Auto merge of rust-lang#102068 - cjgillot:erased-lifetime-print, r=eholk

Always print '_, even for erased lifetimes.

Explicit lifetime arguments are now the recommended syntax in rust 2018 and rust 2021.  This PR applies this discipline to rustc itself.

Author: bors

tests/ui/inefficient_to_string.stderr

@@ -35,21 +35,21 @@ LL |     let _: String = rrrstring.to_string();
    |
    = help: `&&std::string::String` implements `ToString` through a slower blanket impl, but `std::string::String` has a fast specialization of `ToString`
 
-error: calling `to_string` on `&&std::borrow::Cow<str>`
+error: calling `to_string` on `&&std::borrow::Cow<'_, str>`
   --> $DIR/inefficient_to_string.rs:29:21
    |
 LL |     let _: String = rrcow.to_string();
    |                     ^^^^^^^^^^^^^^^^^ help: try dereferencing the receiver: `(*rrcow).to_string()`
    |
-   = help: `&std::borrow::Cow<str>` implements `ToString` through a slower blanket impl, but `std::borrow::Cow<str>` has a fast specialization of `ToString`
+   = help: `&std::borrow::Cow<'_, str>` implements `ToString` through a slower blanket impl, but `std::borrow::Cow<'_, str>` has a fast specialization of `ToString`
 
-error: calling `to_string` on `&&&std::borrow::Cow<str>`
+error: calling `to_string` on `&&&std::borrow::Cow<'_, str>`
   --> $DIR/inefficient_to_string.rs:30:21
    |
 LL |     let _: String = rrrcow.to_string();
    |                     ^^^^^^^^^^^^^^^^^^ help: try dereferencing the receiver: `(**rrrcow).to_string()`
    |
-   = help: `&&std::borrow::Cow<str>` implements `ToString` through a slower blanket impl, but `std::borrow::Cow<str>` has a fast specialization of `ToString`
+   = help: `&&std::borrow::Cow<'_, str>` implements `ToString` through a slower blanket impl, but `std::borrow::Cow<'_, str>` has a fast specialization of `ToString`
 
 error: aborting due to 6 previous errors
 

tests/ui/suspicious_to_owned.stderr

@@ -1,24 +1,24 @@
-error: this `to_owned` call clones the std::borrow::Cow<str> itself and does not cause the std::borrow::Cow<str> contents to become owned
+error: this `to_owned` call clones the std::borrow::Cow<'_, str> itself and does not cause the std::borrow::Cow<'_, str> contents to become owned
   --> $DIR/suspicious_to_owned.rs:16:13
    |
 LL |     let _ = cow.to_owned();
    |             ^^^^^^^^^^^^^^ help: consider using, depending on intent: `cow.clone()` or `cow.into_owned()`
    |
    = note: `-D clippy::suspicious-to-owned` implied by `-D warnings`
 
-error: this `to_owned` call clones the std::borrow::Cow<[char; 3]> itself and does not cause the std::borrow::Cow<[char; 3]> contents to become owned
+error: this `to_owned` call clones the std::borrow::Cow<'_, [char; 3]> itself and does not cause the std::borrow::Cow<'_, [char; 3]> contents to become owned
   --> $DIR/suspicious_to_owned.rs:26:13
    |
 LL |     let _ = cow.to_owned();
    |             ^^^^^^^^^^^^^^ help: consider using, depending on intent: `cow.clone()` or `cow.into_owned()`
 
-error: this `to_owned` call clones the std::borrow::Cow<std::vec::Vec<char>> itself and does not cause the std::borrow::Cow<std::vec::Vec<char>> contents to become owned
+error: this `to_owned` call clones the std::borrow::Cow<'_, std::vec::Vec<char>> itself and does not cause the std::borrow::Cow<'_, std::vec::Vec<char>> contents to become owned
   --> $DIR/suspicious_to_owned.rs:36:13
    |
 LL |     let _ = cow.to_owned();
    |             ^^^^^^^^^^^^^^ help: consider using, depending on intent: `cow.clone()` or `cow.into_owned()`
 
-error: this `to_owned` call clones the std::borrow::Cow<str> itself and does not cause the std::borrow::Cow<str> contents to become owned
+error: this `to_owned` call clones the std::borrow::Cow<'_, str> itself and does not cause the std::borrow::Cow<'_, str> contents to become owned
   --> $DIR/suspicious_to_owned.rs:46:13
    |
 LL |     let _ = cow.to_owned();

tests/ui/transmute_ptr_to_ref.stderr

@@ -42,13 +42,13 @@ error: transmute from a pointer type (`*mut U`) to a reference type (`&T`)
 LL |     let _: &T = std::mem::transmute(om);
    |                 ^^^^^^^^^^^^^^^^^^^^^^^ help: try: `&*(om as *const T)`
 
-error: transmute from a pointer type (`*const i32`) to a reference type (`&_issue1231::Foo<u8>`)
+error: transmute from a pointer type (`*const i32`) to a reference type (`&_issue1231::Foo<'_, u8>`)
   --> $DIR/transmute_ptr_to_ref.rs:36:32
    |
 LL |     let _: &Foo<u8> = unsafe { std::mem::transmute::<_, &Foo<_>>(raw) };
    |                                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `&*raw.cast::<Foo<_>>()`
 
-error: transmute from a pointer type (`*const i32`) to a reference type (`&_issue1231::Foo<&u8>`)
+error: transmute from a pointer type (`*const i32`) to a reference type (`&_issue1231::Foo<'_, &u8>`)
   --> $DIR/transmute_ptr_to_ref.rs:38:33
    |
 LL |     let _: &Foo<&u8> = unsafe { std::mem::transmute::<_, &Foo<&_>>(raw) };

tests/ui/useless_conversion.stderr

@@ -46,7 +46,7 @@ error: useless conversion to the same type: `std::string::String`
 LL |     let _ = String::from(format!("A: {:04}", 123));
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider removing `String::from()`: `format!("A: {:04}", 123)`
 
-error: useless conversion to the same type: `std::str::Lines`
+error: useless conversion to the same type: `std::str::Lines<'_>`
   --> $DIR/useless_conversion.rs:65:13
    |
 LL |     let _ = "".lines().into_iter();