Rollup of 4 pull requests#57761

Merged

bors merged 15 commits intorust-lang:masterfrom

Jan 19, 2019

Commits on Jan 9, 2019

Improve docs for Formatter
steveklabnik
committed

Commits on Jan 16, 2019

Make `hir::Stmt` a separate struct.
nnethercote
committed

Commits on Jan 17, 2019

Remove `hir::StmtKind::Decl`.
nnethercote
committed