Fix clippy warnings

[dlrobertson]

The following clippy lints throw errors or warnings. We should either explicitly allow them or fix the code that fails the lint.

Errors

• if_same_then_else

Warnings

• assign_op_pattern
• cast_lossless
• clone_on_copy
• collapsible_if
• cyclomatic_complexity
• duration_subsec
• explicit_iter_loop
• identity_op
• large_enum_variant
• len_without_is_empty
• len_zero
• let_and_return
• match_bool
• match_ref_pats
• needless_lifetimes
• needless_pass_by_value
• needless_range_loop
• needless_return
• new_without_default_derive
• redundant_closure
• redundant_field_names
• search_is_some
• single_match
• too_many_arguments
• trivially_copy_pass_by_ref
• unnecessary_mut_passed
• unreadable_literal
• useless_asref
• useless_let_if_seq
• write_with_newline
• wrong_self_convention

[whitequark]

I'm not extremely enthusiastic about clippy and I believe that blindly following its suggestions can easily degrade code quality. r=me on every PR addressing its lints.

[dlrobertson]

believe that blindly following its suggestions can easily degrade code quality.

I agree 100% with this. I'm definitely not suggesting we blindly follow the suggestions. unreadable_literal is a great example of a lint that IMO doesn't help. IMO 0xffff_ffff does not help readability at all. I do think that we could improve the code quality by following some of these e.g. unnecessary_mut_passed.

r=me on every PR addressing its lints.

Will do.

[jhwgh1968]

After doing a nightly compiler update, I noticed this new warning:

warning[E0713]: borrow may still be in use when destructor runs
  --> src/socket/ref_.rs:61:9
   |
39 | impl<'a, T: Session + 'a> Ref<'a, T> {
   |      -- lifetime `'a` defined here
...
61 |         ref_.socket
   |         ^^^^^^^^^^^ returning this value requires that `*ref_.socket` is borrowed for `'a`
62 |     }
   |     - here, drop of `ref_` needs exclusive access to `*ref_.socket`, because the type `socket::ref_::Ref<'_, T>` implements the `Drop` trait
   |
   = warning: this error has been downgraded to a warning for backwards compatibility with previous releases
   = warning: this represents potential undefined behavior in your code and this warning will become a hard error in the future

Since I presume the code not causing any problems right now, I thought it should be addressed along with the clippy lints. If this should be a separate issue, I can easily create one.

[Dirbaio]

This is now done. Additionally, CI enforces no clippy warnings.