Merge pull request #2438 from smanilov/patch-20

Trivial: fix typo (change `foo` to `bar`)

Author: tshepang

src/return-position-impl-trait-in-trait.md

@@ -356,7 +356,7 @@ trait Foo {
 
 Failing because a down-stream impl could theoretically provide an
 implementation for `RPITIT` without providing an implementation of
-`foo`:
+`bar`:
 
 ```text
 error[E0308]: mismatched types