y); }
+   |            ++++              ~~          ++
 
 error: lifetime may not live long enough
   --> $DIR/issue-90170-elision-mismatch.rs:7:63
@@ -24,6 +34,11 @@ LL | pub fn foo3<'a>(_other: &'a [u8], x: &mut Vec<&u8>, y: &u8) { x.push(y); }
    |                                               |        |
    |                                               |        let's call the lifetime of this reference `'1`
    |                                               let's call the lifetime of this reference `'2`
+   |
+help: consider introducing a named lifetime parameter
+   |
+LL | pub fn foo3<'a>(_other: &'a [u8], x: &mut Vec<&'a u8>, y: &'a u8) { x.push(y); }
+   |                                                ++          ++
 
 error: aborting due to 3 previous errors
 
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-2.nll.stderr b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-2.nll.stderr
index a94f9a79906..5a23f1e0e9d 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-2.nll.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-2.nll.stderr
@@ -7,6 +7,11 @@ LL | fn foo(&mut (ref mut v, w): &mut (&u8, &u8), x: &u8) {
    |                                   let's call the lifetime of this reference `'2`
 LL |     *v = x;
    |     ^^^^^^ assignment requires that `'1` must outlive `'2`
+   |
+help: consider introducing a named lifetime parameter
+   |
+LL | fn foo<'a>(&mut (ref mut v, w): &mut (&'a u8, &u8), x: &'a u8) {
+   |       ++++                             ++               ++
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-3.nll.stderr b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-3.nll.stderr
index 2ed4d6d4401..6ba130308a3 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-3.nll.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-3.nll.stderr
@@ -7,6 +7,11 @@ LL | fn foo(z: &mut Vec<(&u8,&u8)>, (x, y): (&u8, &u8)) {
    |                     let's call the lifetime of this reference `'2`
 LL |     z.push((x,y));
    |     ^^^^^^^^^^^^^ argument requires that `'1` must outlive `'2`
+   |
+help: consider introducing a named lifetime parameter
+   |
+LL | fn foo<'a>(z: &mut Vec<(&'a u8,&u8)>, (x, y): (&'a u8, &u8)) {
+   |       ++++               ++                     ++
 
 error: lifetime may not live long enough
   --> $DIR/ex3-both-anon-regions-3.rs:2:5
@@ -17,6 +22,11 @@ LL | fn foo(z: &mut Vec<(&u8,&u8)>, (x, y): (&u8, &u8)) {
    |                         let's call the lifetime of this reference `'4`
 LL |     z.push((x,y));
    |     ^^^^^^^^^^^^^ argument requires that `'3` must outlive `'4`
+   |
+help: consider introducing a named lifetime parameter
+   |
+LL | fn foo<'a>(z: &mut Vec<(&u8,&'a u8)>, (x, y): (&u8, &'a u8)) {
+   |       ++++                   ++                      ++
 
