Adding upstream version 124.0.1.upstream/124.0.1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

14 files changed, 5640 insertions, 0 deletions

diff --git a/third_party/rust/ron/src/de/id.rs b/third_party/rust/ron/src/de/id.rs
new file mode 100644
index 0000000000..e7230da5fc
--- /dev/null
+++ b/third_party/rust/ron/src/de/id.rs
@@ -0,0 +1,246 @@
+use serde::de::{self, Visitor};
+
+use super::{Deserializer, Error, Result};
+
+pub struct IdDeserializer<'a, 'b: 'a> {
+    d: &'a mut Deserializer<'b>,
+}
+
+impl<'a, 'b: 'a> IdDeserializer<'a, 'b> {
+    pub fn new(d: &'a mut Deserializer<'b>) -> Self {
+        IdDeserializer { d }
+    }
+}
+
+impl<'a, 'b: 'a, 'c> de::Deserializer<'b> for &'c mut IdDeserializer<'a, 'b> {
+    type Error = Error;
+
+    fn deserialize_identifier<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        self.d.deserialize_identifier(visitor)
+    }
+
+    fn deserialize_str<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        self.deserialize_identifier(visitor)
+    }
+
+    fn deserialize_any<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        self.deserialize_identifier(visitor)
+    }
+
+    fn deserialize_bool<V>(self, _: V) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        Err(Error::ExpectedIdentifier)
+    }
+
+    fn deserialize_i8<V>(self, _: V) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        Err(Error::ExpectedIdentifier)
+    }
+
+    fn deserialize_i16<V>(self, _: V) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        Err(Error::ExpectedIdentifier)
+    }
+
+    fn deserialize_i32<V>(self, _: V) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        Err(Error::ExpectedIdentifier)
+    }
+
+    fn deserialize_i64<V>(self, _: V) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        Err(Error::ExpectedIdentifier)
+    }
+
+    #[cfg(feature = "integer128")]
+    fn deserialize_i128<V>(self, _: V) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        Err(Error::ExpectedIdentifier)
+    }
+
+    fn deserialize_u8<V>(self, _: V) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        Err(Error::ExpectedIdentifier)
+    }
+
+    fn deserialize_u16<V>(self, _: V) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        Err(Error::ExpectedIdentifier)
+    }
+
+    fn deserialize_u32<V>(self, _: V) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        Err(Error::ExpectedIdentifier)
+    }
+
+    fn deserialize_u64<V>(self, _: V) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        Err(Error::ExpectedIdentifier)
+    }
+
+    #[cfg(feature = "integer128")]
+    fn deserialize_u128<V>(self, _: V) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        Err(Error::ExpectedIdentifier)
+    }
+
+    fn deserialize_f32<V>(self, _: V) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        Err(Error::ExpectedIdentifier)
+    }
+
+    fn deserialize_f64<V>(self, _: V) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        Err(Error::ExpectedIdentifier)
+    }
+
+    fn deserialize_char<V>(self, _: V) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        Err(Error::ExpectedIdentifier)
+    }
+
+    fn deserialize_string<V>(self, _: V) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        Err(Error::ExpectedIdentifier)
+    }
+
+    fn deserialize_bytes<V>(self, _: V) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        Err(Error::ExpectedIdentifier)
+    }
+
+    fn deserialize_byte_buf<V>(self, _: V) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        Err(Error::ExpectedIdentifier)
+    }
+
+    fn deserialize_option<V>(self, _: V) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        Err(Error::ExpectedIdentifier)
+    }
+
+    fn deserialize_unit<V>(self, _: V) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        Err(Error::ExpectedIdentifier)
+    }
+
+    fn deserialize_unit_struct<V>(self, _: &'static str, _: V) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        Err(Error::ExpectedIdentifier)
+    }
+
+    fn deserialize_newtype_struct<V>(self, _: &'static str, _: V) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        Err(Error::ExpectedIdentifier)
+    }
+
+    fn deserialize_seq<V>(self, _: V) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        Err(Error::ExpectedIdentifier)
+    }
+
+    fn deserialize_tuple<V>(self, _: usize, _: V) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        Err(Error::ExpectedIdentifier)
+    }
+
+    fn deserialize_tuple_struct<V>(self, _: &'static str, _: usize, _: V) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        Err(Error::ExpectedIdentifier)
+    }
+
+    fn deserialize_map<V>(self, _: V) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        Err(Error::ExpectedIdentifier)
+    }
+
+    fn deserialize_struct<V>(
+        self,
+        _: &'static str,
+        _: &'static [&'static str],
+        _: V,
+    ) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        Err(Error::ExpectedIdentifier)
+    }
+
+    fn deserialize_enum<V>(
+        self,
+        _: &'static str,
+        _: &'static [&'static str],
+        _: V,
+    ) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        Err(Error::ExpectedIdentifier)
+    }
+
+    fn deserialize_ignored_any<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        self.deserialize_any(visitor)
+    }
+}
diff --git a/third_party/rust/ron/src/de/mod.rs b/third_party/rust/ron/src/de/mod.rs
new file mode 100644
index 0000000000..c0e62494be
--- /dev/null
+++ b/third_party/rust/ron/src/de/mod.rs
@@ -0,0 +1,869 @@
+/// Deserialization module.
+use std::{borrow::Cow, io, str};
+
+use base64::Engine;
+use serde::{
+    de::{self, DeserializeSeed, Deserializer as _, Visitor},
+    Deserialize,
+};
+
+use self::{id::IdDeserializer, tag::TagDeserializer};
+pub use crate::error::{Error, Position, SpannedError};
+use crate::{
+    error::{Result, SpannedResult},
+    extensions::Extensions,
+    options::Options,
+    parse::{AnyNum, Bytes, ParsedStr, BASE64_ENGINE},
+};
+
+mod id;
+mod tag;
+#[cfg(test)]
+mod tests;
+mod value;
+
+/// The RON deserializer.
+///
+/// If you just want to simply deserialize a value,
+/// you can use the [`from_str`] convenience function.
+pub struct Deserializer<'de> {
+    bytes: Bytes<'de>,
+    newtype_variant: bool,
+    last_identifier: Option<&'de str>,
+    recursion_limit: Option<usize>,
+}
+
+impl<'de> Deserializer<'de> {
+    // Cannot implement trait here since output is tied to input lifetime 'de.
