Auto merge of #104048 - cjgillot:split-lifetime, r=compiler-errors

Separate lifetime ident from lifetime resolution in HIR

Drive-by: change how suggested generic args are computed.
Fixes https://github.com/rust-lang/rust/issues/103815

I recommend reviewing commit-by-commit.

13 files changed, 234 insertions, 72 deletions

diff --git a/src/test/ui/const-generics/generic_const_exprs/issue-102768.stderr b/src/test/ui/const-generics/generic_const_exprs/issue-102768.stderr
index 9deb9b26588..8278edabe3a 100644
--- a/src/test/ui/const-generics/generic_const_exprs/issue-102768.stderr
+++ b/src/test/ui/const-generics/generic_const_exprs/issue-102768.stderr
@@ -11,7 +11,7 @@ LL |     type Y<'a>;
    |          ^ --
 help: add missing lifetime argument
    |
-LL |     fn f2<'a>(arg: Box<dyn X<Y<'a, 1> = &'a ()>>) {}
+LL |     fn f2<'a>(arg: Box<dyn X<Y<'_, 1> = &'a ()>>) {}
    |                                +++
 
 error[E0107]: this associated type takes 0 generic arguments but 1 generic argument was supplied
diff --git a/src/test/ui/constructor-lifetime-args.stderr b/src/test/ui/constructor-lifetime-args.stderr
index b97b6faa3be..bc1141b16c5 100644
--- a/src/test/ui/constructor-lifetime-args.stderr
+++ b/src/test/ui/constructor-lifetime-args.stderr
@@ -13,8 +13,8 @@ LL | struct S<'a, 'b>(&'a u8, &'b u8);
    |        ^ --  --
 help: add missing lifetime argument
    |
-LL |     S::<'static, 'b>(&0, &0);
-   |                ++++
+LL |     S::<'static, 'static>(&0, &0);
+   |                +++++++++
 
 error[E0107]: this struct takes 2 lifetime arguments but 3 lifetime arguments were supplied
   --> $DIR/constructor-lifetime-args.rs:19:5
@@ -45,8 +45,8 @@ LL | enum E<'a, 'b> {
    |      ^ --  --
 help: add missing lifetime argument
    |
-LL |     E::V::<'static, 'b>(&0);
-   |                   ++++
+LL |     E::V::<'static, 'static>(&0);
+   |                   +++++++++
 
 error[E0107]: this enum takes 2 lifetime arguments but 3 lifetime arguments were supplied
   --> $DIR/constructor-lifetime-args.rs:24:8
diff --git a/src/test/ui/generic-associated-types/elided-in-expr-position.stderr b/src/test/ui/generic-associated-types/elided-in-expr-position.stderr
index 20f35c3c137..a9996123f23 100644
--- a/src/test/ui/generic-associated-types/elided-in-expr-position.stderr
+++ b/src/test/ui/generic-associated-types/elided-in-expr-position.stderr
@@ -11,7 +11,7 @@ LL |     type Assoc<'a> where Self: 'a;
    |          ^^^^^ --
 help: add missing lifetime argument
    |
-LL |     fn g(&self) -> Self::Assoc<'a>;
+LL |     fn g(&self) -> Self::Assoc<'_>;
    |                          ~~~~~~~~~
 
 error[E0107]: missing generics for associated type `Trait::Assoc`
@@ -27,7 +27,7 @@ LL |     type Assoc<'a> where Self: 'a;
    |          ^^^^^ --
 help: add missing lifetime argument
    |
-LL |     fn g(&self) -> Self::Assoc<'a> {
+LL |     fn g(&self) -> Self::Assoc<'_> {
    |                          ~~~~~~~~~
 
 error: aborting due to 2 previous errors
diff --git a/src/test/ui/generic-associated-types/gat-trait-path-parenthesised-args.stderr b/src/test/ui/generic-associated-types/gat-trait-path-parenthesised-args.stderr
index e55a21e19f0..165779796e0 100644
--- a/src/test/ui/generic-associated-types/gat-trait-path-parenthesised-args.stderr
+++ b/src/test/ui/generic-associated-types/gat-trait-path-parenthesised-args.stderr
@@ -36,7 +36,7 @@ LL |   type Y<'a>;
    |        ^ --
 help: add missing lifetime argument
    |
-LL | fn foo<'a>(arg: Box<dyn X<Y('a, 'a) = &'a ()>>) {}
+LL | fn foo<'a>(arg: Box<dyn X<Y('_, 'a) = &'a ()>>) {}
    |                             +++
 