 error: aborting due to 2 previous errors
 
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-return-type-is-anon.nll.stderr b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-return-type-is-anon.nll.stderr
index 1a19e81f235..5601335d275 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-return-type-is-anon.nll.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-return-type-is-anon.nll.stderr
@@ -7,6 +7,11 @@ LL |   fn foo<'a>(&self, x: &i32) -> &i32 {
    |              let's call the lifetime of this reference `'2`
 LL |     x
    |     ^ associated function was supposed to return data with lifetime `'2` but it is returning data with lifetime `'1`
+   |
+help: consider introducing a named lifetime parameter and update trait if needed
+   |
+LL |   fn foo<'a>(&'a self, x: &'a i32) -> &i32 {
+   |               ++           ++
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-self-is-anon.nll.stderr b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-self-is-anon.nll.stderr
index 87b13dc1591..e221902c4a9 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-self-is-anon.nll.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-self-is-anon.nll.stderr
@@ -7,6 +7,11 @@ LL |     fn foo<'a>(&self, x: &Foo) -> &Foo {
    |                let's call the lifetime of this reference `'2`
 LL |         if true { x } else { self }
    |                   ^ associated function was supposed to return data with lifetime `'2` but it is returning data with lifetime `'1`
+   |
+help: consider introducing a named lifetime parameter and update trait if needed
+   |
+LL |     fn foo<'a>(&'a self, x: &'a Foo) -> &Foo {
+   |                 ++           ++
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-using-fn-items.nll.stderr b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-using-fn-items.nll.stderr
index 825c45b2434..a909c5fa823 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-using-fn-items.nll.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-using-fn-items.nll.stderr
@@ -7,6 +7,11 @@ LL | fn foo(x:fn(&u8, &u8), y: Vec<&u8>, z: &u8) {
    |                               let's call the lifetime of this reference `'2`
 LL |   y.push(z);
    |   ^^^^^^^^^ argument requires that `'1` must outlive `'2`
+   |
+help: consider introducing a named lifetime parameter
+   |
+LL | fn foo<'a>(x:fn(&u8, &u8), y: Vec<&'a u8>, z: &'a u8) {
+   |       ++++                         ++          ++
 
 error[E0596]: cannot borrow `y` as mutable, as it is not declared as mutable
   --> $DIR/ex3-both-anon-regions-using-fn-items.rs:2:3
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-using-impl-items.nll.stderr b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-using-impl-items.nll.stderr
index f3502674849..9661f1e5144 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-using-impl-items.nll.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-using-impl-items.nll.stderr
@@ -7,6 +7,11 @@ LL |     fn foo(x: &mut Vec<&u8>, y: &u8) {
    |                        let's call the lifetime of this reference `'2`
 LL |         x.push(y);
    |         ^^^^^^^^^ argument requires that `'1` must outlive `'2`
+   |
+help: consider introducing a named lifetime parameter and update trait if needed
+   |
+LL |     fn foo<'a>(x: &mut Vec<&'a u8>, y: &'a u8) {
+   |           ++++              ++          ++
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-using-trait-objects.nll.stderr b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-using-trait-objects.nll.stderr
index 78a828dde86..cce0a31bfbb 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-using-trait-objects.nll.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-using-trait-objects.nll.stderr
@@ -7,6 +7,11 @@ LL | fn foo(x:Box<dyn Fn(&u8, &u8)> , y: Vec<&u8>, z: &u8) {
    |                                         let's call the lifetime of this reference `'2`
 LL |   y.push(z);
    |   ^^^^^^^^^ argument requires that `'1` must outlive `'2`
+   |
+help: consider introducing a named lifetime parameter
+   |
+LL | fn foo<'a>(x:Box<dyn Fn(&'a u8, &'a u8)> , y: Vec<&u8>, z: &u8) {
+   |       ++++               ++      ++
 
 error[E0596]: cannot borrow `y` as mutable, as it is not declared as mutable
   --> $DIR/ex3-both-anon-regions-using-trait-objects.rs:2:3
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions.nll.stderr b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions.nll.stderr
index 6989acfa196..ec9fac0c288 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions.nll.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions.nll.stderr
@@ -7,6 +7,11 @@ LL | fn foo(x: &mut Vec<&u8>, y: &u8) {
    |                    let's call the lifetime of this reference `'2`
 LL |     x.push(y);
    |     ^^^^^^^^^ argument requires that `'1` must outlive `'2`
+   |
+help: consider introducing a named lifetime parameter
+   |
+LL | fn foo<'a>(x: &mut Vec<&'a u8>, y: &'a u8) {
+   |       ++++              ++          ++
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/self/arbitrary_self_types_pin_lifetime_mismatch.nll.stderr b/src/test/ui/self/arbitrary_self_types_pin_lifetime_mismatch.nll.stderr
index b06ebf70477..057146e7cb0 100644
--- a/src/test/ui/self/arbitrary_self_types_pin_lifetime_mismatch.nll.stderr
+++ b/src/test/ui/self/arbitrary_self_types_pin_lifetime_mismatch.nll.stderr
@@ -6,6 +6,11 @@ LL |     fn a(self: Pin<&Foo>, f: &Foo) -> &Foo { f }
    |                    |         |
    |                    |         let's call the lifetime of this reference `'1`
    |                    let's call the lifetime of this reference `'2`
+   |
+help: consider introducing a named lifetime parameter and update trait if needed
+   |
+LL |     fn a<'a>(self: Pin<&'a Foo>, f: &'a Foo) -> &Foo { f }
+   |         ++++            ++           ++
 