+    #[allow(clippy::should_implement_trait)]
+    pub fn from_str(input: &'de str) -> SpannedResult<Self> {
+        Self::from_str_with_options(input, Options::default())
+    }
+
+    pub fn from_bytes(input: &'de [u8]) -> SpannedResult<Self> {
+        Self::from_bytes_with_options(input, Options::default())
+    }
+
+    pub fn from_str_with_options(input: &'de str, options: Options) -> SpannedResult<Self> {
+        Self::from_bytes_with_options(input.as_bytes(), options)
+    }
+
+    pub fn from_bytes_with_options(input: &'de [u8], options: Options) -> SpannedResult<Self> {
+        let mut deserializer = Deserializer {
+            bytes: Bytes::new(input)?,
+            newtype_variant: false,
+            last_identifier: None,
+            recursion_limit: options.recursion_limit,
+        };
+
+        deserializer.bytes.exts |= options.default_extensions;
+
+        Ok(deserializer)
+    }
+
+    pub fn remainder(&self) -> Cow<'_, str> {
+        String::from_utf8_lossy(self.bytes.bytes())
+    }
+
+    pub fn span_error(&self, code: Error) -> SpannedError {
+        self.bytes.span_error(code)
+    }
+}
+
+/// A convenience function for building a deserializer
+/// and deserializing a value of type `T` from a reader.
+pub fn from_reader<R, T>(rdr: R) -> SpannedResult<T>
+where
+    R: io::Read,
+    T: de::DeserializeOwned,
+{
+    Options::default().from_reader(rdr)
+}
+
+/// A convenience function for building a deserializer
+/// and deserializing a value of type `T` from a string.
+pub fn from_str<'a, T>(s: &'a str) -> SpannedResult<T>
+where
+    T: de::Deserialize<'a>,
+{
+    Options::default().from_str(s)
+}
+
+/// A convenience function for building a deserializer
+/// and deserializing a value of type `T` from bytes.
+pub fn from_bytes<'a, T>(s: &'a [u8]) -> SpannedResult<T>
+where
+    T: de::Deserialize<'a>,
+{
+    Options::default().from_bytes(s)
+}
+
+macro_rules! guard_recursion {
+    ($self:expr => $expr:expr) => {{
+        if let Some(limit) = &mut $self.recursion_limit {
+            if let Some(new_limit) = limit.checked_sub(1) {
+                *limit = new_limit;
+            } else {
+                return Err(Error::ExceededRecursionLimit);
+            }
+        }
+
+        let result = $expr;
+
+        if let Some(limit) = &mut $self.recursion_limit {
+            *limit = limit.saturating_add(1);
+        }
+
+        result
+    }};
+}
+
+impl<'de> Deserializer<'de> {
+    /// Check if the remaining bytes are whitespace only,
+    /// otherwise return an error.
+    pub fn end(&mut self) -> Result<()> {
+        self.bytes.skip_ws()?;
+
+        if self.bytes.bytes().is_empty() {
+            Ok(())
+        } else {
+            Err(Error::TrailingCharacters)
+        }
+    }
+
+    /// Called from [`deserialize_any`][serde::Deserializer::deserialize_any]
+    /// when a struct was detected. Decides if there is a unit, tuple or usual
+    /// struct and deserializes it accordingly.
+    ///
+    /// This method assumes there is no identifier left.
+    fn handle_any_struct<V>(&mut self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'de>,
+    {
+        // Create a working copy
+        let mut bytes = self.bytes;
+
+        if bytes.consume("(") {
+            bytes.skip_ws()?;
+
+            if bytes.check_tuple_struct()? {
+                // first argument is technically incorrect, but ignored anyway
+                self.deserialize_tuple(0, visitor)
+            } else {
+                // giving no name results in worse errors but is necessary here
+                self.handle_struct_after_name("", visitor)
+            }
+        } else {
+            visitor.visit_unit()
+        }
+    }
+
+    /// Called from
+    /// [`deserialize_struct`][serde::Deserializer::deserialize_struct],
+    /// [`struct_variant`][serde::de::VariantAccess::struct_variant], and
+    /// [`handle_any_struct`][Self::handle_any_struct]. Handles
+    /// deserialising the enclosing parentheses and everything in between.
+    ///
+    /// This method assumes there is no struct name identifier left.
+    fn handle_struct_after_name<V>(
+        &mut self,
+        name_for_pretty_errors_only: &'static str,
+        visitor: V,
+    ) -> Result<V::Value>
+    where
+        V: Visitor<'de>,
+    {
+        if self.newtype_variant || self.bytes.consume("(") {
+            let old_newtype_variant = self.newtype_variant;
+            self.newtype_variant = false;
+
+            let value = guard_recursion! { self =>
+                visitor
+                    .visit_map(CommaSeparated::new(b')', self))
+                    .map_err(|err| {
+                        struct_error_name(
+                            err,
+                            if !old_newtype_variant && !name_for_pretty_errors_only.is_empty() {
+                                Some(name_for_pretty_errors_only)
+                            } else {
+                                None
+                            },
+                        )
+                    })?
+            };
+
+            self.bytes.skip_ws()?;
+
+            if old_newtype_variant || self.bytes.consume(")") {
+                Ok(value)
+            } else {
+                Err(Error::ExpectedStructLikeEnd)
+            }
+        } else if name_for_pretty_errors_only.is_empty() {
+            Err(Error::ExpectedStructLike)
+        } else {
+            Err(Error::ExpectedNamedStructLike(name_for_pretty_errors_only))
+        }
+    }
+}
+
+impl<'de, 'a> de::Deserializer<'de> for &'a mut Deserializer<'de> {
+    type Error = Error;
+
+    fn deserialize_any<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'de>,
+    {
+        // Newtype variants can only be unwrapped if we receive information
+        //  about the wrapped type - with `deserialize_any` we don't
+        self.newtype_variant = false;
+
+        if self.bytes.consume_ident("true") {
+            return visitor.visit_bool(true);
+        } else if self.bytes.consume_ident("false") {
+            return visitor.visit_bool(false);
+        } else if self.bytes.check_ident("Some") {
+            return self.deserialize_option(visitor);
+        } else if self.bytes.consume_ident("None") {
+            return visitor.visit_none();
+        } else if self.bytes.consume("()") {
+            return visitor.visit_unit();
+        } else if self.bytes.consume_ident("inf") {
+            return visitor.visit_f64(std::f64::INFINITY);
+        } else if self.bytes.consume_ident("-inf") {
+            return visitor.visit_f64(std::f64::NEG_INFINITY);
+        } else if self.bytes.consume_ident("NaN") {
+            return visitor.visit_f64(std::f64::NAN);
+        }
+
+        // `identifier` does not change state if it fails
+        let ident = self.bytes.identifier().ok();
+
+        if ident.is_some() {
+            self.bytes.skip_ws()?;
+
+            return self.handle_any_struct(visitor);
+        }
+
+        match self.bytes.peek_or_eof()? {
+            b'(' => self.handle_any_struct(visitor),
+            b'[' => self.deserialize_seq(visitor),
+            b'{' => self.deserialize_map(visitor),
+            b'0'..=b'9' | b'+' | b'-' => {
+                let any_num: AnyNum = self.bytes.any_num()?;
+
+                match any_num {
+                    AnyNum::F32(x) => visitor.visit_f32(x),
+                    AnyNum::F64(x) => visitor.visit_f64(x),
+                    AnyNum::I8(x) => visitor.visit_i8(x),
+                    AnyNum::U8(x) => visitor.visit_u8(x),
+                    AnyNum::I16(x) => visitor.visit_i16(x),
+                    AnyNum::U16(x) => visitor.visit_u16(x),
+                    AnyNum::I32(x) => visitor.visit_i32(x),
+                    AnyNum::U32(x) => visitor.visit_u32(x),
+                    AnyNum::I64(x) => visitor.visit_i64(x),
+                    AnyNum::U64(x) => visitor.visit_u64(x),
+                    #[cfg(feature = "integer128")]
+                    AnyNum::I128(x) => visitor.visit_i128(x),
+                    #[cfg(feature = "integer128")]
+                    AnyNum::U128(x) => visitor.visit_u128(x),
+                }
+            }
+            b'.' => self.deserialize_f64(visitor),
+            b'"' | b'r' => self.deserialize_string(visitor),
+            b'\'' => self.deserialize_char(visitor),
+            other => Err(Error::UnexpectedByte(other as char)),
+        }
+    }
+
+    fn deserialize_bool<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'de>,
+    {
+        visitor.visit_bool(self.bytes.bool()?)
