Auto merge of #85150 - Dylan-DPC:rollup-q26gbx3, r=Dylan-DPC

Rollup of 6 pull requests

Successful merges:

 - #85050 (Fix suggestions for missing return type lifetime specifiers)
 - #85075 (Improve "panic message is not a string literal" warning)
 - #85096 (Make unchecked_{add,sub,mul} inherent methods unstably const)
 - #85112 (ensure failing promoteds in const/static bodies are handled correctly)
 - #85146 (Provide io::Seek::rewind)
 - #85147 (:arrow_up: rust-analyzer)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

15 files changed, 405 insertions, 22 deletions

diff --git a/src/test/ui/consts/const-eval/erroneous-const.rs b/src/test/ui/consts/const-eval/erroneous-const.rs
index b79ce4a523f..bee5a7cb3ba 100644
--- a/src/test/ui/consts/const-eval/erroneous-const.rs
+++ b/src/test/ui/consts/const-eval/erroneous-const.rs
@@ -10,6 +10,8 @@ impl<T> PrintName<T> {
 
 const fn no_codegen<T>() {
     if false {
+        // This bad constant is only used in dead code in a no-codegen function... and yet we still
+        // must make sure that the build fails.
         let _ = PrintName::<T>::VOID; //~ERROR could not evaluate static initializer
     }
 }
diff --git a/src/test/ui/consts/const-eval/erroneous-const.stderr b/src/test/ui/consts/const-eval/erroneous-const.stderr
index 16ed596628b..7e2a60929c7 100644
--- a/src/test/ui/consts/const-eval/erroneous-const.stderr
+++ b/src/test/ui/consts/const-eval/erroneous-const.stderr
@@ -27,16 +27,16 @@ LL | #![warn(const_err, unconditional_panic)]
    = note: for more information, see issue #71800 <https://github.com/rust-lang/rust/issues/71800>
 
 error[E0080]: could not evaluate static initializer
-  --> $DIR/erroneous-const.rs:13:17
+  --> $DIR/erroneous-const.rs:15:17
    |
 LL |         let _ = PrintName::<T>::VOID;
    |                 ^^^^^^^^^^^^^^^^^^^^
    |                 |
    |                 referenced constant has errors
-   |                 inside `no_codegen::<i32>` at $DIR/erroneous-const.rs:13:17
+   |                 inside `no_codegen::<i32>` at $DIR/erroneous-const.rs:15:17
 ...
 LL | pub static FOO: () = no_codegen::<i32>();
-   |                      ------------------- inside `FOO` at $DIR/erroneous-const.rs:17:22
+   |                      ------------------- inside `FOO` at $DIR/erroneous-const.rs:19:22
 