 error[E0107]: this associated type takes 0 generic arguments but 1 generic argument was supplied
@@ -66,7 +66,7 @@ LL |   type Y<'a>;
    |        ^ --
 help: add missing lifetime argument
    |
-LL | fn bar<'a>(arg: Box<dyn X<Y('a) = ()>>) {}
+LL | fn bar<'a>(arg: Box<dyn X<Y('_) = ()>>) {}
    |                             ++
 
 error: aborting due to 6 previous errors
diff --git a/src/test/ui/generic-associated-types/issue-81862.stderr b/src/test/ui/generic-associated-types/issue-81862.stderr
index ba798084673..9e21c567c73 100644
--- a/src/test/ui/generic-associated-types/issue-81862.stderr
+++ b/src/test/ui/generic-associated-types/issue-81862.stderr
@@ -11,7 +11,7 @@ LL |     type Item<'a>;
    |          ^^^^ --
 help: add missing lifetime argument
    |
-LL |     fn next(&mut self) -> Option<Self::Item<'a>>;
+LL |     fn next(&mut self) -> Option<Self::Item<'_>>;
    |                                        ~~~~~~~~
 
 error: aborting due to previous error
diff --git a/src/test/ui/generic-associated-types/missing_lifetime_args.stderr b/src/test/ui/generic-associated-types/missing_lifetime_args.stderr
index 0ad1f1f8c4d..752587c25a7 100644
--- a/src/test/ui/generic-associated-types/missing_lifetime_args.stderr
+++ b/src/test/ui/generic-associated-types/missing_lifetime_args.stderr
@@ -11,7 +11,7 @@ LL |     type Y<'a, 'b>;
    |          ^ --  --
 help: add missing lifetime arguments
    |
-LL | fn foo<'c, 'd>(_arg: Box<dyn X<Y<'c, 'd> = (&'c u32, &'d u32)>>) {}
+LL | fn foo<'c, 'd>(_arg: Box<dyn X<Y<'_, '_> = (&'c u32, &'d u32)>>) {}
    |                                ~~~~~~~~~
 
 error[E0107]: this struct takes 3 lifetime arguments but 2 lifetime arguments were supplied
@@ -47,7 +47,7 @@ LL | struct Foo<'a, 'b, 'c> {
    |        ^^^ --  --  --
 help: add missing lifetime arguments
    |
-LL | fn f<'a>(_arg: Foo<'a, 'b, 'c>) {}
+LL | fn f<'a>(_arg: Foo<'a, 'a, 'a>) {}
    |                      ++++++++
 
 error: aborting due to 3 previous errors
diff --git a/src/test/ui/generic-associated-types/parse/trait-path-type-error-once-implemented.stderr b/src/test/ui/generic-associated-types/parse/trait-path-type-error-once-implemented.stderr
index e00a414efb9..0a09ec5dc49 100644
--- a/src/test/ui/generic-associated-types/parse/trait-path-type-error-once-implemented.stderr
+++ b/src/test/ui/generic-associated-types/parse/trait-path-type-error-once-implemented.stderr
@@ -11,7 +11,7 @@ LL |     type Y<'a>;
    |          ^ --
 help: add missing lifetime argument
    |
-LL |   fn f2<'a>(arg : Box<dyn X<Y<'a, 1> = &'a ()>>) {}
+LL |   fn f2<'a>(arg : Box<dyn X<Y<'_, 1> = &'a ()>>) {}
    |                               +++
 
