Auto merge of #23998 - nrc:impl-self, r=nikomatsakis

Closes #23909

r? @nikomatsakis (or anyone else, really)

diff --cc src/librustc_privacy/lib.rs
Simple merge

diff --cc src/librustc_trans/save/mod.rs
Simple merge

diff --cc src/librustc_typeck/astconv.rs
Simple merge

diff --cc src/libsyntax/ext/expand.rs
Simple merge