 error: aborting due to previous error; 2 warnings emitted
 
diff --git a/src/test/ui/consts/const-eval/erroneous-const2.rs b/src/test/ui/consts/const-eval/erroneous-const2.rs
new file mode 100644
index 00000000000..aa0f093bf62
--- /dev/null
+++ b/src/test/ui/consts/const-eval/erroneous-const2.rs
@@ -0,0 +1,21 @@
+//! Make sure we error on erroneous consts even if they are unused.
+#![warn(const_err, unconditional_panic)]
+
+struct PrintName<T>(T);
+impl<T> PrintName<T> {
+    const VOID: () = [()][2]; //~WARN any use of this value will cause an error
+    //~^ WARN this operation will panic at runtime
+    //~| WARN this was previously accepted by the compiler but is being phased out
+}
+
+pub static FOO: () = {
+    if false {
+        // This bad constant is only used in dead code in a static initializer... and yet we still
+        // must make sure that the build fails.
+        let _ = PrintName::<i32>::VOID; //~ERROR could not evaluate static initializer
+    }
+};
+
+fn main() {
+    FOO
+}
diff --git a/src/test/ui/consts/const-eval/erroneous-const2.stderr b/src/test/ui/consts/const-eval/erroneous-const2.stderr
new file mode 100644
index 00000000000..813d3ee249f
--- /dev/null
+++ b/src/test/ui/consts/const-eval/erroneous-const2.stderr
@@ -0,0 +1,37 @@
+warning: this operation will panic at runtime
+  --> $DIR/erroneous-const2.rs:6:22
+   |
+LL |     const VOID: () = [()][2];
+   |                      ^^^^^^^ index out of bounds: the length is 1 but the index is 2
+   |
+note: the lint level is defined here
+  --> $DIR/erroneous-const2.rs:2:20
+   |
+LL | #![warn(const_err, unconditional_panic)]
+   |                    ^^^^^^^^^^^^^^^^^^^
+
+warning: any use of this value will cause an error
+  --> $DIR/erroneous-const2.rs:6:22
+   |
+LL |     const VOID: () = [()][2];
+   |     -----------------^^^^^^^-
+   |                      |
+   |                      index out of bounds: the length is 1 but the index is 2
+   |
+note: the lint level is defined here
+  --> $DIR/erroneous-const2.rs:2:9
+   |
+LL | #![warn(const_err, unconditional_panic)]
+   |         ^^^^^^^^^
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #71800 <https://github.com/rust-lang/rust/issues/71800>
+
+error[E0080]: could not evaluate static initializer
+  --> $DIR/erroneous-const2.rs:15:17
+   |
+LL |         let _ = PrintName::<i32>::VOID;
+   |                 ^^^^^^^^^^^^^^^^^^^^^^ referenced constant has errors
+
+error: aborting due to previous error; 2 warnings emitted
+
+For more information about this error, try `rustc --explain E0080`.
diff --git a/src/test/ui/consts/const-eval/promoted_errors.noopt.stderr b/src/test/ui/consts/const-eval/promoted_errors.noopt.stderr
index 6f266801bdb..77e7d484071 100644
--- a/src/test/ui/consts/const-eval/promoted_errors.noopt.stderr
+++ b/src/test/ui/consts/const-eval/promoted_errors.noopt.stderr
@@ -1,12 +1,12 @@
 warning: any use of this value will cause an error
-  --> $DIR/promoted_errors.rs:13:5
+  --> $DIR/promoted_errors.rs:15:5
    |
 LL |       0 - 1
    |       ^^^^^
    |       |
    |       attempt to compute `0_u32 - 1_u32`, which would overflow
-   |       inside `overflow` at $DIR/promoted_errors.rs:13:5
-   |       inside `X` at $DIR/promoted_errors.rs:33:29
+   |       inside `overflow` at $DIR/promoted_errors.rs:15:5
+   |       inside `X` at $DIR/promoted_errors.rs:38:29
 ...
 LL | / const X: () = {
 LL | |     let _x: &'static u32 = &overflow();
@@ -18,7 +18,7 @@ LL | | };
    | |__-
    |
 note: the lint level is defined here
-  --> $DIR/promoted_errors.rs:9:9
+  --> $DIR/promoted_errors.rs:11:9
    |
 LL | #![warn(const_err, arithmetic_overflow, unconditional_panic)]
    |         ^^^^^^^^^
@@ -26,7 +26,7 @@ LL | #![warn(const_err, arithmetic_overflow, unconditional_panic)]
    = note: for more information, see issue #71800 <https://github.com/rust-lang/rust/issues/71800>
 
