Add regression test for #71546

Author: JohnTitor

src/test/ui/borrowck/issue-71546.rs

@@ -0,0 +1,16 @@
+// Regression test for #71546.
+
+pub fn serialize_as_csv<V>(value: &V) -> Result<String, &str>
+where
+    V: 'static,
+    for<'a> &'a V: IntoIterator,
+    for<'a> <&'a V as IntoIterator>::Item: ToString + 'static,
+{
+    let csv_str: String = value //~ ERROR: the associated type `<&'a V as IntoIterator>::Item` may not live long enough
+        .into_iter()
+        .map(|elem| elem.to_string())
+        .collect::<String>();
+    Ok(csv_str)
+}
+
+fn main() {}

src/test/ui/borrowck/issue-71546.stderr

@@ -0,0 +1,20 @@
+error[E0310]: the associated type `<&'a V as IntoIterator>::Item` may not live long enough
+  --> $DIR/issue-71546.rs:9:27
+   |
+LL |       let csv_str: String = value
+   |  ___________________________^
+LL | |         .into_iter()
+LL | |         .map(|elem| elem.to_string())
+   | |_____________________________________^
+   |
+   = help: consider adding an explicit lifetime bound `<&'a V as IntoIterator>::Item: 'static`...
+   = note: ...so that the type `<&'a V as IntoIterator>::Item` will meet its required lifetime bounds...
+note: ...that is required by this bound
+  --> $DIR/issue-71546.rs:7:55
+   |
+LL |     for<'a> <&'a V as IntoIterator>::Item: ToString + 'static,
+   |                                                       ^^^^^^^
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0310`.