+    }
+
+    fn deserialize_i8<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'de>,
+    {
+        visitor.visit_i8(self.bytes.signed_integer()?)
+    }
+
+    fn deserialize_i16<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'de>,
+    {
+        visitor.visit_i16(self.bytes.signed_integer()?)
+    }
+
+    fn deserialize_i32<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'de>,
+    {
+        visitor.visit_i32(self.bytes.signed_integer()?)
+    }
+
+    fn deserialize_i64<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'de>,
+    {
+        visitor.visit_i64(self.bytes.signed_integer()?)
+    }
+
+    #[cfg(feature = "integer128")]
+    fn deserialize_i128<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'de>,
+    {
+        visitor.visit_i128(self.bytes.signed_integer()?)
+    }
+
+    fn deserialize_u8<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'de>,
+    {
+        visitor.visit_u8(self.bytes.unsigned_integer()?)
+    }
+
+    fn deserialize_u16<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'de>,
+    {
+        visitor.visit_u16(self.bytes.unsigned_integer()?)
+    }
+
+    fn deserialize_u32<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'de>,
+    {
+        visitor.visit_u32(self.bytes.unsigned_integer()?)
+    }
+
+    fn deserialize_u64<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'de>,
+    {
+        visitor.visit_u64(self.bytes.unsigned_integer()?)
+    }
+
+    #[cfg(feature = "integer128")]
+    fn deserialize_u128<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'de>,
+    {
+        visitor.visit_u128(self.bytes.unsigned_integer()?)
+    }
+
+    fn deserialize_f32<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'de>,
+    {
+        visitor.visit_f32(self.bytes.float()?)
+    }
+
+    fn deserialize_f64<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'de>,
+    {
+        visitor.visit_f64(self.bytes.float()?)
+    }
+
+    fn deserialize_char<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'de>,
+    {
+        visitor.visit_char(self.bytes.char()?)
+    }
+
+    fn deserialize_str<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'de>,
+    {
+        match self.bytes.string()? {
+            ParsedStr::Allocated(s) => visitor.visit_string(s),
+            ParsedStr::Slice(s) => visitor.visit_borrowed_str(s),
+        }
+    }
+
+    fn deserialize_string<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'de>,
+    {
+        self.deserialize_str(visitor)
+    }
+
+    fn deserialize_bytes<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'de>,
+    {
+        self.deserialize_byte_buf(visitor)
+    }
+
+    fn deserialize_byte_buf<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'de>,
+    {
+        if let Some(b'[') = self.bytes.peek() {
+            let bytes = Vec::<u8>::deserialize(self)?;
+            return visitor.visit_byte_buf(bytes);
+        }
+
+        let res = {
+            let string = self.bytes.string()?;
+            let base64_str = match string {
+                ParsedStr::Allocated(ref s) => s.as_str(),
+                ParsedStr::Slice(s) => s,
+            };
+            BASE64_ENGINE.decode(base64_str)
+        };
+
+        match res {
+            Ok(byte_buf) => visitor.visit_byte_buf(byte_buf),
+            Err(err) => Err(Error::Base64Error(err)),
+        }
+    }
+
+    fn deserialize_option<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'de>,
+    {
+        if self.bytes.consume("None") {
+            visitor.visit_none()
+        } else if self.bytes.consume("Some") && {
+            self.bytes.skip_ws()?;
+            self.bytes.consume("(")
+        } {
+            self.bytes.skip_ws()?;
+
+            let v = guard_recursion! { self => visitor.visit_some(&mut *self)? };
+
+            self.bytes.comma()?;
+
+            if self.bytes.consume(")") {
+                Ok(v)
+            } else {
+                Err(Error::ExpectedOptionEnd)
+            }
+        } else if self.bytes.exts.contains(Extensions::IMPLICIT_SOME) {
+            guard_recursion! { self => visitor.visit_some(&mut *self) }
+        } else {
+            Err(Error::ExpectedOption)
+        }
+    }
+
+    // In Serde, unit means an anonymous value containing no data.