 warning: any use of this value will cause an error
-  --> $DIR/promoted_errors.rs:33:28
+  --> $DIR/promoted_errors.rs:38:28
    |
 LL | / const X: () = {
 LL | |     let _x: &'static u32 = &overflow();
diff --git a/src/test/ui/consts/const-eval/promoted_errors.opt.stderr b/src/test/ui/consts/const-eval/promoted_errors.opt.stderr
index 892f57bfdfc..6b17346e6ec 100644
--- a/src/test/ui/consts/const-eval/promoted_errors.opt.stderr
+++ b/src/test/ui/consts/const-eval/promoted_errors.opt.stderr
@@ -1,12 +1,12 @@
 warning: any use of this value will cause an error
-  --> $DIR/promoted_errors.rs:18:5
+  --> $DIR/promoted_errors.rs:20:5
    |
 LL |       1 / 0
    |       ^^^^^
    |       |
    |       attempt to divide `1_i32` by zero
-   |       inside `div_by_zero1` at $DIR/promoted_errors.rs:18:5
-   |       inside `X` at $DIR/promoted_errors.rs:36:29
+   |       inside `div_by_zero1` at $DIR/promoted_errors.rs:20:5
+   |       inside `X` at $DIR/promoted_errors.rs:41:29
 ...
 LL | / const X: () = {
 LL | |     let _x: &'static u32 = &overflow();
@@ -18,7 +18,7 @@ LL | | };
    | |__-
    |
 note: the lint level is defined here
-  --> $DIR/promoted_errors.rs:9:9
+  --> $DIR/promoted_errors.rs:11:9
    |
 LL | #![warn(const_err, arithmetic_overflow, unconditional_panic)]
    |         ^^^^^^^^^
@@ -26,7 +26,7 @@ LL | #![warn(const_err, arithmetic_overflow, unconditional_panic)]
    = note: for more information, see issue #71800 <https://github.com/rust-lang/rust/issues/71800>
 
 warning: any use of this value will cause an error
-  --> $DIR/promoted_errors.rs:36:28
+  --> $DIR/promoted_errors.rs:41:28
    |
 LL | / const X: () = {
 LL | |     let _x: &'static u32 = &overflow();
diff --git a/src/test/ui/consts/const-eval/promoted_errors.opt_with_overflow_checks.stderr b/src/test/ui/consts/const-eval/promoted_errors.opt_with_overflow_checks.stderr
index 6f266801bdb..77e7d484071 100644
--- a/src/test/ui/consts/const-eval/promoted_errors.opt_with_overflow_checks.stderr
+++ b/src/test/ui/consts/const-eval/promoted_errors.opt_with_overflow_checks.stderr
@@ -1,12 +1,12 @@
 warning: any use of this value will cause an error
-  --> $DIR/promoted_errors.rs:13:5
+  --> $DIR/promoted_errors.rs:15:5
    |
 LL |       0 - 1
    |       ^^^^^
    |       |
    |       attempt to compute `0_u32 - 1_u32`, which would overflow
-   |       inside `overflow` at $DIR/promoted_errors.rs:13:5
-   |       inside `X` at $DIR/promoted_errors.rs:33:29
+   |       inside `overflow` at $DIR/promoted_errors.rs:15:5
+   |       inside `X` at $DIR/promoted_errors.rs:38:29
 ...
 LL | / const X: () = {
 LL | |     let _x: &'static u32 = &overflow();
@@ -18,7 +18,7 @@ LL | | };
    | |__-
    |
 note: the lint level is defined here
-  --> $DIR/promoted_errors.rs:9:9
+  --> $DIR/promoted_errors.rs:11:9
    |
 LL | #![warn(const_err, arithmetic_overflow, unconditional_panic)]
    |         ^^^^^^^^^
@@ -26,7 +26,7 @@ LL | #![warn(const_err, arithmetic_overflow, unconditional_panic)]
    = note: for more information, see issue #71800 <https://github.com/rust-lang/rust/issues/71800>
 
 warning: any use of this value will cause an error
-  --> $DIR/promoted_errors.rs:33:28
+  --> $DIR/promoted_errors.rs:38:28
    |
 LL | / const X: () = {
 LL | |     let _x: &'static u32 = &overflow();
diff --git a/src/test/ui/consts/const-eval/promoted_errors.rs b/src/test/ui/consts/const-eval/promoted_errors.rs
index 7840f67c216..5bafea1ed46 100644
--- a/src/test/ui/consts/const-eval/promoted_errors.rs
+++ b/src/test/ui/consts/const-eval/promoted_errors.rs
@@ -6,6 +6,8 @@
 // build-pass
 // ignore-pass (test emits codegen-time warnings and verifies that they are not errors)
 
