1 error[E0594]: cannot assign to data in an index of `BTreeMap<u32, u32>`
2 --> $DIR/btreemap-index-mut.rs:5:5
5 | ^^^^^^^^^^^ cannot assign
7 = help: trait `IndexMut` is required to modify indexed content, but it is not implemented for `BTreeMap<u32, u32>`
8 help: to modify a `BTreeMap<u32, u32>`, use `.get_mut()`, `.insert()` or the entry API
10 LL | map.insert(&0, 1);
12 LL | map.get_mut(&0).map(|val| { *val = 1; });
13 | ~~~~~~~~~ ~~~~~~~~~~~~~~~~~~ ++++
14 LL | let val = map.entry(&0).or_insert(1);
15 | +++++++++ ~~~~~~~ ~~~~~~~~~~~~ +
17 error: aborting due to previous error
19 For more information about this error, try `rustc --explain E0594`.