 error[E0107]: this associated type takes 0 generic arguments but 1 generic argument was supplied
diff --git a/src/test/ui/generics/wrong-number-of-args.stderr b/src/test/ui/generics/wrong-number-of-args.stderr
index 388c23fc24f..0475eb908a7 100644
--- a/src/test/ui/generics/wrong-number-of-args.stderr
+++ b/src/test/ui/generics/wrong-number-of-args.stderr
@@ -812,8 +812,8 @@ LL |         trait GenericLifetimeLifetimeAT<'a, 'b> {
    |               ^^^^^^^^^^^^^^^^^^^^^^^^^ --  --
 help: add missing lifetime argument
    |
-LL |         type B = Box<dyn GenericLifetimeLifetimeAT<'static, 'b, AssocTy=()>>;
-   |                                                           ++++
+LL |         type B = Box<dyn GenericLifetimeLifetimeAT<'static, 'static, AssocTy=()>>;
+   |                                                           +++++++++
 
 error[E0107]: this trait takes 1 generic argument but 0 generic arguments were supplied
   --> $DIR/wrong-number-of-args.rs:287:26
@@ -846,8 +846,8 @@ LL |         trait GenericLifetimeLifetimeTypeAT<'a, 'b, A> {
    |               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ --  --
 help: add missing lifetime argument
    |
-LL |         type B = Box<dyn GenericLifetimeLifetimeTypeAT<'static, 'b, AssocTy=()>>;
-   |                                                               ++++
+LL |         type B = Box<dyn GenericLifetimeLifetimeTypeAT<'static, 'static, AssocTy=()>>;
+   |                                                               +++++++++
 
 error[E0107]: this trait takes 1 generic argument but 0 generic arguments were supplied
   --> $DIR/wrong-number-of-args.rs:294:26
@@ -880,8 +880,8 @@ LL |         trait GenericLifetimeLifetimeTypeAT<'a, 'b, A> {
    |               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ --  --
 help: add missing lifetime argument
    |
-LL |         type C = Box<dyn GenericLifetimeLifetimeTypeAT<'static, 'b, (), AssocTy=()>>;
-   |                                                               ++++
+LL |         type C = Box<dyn GenericLifetimeLifetimeTypeAT<'static, 'static, (), AssocTy=()>>;
+   |                                                               +++++++++
 
 error[E0107]: missing generics for struct `HashMap`
   --> $DIR/wrong-number-of-args.rs:310:18
diff --git a/src/test/ui/methods/method-call-lifetime-args-fail.stderr b/src/test/ui/methods/method-call-lifetime-args-fail.stderr
index 835edb4b0ae..249b48ab194 100644
--- a/src/test/ui/methods/method-call-lifetime-args-fail.stderr
+++ b/src/test/ui/methods/method-call-lifetime-args-fail.stderr
@@ -13,8 +13,8 @@ LL |     fn early<'a, 'b>(self) -> (&'a u8, &'b u8) { loop {} }
    |        ^^^^^ --  --
 help: add missing lifetime argument
    |
-LL |     S.early::<'static, 'b>();
-   |                      ++++
+LL |     S.early::<'static, 'static>();
+   |                      +++++++++
 
 error[E0107]: this associated function takes 2 lifetime arguments but 3 lifetime arguments were supplied
   --> $DIR/method-call-lifetime-args-fail.rs:18:7
@@ -213,8 +213,8 @@ LL |     fn early<'a, 'b>(self) -> (&'a u8, &'b u8) { loop {} }
    |        ^^^^^ --  --
 help: add missing lifetime argument
    |
-LL |     S::early::<'static, 'b>(S);
-   |                       ++++
+LL |     S::early::<'static, 'static>(S);
+   |                       +++++++++
 