+//! This test ensures that when we promote code that fails to evaluate, the build still succeeds.
+
 #![warn(const_err, arithmetic_overflow, unconditional_panic)]
 
 // The only way to have promoteds that fail is in `const fn` called from `const`/`static`.
@@ -29,6 +31,9 @@ const fn oob() -> i32 {
     [1, 2, 3][4]
 }
 
+// An unused constant containing failing promoteds.
+// This should work as long as `const_err` can be turned into just a warning;
+// once it turns into a hard error, just remove `X`.
 const X: () = {
     let _x: &'static u32 = &overflow();
     //[opt_with_overflow_checks,noopt]~^ WARN any use of this value will cause an error
@@ -41,4 +46,21 @@ const X: () = {
     let _x: &'static i32 = &oob();
 };
 
-fn main() {}
+const fn mk_false() -> bool { false }
+
+// An actually used constant referencing failing promoteds in dead code.
+// This needs to always work.
+const Y: () = {
+    if mk_false() {
+        let _x: &'static u32 = &overflow();
+        let _x: &'static i32 = &div_by_zero1();
+        let _x: &'static i32 = &div_by_zero2();
+        let _x: &'static i32 = &div_by_zero3();
+        let _x: &'static i32 = &oob();
+    }
+    ()
+};
+
+fn main() {
+    let _y = Y;
+}
diff --git a/src/test/ui/non-fmt-panic.rs b/src/test/ui/non-fmt-panic.rs
index c80a90b3eaa..77390aae2d6 100644
--- a/src/test/ui/non-fmt-panic.rs
+++ b/src/test/ui/non-fmt-panic.rs
@@ -36,6 +36,8 @@ fn main() {
     panic!(a!()); //~ WARN panic message is not a string literal
 
     panic!(format!("{}", 1)); //~ WARN panic message is not a string literal
+    assert!(false, format!("{}", 1)); //~ WARN panic message is not a string literal
+    debug_assert!(false, format!("{}", 1)); //~ WARN panic message is not a string literal
 
     panic![123]; //~ WARN panic message is not a string literal
     panic!{123}; //~ WARN panic message is not a string literal
diff --git a/src/test/ui/non-fmt-panic.stderr b/src/test/ui/non-fmt-panic.stderr
index 7a333b3e76a..3278eb5f023 100644
--- a/src/test/ui/non-fmt-panic.stderr
+++ b/src/test/ui/non-fmt-panic.stderr
@@ -213,7 +213,33 @@ LL |     panic!("{}", 1);
    |           --     --
 
 warning: panic message is not a string literal
-  --> $DIR/non-fmt-panic.rs:40:12
+  --> $DIR/non-fmt-panic.rs:39:20
+   |
+LL |     assert!(false, format!("{}", 1));
+   |                    ^^^^^^^^^^^^^^^^
+   |
+   = note: this is no longer accepted in Rust 2021
+   = note: the assert!() macro supports formatting, so there's no need for the format!() macro here
+help: remove the `format!(..)` macro call
+   |
+LL |     assert!(false, "{}", 1);
+   |                   --     --
+
+warning: panic message is not a string literal
+  --> $DIR/non-fmt-panic.rs:40:26
+   |
+LL |     debug_assert!(false, format!("{}", 1));
+   |                          ^^^^^^^^^^^^^^^^
+   |
+   = note: this is no longer accepted in Rust 2021
+   = note: the debug_assert!() macro supports formatting, so there's no need for the format!() macro here
+help: remove the `format!(..)` macro call
+   |
+LL |     debug_assert!(false, "{}", 1);
+   |                         --     --
+
+warning: panic message is not a string literal
+  --> $DIR/non-fmt-panic.rs:42:12
    |
 LL |     panic![123];
    |            ^^^
@@ -229,7 +255,7 @@ LL |     std::panic::panic_any(123);
    |     ^^^^^^^^^^^^^^^^^^^^^^   ^
 
 warning: panic message is not a string literal
-  --> $DIR/non-fmt-panic.rs:41:12
+  --> $DIR/non-fmt-panic.rs:43:12
    |
 LL |     panic!{123};
    |            ^^^
@@ -244,5 +270,5 @@ help: or use std::panic::panic_any instead
 LL |     std::panic::panic_any(123);
    |     ^^^^^^^^^^^^^^^^^^^^^^   ^
 
