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-rw-r--r--src/test/ui/variance-intersection-of-ref-and-opt-ref.rs25
1 files changed, 25 insertions, 0 deletions
diff --git a/src/test/ui/variance-intersection-of-ref-and-opt-ref.rs b/src/test/ui/variance-intersection-of-ref-and-opt-ref.rs
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index 000000000..74707a98d
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+++ b/src/test/ui/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);
+}