 error[E0107]: this associated function takes 2 lifetime arguments but 3 lifetime arguments were supplied
   --> $DIR/method-call-lifetime-args-fail.rs:65:8
diff --git a/src/test/ui/stats/hir-stats.stderr b/src/test/ui/stats/hir-stats.stderr
index 012bc848d4b..2a0e9497a21 100644
--- a/src/test/ui/stats/hir-stats.stderr
+++ b/src/test/ui/stats/hir-stats.stderr
@@ -119,7 +119,7 @@ hir-stats HIR STATS
 hir-stats Name                Accumulated Size         Count     Item Size
 hir-stats ----------------------------------------------------------------
 hir-stats ForeignItemRef            24 ( 0.3%)             1            24
-hir-stats Lifetime                  32 ( 0.3%)             1            32
+hir-stats Lifetime                  24 ( 0.3%)             1            24
 hir-stats Mod                       32 ( 0.3%)             1            32
 hir-stats ExprField                 40 ( 0.4%)             1            40
 hir-stats TraitItemRef              56 ( 0.6%)             2            28
@@ -152,7 +152,7 @@ hir-stats - Struct                    72 ( 0.8%)             1
 hir-stats - Binding                  216 ( 2.4%)             3
 hir-stats GenericParam             400 ( 4.4%)             5            80
 hir-stats Generics                 560 ( 6.1%)            10            56
-hir-stats Ty                       720 ( 7.8%)            15            48
+hir-stats Ty                       720 ( 7.9%)            15            48
 hir-stats - Ptr                       48 ( 0.5%)             1
 hir-stats - Rptr                      48 ( 0.5%)             1
 hir-stats - Path                     624 ( 6.8%)            13
@@ -171,8 +171,8 @@ hir-stats - ForeignMod                80 ( 0.9%)             1
 hir-stats - Impl                      80 ( 0.9%)             1
 hir-stats - Fn                       160 ( 1.7%)             2
 hir-stats - Use                      400 ( 4.4%)             5
-hir-stats Path                   1_280 (13.9%)            32            40
+hir-stats Path                   1_280 (14.0%)            32            40
 hir-stats PathSegment            1_920 (20.9%)            40            48
 hir-stats ----------------------------------------------------------------
-hir-stats Total                  9_176
+hir-stats Total                  9_168
 hir-stats
diff --git a/src/test/ui/suggestions/impl-trait-missing-lifetime-gated.rs b/src/test/ui/suggestions/impl-trait-missing-lifetime-gated.rs
index fe291e021bc..9839e973bdf 100644
--- a/src/test/ui/suggestions/impl-trait-missing-lifetime-gated.rs
+++ b/src/test/ui/suggestions/impl-trait-missing-lifetime-gated.rs
@@ -2,20 +2,62 @@
 // gate-test-anonymous_lifetime_in_impl_trait
 // Verify the behaviour of `feature(anonymous_lifetime_in_impl_trait)`.
 
-fn f(_: impl Iterator<Item = &'_ ()>) {}
-//~^ ERROR anonymous lifetimes in `impl Trait` are unstable
+mod elided {
+    fn f(_: impl Iterator<Item = &()>) {}
+    //~^ ERROR anonymous lifetimes in `impl Trait` are unstable
 
-fn g(x: impl Iterator<Item = &'_ ()>) -> Option<&'_ ()> { x.next() }
-//~^ ERROR anonymous lifetimes in `impl Trait` are unstable
-//~| ERROR missing lifetime specifier
+    fn g(mut x: impl Iterator<Item = &()>) -> Option<&()> { x.next() }
+    //~^ ERROR anonymous lifetimes in `impl Trait` are unstable
+    //~| ERROR missing lifetime specifier
 
-// Anonymous lifetimes in async fn are already allowed.
-// This is understood as `fn foo<'_1>(_: impl Iterator<Item = &'_1 ()>) {}`.
-async fn h(_: impl Iterator<Item = &'_ ()>) {}
+    // Anonymous lifetimes in async fn are already allowed.
+    // This is understood as `fn foo<'_1>(_: impl Iterator<Item = &'_1 ()>) {}`.
+    async fn h(_: impl Iterator<Item = &()>) {}
 
