New upstream version 1.70.0+dfsg1

[rustc.git] / tests / ui / variance / variance-intersection-of-ref-and-opt-ref.rs

diff --git a/tests/ui/variance/variance-intersection-of-ref-and-opt-ref.rs b/tests/ui/variance/variance-intersection-of-ref-and-opt-ref.rs
new file mode 100644 (file)
index 0000000..74707a9
--- /dev/null
+++ b/tests/ui/variance/variance-intersection-of-ref-and-opt-ref.rs
@@ -0,0 +1,25 @@
+// run-pass
+// Elaborated version of the opening example from RFC 738. This failed
+// to compile before variance because invariance of `Option` prevented
+// us from approximating the lifetimes of `field1` and `field2` to a
+// common intersection.
+
+#![allow(dead_code)]
+
+struct List<'l> {
+    field1: &'l i32,
+    field2: Option<&'l i32>,
+}
+
+fn foo(field1: &i32, field2: Option<&i32>) -> i32 {
+    let list = List { field1: field1, field2: field2 };
+    *list.field1 + list.field2.cloned().unwrap_or(0)
+}
+
+fn main() {
+    let x = 22;
+    let y = Some(3);
+    let z = None;
+    assert_eq!(foo(&x, y.as_ref()), 25);
+    assert_eq!(foo(&x, z.as_ref()), 22);
+}