Clarify the scope-related explanation 
Clarify the scope-related explanation 

Based on the review made by dtolnay.
aidancully/rust,aidancully/rust,aidancully/rust,graydon/rust,graydon/rust,graydon/rust,graydon/rust,aidancully/rust,aidancully/rust,graydon/rust,graydon/rust,aidancully/rust