 error: lifetime may not live long enough
   --> $DIR/arbitrary_self_types_pin_lifetime_mismatch.rs:14:69
@@ -15,6 +20,11 @@ LL |     fn c(self: Pin<&Self>, f: &Foo, g: &Foo) -> (Pin<&Foo>, &Foo) { (self,
    |                    |          |
    |                    |          let's call the lifetime of this reference `'1`
    |                    let's call the lifetime of this reference `'2`
+   |
+help: consider introducing a named lifetime parameter and update trait if needed
+   |
+LL |     fn c<'a>(self: Pin<&'a Self>, f: &'a Foo, g: &Foo) -> (Pin<&Foo>, &Foo) { (self, f) }
+   |         ++++            ++            ++
 
 error: lifetime may not live long enough
   --> $DIR/arbitrary_self_types_pin_lifetime_mismatch.rs:21:58
diff --git a/src/test/ui/self/elision/lt-ref-self.nll.stderr b/src/test/ui/self/elision/lt-ref-self.nll.stderr
index 1934207527b..2e26c703b65 100644
--- a/src/test/ui/self/elision/lt-ref-self.nll.stderr
+++ b/src/test/ui/self/elision/lt-ref-self.nll.stderr
@@ -7,6 +7,11 @@ LL |     fn ref_self(&self, f: &u32) -> &u32 {
    |                 let's call the lifetime of this reference `'2`
 LL |         f
    |         ^ associated function was supposed to return data with lifetime `'2` but it is returning data with lifetime `'1`
+   |
+help: consider introducing a named lifetime parameter and update trait if needed
+   |
+LL |     fn ref_self<'a>(&'a self, f: &'a u32) -> &u32 {
+   |                ++++  ++           ++
 
 error: lifetime may not live long enough
   --> $DIR/lt-ref-self.rs:23:9
@@ -17,6 +22,11 @@ LL |     fn ref_Self(self: &Self, f: &u32) -> &u32 {
    |                       let's call the lifetime of this reference `'2`
 LL |         f
    |         ^ associated function was supposed to return data with lifetime `'2` but it is returning data with lifetime `'1`
+   |
+help: consider introducing a named lifetime parameter and update trait if needed
+   |
+LL |     fn ref_Self<'a>(self: &'a Self, f: &'a u32) -> &u32 {
+   |                ++++        ++           ++
 
 error: lifetime may not live long enough
   --> $DIR/lt-ref-self.rs:29:9
@@ -27,6 +37,11 @@ LL |     fn box_ref_Self(self: Box<&Self>, f: &u32) -> &u32 {
    |                               let's call the lifetime of this reference `'2`
 LL |         f
    |         ^ associated function was supposed to return data with lifetime `'2` but it is returning data with lifetime `'1`
+   |
+help: consider introducing a named lifetime parameter and update trait if needed
+   |
+LL |     fn box_ref_Self<'a>(self: Box<&'a Self>, f: &'a u32) -> &u32 {
+   |                    ++++            ++            ++
 
