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-rw-r--r--src/test/ui/issues/issue-52126-assign-op-invariance.rs49
1 files changed, 49 insertions, 0 deletions
diff --git a/src/test/ui/issues/issue-52126-assign-op-invariance.rs b/src/test/ui/issues/issue-52126-assign-op-invariance.rs
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index 000000000..c96cfdf3c
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+++ b/src/test/ui/issues/issue-52126-assign-op-invariance.rs
@@ -0,0 +1,49 @@
+// Issue 52126: With respect to variance, the assign-op's like += were
+// accidentally lumped together with other binary op's. In both cases
+// we were coercing the LHS of the op to the expected supertype.
+//
+// The problem is that since the LHS of += is modified, we need the
+// parameter to be invariant with respect to the overall type, not
+// covariant.
+
+use std::collections::HashMap;
+use std::ops::AddAssign;
+
+pub fn main() {
+ panics();
+}
+
+pub struct Counter<'l> {
+ map: HashMap<&'l str, usize>,
+}
+
+impl<'l> AddAssign for Counter<'l>
+{
+ fn add_assign(&mut self, rhs: Counter<'l>) {
+ rhs.map.into_iter().for_each(|(key, val)| {
+ let count = self.map.entry(key).or_insert(0);
+ *count += val;
+ });
+ }
+}
+
+/// Often crashes, if not prints invalid strings.
+pub fn panics() {
+ let mut acc = Counter{map: HashMap::new()};
+ for line in vec!["123456789".to_string(), "12345678".to_string()] {
+ let v: Vec<&str> = line.split_whitespace().collect();
+ //~^ ERROR `line` does not live long enough
+ // println!("accumulator before add_assign {:?}", acc.map);
+ let mut map = HashMap::new();
+ for str_ref in v {
+ let e = map.entry(str_ref);
+ println!("entry: {:?}", e);
+ let count = e.or_insert(0);
+ *count += 1;
+ }
+ let cnt2 = Counter{map};
+ acc += cnt2;
+ // println!("accumulator after add_assign {:?}", acc.map);
+ // line gets dropped here but references are kept in acc.map
+ }
+}