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+A binary assignment operator like `+=` or `^=` was applied to a type that
+doesn't support it.
+
+Erroneous code example:
+
+```compile_fail,E0368
+let mut x = 12f32; // error: binary operation `<<` cannot be applied to
+                   //        type `f32`
+
+x <<= 2;
+```
+
+To fix this error, please check that this type implements this binary
+operation. Example:
+
+```
+let mut x = 12u32; // the `u32` type does implement the `ShlAssign` trait
+
+x <<= 2; // ok!
+```
+
+It is also possible to overload most operators for your own type by
+implementing the `[OP]Assign` traits from `std::ops`.
+
+Another problem you might be facing is this: suppose you've overloaded the `+`
+operator for some type `Foo` by implementing the `std::ops::Add` trait for
+`Foo`, but you find that using `+=` does not work, as in this example:
+
+```compile_fail,E0368
+use std::ops::Add;
+
+struct Foo(u32);
+
+impl Add for Foo {
+    type Output = Foo;
+
+    fn add(self, rhs: Foo) -> Foo {
+        Foo(self.0 + rhs.0)
+    }
+}
+
+fn main() {
+    let mut x: Foo = Foo(5);
+    x += Foo(7); // error, `+= cannot be applied to the type `Foo`
+}
+```
+
+This is because `AddAssign` is not automatically implemented, so you need to
+manually implement it for your type.