 error: lifetime may not live long enough
   --> $DIR/lt-ref-self.rs:35:9
@@ -37,6 +52,11 @@ LL |     fn pin_ref_Self(self: Pin<&Self>, f: &u32) -> &u32 {
    |                               let's call the lifetime of this reference `'2`
 LL |         f
    |         ^ associated function was supposed to return data with lifetime `'2` but it is returning data with lifetime `'1`
+   |
+help: consider introducing a named lifetime parameter and update trait if needed
+   |
+LL |     fn pin_ref_Self<'a>(self: Pin<&'a Self>, f: &'a u32) -> &u32 {
+   |                    ++++            ++            ++
 
 error: lifetime may not live long enough
   --> $DIR/lt-ref-self.rs:41:9
@@ -47,6 +67,11 @@ LL |     fn box_box_ref_Self(self: Box<Box<&Self>>, f: &u32) -> &u32 {
    |                                       let's call the lifetime of this reference `'2`
 LL |         f
    |         ^ associated function was supposed to return data with lifetime `'2` but it is returning data with lifetime `'1`
+   |
+help: consider introducing a named lifetime parameter and update trait if needed
+   |
+LL |     fn box_box_ref_Self<'a>(self: Box<Box<&'a Self>>, f: &'a u32) -> &u32 {
+   |                        ++++                ++             ++
 
 error: lifetime may not live long enough
   --> $DIR/lt-ref-self.rs:47:9
@@ -57,6 +82,11 @@ LL |     fn box_pin_Self(self: Box<Pin<&Self>>, f: &u32) -> &u32 {
    |                                   let's call the lifetime of this reference `'2`
 LL |         f
    |         ^ associated function was supposed to return data with lifetime `'2` but it is returning data with lifetime `'1`
+   |
+help: consider introducing a named lifetime parameter and update trait if needed
+   |
+LL |     fn box_pin_Self<'a>(self: Box<Pin<&'a Self>>, f: &'a u32) -> &u32 {
+   |                    ++++                ++             ++
 
 error: aborting due to 6 previous errors
 
diff --git a/src/test/ui/self/elision/ref-mut-self.nll.stderr b/src/test/ui/self/elision/ref-mut-self.nll.stderr
index f1f4d341b2b..fd4ecae3cfe 100644
--- a/src/test/ui/self/elision/ref-mut-self.nll.stderr
+++ b/src/test/ui/self/elision/ref-mut-self.nll.stderr
@@ -7,6 +7,11 @@ LL |     fn ref_self(&mut self, f: &u32) -> &u32 {
    |                 let's call the lifetime of this reference `'2`
 LL |         f
    |         ^ associated function was supposed to return data with lifetime `'2` but it is returning data with lifetime `'1`
+   |
+help: consider introducing a named lifetime parameter and update trait if needed
+   |
+LL |     fn ref_self<'a>(&'a mut self, f: &'a u32) -> &u32 {
+   |                ++++  ++               ++
 
 error: lifetime may not live long enough
   --> $DIR/ref-mut-self.rs:23:9
@@ -17,6 +22,11 @@ LL |     fn ref_Self(self: &mut Self, f: &u32) -> &u32 {
    |                       let's call the lifetime of this reference `'2`
 LL |         f
    |         ^ associated function was supposed to return data with lifetime `'2` but it is returning data with lifetime `'1`
+   |
+help: consider introducing a named lifetime parameter and update trait if needed
+   |
+LL |     fn ref_Self<'a>(self: &'a mut Self, f: &'a u32) -> &u32 {
+   |                ++++        ++               ++
 
 error: lifetime may not live long enough
   --> $DIR/ref-mut-self.rs:29:9
@@ -27,6 +37,11 @@ LL |     fn box_ref_Self(self: Box<&mut Self>, f: &u32) -> &u32 {
    |                               let's call the lifetime of this reference `'2`
 LL |         f
    |         ^ associated function was supposed to return data with lifetime `'2` but it is returning data with lifetime `'1`
+   |
+help: consider introducing a named lifetime parameter and update trait if needed
+   |
+LL |     fn box_ref_Self<'a>(self: Box<&'a mut Self>, f: &'a u32) -> &u32 {
+   |                    ++++            ++                ++
 