+    fn deserialize_unit<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'de>,
+    {
+        if self.newtype_variant || self.bytes.consume("()") {
+            self.newtype_variant = false;
+
+            visitor.visit_unit()
+        } else {
+            Err(Error::ExpectedUnit)
+        }
+    }
+
+    fn deserialize_unit_struct<V>(self, name: &'static str, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'de>,
+    {
+        if self.newtype_variant || self.bytes.consume_struct_name(name)? {
+            self.newtype_variant = false;
+
+            visitor.visit_unit()
+        } else {
+            self.deserialize_unit(visitor)
+        }
+    }
+
+    fn deserialize_newtype_struct<V>(self, name: &'static str, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'de>,
+    {
+        if self.bytes.exts.contains(Extensions::UNWRAP_NEWTYPES) || self.newtype_variant {
+            self.newtype_variant = false;
+
+            return guard_recursion! { self => visitor.visit_newtype_struct(&mut *self) };
+        }
+
+        self.bytes.consume_struct_name(name)?;
+
+        self.bytes.skip_ws()?;
+
+        if self.bytes.consume("(") {
+            self.bytes.skip_ws()?;
+            let value = guard_recursion! { self => visitor.visit_newtype_struct(&mut *self)? };
+            self.bytes.comma()?;
+
+            if self.bytes.consume(")") {
+                Ok(value)
+            } else {
+                Err(Error::ExpectedStructLikeEnd)
+            }
+        } else if name.is_empty() {
+            Err(Error::ExpectedStructLike)
+        } else {
+            Err(Error::ExpectedNamedStructLike(name))
+        }
+    }
+
+    fn deserialize_seq<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'de>,
+    {
+        self.newtype_variant = false;
+
+        if self.bytes.consume("[") {
+            let value = guard_recursion! { self =>
+                visitor.visit_seq(CommaSeparated::new(b']', self))?
+            };
+            self.bytes.skip_ws()?;
+
+            if self.bytes.consume("]") {
+                Ok(value)
+            } else {
+                Err(Error::ExpectedArrayEnd)
+            }
+        } else {
+            Err(Error::ExpectedArray)
+        }
+    }
+
+    fn deserialize_tuple<V>(self, _len: usize, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'de>,
+    {
+        if self.newtype_variant || self.bytes.consume("(") {
+            let old_newtype_variant = self.newtype_variant;
+            self.newtype_variant = false;
+
+            let value = guard_recursion! { self =>
+                visitor.visit_seq(CommaSeparated::new(b')', self))?
+            };
+            self.bytes.skip_ws()?;
+
+            if old_newtype_variant || self.bytes.consume(")") {
+                Ok(value)
+            } else {
+                Err(Error::ExpectedStructLikeEnd)
+            }
+        } else {
+            Err(Error::ExpectedStructLike)
+        }
+    }
+
+    fn deserialize_tuple_struct<V>(
+        self,
+        name: &'static str,
+        len: usize,
+        visitor: V,
+    ) -> Result<V::Value>
+    where
+        V: Visitor<'de>,
+    {
+        if !self.newtype_variant {
+            self.bytes.consume_struct_name(name)?;
+        }
+
+        self.deserialize_tuple(len, visitor).map_err(|e| match e {
+            Error::ExpectedStructLike if !name.is_empty() => Error::ExpectedNamedStructLike(name),
+            e => e,
+        })
+    }
+
+    fn deserialize_map<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'de>,
+    {
+        self.newtype_variant = false;
+
+        if self.bytes.consume("{") {
+            let value = guard_recursion! { self =>
+                visitor.visit_map(CommaSeparated::new(b'}', self))?
+            };
+            self.bytes.skip_ws()?;
+
+            if self.bytes.consume("}") {
+                Ok(value)
+            } else {
+                Err(Error::ExpectedMapEnd)
+            }
+        } else {
+            Err(Error::ExpectedMap)
+        }
+    }
+
+    fn deserialize_struct<V>(
+        self,
+        name: &'static str,
+        _fields: &'static [&'static str],
+        visitor: V,
+    ) -> Result<V::Value>
+    where
+        V: Visitor<'de>,
+    {
+        if !self.newtype_variant {
+            self.bytes.consume_struct_name(name)?;
+        }
+
+        self.bytes.skip_ws()?;
+
+        self.handle_struct_after_name(name, visitor)
+    }
+
+    fn deserialize_enum<V>(
+        self,
+        name: &'static str,
+        _variants: &'static [&'static str],
+        visitor: V,
+    ) -> Result<V::Value>
+    where
+        V: Visitor<'de>,
+    {
+        self.newtype_variant = false;
+
+        match guard_recursion! { self => visitor.visit_enum(Enum::new(self)) } {
+            Ok(value) => Ok(value),
+            Err(Error::NoSuchEnumVariant {
+                expected,
+                found,
+                outer: None,
+            }) if !name.is_empty() => Err(Error::NoSuchEnumVariant {
+                expected,
+                found,
+                outer: Some(String::from(name)),
+            }),
+            Err(e) => Err(e),
+        }
+    }
+
+    fn deserialize_identifier<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'de>,
+    {
+        let identifier = str::from_utf8(self.bytes.identifier()?).map_err(Error::from)?;
+
+        self.last_identifier = Some(identifier);
+
+        visitor.visit_borrowed_str(identifier)
+    }
+
+    fn deserialize_ignored_any<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'de>,
+    {
+        self.deserialize_any(visitor)
+    }
+}
+
+struct CommaSeparated<'a, 'de: 'a> {
+    de: &'a mut Deserializer<'de>,
+    terminator: u8,
+    had_comma: bool,
+}
+
+impl<'a, 'de> CommaSeparated<'a, 'de> {
+    fn new(terminator: u8, de: &'a mut Deserializer<'de>) -> Self {
+        CommaSeparated {
+            de,
+            terminator,
+            had_comma: true,
+        }
+    }
+
+    fn has_element(&mut self) -> Result<bool> {
+        self.de.bytes.skip_ws()?;
+
+        match (
+            self.had_comma,
+            self.de.bytes.peek_or_eof()? != self.terminator,
+        ) {
+            // Trailing comma, maybe has a next element
+            (true, has_element) => Ok(has_element),
+            // No trailing comma but terminator
+            (false, false) => Ok(false),
+            // No trailing comma or terminator
+            (false, true) => Err(Error::ExpectedComma),
+        }
+    }
+}
+
+impl<'de, 'a> de::SeqAccess<'de> for CommaSeparated<'a, 'de> {
+    type Error = Error;
+
+    fn next_element_seed<T>(&mut self, seed: T) -> Result<Option<T::Value>>
+    where
+        T: DeserializeSeed<'de>,
+    {
+        if self.has_element()? {
+            let res = guard_recursion! { self.de => seed.deserialize(&mut *self.de)? };
+
+            self.had_comma = self.de.bytes.comma()?;
+
+            Ok(Some(res))
+        } else {
+            Ok(None)
+        }
+    }
+}
+
+impl<'de, 'a> de::MapAccess<'de> for CommaSeparated<'a, 'de> {
+    type Error = Error;
+
+    fn next_key_seed<K>(&mut self, seed: K) -> Result<Option<K::Value>>
+    where
+        K: DeserializeSeed<'de>,
+    {
+        if self.has_element()? {
+            if self.terminator == b')' {
+                guard_recursion! { self.de =>
+                    seed.deserialize(&mut IdDeserializer::new(&mut *self.de)).map(Some)
+                }
+            } else {
+                guard_recursion! { self.de => seed.deserialize(&mut *self.de).map(Some) }
+            }
+        } else {
+            Ok(None)
+        }
+    }
+
+    fn next_value_seed<V>(&mut self, seed: V) -> Result<V::Value>
+    where
+        V: DeserializeSeed<'de>,
+    {
+        self.de.bytes.skip_ws()?;
+
+        if self.de.bytes.consume(":") {
+            self.de.bytes.skip_ws()?;
+
+            let res = guard_recursion! { self.de =>
+                seed.deserialize(&mut TagDeserializer::new(&mut *self.de))?
