1 error[E0368]: binary assignment operation `+=` cannot be applied to type `Foo`
2 --> $DIR/assignment-operator-unimplemented.rs:6:3
7 | cannot use `+=` on type `Foo`
9 = note: an implementation of `std::ops::AddAssign` might be missing for `Foo`
11 error: aborting due to previous error
13 For more information about this error, try `rustc --explain E0368`.