 error: lifetime may not live long enough
   --> $DIR/ref-mut-self.rs:35:9
@@ -37,6 +52,11 @@ LL |     fn pin_ref_Self(self: Pin<&mut Self>, f: &u32) -> &u32 {
    |                               let's call the lifetime of this reference `'2`
 LL |         f
    |         ^ associated function was supposed to return data with lifetime `'2` but it is returning data with lifetime `'1`
+   |
+help: consider introducing a named lifetime parameter and update trait if needed
+   |
+LL |     fn pin_ref_Self<'a>(self: Pin<&'a mut Self>, f: &'a u32) -> &u32 {
+   |                    ++++            ++                ++
 
 error: lifetime may not live long enough
   --> $DIR/ref-mut-self.rs:41:9
@@ -47,6 +67,11 @@ LL |     fn box_box_ref_Self(self: Box<Box<&mut Self>>, f: &u32) -> &u32 {
    |                                       let's call the lifetime of this reference `'2`
 LL |         f
    |         ^ associated function was supposed to return data with lifetime `'2` but it is returning data with lifetime `'1`
+   |
+help: consider introducing a named lifetime parameter and update trait if needed
+   |
+LL |     fn box_box_ref_Self<'a>(self: Box<Box<&'a mut Self>>, f: &'a u32) -> &u32 {
+   |                        ++++                ++                 ++
 
 error: lifetime may not live long enough
   --> $DIR/ref-mut-self.rs:47:9
@@ -57,6 +82,11 @@ LL |     fn box_pin_ref_Self(self: Box<Pin<&mut Self>>, f: &u32) -> &u32 {
    |                                       let's call the lifetime of this reference `'2`
 LL |         f
    |         ^ associated function was supposed to return data with lifetime `'2` but it is returning data with lifetime `'1`
+   |
+help: consider introducing a named lifetime parameter and update trait if needed
+   |
+LL |     fn box_pin_ref_Self<'a>(self: Box<Pin<&'a mut Self>>, f: &'a u32) -> &u32 {
+   |                        ++++                ++                 ++
 
 error: aborting due to 6 previous errors
 
diff --git a/src/test/ui/self/elision/ref-mut-struct.nll.stderr b/src/test/ui/self/elision/ref-mut-struct.nll.stderr
index de7eb02d7a7..ede790c0611 100644
--- a/src/test/ui/self/elision/ref-mut-struct.nll.stderr
+++ b/src/test/ui/self/elision/ref-mut-struct.nll.stderr
@@ -7,6 +7,11 @@ LL |     fn ref_Struct(self: &mut Struct, f: &u32) -> &u32 {
    |                         let's call the lifetime of this reference `'2`
 LL |         f
    |         ^ associated function was supposed to return data with lifetime `'2` but it is returning data with lifetime `'1`
+   |
+help: consider introducing a named lifetime parameter and update trait if needed
+   |
+LL |     fn ref_Struct<'a>(self: &'a mut Struct, f: &'a u32) -> &u32 {
+   |                  ++++        ++                 ++
 
 error: lifetime may not live long enough
   --> $DIR/ref-mut-struct.rs:21:9
@@ -17,6 +22,11 @@ LL |     fn box_ref_Struct(self: Box<&mut Struct>, f: &u32) -> &u32 {
    |                                 let's call the lifetime of this reference `'2`
 LL |         f
    |         ^ associated function was supposed to return data with lifetime `'2` but it is returning data with lifetime `'1`
+   |
+help: consider introducing a named lifetime parameter and update trait if needed
+   |
+LL |     fn box_ref_Struct<'a>(self: Box<&'a mut Struct>, f: &'a u32) -> &u32 {
+   |                      ++++            ++                  ++
 