+            };
+
+            self.had_comma = self.de.bytes.comma()?;
+
+            Ok(res)
+        } else {
+            Err(Error::ExpectedMapColon)
+        }
+    }
+}
+
+struct Enum<'a, 'de: 'a> {
+    de: &'a mut Deserializer<'de>,
+}
+
+impl<'a, 'de> Enum<'a, 'de> {
+    fn new(de: &'a mut Deserializer<'de>) -> Self {
+        Enum { de }
+    }
+}
+
+impl<'de, 'a> de::EnumAccess<'de> for Enum<'a, 'de> {
+    type Error = Error;
+    type Variant = Self;
+
+    fn variant_seed<V>(self, seed: V) -> Result<(V::Value, Self::Variant)>
+    where
+        V: DeserializeSeed<'de>,
+    {
+        self.de.bytes.skip_ws()?;
+
+        let value = guard_recursion! { self.de => seed.deserialize(&mut *self.de)? };
+
+        Ok((value, self))
+    }
+}
+
+impl<'de, 'a> de::VariantAccess<'de> for Enum<'a, 'de> {
+    type Error = Error;
+
+    fn unit_variant(self) -> Result<()> {
+        Ok(())
+    }
+
+    fn newtype_variant_seed<T>(self, seed: T) -> Result<T::Value>
+    where
+        T: DeserializeSeed<'de>,
+    {
+        let newtype_variant = self.de.last_identifier;
+
+        self.de.bytes.skip_ws()?;
+
+        if self.de.bytes.consume("(") {
+            self.de.bytes.skip_ws()?;
+
+            self.de.newtype_variant = self
+                .de
+                .bytes
+                .exts
+                .contains(Extensions::UNWRAP_VARIANT_NEWTYPES);
+
+            let val = guard_recursion! { self.de =>
+                seed
+                    .deserialize(&mut *self.de)
+                    .map_err(|err| struct_error_name(err, newtype_variant))?
+            };
+
+            self.de.newtype_variant = false;
+
+            self.de.bytes.comma()?;
+
+            if self.de.bytes.consume(")") {
+                Ok(val)
+            } else {
+                Err(Error::ExpectedStructLikeEnd)
+            }
+        } else {
+            Err(Error::ExpectedStructLike)
+        }
+    }
+
+    fn tuple_variant<V>(self, len: usize, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'de>,
+    {
+        self.de.bytes.skip_ws()?;
+
+        self.de.deserialize_tuple(len, visitor)
+    }
+
+    fn struct_variant<V>(self, _fields: &'static [&'static str], visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'de>,
+    {
+        let struct_variant = self.de.last_identifier;
+
+        self.de.bytes.skip_ws()?;
+
+        self.de
+            .handle_struct_after_name("", visitor)
+            .map_err(|err| struct_error_name(err, struct_variant))
+    }
+}
+
+fn struct_error_name(error: Error, name: Option<&str>) -> Error {
+    match error {
+        Error::NoSuchStructField {
+            expected,
+            found,
+            outer: None,
+        } => Error::NoSuchStructField {
+            expected,
+            found,
+            outer: name.map(ToOwned::to_owned),
+        },
+        Error::MissingStructField { field, outer: None } => Error::MissingStructField {
+            field,
+            outer: name.map(ToOwned::to_owned),
+        },
+        Error::DuplicateStructField { field, outer: None } => Error::DuplicateStructField {
+            field,
+            outer: name.map(ToOwned::to_owned),
+        },
+        e => e,
+    }
+}
diff --git a/third_party/rust/ron/src/de/tag.rs b/third_party/rust/ron/src/de/tag.rs
new file mode 100644
index 0000000000..9e204ff847
--- /dev/null
+++ b/third_party/rust/ron/src/de/tag.rs
@@ -0,0 +1,251 @@
+use serde::de::{self, Visitor};
+
+use super::{Deserializer, Error, Result};
+
+pub struct TagDeserializer<'a, 'b: 'a> {
+    d: &'a mut Deserializer<'b>,
+}
+
+impl<'a, 'b: 'a> TagDeserializer<'a, 'b> {
+    pub fn new(d: &'a mut Deserializer<'b>) -> Self {
+        TagDeserializer { d }
+    }
+}
+
+impl<'a, 'b: 'a, 'c> de::Deserializer<'b> for &'c mut TagDeserializer<'a, 'b> {
+    type Error = Error;
+
+    fn deserialize_str<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        self.d.deserialize_str(visitor)
+    }
+
+    fn deserialize_identifier<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        self.deserialize_str(visitor)
+    }
+
+    fn deserialize_any<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        self.d.deserialize_any(visitor)
+    }
+
+    fn deserialize_bool<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        self.d.deserialize_bool(visitor)
+    }
+
+    fn deserialize_i8<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        self.d.deserialize_i8(visitor)
+    }
+
+    fn deserialize_i16<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        self.d.deserialize_i16(visitor)
+    }
+
+    fn deserialize_i32<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        self.d.deserialize_i32(visitor)
+    }
+
+    fn deserialize_i64<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        self.d.deserialize_i64(visitor)
+    }
+
+    #[cfg(feature = "integer128")]
+    fn deserialize_i128<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        self.d.deserialize_i128(visitor)
+    }
+
+    fn deserialize_u8<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        self.d.deserialize_u8(visitor)
+    }
+
+    fn deserialize_u16<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        self.d.deserialize_u16(visitor)
+    }
+
+    fn deserialize_u32<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        self.d.deserialize_u32(visitor)
+    }
+
+    fn deserialize_u64<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        self.d.deserialize_u64(visitor)
+    }
+
+    #[cfg(feature = "integer128")]
+    fn deserialize_u128<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        self.d.deserialize_u128(visitor)
+    }
+
+    fn deserialize_f32<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        self.d.deserialize_f32(visitor)
+    }
+
+    fn deserialize_f64<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        self.d.deserialize_f64(visitor)
+    }
+
+    fn deserialize_char<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        self.d.deserialize_char(visitor)
+    }
+
+    fn deserialize_string<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        self.d.deserialize_string(visitor)
