…erenity-rs#2646)

This avoids having to allocate to store fixed length (replaced with normal
array) or fixed capacity (replaced with `ArrayVec`) collections as vectors for
the purposes of putting them through the `Request` plumbing.

Slight behavioral change - before, setting `params` to `Some(vec![])`
would still append a question mark to the end of the url. Now, we check
if the params array `is_empty` instead of `is_some`, so the question
mark won't be appended if the params list is empty.

Co-authored-by: Michael Krasnitski <42564254+mkrasnitski@users.noreply.github.com>

These are unnecessary. Accepting `impl Into<Arc<T>>` allows passing either `T` or `Arc<T>`.

This trades a heap allocation for messages sent along with thread
creation for `Message`'s inline size dropping from 1176 bytes to 760
bytes,

…l models (serenity-rs#2656)

This shrinks type sizes by a lot; however, it makes the user experience slightly
different:

- `FixedString` must be converted to String with `.into()` or `.into_string()`
  before it can be pushed to, but dereferences to `&str` as is.
- `FixedArray` must be converted to `Vec` with `.into()` or `.into_vec()`
  before it can be pushed to, but dereferences to `&[T]` as is.

The crate of these types is currently a Git dependency, but this is fine for
the `next` branch. It needs some basic testing, which Serenity is perfect for,
before a release will be made to crates.io.

…s push over the limit (serenity-rs#2660)

Fixes serenity-rs#2664

…enity-rs#2668)

This commit:

- switches from `u64` to `i64` in `CreateCommandOption::min_int_value` and
`CreateCommandOption::max_int_value` to accommodate negative integers in
Discord's integer range (between -2^53 and 2^53). Values outside this
range will cause Discord's API to return an error.
- switches from `i32` to `i64` in `CreateCommandOption::add_int_choice` and
`CreateCommandOption::add_int_choice_localized` to accommodate Discord's
complete integer range (between -2^53 and 2^53). Values outside this
range will cause Discord's API to return an error.

This cache was just duplicating information already present in `Guild::members`
and therefore should be removed. 

This saves around 700 MBs for my bot (pre-`FixedString`).

This has to refactor `utils::content_safe` to always take a `Guild` instead
of`Cache`, but in practice it was mostly pulling from the guild cache anyway
and this means it is more likely to respect nicknames and other information,
while losing the ability to clean mentions from DMs, which do not matter.

`Embed::fields` previously had to stay as a `Vec` due to `CreateEmbed` wrapping
around it, but by implementing `Serialize` manually we can overwrite the
`Embed::fields` with a normal `Vec`, for a small performance hit on
serialization while saving some space for all stored `Embed`s.

Simply missed these when finding and replacing.

This uses the `bool_to_bitflags` macro to remove boolean (and optional boolean)
fields from structs and pack them into a bitflags invocation, so a struct with
many bools will only use one or two bytes, instead of a byte per bool as is.

This requires using getters and setters for the boolean fields, which changes
user experience and is hard to document, which is a significant downside, but
is such a nice change and will just become more and more efficient as time goes
on.

…rs#2681)

This swaps fields that store `Option<Int>` for `Option<NonMaxInt>` where the
maximum value would be ludicrous. Since `nonmax` uses `NonZero` internally,
this gives us niche optimisations, so model sizes can drop some more.

I have had to include a workaround for [serenity-rs#17] in `optional_string` by making my
own `TryFrom<u64>`, so that should be removable once that issue is fixed.

[serenity-rs#17]: LPGhatguy/nonmax#17

A couple of clippy bugs have been fixed and I have shrunk model
sizes enough to make `clippy::large_enum_variant` go away.

A discord bot library should not be using the tools reserved for low
level OS interaction/data structure libraries.

)

Discord seems to internally default Ids to 0, which is a bug whenever
exposed, but this makes ID parsing more resilient. I also took the
liberty to remove the `From<NonZero*>` implementations, to prevent future
headaches, as it was impossible to not break public API as we exposed
`NonZero` in `*Id::parse`.

…nity-rs#2694)

This, 
1. shrinks the size of Request, when copied around, as it doesn't have
to store the max capacity at all times
2. shrinks llvm-lines (compile time metric) for my bot in debug from
`1,153,519` to `1,131,480` as no monomorphisation has to be performed
for `MAX_PARAMS`.

Follow-up to serenity-rs#2694.

When `Request::params` was made into an ArrayVec, the `Option` around it
was removed in order to avoid having to add a turbofish on `None` to
specify the value of `MAX_PARAMS`. Also, `Request::new` also needed to
be changed so that the value of `MAX_PARAMS` could be inferred. Now that
the field is a slice again, we can wrap it in `Option` again (at no cost
to size, thanks to niche opts).

We ensure we never store the redundant `Some(&[])` by checking for an
empty slice and storing `None` instead. This way, we ensure we never
read an empty slice out of the `Some` variant.

The instrument macros generate 2% of Serenity's release mode llvm-lines,
and are proc-macros so hurt compile time in that way, so this limits
them to opt-in. This commit also fixes the issues that the instrument macro
was hiding, such as results that didn't ever error and missing
documentation.