 error: lifetime may not live long enough
   --> $DIR/ref-mut-struct.rs:27:9
@@ -27,6 +37,11 @@ LL |     fn pin_ref_Struct(self: Pin<&mut Struct>, f: &u32) -> &u32 {
    |                                 let's call the lifetime of this reference `'2`
 LL |         f
    |         ^ associated function was supposed to return data with lifetime `'2` but it is returning data with lifetime `'1`
+   |
+help: consider introducing a named lifetime parameter and update trait if needed
+   |
+LL |     fn pin_ref_Struct<'a>(self: Pin<&'a mut Struct>, f: &'a u32) -> &u32 {
+   |                      ++++            ++                  ++
 
 error: lifetime may not live long enough
   --> $DIR/ref-mut-struct.rs:33:9
@@ -37,6 +52,11 @@ LL |     fn box_box_ref_Struct(self: Box<Box<&mut Struct>>, f: &u32) -> &u32 {
    |                                         let's call the lifetime of this reference `'2`
 LL |         f
    |         ^ associated function was supposed to return data with lifetime `'2` but it is returning data with lifetime `'1`
+   |
+help: consider introducing a named lifetime parameter and update trait if needed
+   |
+LL |     fn box_box_ref_Struct<'a>(self: Box<Box<&'a mut Struct>>, f: &'a u32) -> &u32 {
+   |                          ++++                ++                   ++
 
 error: lifetime may not live long enough
   --> $DIR/ref-mut-struct.rs:39:9
@@ -47,6 +67,11 @@ LL |     fn box_pin_ref_Struct(self: Box<Pin<&mut Struct>>, f: &u32) -> &u32 {
    |                                         let's call the lifetime of this reference `'2`
 LL |         f
    |         ^ associated function was supposed to return data with lifetime `'2` but it is returning data with lifetime `'1`
+   |
+help: consider introducing a named lifetime parameter and update trait if needed
+   |
+LL |     fn box_pin_ref_Struct<'a>(self: Box<Pin<&'a mut Struct>>, f: &'a u32) -> &u32 {
+   |                          ++++                ++                   ++
 
 error: aborting due to 5 previous errors
 
diff --git a/src/test/ui/self/elision/ref-self.nll.stderr b/src/test/ui/self/elision/ref-self.nll.stderr
index f2b7b0ad019..c0efc35fa6c 100644
--- a/src/test/ui/self/elision/ref-self.nll.stderr
+++ b/src/test/ui/self/elision/ref-self.nll.stderr
@@ -7,6 +7,11 @@ LL |     fn ref_self(&self, f: &u32) -> &u32 {
    |                 let's call the lifetime of this reference `'2`
 LL |         f
    |         ^ associated function was supposed to return data with lifetime `'2` but it is returning data with lifetime `'1`
+   |
+help: consider introducing a named lifetime parameter and update trait if needed
+   |
+LL |     fn ref_self<'a>(&'a self, f: &'a u32) -> &u32 {
+   |                ++++  ++           ++
 
 error: lifetime may not live long enough
   --> $DIR/ref-self.rs:33:9
@@ -17,6 +22,11 @@ LL |     fn ref_Self(self: &Self, f: &u32) -> &u32 {
    |                       let's call the lifetime of this reference `'2`
 LL |         f
    |         ^ associated function was supposed to return data with lifetime `'2` but it is returning data with lifetime `'1`
+   |
+help: consider introducing a named lifetime parameter and update trait if needed
+   |
+LL |     fn ref_Self<'a>(self: &'a Self, f: &'a u32) -> &u32 {
+   |                ++++        ++           ++
 