-warning: 18 warnings emitted
+warning: 20 warnings emitted
 
diff --git a/src/test/ui/suggestions/issue-84592.rs b/src/test/ui/suggestions/issue-84592.rs
new file mode 100644
index 00000000000..aa246aaa3d4
--- /dev/null
+++ b/src/test/ui/suggestions/issue-84592.rs
@@ -0,0 +1,17 @@
+/* Checks whether issue #84592 has been resolved. The issue was
+ * that in this example, there are two expected/missing lifetime
+ * parameters with *different spans*, leading to incorrect
+ * suggestions from rustc.
+ */
+
+struct TwoLifetimes<'x, 'y> {
+    x: &'x (),
+    y: &'y (),
+}
+
+fn two_lifetimes_needed(a: &(), b: &()) -> TwoLifetimes<'_, '_> {
+//~^ ERROR missing lifetime specifiers [E0106]
+    TwoLifetimes { x: &(), y: &() }
+}
+
+fn main() {}
diff --git a/src/test/ui/suggestions/issue-84592.stderr b/src/test/ui/suggestions/issue-84592.stderr
new file mode 100644
index 00000000000..02f9241a6d2
--- /dev/null
+++ b/src/test/ui/suggestions/issue-84592.stderr
@@ -0,0 +1,17 @@
+error[E0106]: missing lifetime specifiers
+  --> $DIR/issue-84592.rs:12:57
+   |
+LL | fn two_lifetimes_needed(a: &(), b: &()) -> TwoLifetimes<'_, '_> {
+   |                            ---     ---                  ^^  ^^ expected named lifetime parameter
+   |                                                         |
+   |                                                         expected named lifetime parameter
+   |
+   = help: this function's return type contains a borrowed value, but the signature does not say whether it is borrowed from `a` or `b`
+help: consider introducing a named lifetime parameter
+   |
+LL | fn two_lifetimes_needed<'a>(a: &'a (), b: &'a ()) -> TwoLifetimes<'a, 'a> {
+   |                        ^^^^    ^^^^^^     ^^^^^^                  ^^  ^^
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0106`.
diff --git a/src/test/ui/suggestions/missing-lt-for-hrtb.stderr b/src/test/ui/suggestions/missing-lt-for-hrtb.stderr
index 2cb63500e48..a7a44b511db 100644
--- a/src/test/ui/suggestions/missing-lt-for-hrtb.stderr
+++ b/src/test/ui/suggestions/missing-lt-for-hrtb.stderr
@@ -44,6 +44,10 @@ note: these named lifetimes are available to use
    |
 LL | struct V<'a>(&'a dyn for<'b> Fn(&X) -> &X);
    |          ^^              ^^
+help: consider using one of the available lifetimes here
+   |
+LL | struct V<'a>(&'a dyn for<'b> Fn(&X) -> &'lifetime X);
+   |                                        ^^^^^^^^^^
 