-// Anonymous lifetimes in async fn are already allowed.
-// But that lifetime does not participate in resolution.
-async fn i(x: impl Iterator<Item = &'_ ()>) -> Option<&'_ ()> { x.next() }
-//~^ ERROR missing lifetime specifier
+    // Anonymous lifetimes in async fn are already allowed.
+    // But that lifetime does not participate in resolution.
+    async fn i(mut x: impl Iterator<Item = &()>) -> Option<&()> { x.next() }
+    //~^ ERROR missing lifetime specifier
+}
+
+mod underscore {
+    fn f(_: impl Iterator<Item = &'_ ()>) {}
+    //~^ ERROR anonymous lifetimes in `impl Trait` are unstable
+
+    fn g(mut x: impl Iterator<Item = &'_ ()>) -> Option<&'_ ()> { x.next() }
+    //~^ ERROR anonymous lifetimes in `impl Trait` are unstable
+    //~| ERROR missing lifetime specifier
+
+    // Anonymous lifetimes in async fn are already allowed.
+    // This is understood as `fn foo<'_1>(_: impl Iterator<Item = &'_1 ()>) {}`.
+    async fn h(_: impl Iterator<Item = &'_ ()>) {}
+
+    // Anonymous lifetimes in async fn are already allowed.
+    // But that lifetime does not participate in resolution.
+    async fn i(mut x: impl Iterator<Item = &'_ ()>) -> Option<&'_ ()> { x.next() }
+    //~^ ERROR missing lifetime specifier
+}
+
+mod alone_in_path {
+    trait Foo<'a> { fn next(&mut self) -> Option<&'a ()>; }
+
+    fn f(_: impl Foo) {}
+    //~^ ERROR anonymous lifetimes in `impl Trait` are unstable
+
+    fn g(mut x: impl Foo) -> Option<&()> { x.next() }
+    //~^ ERROR anonymous lifetimes in `impl Trait` are unstable
+    //~| ERROR missing lifetime specifier
+}
+
+mod in_path {
+    trait Foo<'a, T> { fn next(&mut self) -> Option<&'a T>; }
+
+    fn f(_: impl Foo<()>) {}
+    //~^ ERROR anonymous lifetimes in `impl Trait` are unstable
+
+    fn g(mut x: impl Foo<()>) -> Option<&()> { x.next() }
+    //~^ ERROR anonymous lifetimes in `impl Trait` are unstable
+    //~| ERROR missing lifetime specifier
+}
 
 fn main() {}
diff --git a/src/test/ui/suggestions/impl-trait-missing-lifetime-gated.stderr b/src/test/ui/suggestions/impl-trait-missing-lifetime-gated.stderr
index 9833da13ffc..50806a67255 100644
--- a/src/test/ui/suggestions/impl-trait-missing-lifetime-gated.stderr
+++ b/src/test/ui/suggestions/impl-trait-missing-lifetime-gated.stderr
@@ -1,52 +1,172 @@
 error[E0106]: missing lifetime specifier
-  --> $DIR/impl-trait-missing-lifetime-gated.rs:8:50
+  --> $DIR/impl-trait-missing-lifetime-gated.rs:9:54
    |
-LL | fn g(x: impl Iterator<Item = &'_ ()>) -> Option<&'_ ()> { x.next() }
-   |                                                  ^^ expected named lifetime parameter
+LL |     fn g(mut x: impl Iterator<Item = &()>) -> Option<&()> { x.next() }
+   |                                                      ^ expected named lifetime parameter
    |
    = help: this function's return type contains a borrowed value, but there is no value for it to be borrowed from
 help: consider using the `'static` lifetime
    |
-LL | fn g(x: impl Iterator<Item = &'_ ()>) -> Option<&'static ()> { x.next() }
-   |                                                  ~~~~~~~
+LL |     fn g(mut x: impl Iterator<Item = &()>) -> Option<&'static ()> { x.next() }
+   |                                                       +++++++
 
