Document `with_opaque_type_inference`'s use cases.
Document `with_opaque_type_inference`'s use cases.

graydon/rust,graydon/rust,graydon/rust,graydon/rust,aidancully/rust,graydon/rust,aidancully/rust,aidancully/rust,graydon/rust,aidancully/rust,aidancully/rust,aidancully/rust