 error[E0106]: missing lifetime specifier
   --> $DIR/missing-lt-for-hrtb.rs:5:41
diff --git a/src/test/ui/suggestions/return-elided-lifetime.rs b/src/test/ui/suggestions/return-elided-lifetime.rs
new file mode 100644
index 00000000000..ca336bbb056
--- /dev/null
+++ b/src/test/ui/suggestions/return-elided-lifetime.rs
@@ -0,0 +1,37 @@
+/* Checks all four scenarios possible in report_elision_failure() of
+ * rustc_resolve::late::lifetimes::LifetimeContext related to returning
+ * borrowed values, in various configurations.
+ */
+
+fn f1() -> &i32 { loop {} }
+//~^ ERROR missing lifetime specifier [E0106]
+fn f1_() -> (&i32, &i32) { loop {} }
+//~^ ERROR missing lifetime specifier [E0106]
+//~^^ ERROR missing lifetime specifier [E0106]
+
+fn f2(a: i32, b: i32) -> &i32 { loop {} }
+//~^ ERROR missing lifetime specifier [E0106]
+fn f2_(a: i32, b: i32) -> (&i32, &i32) { loop {} }
+//~^ ERROR missing lifetime specifier [E0106]
+//~^^ ERROR missing lifetime specifier [E0106]
+
+struct S<'a, 'b> { a: &'a i32, b: &'b i32 }
+fn f3(s: &S) -> &i32 { loop {} }
+//~^ ERROR missing lifetime specifier [E0106]
+fn f3_(s: &S, t: &S) -> (&i32, &i32) { loop {} }
+//~^ ERROR missing lifetime specifier [E0106]
+//~^^ ERROR missing lifetime specifier [E0106]
+
+fn f4<'a, 'b>(a: &'a i32, b: &'b i32) -> &i32 { loop {} }
+//~^ ERROR missing lifetime specifier [E0106]
+fn f4_<'a, 'b>(a: &'a i32, b: &'b i32) -> (&i32, &i32) { loop {} }
+//~^ ERROR missing lifetime specifier [E0106]
+//~^^ ERROR missing lifetime specifier [E0106]
+
+fn f5<'a>(a: &'a i32, b: &i32) -> &i32 { loop {} }
+//~^ ERROR missing lifetime specifier [E0106]
+fn f5_<'a>(a: &'a i32, b: &i32) -> (&i32, &i32) { loop {} }
+//~^ ERROR missing lifetime specifier [E0106]
+//~^^ ERROR missing lifetime specifier [E0106]
+
+fn main() {}
diff --git a/src/test/ui/suggestions/return-elided-lifetime.stderr b/src/test/ui/suggestions/return-elided-lifetime.stderr
new file mode 100644
index 00000000000..888cd5e58ab
--- /dev/null
+++ b/src/test/ui/suggestions/return-elided-lifetime.stderr
@@ -0,0 +1,198 @@
+error[E0106]: missing lifetime specifier
+  --> $DIR/return-elided-lifetime.rs:6:12
+   |
+LL | fn f1() -> &i32 { loop {} }
+   |            ^ 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 f1() -> &'static i32 { loop {} }
+   |            ^^^^^^^^
+
+error[E0106]: missing lifetime specifier
+  --> $DIR/return-elided-lifetime.rs:8:14
+   |
+LL | fn f1_() -> (&i32, &i32) { loop {} }
+   |              ^ 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 f1_() -> (&'static i32, &i32) { loop {} }
+   |              ^^^^^^^^
+
+error[E0106]: missing lifetime specifier
+  --> $DIR/return-elided-lifetime.rs:8:20
+   |
+LL | fn f1_() -> (&i32, &i32) { loop {} }
+   |                    ^ 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 f1_() -> (&i32, &'static i32) { loop {} }
+   |                    ^^^^^^^^
+
+error[E0106]: missing lifetime specifier
+  --> $DIR/return-elided-lifetime.rs:12:26
+   |
+LL | fn f2(a: i32, b: i32) -> &i32 { loop {} }
+   |                          ^ expected named lifetime parameter
+   |
+   = help: this function's return type contains a borrowed value with an elided lifetime, but the lifetime cannot be derived from the arguments
+help: consider using the `'static` lifetime
+   |
+LL | fn f2(a: i32, b: i32) -> &'static i32 { loop {} }
+   |                          ^^^^^^^^
+
