Auto merge of #90446 - cjgillot:late-elided, r=jackh726

Lint elided lifetimes in path during lifetime resolution.

The lifetime elision lint is known to be brittle and can be redundant with later lifetime resolution errors. This PR aims to remove the redundancy by performing the lint after lifetime resolution.

This PR proposes to carry the information that an elision should be linted against by using a special `LifetimeName`. I am not certain this is the best solution, but it is certainly the easiest.

Fixes https://github.com/rust-lang/rust/issues/60199
Fixes https://github.com/rust-lang/rust/issues/55768
Fixes https://github.com/rust-lang/rust/issues/63110
Fixes https://github.com/rust-lang/rust/issues/71957

6 files changed, 178 insertions, 46 deletions

diff --git a/src/test/ui/in-band-lifetimes/elided-lifetimes.fixed b/src/test/ui/in-band-lifetimes/elided-lifetimes.fixed
index 2998f05efba..87a79b88137 100644
--- a/src/test/ui/in-band-lifetimes/elided-lifetimes.fixed
+++ b/src/test/ui/in-band-lifetimes/elided-lifetimes.fixed
@@ -5,23 +5,24 @@
 #![deny(elided_lifetimes_in_paths)]
 //~^ NOTE the lint level is defined here
 
-use std::cell::{RefCell, Ref};
+use std::cell::{Ref, RefCell};
 
-
-struct Foo<'a> { x: &'a u32 }
+struct Foo<'a> {
+    x: &'a u32,
+}
 
 fn foo(x: &Foo<'_>) {
     //~^ ERROR hidden lifetime parameters in types are deprecated
-    //~| HELP indicate the anonymous lifetime
+    //~| NOTE expected named lifetime parameter
+    //~| HELP consider using the `'_` lifetime
 }
 
 fn bar(x: &Foo<'_>) {}
 
-
 struct Wrapped<'a>(&'a str);
 
 struct WrappedWithBow<'a> {
-    gift: &'a str
+    gift: &'a str,
 }
 
 struct MatchedSet<'a, 'b> {
@@ -31,22 +32,34 @@ struct MatchedSet<'a, 'b> {
 
 fn wrap_gift(gift: &str) -> Wrapped<'_> {
     //~^ ERROR hidden lifetime parameters in types are deprecated
-    //~| HELP indicate the anonymous lifetime
+    //~| NOTE expected named lifetime parameter
+    //~| HELP consider using the `'_` lifetime
     Wrapped(gift)
 }
 
 fn wrap_gift_with_bow(gift: &str) -> WrappedWithBow<'_> {
     //~^ ERROR hidden lifetime parameters in types are deprecated
-    //~| HELP indicate the anonymous lifetime
+    //~| NOTE expected named lifetime parameter
+    //~| HELP consider using the `'_` lifetime
     WrappedWithBow { gift }
 }
 
 fn inspect_matched_set(set: MatchedSet<'_, '_>) {
     //~^ ERROR hidden lifetime parameters in types are deprecated
-    //~| HELP indicate the anonymous lifetime
+    //~| NOTE expected 2 lifetime parameters
+    //~| HELP consider using the `'_` lifetime
     println!("{} {}", set.one, set.another);
 }
 
+// Verify that the lint does not fire, because the added `'_` wouldn't be resolved correctly.
+fn match_sets() -> MatchedSet<'static, 'static> {
+    //~^ ERROR missing lifetime specifiers
+    //~| NOTE expected 2 lifetime parameters
+    //~| HELP this function's return type contains a borrowed value
+    //~| HELP consider using the `'static` lifetime
+    MatchedSet { one: "one", another: "another" }
+}
+
 macro_rules! autowrapper {
     ($type_name:ident, $fn_name:ident, $lt:lifetime) => {
         struct $type_name<$lt> {
@@ -55,7 +68,11 @@ macro_rules! autowrapper {
 
         fn $fn_name(gift: &str) -> $type_name<'_> {
             //~^ ERROR hidden lifetime parameters in types are deprecated
-            //~| HELP indicate the anonymous lifetime
+            //~| NOTE expected named lifetime parameter
+            //~| HELP consider using the `'_` lifetime
+            //~| ERROR hidden lifetime parameters in types are deprecated
+            //~| NOTE expected named lifetime parameter
+            //~| HELP consider using the `'_` lifetime
             $type_name { gift }
         }
     }
@@ -65,19 +82,34 @@ autowrapper!(Autowrapped, autowrap_gift, 'a);
 //~^ NOTE in this expansion of autowrapper!
 //~| NOTE in this expansion of autowrapper!
 