+    }
+
+    fn deserialize_bytes<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        self.d.deserialize_bytes(visitor)
+    }
+
+    fn deserialize_byte_buf<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        self.d.deserialize_byte_buf(visitor)
+    }
+
+    fn deserialize_option<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        self.d.deserialize_option(visitor)
+    }
+
+    fn deserialize_unit<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        self.d.deserialize_unit(visitor)
+    }
+
+    fn deserialize_unit_struct<V>(self, name: &'static str, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        self.d.deserialize_unit_struct(name, visitor)
+    }
+
+    fn deserialize_newtype_struct<V>(self, name: &'static str, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        self.d.deserialize_newtype_struct(name, visitor)
+    }
+
+    fn deserialize_seq<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        self.d.deserialize_seq(visitor)
+    }
+
+    fn deserialize_tuple<V>(self, len: usize, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        self.d.deserialize_tuple(len, visitor)
+    }
+
+    fn deserialize_tuple_struct<V>(
+        self,
+        name: &'static str,
+        len: usize,
+        visitor: V,
+    ) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        self.d.deserialize_tuple_struct(name, len, visitor)
+    }
+
+    fn deserialize_map<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        self.d.deserialize_map(visitor)
+    }
+
+    fn deserialize_struct<V>(
+        self,
+        name: &'static str,
+        fields: &'static [&'static str],
+        visitor: V,
+    ) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        self.d.deserialize_struct(name, fields, visitor)
+    }
+
+    fn deserialize_enum<V>(
+        self,
+        name: &'static str,
+        variants: &'static [&'static str],
+        visitor: V,
+    ) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        self.d.deserialize_enum(name, variants, visitor)
+    }
+
+    fn deserialize_ignored_any<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'b>,
+    {
+        self.d.deserialize_ignored_any(visitor)
+    }
+}
diff --git a/third_party/rust/ron/src/de/tests.rs b/third_party/rust/ron/src/de/tests.rs
new file mode 100644
index 0000000000..2c46eb68f9
--- /dev/null
+++ b/third_party/rust/ron/src/de/tests.rs
@@ -0,0 +1,363 @@
+use serde_bytes;
+use serde_derive::Deserialize;
+
+use crate::{
+    de::from_str,
+    error::{Error, Position, SpannedError, SpannedResult},
+    parse::{AnyNum, Bytes},
+};
+
+#[derive(Debug, PartialEq, Deserialize)]
+struct EmptyStruct1;
+
+#[derive(Debug, PartialEq, Deserialize)]
+struct EmptyStruct2 {}
+
+#[derive(Clone, Copy, Debug, PartialEq, Deserialize)]
+struct MyStruct {
+    x: f32,
+    y: f32,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Deserialize)]
+enum MyEnum {
+    A,
+    B(bool),
+    C(bool, f32),
+    D { a: i32, b: i32 },
+}
+
+#[derive(Debug, Deserialize, PartialEq)]
+struct BytesStruct {
+    small: Vec<u8>,
+    #[serde(with = "serde_bytes")]
+    large: Vec<u8>,
+}
+
+#[test]
+fn test_empty_struct() {
+    assert_eq!(Ok(EmptyStruct1), from_str("EmptyStruct1"));
+    assert_eq!(Ok(EmptyStruct2 {}), from_str("EmptyStruct2()"));
+}
+
+#[test]
+fn test_struct() {
+    let my_struct = MyStruct { x: 4.0, y: 7.0 };
+
+    assert_eq!(Ok(my_struct), from_str("MyStruct(x:4,y:7,)"));
+    assert_eq!(Ok(my_struct), from_str("(x:4,y:7)"));
+
+    #[derive(Debug, PartialEq, Deserialize)]
+    struct NewType(i32);
+
+    assert_eq!(Ok(NewType(42)), from_str("NewType(42)"));
+    assert_eq!(Ok(NewType(33)), from_str("(33)"));
+
+    #[derive(Debug, PartialEq, Deserialize)]
+    struct TupleStruct(f32, f32);
+
+    assert_eq!(Ok(TupleStruct(2.0, 5.0)), from_str("TupleStruct(2,5,)"));
+    assert_eq!(Ok(TupleStruct(3.0, 4.0)), from_str("(3,4)"));
+}
+
+#[test]
+fn test_option() {
+    assert_eq!(Ok(Some(1u8)), from_str("Some(1)"));
+    assert_eq!(Ok(None::<u8>), from_str("None"));
+}
+
+#[test]
+fn test_enum() {
+    assert_eq!(Ok(MyEnum::A), from_str("A"));
+    assert_eq!(Ok(MyEnum::B(true)), from_str("B(true,)"));
+    assert_eq!(Ok(MyEnum::C(true, 3.5)), from_str("C(true,3.5,)"));
+    assert_eq!(Ok(MyEnum::D { a: 2, b: 3 }), from_str("D(a:2,b:3,)"));
+}
+
+#[test]
+fn test_array() {
+    let empty: [i32; 0] = [];
+    assert_eq!(Ok(empty), from_str("()"));
+    let empty_array = empty.to_vec();
+    assert_eq!(Ok(empty_array), from_str("[]"));
+
+    assert_eq!(Ok([2, 3, 4i32]), from_str("(2,3,4,)"));
+    assert_eq!(Ok([2, 3, 4i32].to_vec()), from_str("[2,3,4,]"));
+}
+
+#[test]
+fn test_map() {
+    use std::collections::HashMap;
+
+    let mut map = HashMap::new();
+    map.insert((true, false), 4);
+    map.insert((false, false), 123);
+
+    assert_eq!(
+        Ok(map),
+        from_str(
+            "{
+        (true,false,):4,
+        (false,false,):123,
+    }"
+        )
+    );
+}
+
+#[test]
+fn test_string() {
+    let s: String = from_str("\"String\"").unwrap();
+    assert_eq!("String", s);
+
+    let raw: String = from_str("r\"String\"").unwrap();
+    assert_eq!("String", raw);
+
+    let raw_hashes: String = from_str("r#\"String\"#").unwrap();
+    assert_eq!("String", raw_hashes);
+
+    let raw_hashes_multiline: String = from_str("r#\"String with\nmultiple\nlines\n\"#").unwrap();
+    assert_eq!("String with\nmultiple\nlines\n", raw_hashes_multiline);
+
+    let raw_hashes_quote: String = from_str("r##\"String with \"#\"##").unwrap();
+    assert_eq!("String with \"#", raw_hashes_quote);
+}
+
+#[test]
+fn test_char() {
+    assert_eq!(Ok('c'), from_str("'c'"));
+}
+
+#[test]
+fn test_escape_char() {
+    assert_eq!('\'', from_str::<char>("'\\''").unwrap());
+}
+
+#[test]
+fn test_escape() {
+    assert_eq!("\"Quoted\"", from_str::<String>(r#""\"Quoted\"""#).unwrap());
+}
+
+#[test]
+fn test_comment() {
+    assert_eq!(
+        MyStruct { x: 1.0, y: 2.0 },
+        from_str(
+            "(
+x: 1.0, // x is just 1
+// There is another comment in the very next line..
