auto merge of #14465 : Ryman/rust/patch-1, r=alexcrichton

Author: bors

src/doc/rust.md

@@ -1435,7 +1435,7 @@ trait Circle : Shape { fn radius() -> f64; }
 ~~~~
 
 the syntax `Circle : Shape` means that types that implement `Circle` must also have an implementation for `Shape`.
-Multiple supertraits are separated by spaces, `trait Circle : Shape Eq { }`.
+Multiple supertraits are separated by `+`, `trait Circle : Shape + Eq { }`.
 In an implementation of `Circle` for a given type `T`, methods can refer to `Shape` methods,
 since the typechecker checks that any type with an implementation of `Circle` also has an implementation of `Shape`.