+// Verify that rustfix does not try to apply the fix twice.
+autowrapper!(AutowrappedAgain, autowrap_gift_again, 'a);
+//~^ NOTE in this expansion of autowrapper!
+//~| NOTE in this expansion of autowrapper!
+
 macro_rules! anytuple_ref_ty {
     ($($types:ty),*) => {
         Ref<'_, ($($types),*)>
         //~^ ERROR hidden lifetime parameters in types are deprecated
-        //~| HELP indicate the anonymous lifetime
+        //~| NOTE expected named lifetime parameter
+        //~| HELP consider using the `'_` lifetime
     }
 }
 
+#[allow(elided_lifetimes_in_paths)]
+mod blah {
+    struct Thing<'a>(&'a i32);
+    struct Bar<T>(T);
+
+    fn foo(b: Bar<Thing>) {}
+}
+
 fn main() {
     let honesty = RefCell::new((4, 'e'));
     let loyalty: Ref<'_, (u32, char)> = honesty.borrow();
     //~^ ERROR hidden lifetime parameters in types are deprecated
-    //~| HELP indicate the anonymous lifetime
+    //~| NOTE expected named lifetime parameter
+    //~| HELP consider using the `'_` lifetime
     let generosity = Ref::map(loyalty, |t| &t.0);
 
     let laughter = RefCell::new((true, "magic"));
diff --git a/src/test/ui/in-band-lifetimes/elided-lifetimes.rs b/src/test/ui/in-band-lifetimes/elided-lifetimes.rs
index b729a15a29e..28323a22427 100644
--- a/src/test/ui/in-band-lifetimes/elided-lifetimes.rs
+++ b/src/test/ui/in-band-lifetimes/elided-lifetimes.rs
@@ -5,23 +5,24 @@
 #![deny(elided_lifetimes_in_paths)]
 //~^ NOTE the lint level is defined here
 
-use std::cell::{RefCell, Ref};
+use std::cell::{Ref, RefCell};
 
-
-struct Foo<'a> { x: &'a u32 }
+struct Foo<'a> {
+    x: &'a u32,
+}
 
 fn foo(x: &Foo) {
     //~^ ERROR hidden lifetime parameters in types are deprecated
-    //~| HELP indicate the anonymous lifetime
+    //~| NOTE expected named lifetime parameter
+    //~| HELP consider using the `'_` lifetime
 }
 
 fn bar(x: &Foo<'_>) {}
 
-
 struct Wrapped<'a>(&'a str);
 
 struct WrappedWithBow<'a> {
-    gift: &'a str
+    gift: &'a str,
 }
 
 struct MatchedSet<'a, 'b> {
@@ -31,22 +32,34 @@ struct MatchedSet<'a, 'b> {
 
 fn wrap_gift(gift: &str) -> Wrapped {
     //~^ ERROR hidden lifetime parameters in types are deprecated
-    //~| HELP indicate the anonymous lifetime
+    //~| NOTE expected named lifetime parameter
+    //~| HELP consider using the `'_` lifetime
     Wrapped(gift)
 }
 
 fn wrap_gift_with_bow(gift: &str) -> WrappedWithBow {
     //~^ ERROR hidden lifetime parameters in types are deprecated
-    //~| HELP indicate the anonymous lifetime
+    //~| NOTE expected named lifetime parameter
+    //~| HELP consider using the `'_` lifetime
     WrappedWithBow { gift }
 }
 
 fn inspect_matched_set(set: MatchedSet) {
     //~^ ERROR hidden lifetime parameters in types are deprecated
-    //~| HELP indicate the anonymous lifetime
+    //~| NOTE expected 2 lifetime parameters
+    //~| HELP consider using the `'_` lifetime
     println!("{} {}", set.one, set.another);
 }
 
