Merge #1491

1491: More clippy r=matklad a=kjeremy

A few more clippy changes.

I'm a little unsure of the second commit. It's the trivially_copy_pass_by_ref lint and there are a number of places in the code we could use it if it makes sense.

Co-authored-by: Jeremy Kolb <kjeremy@gmail.com>

diff --cc crates/ra_hir/src/code_model.rs
Simple merge

diff --cc crates/ra_hir/src/ty/infer.rs
Simple merge