This count should mean the number of fields expected in the serialized form,
so if some fields are skipped, they shouldn't be counted

Methods affected:
- Deserializer::deserialize_tuple
- Deserializer::deserialize_tuple_struct
- VariantAccess::tuple_variant

Fix incorrect count of fields passed to tuple deserialization methods

    error: it is more concise to loop over references to containers instead of using explicit iteration methods
        --> serde/src/private/de.rs:2761:22
         |
    2761 |         for entry in self.0.iter_mut() {
         |                      ^^^^^^^^^^^^^^^^^ help: to write this more concisely, try: `&mut *self.0`
         |
         = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#explicit_iter_loop
         = note: `-D clippy::explicit-iter-loop` implied by `-D clippy::pedantic`

    error: it is more concise to loop over references to containers instead of using explicit iteration methods
       --> serde_derive/src/internals/check.rs:202:20
        |
    202 |     for variant in variants.iter() {
        |                    ^^^^^^^^^^^^^^^ help: to write this more concisely, try: `variants`
        |
        = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#explicit_iter_loop
        = note: `-D clippy::explicit-iter-loop` implied by `-D clippy::pedantic`

    error: it is more concise to loop over references to containers instead of using explicit iteration methods
       --> serde_derive/src/bound.rs:262:28
        |
    262 |             for variant in variants.iter() {
        |                            ^^^^^^^^^^^^^^^ help: to write this more concisely, try: `variants`
        |
        = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#explicit_iter_loop

    error: try not to call a closure in the expression where it is declared
        --> serde/src/de/impls.rs:1590:76
         |
    1590 |                       <(_, u16)>::deserialize(deserializer).map(|(ip, port)| $new(ip, port))
         |                                                                              ^^^^^^^^^^^^^^
    ...
    1620 | / parse_socket_impl!("IPv6 socket address" net::SocketAddrV6, |ip, port| net::SocketAddrV6::new(
    1621 | |     ip, port, 0, 0
    1622 | | ));
         | |__- in this macro invocation
         |
         = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#redundant_closure_call
         = note: `-D clippy::redundant-closure-call` implied by `-D clippy::all`
         = note: this error originates in the macro `parse_socket_impl` (in Nightly builds, run with -Z macro-backtrace for more info)

    error: explicit call to `.into_iter()` in function argument accepting `IntoIterator`
       --> test_suite/tests/test_de.rs:202:12
        |
    202 |     .chain(vec![Token::MapEnd].into_iter())
        |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider removing the `.into_iter()`: `vec![Token::MapEnd]`
        |
    note: this parameter accepts any `IntoIterator`, so you don't need to call `.into_iter()`
       --> /home/david/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/iter/traits/iterator.rs:522:12
        |
    522 |         U: IntoIterator<Item = Self::Item>,
        |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#useless_conversion
        = note: `-D clippy::useless-conversion` implied by `-D clippy::all`