Add regression test for issue #91831

tests/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-one-is-struct-5.rs

@@ -0,0 +1,13 @@
+// Regression test for #91831
+
+struct Foo<'a>(&'a i32);
+
+impl<'a> Foo<'a> {
+ fn modify(&'a mut self) {}
+}
+
+fn bar(foo: &mut Foo) {
+ foo.modify(); //~ ERROR lifetime may not live long enough
+}
+
+fn main() {}

tests/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-one-is-struct-5.stderr

@@ -0,0 +1,20 @@
+error: lifetime may not live long enough
+ --> $DIR/ex3-both-anon-regions-one-is-struct-5.rs:10:5
+ |
+LL | fn bar(foo: &mut Foo) {
+ | --- - let's call the lifetime of this reference `'1`
+ | |
+ | has type `&mut Foo<'2>`
+LL | foo.modify();
+ | ^^^^^^^^^^^^ argument requires that `'1` must outlive `'2`
+ |
+ = note: requirement occurs because of a mutable reference to `Foo<'_>`
+ = note: mutable references are invariant over their type parameter
+ = help: see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance
+help: consider introducing a named lifetime parameter
+ |
+LL | fn bar<'a>(foo: &'a mut Foo<'a>) {
+ | ++++ ++ ++++
+
+error: aborting due to 1 previous error
+