+// Verify that the lint does not fire, because the added `'_` wouldn't be resolved correctly.
+fn match_sets() -> MatchedSet {
+    //~^ ERROR missing lifetime specifiers
+    //~| NOTE expected 2 lifetime parameters
+    //~| HELP this function's return type contains a borrowed value
+    //~| HELP consider using the `'static` lifetime
+    MatchedSet { one: "one", another: "another" }
+}
+
 macro_rules! autowrapper {
     ($type_name:ident, $fn_name:ident, $lt:lifetime) => {
         struct $type_name<$lt> {
@@ -55,7 +68,11 @@ macro_rules! autowrapper {
 
         fn $fn_name(gift: &str) -> $type_name {
             //~^ ERROR hidden lifetime parameters in types are deprecated
-            //~| HELP indicate the anonymous lifetime
+            //~| NOTE expected named lifetime parameter
+            //~| HELP consider using the `'_` lifetime
+            //~| ERROR hidden lifetime parameters in types are deprecated
+            //~| NOTE expected named lifetime parameter
+            //~| HELP consider using the `'_` lifetime
             $type_name { gift }
         }
     }
@@ -65,19 +82,34 @@ autowrapper!(Autowrapped, autowrap_gift, 'a);
 //~^ NOTE in this expansion of autowrapper!
 //~| NOTE in this expansion of autowrapper!
 
+// Verify that rustfix does not try to apply the fix twice.
+autowrapper!(AutowrappedAgain, autowrap_gift_again, 'a);
+//~^ NOTE in this expansion of autowrapper!
+//~| NOTE in this expansion of autowrapper!
+
 macro_rules! anytuple_ref_ty {
     ($($types:ty),*) => {
         Ref<($($types),*)>
         //~^ ERROR hidden lifetime parameters in types are deprecated
-        //~| HELP indicate the anonymous lifetime
+        //~| NOTE expected named lifetime parameter
+        //~| HELP consider using the `'_` lifetime
     }
 }
 
+#[allow(elided_lifetimes_in_paths)]
+mod blah {
+    struct Thing<'a>(&'a i32);
+    struct Bar<T>(T);
+
+    fn foo(b: Bar<Thing>) {}
+}
+
 fn main() {
     let honesty = RefCell::new((4, 'e'));
     let loyalty: Ref<(u32, char)> = honesty.borrow();
     //~^ ERROR hidden lifetime parameters in types are deprecated
-    //~| HELP indicate the anonymous lifetime
+    //~| NOTE expected named lifetime parameter
+    //~| HELP consider using the `'_` lifetime
     let generosity = Ref::map(loyalty, |t| &t.0);
 
     let laughter = RefCell::new((true, "magic"));
diff --git a/src/test/ui/in-band-lifetimes/elided-lifetimes.stderr b/src/test/ui/in-band-lifetimes/elided-lifetimes.stderr
index 037ce401b3c..2e65461b321 100644
--- a/src/test/ui/in-band-lifetimes/elided-lifetimes.stderr
+++ b/src/test/ui/in-band-lifetimes/elided-lifetimes.stderr
@@ -1,60 +1,120 @@
 error: hidden lifetime parameters in types are deprecated
-  --> $DIR/elided-lifetimes.rs:13:12
+  --> $DIR/elided-lifetimes.rs:14:12
    |
 LL | fn foo(x: &Foo) {
-   |            ^^^- help: indicate the anonymous lifetime: `<'_>`
+   |            ^^^ expected named lifetime parameter
    |
 note: the lint level is defined here
   --> $DIR/elided-lifetimes.rs:5:9
    |
 LL | #![deny(elided_lifetimes_in_paths)]
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^
+help: consider using the `'_` lifetime
+   |
+LL | fn foo(x: &Foo<'_>) {
+   |            ~~~~~~~
 
 error: hidden lifetime parameters in types are deprecated
-  --> $DIR/elided-lifetimes.rs:32:29
+  --> $DIR/elided-lifetimes.rs:33:29
    |
 LL | fn wrap_gift(gift: &str) -> Wrapped {
-   |                             ^^^^^^^- help: indicate the anonymous lifetime: `<'_>`
+   |                             ^^^^^^^ expected named lifetime parameter
+   |
+help: consider using the `'_` lifetime
+   |
+LL | fn wrap_gift(gift: &str) -> Wrapped<'_> {
+   |                             ~~~~~~~~~~~
 
