Remove option_if_let_else clippy suppression

    warning: field `0` is never read
      --> tests/test_error.rs:58:11
       |
    58 |         C(C),
       |         - ^
       |         |
       |         field in this variant
       |
       = note: `#[warn(dead_code)]` on by default
    help: consider changing the field to be of unit type to suppress this warning while preserving the field numbering, or remove the field
       |
    58 |         C(()),
       |           ~~

    warning: field `0` is never read
       --> tests/test_error.rs:165:11
        |
    165 |         V(usize),
        |         - ^^^^^
        |         |
        |         field in this variant
        |
    help: consider changing the field to be of unit type to suppress this warning while preserving the field numbering, or remove the field
        |
    165 |         V(()),
        |           ~~

    warning: field `0` is never read
       --> tests/test_error.rs:217:15
        |
    217 |         Inner(Inner),
        |         ----- ^^^^^
        |         |
        |         field in this variant
        |
    help: consider changing the field to be of unit type to suppress this warning while preserving the field numbering, or remove the field
        |
    217 |         Inner(()),
        |               ~~

    warning: field `0` is never read
       --> tests/test_error.rs:221:17
        |
    221 |         Variant(Vec<usize>),
        |         ------- ^^^^^^^^^^
        |         |
        |         field in this variant
        |
    help: consider changing the field to be of unit type to suppress this warning while preserving the field numbering, or remove the field
        |
    221 |         Variant(()),
        |                 ~~

    warning: field `0` is never read
       --> tests/test_error.rs:250:11
        |
    250 |         V(usize),
        |         - ^^^^^
        |         |
        |         field in this variant
        |
    help: consider changing the field to be of unit type to suppress this warning while preserving the field numbering, or remove the field
        |
    250 |         V(()),
        |           ~~

    warning: fields `0` and `1` are never read
       --> tests/test_error.rs:367:14
        |
    367 |     struct S(usize, Option<Box<S>>);
        |            - ^^^^^  ^^^^^^^^^^^^^^
        |            |
        |            fields in this struct
        |
        = note: `S` has a derived impl for the trait `Debug`, but this is intentionally ignored during dead code analysis
    help: consider changing the fields to be of unit type to suppress this warning while preserving the field numbering, or remove the fields
        |
    367 |     struct S((), ());
        |              ~~  ~~

    warning: field `0` is never read
       --> tests/test_error.rs:378:14
        |
    378 |     struct S(Option<Box<S>>);
        |            - ^^^^^^^^^^^^^^
        |            |
        |            field in this struct
        |
        = note: `S` has a derived impl for the trait `Debug`, but this is intentionally ignored during dead code analysis
    help: consider changing the field to be of unit type to suppress this warning while preserving the field numbering, or remove the field
        |
    378 |     struct S(());
        |              ~~

    warning: fields `0` and `1` are never read
       --> tests/test_error.rs:403:14
        |
    403 |     struct S(usize, Option<Box<S>>);
        |            - ^^^^^  ^^^^^^^^^^^^^^
        |            |
        |            fields in this struct
        |
        = note: `S` has a derived impl for the trait `Debug`, but this is intentionally ignored during dead code analysis
    help: consider changing the fields to be of unit type to suppress this warning while preserving the field numbering, or remove the fields
        |
    403 |     struct S((), ());
        |              ~~  ~~

Add swap_remove and shift_remove methods on Mapping

Markdown takes care of rendering these to a curly quote.

    warning: the item `FromIterator` is imported redundantly
       --> src/mapping.rs:10:5
        |
    10  | use std::iter::FromIterator;
        |     ^^^^^^^^^^^^^^^^^^^^^^^
        |
       ::: nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/prelude/mod.rs:129:13
        |
    129 |     pub use core::prelude::rust_2021::*;
        |             ------------------------ the item `FromIterator` is already defined here
        |
        = note: `#[warn(unused_imports)]` on by default

    warning: the item `FromIterator` is imported redundantly
       --> src/value/from.rs:148:5
        |
    148 | use std::iter::FromIterator;
        |     ^^^^^^^^^^^^^^^^^^^^^^^
        |
       ::: nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/prelude/mod.rs:129:13
        |
    129 |     pub use core::prelude::rust_2021::*;
        |             ------------------------ the item `FromIterator` is already defined here

    warning: non-local `impl` definition, they should be avoided as they go against expectation
       --> tests/test_error.rs:412:13
        |
    412 | /             impl<'de> Visitor<'de> for X {
    413 | |                 type Value = X;
    414 | |
    415 | |                 fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
    ...   |
    429 | |                 }
    430 | |             }
        | |_____________^
        |
        = help: move this `impl` block outside the of the current associated function `deserialize` and up 2 bodies
        = note: an `impl` definition is non-local if it is nested inside an item and neither the type nor the trait are at the same nesting level as the `impl` block
        = note: one exception to the rule are anon-const (`const _: () = { ... }`) at top-level module and anon-const at the same nesting as the trait or type
        = note: this lint may become deny-by-default in the edition 2024 and higher, see the tracking issue <rust-lang/rust#120363>
        = note: `#[warn(non_local_definitions)]` on by default

New in nightly-2024-03-24 from rust-lang/rust#119552.

