auto merge of #5558 : nikomatsakis/rust/issue-4920-autoref-index-operator, r=nikomatsakis

Per discussion on IRC.

r? @pcwalton

diff --cc src/librustc/middle/typeck/check/mod.rs
Simple merge

diff --cc src/libsyntax/ast.rs
Simple merge

diff --cc src/libsyntax/parse/parser.rs
Simple merge

diff --cc src/libsyntax/print/pprust.rs
Simple merge