 error: hidden lifetime parameters in types are deprecated
-  --> $DIR/elided-lifetimes.rs:38:38
+  --> $DIR/elided-lifetimes.rs:40:38
    |
 LL | fn wrap_gift_with_bow(gift: &str) -> WrappedWithBow {
-   |                                      ^^^^^^^^^^^^^^- help: indicate the anonymous lifetime: `<'_>`
+   |                                      ^^^^^^^^^^^^^^ expected named lifetime parameter
+   |
+help: consider using the `'_` lifetime
+   |
+LL | fn wrap_gift_with_bow(gift: &str) -> WrappedWithBow<'_> {
+   |                                      ~~~~~~~~~~~~~~~~~~
 
 error: hidden lifetime parameters in types are deprecated
-  --> $DIR/elided-lifetimes.rs:44:29
+  --> $DIR/elided-lifetimes.rs:47:29
    |
 LL | fn inspect_matched_set(set: MatchedSet) {
-   |                             ^^^^^^^^^^- help: indicate the anonymous lifetimes: `<'_, '_>`
+   |                             ^^^^^^^^^^ expected 2 lifetime parameters
+   |
+help: consider using the `'_` lifetime
+   |
+LL | fn inspect_matched_set(set: MatchedSet<'_, '_>) {
+   |                             ~~~~~~~~~~~~~~~~~~
+
+error[E0106]: missing lifetime specifiers
+  --> $DIR/elided-lifetimes.rs:55:20
+   |
+LL | fn match_sets() -> MatchedSet {
+   |                    ^^^^^^^^^^ expected 2 lifetime parameters
+   |
+   = 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 match_sets() -> MatchedSet<'static, 'static> {
+   |                    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 error: hidden lifetime parameters in types are deprecated
-  --> $DIR/elided-lifetimes.rs:56:36
+  --> $DIR/elided-lifetimes.rs:69:36
    |
 LL |         fn $fn_name(gift: &str) -> $type_name {
-   |                                    ^^^^^^^^^^- help: indicate the anonymous lifetime: `<'_>`
+   |                                    ^^^^^^^^^^ expected named lifetime parameter
 ...
 LL | autowrapper!(Autowrapped, autowrap_gift, 'a);
    | -------------------------------------------- in this macro invocation
    |
    = note: this error originates in the macro `autowrapper` (in Nightly builds, run with -Z macro-backtrace for more info)
+help: consider using the `'_` lifetime
+   |
+LL |         fn $fn_name(gift: &str) -> $type_name<'_> {
+   |                                    ~~~~~~~~~~~~~~
 
 error: hidden lifetime parameters in types are deprecated
-  --> $DIR/elided-lifetimes.rs:78:18
+  --> $DIR/elided-lifetimes.rs:69:36
+   |
+LL |         fn $fn_name(gift: &str) -> $type_name {
+   |                                    ^^^^^^^^^^ expected named lifetime parameter
+...
+LL | autowrapper!(AutowrappedAgain, autowrap_gift_again, 'a);
+   | ------------------------------------------------------- in this macro invocation
+   |
+   = note: this error originates in the macro `autowrapper` (in Nightly builds, run with -Z macro-backtrace for more info)
+help: consider using the `'_` lifetime
+   |
+LL |         fn $fn_name(gift: &str) -> $type_name<'_> {
+   |                                    ~~~~~~~~~~~~~~
+
+error: hidden lifetime parameters in types are deprecated
+  --> $DIR/elided-lifetimes.rs:109:22
    |
 LL |     let loyalty: Ref<(u32, char)> = honesty.borrow();
-   |                  ^^^^^^^^^^^^^^^^ help: indicate the anonymous lifetime: `Ref<'_, (u32, char)>`
+   |                      ^ expected named lifetime parameter
+   |
+help: consider using the `'_` lifetime
+   |
+LL |     let loyalty: Ref<'_, (u32, char)> = honesty.borrow();
+   |                      +++
 
 error: hidden lifetime parameters in types are deprecated
-  --> $DIR/elided-lifetimes.rs:70:9
+  --> $DIR/elided-lifetimes.rs:92:13
    |
 LL |         Ref<($($types),*)>
-   |         ^^^^^^^^^^^^^^^^^^ help: indicate the anonymous lifetime: `Ref<'_, ($($types),*)>`
+   |             ^ expected named lifetime parameter
 ...
 LL |     let yellow: anytuple_ref_ty!(bool, &str) = laughter.borrow();
    |                 ---------------------------- in this macro invocation
    |
    = note: this error originates in the macro `anytuple_ref_ty` (in Nightly builds, run with -Z macro-backtrace for more info)
+help: consider using the `'_` lifetime
+   |
+LL |         Ref<'_, ($($types),*)>
+   |             +++
 