This signature is hard to use as `None` cannot infer the type of the
generic. I also replaced `Option<u8>` with `Option<NonMaxU8>` as it's
more efficient and will make the user think of the maximum value.

…nity-rs#2698)

This removes inefficient `IntoIterator` generics and instead takes what is
actually required. I also reworked `reorder_channels` to allow for keeping the
generic, as it actually does only just need iterator semantics.

Previously, someone assumed that `Ratelimiter` was going to be cloned, so
put a ton of `Arc`s everywhere. This was unneeded, and before dashmap,
so the buckets were also stored massively inefficiently. This fixes all
that.

I had to shuffle around the `Ratelimit` methods a little bit to return
their sleep time instead of sleeping themselves, so I didn't have to
hold a dashmap lock over an `.await`.

This removes multiple error variants and overall cleans up the codebase
by moving overflow checks into two `ModelError` variants.

Shrinks `size_of::<Error>` from 136 bytes to 64 bytes, while removing unused
variants. This will improve performance for any method returning
`Result<T>` where `T` is less than the size of `Error` as both `Result`'s
`Ok` and `Err` have to be allocated stack space.

The compiler knows best as inlining is quite complicated. This should
help with compile times, significantly.

`Into<*Id>` is often entirely unnecessary, and at worst hides the type of
the Id with hard-coded Ids. This fixes this by just using the Id type
itself, which also helps with monomorphisation bloat.

I also removed `AsRef<str>`, as this can just be `&str` without
requiring a generic and without requiring a call to as_ref in the
function, while also not accidentally taking ownership of a `String`
passed in misleadingly.

If deserialization fails, we should allow the specific deserialization error to
be logged so that it can be reported to the Serenity maintainers. As it stands,
any events that fail to deserialize normally will "succeed" when deserialized
into the `Unknown` variant, throwing away any extra information about the
error.

Because deserialization errors are immediately logged when they happen,
explicitly whitelist `Error::Json` in `Shard::handle_event` to prevent
duplicate logs.

`Value` is bad to use and is slow. I also used `Arc<str>` to store `path` as
this is cloned a couple times.

`small-fixed-array` v0.2 removes implicit truncation and makes all
truncations explicit.

I also changed FixedString initialization from literals to use
`from_str_trunc` to take advantage of SSO if possible.

The `@everyone` role sometimes has a role position of -1, but not always!

This is documented as max 99 for voice channels, but 10k for stage
channels.

This example depended on rillrate, which has been archived for over a
year.

…#2661)

When a session is first kicked off and we need to start many shards, we
can use the value of `max_concurrency` to kick off multiple shards in
parallel.

Replaces the typemap with `dyn Any`, which is what typemap used
internally anyway. This gives the user more control over locking,
removes boilerplate, and is less confusing for beginners to learn.

This incurs an extra ref count, but this should be negligible for the
more permissive type. An explanation of how this works is that:

- `Arc` is just a shared pointer to `ArcInner`
- `ArcInner` stores the concrete Data type
- Each `Arc` stores the dyn vtable ptr
- `Arc` checks the vtable ptr to get the type id, then it can just give
out a new `Arc` referring to the `ArcInner` concretely.

)

This is mostly for usage in `poise` to provide a nicer error message in
its situation. I also changed `Client::data` to provide `Arc` as well.

This also removes the impls of `From<{i32,u64}> for Colour`, as it only
makes sense to convert infallibly from `u32`.

…2732)

Because builder fields are all private, it doesn't make sense to compare
them directly. From a user's perspective, they have no idea what the
builder might contain. This also lets us change their internals easier,
without worrying about equality.

This should improve compile times even more, by compiling a lot more
methods in Serenity, instead of the user's code.

`simd-json` is not a performance improvement for Serenity.

It has a ton of sketchy uses of `unsafe`, increases the maintenance burden, and
leads to Serenity containing a json compatibility layer(!). 

This commit removes all that, although a faster json decoding implementation is
on the table in the future if the compatibility layer is kept out of tree and
it is measurably faster for Serenity's usecase.

This replaces fancy iter stuff with just writing the code, and therefore
reduces the code size significantly and spawns less tasks.

…2742)

There was a comment here that said it was called by simd-json, so I
removed the function, but it turns out that serde_json also calls it.

Avoids cloning entire event structs when dispatching. To reduce code
size and allocations all the state is bundled up into a temporary struct
called DispatchContext, but this isn't user facing at all. This
regresses code size a bit, but is worth it for runtime performance, and
probably reduces actual code sizes as `FullEvent` doesn't have to be
moved around as much.

…s#2741)

Removes unnecessary trait, which only limited the signatures to always
take `CacheHttp` and required the async_trait boxing and compile time
cost. This also makes a lot less methods generic, improving compile
times.

…rs#2746)

Saves a couple bytes in each model by replacing the enums with a simpler
and more accurate representation, a newtype with named statics.
https://www.diffchecker.com/ohzayL9Z/

`SecretString` is nice to have, but this is more efficient, and
`SecretString` is defense in depth we can do without.

This PR carries out the removal after the deprecation made on current.

This re-adds Secret to the bot token, without losing the `Arc<str>` opt.
This works by using a newtype to Zeroise on last drop, using
`Arc::get_mut`.