+// And y is indeed
+y: 2.0 // 2!
+    )"
+        )
+        .unwrap()
+    );
+}
+
+fn err<T>(kind: Error, line: usize, col: usize) -> SpannedResult<T> {
+    Err(SpannedError {
+        code: kind,
+        position: Position { line, col },
+    })
+}
+
+#[test]
+fn test_err_wrong_value() {
+    use std::collections::HashMap;
+
+    use self::Error::*;
+
+    assert_eq!(from_str::<f32>("'c'"), err(ExpectedFloat, 1, 1));
+    assert_eq!(from_str::<String>("'c'"), err(ExpectedString, 1, 1));
+    assert_eq!(from_str::<HashMap<u32, u32>>("'c'"), err(ExpectedMap, 1, 1));
+    assert_eq!(from_str::<[u8; 5]>("'c'"), err(ExpectedStructLike, 1, 1));
+    assert_eq!(from_str::<Vec<u32>>("'c'"), err(ExpectedArray, 1, 1));
+    assert_eq!(from_str::<MyEnum>("'c'"), err(ExpectedIdentifier, 1, 1));
+    assert_eq!(
+        from_str::<MyStruct>("'c'"),
+        err(ExpectedNamedStructLike("MyStruct"), 1, 1)
+    );
+    assert_eq!(
+        from_str::<MyStruct>("NotMyStruct(x: 4, y: 2)"),
+        err(
+            ExpectedDifferentStructName {
+                expected: "MyStruct",
+                found: String::from("NotMyStruct")
+            },
+            1,
+            12
+        )
+    );
+    assert_eq!(from_str::<(u8, bool)>("'c'"), err(ExpectedStructLike, 1, 1));
+    assert_eq!(from_str::<bool>("notabool"), err(ExpectedBoolean, 1, 1));
+
+    assert_eq!(
+        from_str::<MyStruct>("MyStruct(\n    x: true)"),
+        err(ExpectedFloat, 2, 8)
+    );
+    assert_eq!(
+        from_str::<MyStruct>("MyStruct(\n    x: 3.5, \n    y:)"),
+        err(ExpectedFloat, 3, 7)
+    );
+}
+
+#[test]
+fn test_perm_ws() {
+    assert_eq!(
+        from_str::<MyStruct>("\nMyStruct  \t ( \n x   : 3.5 , \t y\n: 4.5 \n ) \t\n"),
+        Ok(MyStruct { x: 3.5, y: 4.5 })
+    );
+}
+
+#[test]
+fn untagged() {
+    #[derive(Deserialize, Debug, PartialEq)]
+    #[serde(untagged)]
+    enum Untagged {
+        U8(u8),
+        Bool(bool),
+    }
+
+    assert_eq!(from_str::<Untagged>("true").unwrap(), Untagged::Bool(true));
+    assert_eq!(from_str::<Untagged>("8").unwrap(), Untagged::U8(8));
+}
+
+#[test]
+fn rename() {
+    #[derive(Deserialize, Debug, PartialEq)]
+    enum Foo {
+        #[serde(rename = "2d")]
+        D2,
+        #[serde(rename = "triangle-list")]
+        TriangleList,
+    }
+    assert_eq!(from_str::<Foo>("r#2d").unwrap(), Foo::D2);
+    assert_eq!(
+        from_str::<Foo>("r#triangle-list").unwrap(),
+        Foo::TriangleList
+    );
+}
+
+#[test]
+fn forgot_apostrophes() {
+    let de: SpannedResult<(i32, String)> = from_str("(4, \"Hello)");
+
+    assert!(matches!(
+        de,
+        Err(SpannedError {
+            code: Error::ExpectedStringEnd,
+            position: _,
+        })
+    ));
+}
+
+#[test]
+fn expected_attribute() {
+    let de: SpannedResult<String> = from_str("#\"Hello\"");
+
+    assert_eq!(de, err(Error::ExpectedAttribute, 1, 2));
+}
+
+#[test]
+fn expected_attribute_end() {
+    let de: SpannedResult<String> = from_str("#![enable(unwrap_newtypes) \"Hello\"");
+
+    assert_eq!(de, err(Error::ExpectedAttributeEnd, 1, 28));
+}
+
+#[test]
+fn invalid_attribute() {
+    let de: SpannedResult<String> = from_str("#![enable(invalid)] \"Hello\"");
+
+    assert_eq!(
+        de,
+        err(Error::NoSuchExtension("invalid".to_string()), 1, 18)
+    );
+}
+
+#[test]
+fn multiple_attributes() {
+    #[derive(Debug, Deserialize, PartialEq)]
+    struct New(String);
+    let de: SpannedResult<New> =
+        from_str("#![enable(unwrap_newtypes)] #![enable(unwrap_newtypes)] \"Hello\"");
+
+    assert_eq!(de, Ok(New("Hello".to_owned())));
+}
+
+#[test]
+fn uglified_attribute() {
+    let de: SpannedResult<()> = from_str(
+        "#   !\
+    // We definitely want to add a comment here
+    [\t\tenable( // best style ever
+            unwrap_newtypes  ) ] ()",
+    );
+
+    assert_eq!(de, Ok(()));
+}
+
+#[test]
+fn implicit_some() {
+    use serde::de::DeserializeOwned;
+
+    fn de<T: DeserializeOwned>(s: &str) -> Option<T> {
+        let enable = "#![enable(implicit_some)]\n".to_string();
+
+        from_str::<Option<T>>(&(enable + s)).unwrap()
+    }
+
+    assert_eq!(de("'c'"), Some('c'));
+    assert_eq!(de("5"), Some(5));
+    assert_eq!(de("\"Hello\""), Some("Hello".to_owned()));
+    assert_eq!(de("false"), Some(false));
+    assert_eq!(
+        de("MyStruct(x: .4, y: .5)"),
+        Some(MyStruct { x: 0.4, y: 0.5 })
+    );
+
+    assert_eq!(de::<char>("None"), None);
+
+    // Not concise
+    assert_eq!(de::<Option<Option<char>>>("None"), None);
+}
+
+#[test]
+fn ws_tuple_newtype_variant() {
+    assert_eq!(Ok(MyEnum::B(true)), from_str("B  ( \n true \n ) "));
+}
+
+#[test]
+fn test_byte_stream() {
+    assert_eq!(
+        Ok(BytesStruct {
+            small: vec![1, 2],
+            large: vec![1, 2, 3, 4]
+        }),
+        from_str("BytesStruct( small:[1, 2], large:\"AQIDBA==\" )"),
+    );
+}
+
+#[test]