-error: aborting due to 7 previous errors
+error: aborting due to 9 previous errors
 
+For more information about this error, try `rustc --explain E0106`.
diff --git a/src/test/ui/lint/force-warn/allowed-by-default-lint.stderr b/src/test/ui/lint/force-warn/allowed-by-default-lint.stderr
index baa47cbb10f..f5e8b41b163 100644
--- a/src/test/ui/lint/force-warn/allowed-by-default-lint.stderr
+++ b/src/test/ui/lint/force-warn/allowed-by-default-lint.stderr
@@ -2,9 +2,13 @@ warning: hidden lifetime parameters in types are deprecated
   --> $DIR/allowed-by-default-lint.rs:9:12
    |
 LL | fn foo(x: &Foo) {}
-   |            ^^^- help: indicate the anonymous lifetime: `<'_>`
+   |            ^^^ expected named lifetime parameter
    |
    = note: requested on the command line with `--force-warn elided-lifetimes-in-paths`
+help: consider using the `'_` lifetime
+   |
+LL | fn foo(x: &Foo<'_>) {}
+   |            ~~~~~~~
 
 warning: 1 warning emitted
 
diff --git a/src/test/ui/lint/reasons.rs b/src/test/ui/lint/reasons.rs
index 34cac4968a8..b1792e2e9cb 100644
--- a/src/test/ui/lint/reasons.rs
+++ b/src/test/ui/lint/reasons.rs
@@ -1,7 +1,6 @@
 // check-pass
 
 #![feature(lint_reasons)]
-
 #![warn(elided_lifetimes_in_paths,
         //~^ NOTE the lint level is defined here
         reason = "explicit anonymous lifetimes aid reasoning about ownership")]
@@ -20,8 +19,9 @@ pub struct CheaterDetectionMechanism {}
 impl fmt::Debug for CheaterDetectionMechanism {
     fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
         //~^ WARN hidden lifetime parameters in types are deprecated
+        //~| NOTE expected named lifetime parameter
         //~| NOTE explicit anonymous lifetimes aid
-        //~| HELP indicate the anonymous lifetime
+        //~| HELP consider using the `'_` lifetime
         fmt.debug_struct("CheaterDetectionMechanism").finish()
     }
 }
diff --git a/src/test/ui/lint/reasons.stderr b/src/test/ui/lint/reasons.stderr
index 150237c6be2..f797c89a032 100644
--- a/src/test/ui/lint/reasons.stderr
+++ b/src/test/ui/lint/reasons.stderr
@@ -1,15 +1,19 @@
 warning: hidden lifetime parameters in types are deprecated
-  --> $DIR/reasons.rs:21:29
+  --> $DIR/reasons.rs:20:29
    |
 LL |     fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
-   |                             ^^^^^^^^^^^^^^- help: indicate the anonymous lifetime: `<'_>`
+   |                             ^^^^^^^^^^^^^^ expected named lifetime parameter
    |
    = note: explicit anonymous lifetimes aid reasoning about ownership
 note: the lint level is defined here
-  --> $DIR/reasons.rs:5:9
+  --> $DIR/reasons.rs:4:9
    |
 LL | #![warn(elided_lifetimes_in_paths,
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^
+help: consider using the `'_` lifetime
+   |
+LL |     fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+   |                             ~~~~~~~~~~~~~~~~~~
 
 warning: variable `Social_exchange_psychology` should have a snake case name
   --> $DIR/reasons.rs:30:9
@@ -20,7 +24,7 @@ LL |     let Social_exchange_psychology = CheaterDetectionMechanism {};
    = note: people shouldn't have to change their usual style habits
            to contribute to our project
 note: the lint level is defined here
-  --> $DIR/reasons.rs:9:5
+  --> $DIR/reasons.rs:8:5
    |
 LL |     nonstandard_style,
    |     ^^^^^^^^^^^^^^^^^