Suggest adding a lifetime constraint when opaque type is responsible for "does not live long enough" error

2 files changed, 32 insertions, 0 deletions

diff --git a/src/test/ui/impl-trait/does-not-live-long-enough.rs b/src/test/ui/impl-trait/does-not-live-long-enough.rs
new file mode 100644
index 00000000000..6179132b3f6
--- /dev/null
+++ b/src/test/ui/impl-trait/does-not-live-long-enough.rs
@@ -0,0 +1,11 @@
+struct List {
+    data: Vec<String>,
+}
+impl List {
+    fn started_with<'a>(&'a self, prefix: &'a str) -> impl Iterator<Item=&'a str> {
+        self.data.iter().filter(|s| s.starts_with(prefix)).map(|s| s.as_ref())
+        //~^ ERROR does not live long enough
+    }
+}
+
+fn main() {}
diff --git a/src/test/ui/impl-trait/does-not-live-long-enough.stderr b/src/test/ui/impl-trait/does-not-live-long-enough.stderr
new file mode 100644
index 00000000000..ddf81138daf
--- /dev/null
+++ b/src/test/ui/impl-trait/does-not-live-long-enough.stderr
@@ -0,0 +1,21 @@
+error[E0597]: `prefix` does not live long enough
+  --> $DIR/does-not-live-long-enough.rs:6:51
+   |
+LL |     fn started_with<'a>(&'a self, prefix: &'a str) -> impl Iterator<Item=&'a str> {
+   |                     -- lifetime `'a` defined here     --------------------------- opaque type requires that `prefix` is borrowed for `'a`
+LL |         self.data.iter().filter(|s| s.starts_with(prefix)).map(|s| s.as_ref())
+   |                                 ---               ^^^^^^ borrowed value does not live long enough
+   |                                 |
+   |                                 value captured here
+LL |
+LL |     }
+   |     - `prefix` dropped here while still borrowed
+   |
+help: you can add a constraint to the opaque type to make it last less than `'static` and match `'a`
+   |
+LL |     fn started_with<'a>(&'a self, prefix: &'a str) -> impl Iterator<Item=&'a str> + 'a {
+   |                                                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0597`.