+error[E0106]: missing lifetime specifier
+  --> $DIR/return-elided-lifetime.rs:14:28
+   |
+LL | fn f2_(a: i32, b: i32) -> (&i32, &i32) { loop {} }
+   |                            ^ expected named lifetime parameter
+   |
+   = help: this function's return type contains a borrowed value with an elided lifetime, but the lifetime cannot be derived from the arguments
+help: consider using the `'static` lifetime
+   |
+LL | fn f2_(a: i32, b: i32) -> (&'static i32, &i32) { loop {} }
+   |                            ^^^^^^^^
+
+error[E0106]: missing lifetime specifier
+  --> $DIR/return-elided-lifetime.rs:14:34
+   |
+LL | fn f2_(a: i32, b: i32) -> (&i32, &i32) { loop {} }
+   |                                  ^ expected named lifetime parameter
+   |
+   = help: this function's return type contains a borrowed value with an elided lifetime, but the lifetime cannot be derived from the arguments
+help: consider using the `'static` lifetime
+   |
+LL | fn f2_(a: i32, b: i32) -> (&i32, &'static i32) { loop {} }
+   |                                  ^^^^^^^^
+
+error[E0106]: missing lifetime specifier
+  --> $DIR/return-elided-lifetime.rs:19:17
+   |
+LL | fn f3(s: &S) -> &i32 { loop {} }
+   |          --     ^ expected named lifetime parameter
+   |
+   = help: this function's return type contains a borrowed value, but the signature does not say which one of `s`'s 3 lifetimes it is borrowed from
+help: consider introducing a named lifetime parameter
+   |
+LL | fn f3<'a>(s: &'a S) -> &'a i32 { loop {} }
+   |      ^^^^    ^^^^^     ^^^
+
+error[E0106]: missing lifetime specifier
+  --> $DIR/return-elided-lifetime.rs:21:26
+   |
+LL | fn f3_(s: &S, t: &S) -> (&i32, &i32) { loop {} }
+   |           --     --      ^ expected named lifetime parameter
+   |
+   = help: this function's return type contains a borrowed value, but the signature does not say whether it is borrowed from one of `s`'s 3 lifetimes or one of `t`'s 3 lifetimes
+help: consider introducing a named lifetime parameter
+   |
+LL | fn f3_<'a>(s: &'a S, t: &'a S) -> (&'a i32, &i32) { loop {} }
+   |       ^^^^    ^^^^^     ^^^^^      ^^^
+
+error[E0106]: missing lifetime specifier
+  --> $DIR/return-elided-lifetime.rs:21:32
+   |
+LL | fn f3_(s: &S, t: &S) -> (&i32, &i32) { loop {} }
+   |           --     --            ^ expected named lifetime parameter
+   |
+   = help: this function's return type contains a borrowed value, but the signature does not say whether it is borrowed from one of `s`'s 3 lifetimes or one of `t`'s 3 lifetimes
+help: consider introducing a named lifetime parameter
+   |
+LL | fn f3_<'a>(s: &'a S, t: &'a S) -> (&i32, &'a i32) { loop {} }
+   |       ^^^^    ^^^^^     ^^^^^            ^^^
+
+error[E0106]: missing lifetime specifier
+  --> $DIR/return-elided-lifetime.rs:25:42
+   |
+LL | fn f4<'a, 'b>(a: &'a i32, b: &'b i32) -> &i32 { loop {} }
+   |                  -------     -------     ^ expected named lifetime parameter
+   |
+   = help: this function's return type contains a borrowed value, but the signature does not say whether it is borrowed from `a` or `b`
+note: these named lifetimes are available to use
+  --> $DIR/return-elided-lifetime.rs:25:7
+   |
+LL | fn f4<'a, 'b>(a: &'a i32, b: &'b i32) -> &i32 { loop {} }
+   |       ^^  ^^
+help: consider using one of the available lifetimes here
+   |
+LL | fn f4<'a, 'b>(a: &'a i32, b: &'b i32) -> &'lifetime i32 { loop {} }