 error[E0106]: missing lifetime specifier
-  --> $DIR/impl-trait-missing-lifetime-gated.rs:18:56
+  --> $DIR/impl-trait-missing-lifetime-gated.rs:19:60
    |
-LL | async fn i(x: impl Iterator<Item = &'_ ()>) -> Option<&'_ ()> { x.next() }
-   |                                                        ^^ expected named lifetime parameter
+LL |     async fn i(mut x: impl Iterator<Item = &()>) -> Option<&()> { x.next() }
+   |                                                            ^ expected named lifetime parameter
    |
    = help: this function's return type contains a borrowed value, but there is no value for it to be borrowed from
 help: consider using the `'static` lifetime
    |
-LL | async fn i(x: impl Iterator<Item = &'_ ()>) -> Option<&'static ()> { x.next() }
-   |                                                        ~~~~~~~
+LL |     async fn i(mut x: impl Iterator<Item = &()>) -> Option<&'static ()> { x.next() }
+   |                                                             +++++++
+
+error[E0106]: missing lifetime specifier
+  --> $DIR/impl-trait-missing-lifetime-gated.rs:27:58
+   |
+LL |     fn g(mut x: impl Iterator<Item = &'_ ()>) -> Option<&'_ ()> { x.next() }
+   |                                                          ^^ expected named lifetime parameter
+   |
+   = help: this function's return type contains a borrowed value, but there is no value for it to be borrowed from
+help: consider using the `'static` lifetime
+   |
+LL |     fn g(mut x: impl Iterator<Item = &'_ ()>) -> Option<&'static ()> { x.next() }
+   |                                                          ~~~~~~~
+
+error[E0106]: missing lifetime specifier
+  --> $DIR/impl-trait-missing-lifetime-gated.rs:37:64
+   |
+LL |     async fn i(mut x: impl Iterator<Item = &'_ ()>) -> Option<&'_ ()> { x.next() }
+   |                                                                ^^ expected named lifetime parameter
+   |
+   = help: this function's return type contains a borrowed value, but there is no value for it to be borrowed from
+help: consider using the `'static` lifetime
+   |
+LL |     async fn i(mut x: impl Iterator<Item = &'_ ()>) -> Option<&'static ()> { x.next() }
+   |                                                                ~~~~~~~
+
+error[E0106]: missing lifetime specifier
+  --> $DIR/impl-trait-missing-lifetime-gated.rs:47:37
+   |
+LL |     fn g(mut x: impl Foo) -> Option<&()> { x.next() }
+   |                                     ^ expected named lifetime parameter
+   |
+   = help: this function's return type contains a borrowed value, but there is no value for it to be borrowed from
+help: consider using the `'static` lifetime
+   |
+LL |     fn g(mut x: impl Foo) -> Option<&'static ()> { x.next() }
+   |                                      +++++++
+
+error[E0106]: missing lifetime specifier
+  --> $DIR/impl-trait-missing-lifetime-gated.rs:58:41
+   |
+LL |     fn g(mut x: impl Foo<()>) -> Option<&()> { x.next() }
+   |                                         ^ expected named lifetime parameter
+   |
+   = help: this function's return type contains a borrowed value, but there is no value for it to be borrowed from
+help: consider using the `'static` lifetime
+   |
+LL |     fn g(mut x: impl Foo<()>) -> Option<&'static ()> { x.next() }
+   |                                          +++++++
+
+error[E0658]: anonymous lifetimes in `impl Trait` are unstable
+  --> $DIR/impl-trait-missing-lifetime-gated.rs:6:35
+   |
+LL |     fn f(_: impl Iterator<Item = &()>) {}
+   |                                   ^ expected named lifetime parameter
+   |
+   = help: add `#![feature(anonymous_lifetime_in_impl_trait)]` to the crate attributes to enable
+help: consider introducing a named lifetime parameter
+   |
+LL |     fn f<'a>(_: impl Iterator<Item = &'a ()>) {}
+   |         ++++                          ++
+
+error[E0658]: anonymous lifetimes in `impl Trait` are unstable
+  --> $DIR/impl-trait-missing-lifetime-gated.rs:9:39
+   |
+LL |     fn g(mut x: impl Iterator<Item = &()>) -> Option<&()> { x.next() }
+   |                                       ^ expected named lifetime parameter
+   |
+   = help: add `#![feature(anonymous_lifetime_in_impl_trait)]` to the crate attributes to enable
+help: consider introducing a named lifetime parameter
+   |
+LL |     fn g<'a>(mut x: impl Iterator<Item = &'a ()>) -> Option<&()> { x.next() }
+   |         ++++                              ++
+
+error[E0658]: anonymous lifetimes in `impl Trait` are unstable
+  --> $DIR/impl-trait-missing-lifetime-gated.rs:24:35
+   |
+LL |     fn f(_: impl Iterator<Item = &'_ ()>) {}
+   |                                   ^^ expected named lifetime parameter
+   |
+   = help: add `#![feature(anonymous_lifetime_in_impl_trait)]` to the crate attributes to enable
+help: consider introducing a named lifetime parameter
+   |
+LL |     fn f<'a>(_: impl Iterator<Item = &'a ()>) {}
+   |         ++++                          ~~
+
+error[E0658]: anonymous lifetimes in `impl Trait` are unstable
+  --> $DIR/impl-trait-missing-lifetime-gated.rs:27:39
+   |
+LL |     fn g(mut x: impl Iterator<Item = &'_ ()>) -> Option<&'_ ()> { x.next() }
+   |                                       ^^ expected named lifetime parameter
+   |
+   = help: add `#![feature(anonymous_lifetime_in_impl_trait)]` to the crate attributes to enable
+help: consider introducing a named lifetime parameter
+   |
+LL |     fn g<'a>(mut x: impl Iterator<Item = &'a ()>) -> Option<&'_ ()> { x.next() }
+   |         ++++                              ~~
+
+error[E0658]: anonymous lifetimes in `impl Trait` are unstable
+  --> $DIR/impl-trait-missing-lifetime-gated.rs:44:18
+   |
+LL |     fn f(_: impl Foo) {}
+   |                  ^^^ expected named lifetime parameter
+   |
+   = help: add `#![feature(anonymous_lifetime_in_impl_trait)]` to the crate attributes to enable
+help: consider introducing a named lifetime parameter
+   |
+LL |     fn f<'a>(_: impl Foo<'a>) {}
+   |         ++++            ++++
+
+error[E0658]: anonymous lifetimes in `impl Trait` are unstable
+  --> $DIR/impl-trait-missing-lifetime-gated.rs:47:22
+   |
+LL |     fn g(mut x: impl Foo) -> Option<&()> { x.next() }
+   |                      ^^^ expected named lifetime parameter
+   |
+   = help: add `#![feature(anonymous_lifetime_in_impl_trait)]` to the crate attributes to enable
+help: consider introducing a named lifetime parameter
+   |
+LL |     fn g<'a>(mut x: impl Foo<'a>) -> Option<&()> { x.next() }
+   |         ++++                ++++
 
