base check
same fields different struct
reordered fields
different paths to the same struct
same for tuple structs
style: use `zip`-the-function all over the place
makes the code a bit more concise by removing the need for explicit
`.iter()`
style: move precondition checking to the match guard
the match arms above put the "sanity" checks in the guard, and call only
`check_pat` in the body. With this commit, the (tuple) struct cases
follow that convention as well. Well, almost -- I think the ident check
belongs to the second category of checks, so I put it in the body as
well
misc: use `None` in the pattern directly
this'll probably be marginally faster thanks to the equality check being
now structural
move the tests to the right file
Removing `.map(identity)` may result in invalid code if the receiver of
`map()` is an immutable binding, and the result of `map()` is used as
the receiver of a method call expecting a mutable reference.