 error: lifetime may not live long enough
   --> $DIR/ref-self.rs:39:9
@@ -27,6 +37,11 @@ LL |     fn box_ref_Self(self: Box<&Self>, f: &u32) -> &u32 {
    |                               let's call the lifetime of this reference `'2`
 LL |         f
    |         ^ associated function was supposed to return data with lifetime `'2` but it is returning data with lifetime `'1`
+   |
+help: consider introducing a named lifetime parameter and update trait if needed
+   |
+LL |     fn box_ref_Self<'a>(self: Box<&'a Self>, f: &'a u32) -> &u32 {
+   |                    ++++            ++            ++
 
 error: lifetime may not live long enough
   --> $DIR/ref-self.rs:45:9
@@ -37,6 +52,11 @@ LL |     fn pin_ref_Self(self: Pin<&Self>, f: &u32) -> &u32 {
    |                               let's call the lifetime of this reference `'2`
 LL |         f
    |         ^ associated function was supposed to return data with lifetime `'2` but it is returning data with lifetime `'1`
+   |
+help: consider introducing a named lifetime parameter and update trait if needed
+   |
+LL |     fn pin_ref_Self<'a>(self: Pin<&'a Self>, f: &'a u32) -> &u32 {
+   |                    ++++            ++            ++
 
 error: lifetime may not live long enough
   --> $DIR/ref-self.rs:51:9
@@ -47,6 +67,11 @@ LL |     fn box_box_ref_Self(self: Box<Box<&Self>>, f: &u32) -> &u32 {
    |                                       let's call the lifetime of this reference `'2`
 LL |         f
    |         ^ associated function was supposed to return data with lifetime `'2` but it is returning data with lifetime `'1`
+   |
+help: consider introducing a named lifetime parameter and update trait if needed
+   |
+LL |     fn box_box_ref_Self<'a>(self: Box<Box<&'a Self>>, f: &'a u32) -> &u32 {
+   |                        ++++                ++             ++
 
 error: lifetime may not live long enough
   --> $DIR/ref-self.rs:57:9
@@ -57,6 +82,11 @@ LL |     fn box_pin_ref_Self(self: Box<Pin<&Self>>, f: &u32) -> &u32 {
    |                                       let's call the lifetime of this reference `'2`
 LL |         f
    |         ^ associated function was supposed to return data with lifetime `'2` but it is returning data with lifetime `'1`
+   |
+help: consider introducing a named lifetime parameter and update trait if needed
+   |
+LL |     fn box_pin_ref_Self<'a>(self: Box<Pin<&'a Self>>, f: &'a u32) -> &u32 {
+   |                        ++++                ++             ++
 
 error: lifetime may not live long enough
   --> $DIR/ref-self.rs:63:9
@@ -67,6 +97,11 @@ LL |     fn wrap_ref_Self_Self(self: Wrap<&Self, Self>, f: &u8) -> &u8 {
    |                                      let's call the lifetime of this reference `'2`
 LL |         f
    |         ^ associated function was supposed to return data with lifetime `'2` but it is returning data with lifetime `'1`
+   |
+help: consider introducing a named lifetime parameter and update trait if needed
+   |
+LL |     fn wrap_ref_Self_Self<'a>(self: Wrap<&'a Self, Self>, f: &'a u8) -> &u8 {
+   |                          ++++             ++                  ++
 
 error: aborting due to 7 previous errors
 
diff --git a/src/test/ui/self/elision/ref-struct.nll.stderr b/src/test/ui/self/elision/ref-struct.nll.stderr
index 70453b0ddfc..226923f59ff 100644
--- a/src/test/ui/self/elision/ref-struct.nll.stderr
+++ b/src/test/ui/self/elision/ref-struct.nll.stderr
@@ -7,6 +7,11 @@ LL |     fn ref_Struct(self: &Struct, f: &u32) -> &u32 {
    |                         let's call the lifetime of this reference `'2`
 LL |         f
    |         ^ associated function was supposed to return data with lifetime `'2` but it is returning data with lifetime `'1`
+   |
+help: consider introducing a named lifetime parameter and update trait if needed
+   |
+LL |     fn ref_Struct<'a>(self: &'a Struct, f: &'a u32) -> &u32 {
+   |                  ++++        ++             ++
 