 error[E0658]: anonymous lifetimes in `impl Trait` are unstable
-  --> $DIR/impl-trait-missing-lifetime-gated.rs:5:31
+  --> $DIR/impl-trait-missing-lifetime-gated.rs:55:22
    |
-LL | fn f(_: impl Iterator<Item = &'_ ()>) {}
-   |                               ^^ expected named lifetime parameter
+LL |     fn f(_: impl Foo<()>) {}
+   |                      ^ expected named lifetime parameter
    |
    = help: add `#![feature(anonymous_lifetime_in_impl_trait)]` to the crate attributes to enable
 help: consider introducing a named lifetime parameter
    |
-LL | fn f<'a>(_: impl Iterator<Item = &'_'a  ()>) {}
-   |     ++++                            ++
+LL |     fn f<'a>(_: impl Foo<'a, ()>) {}
+   |         ++++             +++
 
 error[E0658]: anonymous lifetimes in `impl Trait` are unstable
-  --> $DIR/impl-trait-missing-lifetime-gated.rs:8:31
+  --> $DIR/impl-trait-missing-lifetime-gated.rs:58:26
    |
-LL | fn g(x: impl Iterator<Item = &'_ ()>) -> Option<&'_ ()> { x.next() }
-   |                               ^^ expected named lifetime parameter
+LL |     fn g(mut x: impl Foo<()>) -> Option<&()> { x.next() }
+   |                          ^ expected named lifetime parameter
    |
    = help: add `#![feature(anonymous_lifetime_in_impl_trait)]` to the crate attributes to enable
 help: consider introducing a named lifetime parameter
    |
-LL | fn g<'a>(x: impl Iterator<Item = &'_'a  ()>) -> Option<&'_ ()> { x.next() }
-   |     ++++                            ++
+LL |     fn g<'a>(mut x: impl Foo<'a, ()>) -> Option<&()> { x.next() }
+   |         ++++                 +++
 
-error: aborting due to 4 previous errors
+error: aborting due to 14 previous errors
 