+   |                                          ^^^^^^^^^^
+
+error[E0106]: missing lifetime specifier
+  --> $DIR/return-elided-lifetime.rs:27:44
+   |
+LL | fn f4_<'a, 'b>(a: &'a i32, b: &'b i32) -> (&i32, &i32) { loop {} }
+   |                   -------     -------      ^ expected named lifetime parameter
+   |
+   = help: this function's return type contains a borrowed value, but the signature does not say whether it is borrowed from `a` or `b`
+note: these named lifetimes are available to use
+  --> $DIR/return-elided-lifetime.rs:27:8
+   |
+LL | fn f4_<'a, 'b>(a: &'a i32, b: &'b i32) -> (&i32, &i32) { loop {} }
+   |        ^^  ^^
+help: consider using one of the available lifetimes here
+   |
+LL | fn f4_<'a, 'b>(a: &'a i32, b: &'b i32) -> (&'lifetime i32, &i32) { loop {} }
+   |                                            ^^^^^^^^^^
+
+error[E0106]: missing lifetime specifier
+  --> $DIR/return-elided-lifetime.rs:27:50
+   |
+LL | fn f4_<'a, 'b>(a: &'a i32, b: &'b i32) -> (&i32, &i32) { loop {} }
+   |                   -------     -------            ^ expected named lifetime parameter
+   |
+   = help: this function's return type contains a borrowed value, but the signature does not say whether it is borrowed from `a` or `b`
+note: these named lifetimes are available to use
+  --> $DIR/return-elided-lifetime.rs:27:8
+   |
+LL | fn f4_<'a, 'b>(a: &'a i32, b: &'b i32) -> (&i32, &i32) { loop {} }
+   |        ^^  ^^
+help: consider using one of the available lifetimes here
+   |
+LL | fn f4_<'a, 'b>(a: &'a i32, b: &'b i32) -> (&i32, &'lifetime i32) { loop {} }
+   |                                                  ^^^^^^^^^^
+
+error[E0106]: missing lifetime specifier
+  --> $DIR/return-elided-lifetime.rs:31:35
+   |
+LL | fn f5<'a>(a: &'a i32, b: &i32) -> &i32 { loop {} }
+   |              -------     ----     ^ expected named lifetime parameter
+   |
+   = help: this function's return type contains a borrowed value, but the signature does not say whether it is borrowed from `a` or `b`
+help: consider using the `'a` lifetime
+   |
+LL | fn f5<'a>(a: &'a i32, b: &i32) -> &'a i32 { loop {} }
+   |                                   ^^^
+
+error[E0106]: missing lifetime specifier
+  --> $DIR/return-elided-lifetime.rs:33:37
+   |
+LL | fn f5_<'a>(a: &'a i32, b: &i32) -> (&i32, &i32) { loop {} }
+   |               -------     ----      ^ expected named lifetime parameter
+   |
+   = help: this function's return type contains a borrowed value, but the signature does not say whether it is borrowed from `a` or `b`
+help: consider using the `'a` lifetime
+   |
+LL | fn f5_<'a>(a: &'a i32, b: &i32) -> (&'a i32, &i32) { loop {} }
+   |                                     ^^^
+
+error[E0106]: missing lifetime specifier
+  --> $DIR/return-elided-lifetime.rs:33:43
+   |
+LL | fn f5_<'a>(a: &'a i32, b: &i32) -> (&i32, &i32) { loop {} }
+   |               -------     ----            ^ expected named lifetime parameter
+   |
+   = help: this function's return type contains a borrowed value, but the signature does not say whether it is borrowed from `a` or `b`
+help: consider using the `'a` lifetime
+   |
+LL | fn f5_<'a>(a: &'a i32, b: &i32) -> (&i32, &'a i32) { loop {} }
+   |                                           ^^^
+
+error: aborting due to 15 previous errors
+
+For more information about this error, try `rustc --explain E0106`.