    warning: field `b` is never read
      --> tests/test_error.rs:53:13
       |
    52 |     pub struct A {
       |                - field in this struct
    53 |         pub b: Vec<B>,
       |             ^
       |
       = note: `A` has a derived impl for the trait `Debug`, but this is intentionally ignored during dead code analysis
       = note: `#[warn(dead_code)]` on by default

    warning: field `0` is never read
      --> tests/test_error.rs:57:11
       |
    57 |         C(C),
       |         - ^
       |         |
       |         field in this variant
       |
    help: consider changing the field to be of unit type to suppress this warning while preserving the field numbering, or remove the field
       |
    57 |         C(()),
       |           ~~

    warning: field `d` is never read
      --> tests/test_error.rs:61:13
       |
    60 |     pub struct C {
       |                - field in this struct
    61 |         pub d: bool,
       |             ^
       |
       = note: `C` has a derived impl for the trait `Debug`, but this is intentionally ignored during dead code analysis

    warning: fields `v` and `w` are never read
      --> tests/test_error.rs:82:13
       |
    81 |     pub struct Basic {
       |                ----- fields in this struct
    82 |         pub v: bool,
       |             ^
    83 |         pub w: bool,
       |             ^
       |
       = note: `Basic` has a derived impl for the trait `Debug`, but this is intentionally ignored during dead code analysis

    warning: field `c` is never read
       --> tests/test_error.rs:107:13
        |
    106 |     pub struct Wrapper {
        |                ------- field in this struct
    107 |         pub c: (),
        |             ^
        |
        = note: `Wrapper` has a derived impl for the trait `Debug`, but this is intentionally ignored during dead code analysis

    warning: field `0` is never read
       --> tests/test_error.rs:160:11
        |
    160 |         V(usize),
        |         - ^^^^^
        |         |
        |         field in this variant
        |
    help: consider changing the field to be of unit type to suppress this warning while preserving the field numbering, or remove the field
        |
    160 |         V(()),
        |           ~~

    warning: field `0` is never read
       --> tests/test_error.rs:212:15
        |
    212 |         Inner(Inner),
        |         ----- ^^^^^
        |         |
        |         field in this variant
        |
    help: consider changing the field to be of unit type to suppress this warning while preserving the field numbering, or remove the field
        |
    212 |         Inner(()),
        |               ~~

    warning: field `0` is never read
       --> tests/test_error.rs:216:17
        |
    216 |         Variant(Vec<usize>),
        |         ------- ^^^^^^^^^^
        |         |
        |         field in this variant
        |
    help: consider changing the field to be of unit type to suppress this warning while preserving the field numbering, or remove the field
        |
    216 |         Variant(()),
        |                 ~~

    warning: field `0` is never read
       --> tests/test_error.rs:245:11
        |
    245 |         V(usize),
        |         - ^^^^^
        |         |
        |         field in this variant
        |
    help: consider changing the field to be of unit type to suppress this warning while preserving the field numbering, or remove the field
        |
    245 |         V(()),
        |           ~~

    warning: fields `x` and `y` are never read
       --> tests/test_error.rs:260:13
        |
    259 |     pub struct Struct {
        |                ------ fields in this struct
    260 |         pub x: usize,
        |             ^
    261 |         pub y: usize,
        |             ^
        |
        = note: `Struct` has a derived impl for the trait `Debug`, but this is intentionally ignored during dead code analysis

    warning: field `x` is never read
       --> tests/test_error.rs:334:13
        |
    333 |     pub struct S {
        |                - field in this struct
    334 |         pub x: [i32; 1],
        |             ^
        |
        = note: `S` has a derived impl for the trait `Debug`, but this is intentionally ignored during dead code analysis

    warning: field `x` is never read
       --> tests/test_error.rs:347:13
        |
    346 |     pub struct S {
        |                - field in this struct
    347 |         pub x: Option<Box<S>>,
        |             ^
        |
        = note: `S` has a derived impl for the trait `Debug`, but this is intentionally ignored during dead code analysis

    warning: fields `0` and `1` are never read
       --> tests/test_error.rs:359:18
        |
    359 |     pub struct S(pub usize, pub Option<Box<S>>);
        |                - ^^^^^^^^^  ^^^^^^^^^^^^^^^^^^
        |                |
        |                fields in this struct
        |
        = note: `S` has a derived impl for the trait `Debug`, but this is intentionally ignored during dead code analysis
    help: consider changing the fields to be of unit type to suppress this warning while preserving the field numbering, or remove the fields
        |
    359 |     pub struct S((), ());
        |                  ~~  ~~

    warning: field `0` is never read
       --> tests/test_error.rs:370:18
        |
    370 |     pub struct S(pub Option<Box<S>>);
        |                - ^^^^^^^^^^^^^^^^^^
        |                |
        |                field in this struct
        |
        = note: `S` has a derived impl for the trait `Debug`, but this is intentionally ignored during dead code analysis
    help: consider changing the field to be of unit type to suppress this warning while preserving the field numbering, or remove the field
        |
    370 |     pub struct S(());
        |                  ~~

    warning: field `x` is never read
       --> tests/test_error.rs:382:13
        |
    381 |     pub struct S {
        |                - field in this struct
    382 |         pub x: Option<Box<S>>,
        |             ^
        |
        = note: `S` has a derived impl for the trait `Debug`, but this is intentionally ignored during dead code analysis

    warning: fields `0` and `1` are never read
       --> tests/test_error.rs:394:18
        |
    394 |     pub struct S(pub usize, pub Option<Box<S>>);
        |                - ^^^^^^^^^  ^^^^^^^^^^^^^^^^^^
        |                |
        |                fields in this struct
        |
        = note: `S` has a derived impl for the trait `Debug`, but this is intentionally ignored during dead code analysis
    help: consider changing the fields to be of unit type to suppress this warning while preserving the field numbering, or remove the fields
        |
    394 |     pub struct S((), ());
        |                  ~~  ~~