 error: lifetime may not live long enough
   --> $DIR/ref-struct.rs:21:9
@@ -17,6 +22,11 @@ LL |     fn box_ref_Struct(self: Box<&Struct>, f: &u32) -> &u32 {
    |                                 let's call the lifetime of this reference `'2`
 LL |         f
    |         ^ associated function was supposed to return data with lifetime `'2` but it is returning data with lifetime `'1`
+   |
+help: consider introducing a named lifetime parameter and update trait if needed
+   |
+LL |     fn box_ref_Struct<'a>(self: Box<&'a Struct>, f: &'a u32) -> &u32 {
+   |                      ++++            ++              ++
 
 error: lifetime may not live long enough
   --> $DIR/ref-struct.rs:27:9
@@ -27,6 +37,11 @@ LL |     fn pin_ref_Struct(self: Pin<&Struct>, f: &u32) -> &u32 {
    |                                 let's call the lifetime of this reference `'2`
 LL |         f
    |         ^ associated function was supposed to return data with lifetime `'2` but it is returning data with lifetime `'1`
+   |
+help: consider introducing a named lifetime parameter and update trait if needed
+   |
+LL |     fn pin_ref_Struct<'a>(self: Pin<&'a Struct>, f: &'a u32) -> &u32 {
+   |                      ++++            ++              ++
 
 error: lifetime may not live long enough
   --> $DIR/ref-struct.rs:33:9
@@ -37,6 +52,11 @@ LL |     fn box_box_ref_Struct(self: Box<Box<&Struct>>, f: &u32) -> &u32 {
    |                                         let's call the lifetime of this reference `'2`
 LL |         f
    |         ^ associated function was supposed to return data with lifetime `'2` but it is returning data with lifetime `'1`
+   |
+help: consider introducing a named lifetime parameter and update trait if needed
+   |
+LL |     fn box_box_ref_Struct<'a>(self: Box<Box<&'a Struct>>, f: &'a u32) -> &u32 {
+   |                          ++++                ++               ++
 
 error: lifetime may not live long enough
   --> $DIR/ref-struct.rs:39:9
@@ -47,6 +67,11 @@ LL |     fn box_pin_Struct(self: Box<Pin<&Struct>>, f: &u32) -> &u32 {
    |                                     let's call the lifetime of this reference `'2`
 LL |         f
    |         ^ associated function was supposed to return data with lifetime `'2` but it is returning data with lifetime `'1`
+   |
+help: consider introducing a named lifetime parameter and update trait if needed
+   |
+LL |     fn box_pin_Struct<'a>(self: Box<Pin<&'a Struct>>, f: &'a u32) -> &u32 {
+   |                      ++++                ++               ++
 
 error: aborting due to 5 previous errors
 
diff --git a/src/test/ui/underscore-lifetime/underscore-lifetime-elison-mismatch.nll.stderr b/src/test/ui/underscore-lifetime/underscore-lifetime-elison-mismatch.nll.stderr
index 8e10242cb13..a4dece320ec 100644
--- a/src/test/ui/underscore-lifetime/underscore-lifetime-elison-mismatch.nll.stderr
+++ b/src/test/ui/underscore-lifetime/underscore-lifetime-elison-mismatch.nll.stderr
@@ -6,6 +6,11 @@ LL | fn foo(x: &mut Vec<&'_ u8>, y: &'_ u8) { x.push(y); }
    |                    |           |
    |                    |           let's call the lifetime of this reference `'1`
    |                    let's call the lifetime of this reference `'2`
+   |
+help: consider introducing a named lifetime parameter
+   |
+LL | fn foo<'a>(x: &mut Vec<&'a u8>, y: &'a u8) { x.push(y); }
+   |       ++++              ~~          ~~
 
 error: aborting due to previous error