 Some errors have detailed explanations: E0106, E0658.
 For more information about an error, try `rustc --explain E0106`.
diff --git a/src/test/ui/suggestions/missing-lifetime-specifier.stderr b/src/test/ui/suggestions/missing-lifetime-specifier.stderr
index 10fb28c1891..997bbb5e9b5 100644
--- a/src/test/ui/suggestions/missing-lifetime-specifier.stderr
+++ b/src/test/ui/suggestions/missing-lifetime-specifier.stderr
@@ -166,8 +166,8 @@ LL | pub union Qux<'t, 'k, I> {
    |           ^^^ --  --
 help: add missing lifetime argument
    |
-LL |     static e: RefCell<HashMap<i32, Vec<Vec<Qux<'static, 'k, i32>>>>> = RefCell::new(HashMap::new());
-   |                                                       ++++
+LL |     static e: RefCell<HashMap<i32, Vec<Vec<Qux<'static, 'static, i32>>>>> = RefCell::new(HashMap::new());
+   |                                                       +++++++++
 
 error[E0107]: this union takes 2 lifetime arguments but 1 lifetime argument was supplied
   --> $DIR/missing-lifetime-specifier.rs:39:44
@@ -184,8 +184,8 @@ LL | pub union Qux<'t, 'k, I> {
    |           ^^^ --  --
 help: add missing lifetime argument
    |
-LL |     static e: RefCell<HashMap<i32, Vec<Vec<Qux<'static, 'k, i32>>>>> = RefCell::new(HashMap::new());
-   |                                                       ++++
+LL |     static e: RefCell<HashMap<i32, Vec<Vec<Qux<'static, 'static, i32>>>>> = RefCell::new(HashMap::new());
+   |                                                       +++++++++
 
 error[E0107]: this union takes 2 lifetime arguments but 1 lifetime argument was supplied
   --> $DIR/missing-lifetime-specifier.rs:39:44
@@ -202,8 +202,8 @@ LL | pub union Qux<'t, 'k, I> {
    |           ^^^ --  --
 help: add missing lifetime argument
    |
-LL |     static e: RefCell<HashMap<i32, Vec<Vec<Qux<'static, 'k, i32>>>>> = RefCell::new(HashMap::new());
-   |                                                       ++++
+LL |     static e: RefCell<HashMap<i32, Vec<Vec<Qux<'static, 'static, i32>>>>> = RefCell::new(HashMap::new());
+   |                                                       +++++++++
 
 error[E0107]: this union takes 2 lifetime arguments but 1 lifetime argument was supplied
   --> $DIR/missing-lifetime-specifier.rs:39:44
@@ -256,8 +256,8 @@ LL | trait Tar<'t, 'k, I> {}
    |       ^^^ --  --
 help: add missing lifetime argument
    |
-LL |     static f: RefCell<HashMap<i32, Vec<Vec<&Tar<'static, 'k, i32>>>>> = RefCell::new(HashMap::new());
-   |                                                        ++++
+LL |     static f: RefCell<HashMap<i32, Vec<Vec<&Tar<'static, 'static, i32>>>>> = RefCell::new(HashMap::new());
+   |                                                        +++++++++
 
 error[E0107]: this trait takes 2 lifetime arguments but 1 lifetime argument was supplied
   --> $DIR/missing-lifetime-specifier.rs:47:45
@@ -274,8 +274,8 @@ LL | trait Tar<'t, 'k, I> {}
    |       ^^^ --  --
 help: add missing lifetime argument
    |
-LL |     static f: RefCell<HashMap<i32, Vec<Vec<&Tar<'static, 'k, i32>>>>> = RefCell::new(HashMap::new());
-   |                                                        ++++
+LL |     static f: RefCell<HashMap<i32, Vec<Vec<&Tar<'static, 'static, i32>>>>> = RefCell::new(HashMap::new());
+   |                                                        +++++++++
 
 error[E0107]: this trait takes 2 lifetime arguments but 1 lifetime argument was supplied
   --> $DIR/missing-lifetime-specifier.rs:47:45
@@ -292,8 +292,8 @@ LL | trait Tar<'t, 'k, I> {}
    |       ^^^ --  --
 help: add missing lifetime argument
    |
-LL |     static f: RefCell<HashMap<i32, Vec<Vec<&Tar<'static, 'k, i32>>>>> = RefCell::new(HashMap::new());
-   |                                                        ++++
+LL |     static f: RefCell<HashMap<i32, Vec<Vec<&Tar<'static, 'static, i32>>>>> = RefCell::new(HashMap::new());
+   |                                                        +++++++++
 
 error[E0107]: this trait takes 2 lifetime arguments but 1 lifetime argument was supplied
   --> $DIR/missing-lifetime-specifier.rs:47:45