Rollup merge of #65730 - csmoe:return-lifetime, r=nikomatsakis

Suggest to add lifetime constraint at explicit ouput of functions

Closes #62097

5 files changed, 64 insertions, 8 deletions

diff --git a/src/test/ui/async-await/issues/issue-62097.nll.stderr b/src/test/ui/async-await/issues/issue-62097.nll.stderr
new file mode 100644
index 00000000000..0c64f90cb9f
--- /dev/null
+++ b/src/test/ui/async-await/issues/issue-62097.nll.stderr
@@ -0,0 +1,29 @@
+error[E0373]: closure may outlive the current function, but it borrows `self`, which is owned by the current function
+  --> $DIR/issue-62097.rs:13:13
+   |
+LL |         foo(|| self.bar()).await;
+   |             ^^ ---- `self` is borrowed here
+   |             |
+   |             may outlive borrowed value `self`
+   |
+note: function requires argument type to outlive `'static`
+  --> $DIR/issue-62097.rs:13:9
+   |
+LL |         foo(|| self.bar()).await;
+   |         ^^^^^^^^^^^^^^^^^^
+help: to force the closure to take ownership of `self` (and any other referenced variables), use the `move` keyword
+   |
+LL |         foo(move || self.bar()).await;
+   |             ^^^^^^^
+
+error[E0521]: borrowed data escapes outside of function
+  --> $DIR/issue-62097.rs:13:9
+   |
+LL |     pub async fn run_dummy_fn(&self) {
+   |                               ----- `self` is a reference that is only valid in the function body
+LL |         foo(|| self.bar()).await;
+   |         ^^^^^^^^^^^^^^^^^^ `self` escapes the function body here
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0373`.
diff --git a/src/test/ui/async-await/issues/issue-62097.rs b/src/test/ui/async-await/issues/issue-62097.rs
new file mode 100644
index 00000000000..ea482d3667e
--- /dev/null
+++ b/src/test/ui/async-await/issues/issue-62097.rs
@@ -0,0 +1,19 @@
+// edition:2018
+async fn foo<F>(fun: F)
+where
+    F: FnOnce() + 'static
+{
+    fun()
+}
+
+struct Struct;
+
+impl Struct {
+    pub async fn run_dummy_fn(&self) { //~ ERROR cannot infer
+        foo(|| self.bar()).await;
+    }
+
+    pub fn bar(&self) {}
+}
+
+fn main() {}
diff --git a/src/test/ui/async-await/issues/issue-62097.stderr b/src/test/ui/async-await/issues/issue-62097.stderr
new file mode 100644
index 00000000000..94afccc06a9
--- /dev/null
+++ b/src/test/ui/async-await/issues/issue-62097.stderr
@@ -0,0 +1,16 @@
+error: cannot infer an appropriate lifetime
+  --> $DIR/issue-62097.rs:12:31
+   |
+LL |     pub async fn run_dummy_fn(&self) {
+   |                               ^^^^^ ...but this borrow...
+LL |         foo(|| self.bar()).await;
+   |         --- this return type evaluates to the `'static` lifetime...
+   |
+note: ...can't outlive the lifetime `'_` as defined on the method body at 12:31
+  --> $DIR/issue-62097.rs:12:31
+   |
+LL |     pub async fn run_dummy_fn(&self) {
+   |                               ^
+
+error: aborting due to previous error
+
diff --git a/src/test/ui/async-await/issues/issue-63388-2.stderr b/src/test/ui/async-await/issues/issue-63388-2.stderr
index efec160588f..7e45d588c6c 100644
--- a/src/test/ui/async-await/issues/issue-63388-2.stderr
+++ b/src/test/ui/async-await/issues/issue-63388-2.stderr
@@ -20,10 +20,6 @@ note: ...can't outlive the lifetime `'_` as defined on the method body at 11:14
    |
 LL |         foo: &dyn Foo, bar: &'a dyn Foo
    |              ^
-help: you can add a constraint to the return type to make it last less than `'static` and match the lifetime `'_` as defined on the method body at 11:14
-   |
-LL |         foo + '_
-   |
 
 error: aborting due to 2 previous errors
 
diff --git a/src/test/ui/self/arbitrary_self_types_pin_lifetime_impl_trait-async.stderr b/src/test/ui/self/arbitrary_self_types_pin_lifetime_impl_trait-async.stderr
index bce1900ca60..91075ffbdb6 100644
--- a/src/test/ui/self/arbitrary_self_types_pin_lifetime_impl_trait-async.stderr
+++ b/src/test/ui/self/arbitrary_self_types_pin_lifetime_impl_trait-async.stderr
@@ -11,10 +11,6 @@ note: ...can't outlive the lifetime `'_` as defined on the method body at 8:26
    |
 LL |     async fn f(self: Pin<&Self>) -> impl Clone { self }
    |                          ^
-help: you can add a constraint to the return type to make it last less than `'static` and match the lifetime `'_` as defined on the method body at 8:26
-   |
-LL |     async fn f(self: Pin<&Self>) -> impl Clone + '_ { self }
-   |                                     ^^^^^^^^^^^^^^^
 
 error: aborting due to previous error