+fn test_numbers() {
+    assert_eq!(
+        Ok(vec![1234, 12345, 123456, 1234567, 555_555]),
+        from_str("[1_234, 12_345, 1_2_3_4_5_6, 1_234_567, 5_55_55_5]"),
+    );
+}
+
+fn de_any_number(s: &str) -> AnyNum {
+    let mut bytes = Bytes::new(s.as_bytes()).unwrap();
+
+    bytes.any_num().unwrap()
+}
+
+#[test]
+fn test_any_number_precision() {
+    assert_eq!(de_any_number("1"), AnyNum::U8(1));
+    assert_eq!(de_any_number("+1"), AnyNum::I8(1));
+    assert_eq!(de_any_number("-1"), AnyNum::I8(-1));
+    assert_eq!(de_any_number("-1.0"), AnyNum::F32(-1.0));
+    assert_eq!(de_any_number("1."), AnyNum::F32(1.));
+    assert_eq!(de_any_number("-1."), AnyNum::F32(-1.));
+    assert_eq!(de_any_number("0.3"), AnyNum::F64(0.3));
+}
diff --git a/third_party/rust/ron/src/de/value.rs b/third_party/rust/ron/src/de/value.rs
new file mode 100644
index 0000000000..5883a37adc
--- /dev/null
+++ b/third_party/rust/ron/src/de/value.rs
@@ -0,0 +1,338 @@
+use std::fmt;
+
+use serde::{
+    de::{Error, MapAccess, SeqAccess, Visitor},
+    Deserialize, Deserializer,
+};
+
+use crate::{
+    error::SpannedResult,
+    value::{Map, Number, Value},
+};
+
+impl std::str::FromStr for Value {
+    type Err = crate::error::SpannedError;
+
+    /// Creates a value from a string reference.
+    fn from_str(s: &str) -> SpannedResult<Self> {
+        let mut de = super::Deserializer::from_str(s)?;
+
+        let val = Value::deserialize(&mut de).map_err(|e| de.span_error(e))?;
+        de.end().map_err(|e| de.span_error(e))?;
+
+        Ok(val)
+    }
+}
+
+impl<'de> Deserialize<'de> for Value {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        deserializer.deserialize_any(ValueVisitor)
+    }
+}
+
+struct ValueVisitor;
+
+impl<'de> Visitor<'de> for ValueVisitor {
+    type Value = Value;
+
+    fn expecting(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "a RON value")
+    }
+
+    fn visit_bool<E>(self, v: bool) -> Result<Self::Value, E>
+    where
+        E: Error,
+    {
+        Ok(Value::Bool(v))
+    }
+
+    fn visit_i64<E>(self, v: i64) -> Result<Self::Value, E>
+    where
+        E: Error,
+    {
+        Ok(Value::Number(Number::new(v)))
+    }
+
+    #[cfg(feature = "integer128")]
+    fn visit_i128<E>(self, v: i128) -> Result<Self::Value, E>
+    where
+        E: Error,
+    {
+        self.visit_f64(v as f64)
+    }
+
+    fn visit_u64<E>(self, v: u64) -> Result<Self::Value, E>
+    where
+        E: Error,
+    {
+        Ok(Value::Number(Number::new(v)))
+    }
+
+    #[cfg(feature = "integer128")]
+    fn visit_u128<E>(self, v: u128) -> Result<Self::Value, E>
+    where
+        E: Error,
+    {
+        self.visit_f64(v as f64)
+    }
+
+    fn visit_f64<E>(self, v: f64) -> Result<Self::Value, E>
+    where
+        E: Error,
+    {
+        Ok(Value::Number(Number::new(v)))
+    }
+
+    fn visit_char<E>(self, v: char) -> Result<Self::Value, E>
+    where
+        E: Error,
+    {
+        Ok(Value::Char(v))
+    }
+
+    fn visit_str<E>(self, v: &str) -> Result<Self::Value, E>
+    where
+        E: Error,
+    {
+        self.visit_string(v.to_owned())
+    }
+
+    fn visit_string<E>(self, v: String) -> Result<Self::Value, E>
+    where
+        E: Error,
+    {
+        Ok(Value::String(v))
+    }
+
+    fn visit_bytes<E>(self, v: &[u8]) -> Result<Self::Value, E>
+    where
+        E: Error,
+    {
+        self.visit_byte_buf(v.to_vec())
+    }
+
+    fn visit_byte_buf<E>(self, v: Vec<u8>) -> Result<Self::Value, E>
+    where
+        E: Error,
+    {
+        self.visit_string(String::from_utf8(v).map_err(|e| Error::custom(format!("{}", e)))?)
+    }
+
+    fn visit_none<E>(self) -> Result<Self::Value, E>
+    where
+        E: Error,
+    {
+        Ok(Value::Option(None))
+    }
+
+    fn visit_some<D>(self, deserializer: D) -> Result<Self::Value, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        Ok(Value::Option(Some(Box::new(
+            deserializer.deserialize_any(ValueVisitor)?,
+        ))))
+    }
+
+    fn visit_unit<E>(self) -> Result<Self::Value, E>
+    where
+        E: Error,
+    {
+        Ok(Value::Unit)
+    }
+
+    fn visit_newtype_struct<D>(self, deserializer: D) -> Result<Self::Value, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        deserializer.deserialize_any(ValueVisitor)
+    }
+
+    fn visit_seq<A>(self, mut seq: A) -> Result<Self::Value, A::Error>
+    where
+        A: SeqAccess<'de>,
+    {
+        let mut vec = Vec::new();
+        if let Some(cap) = seq.size_hint() {
+            vec.reserve_exact(cap);
+        }
+
+        while let Some(x) = seq.next_element()? {
+            vec.push(x);
+        }
+
+        Ok(Value::Seq(vec))
+    }
+
+    fn visit_map<A>(self, mut map: A) -> Result<Self::Value, A::Error>
+    where
+        A: MapAccess<'de>,
+    {
+        let mut res: Map = Map::new();
+
+        while let Some(entry) = map.next_entry()? {
+            res.insert(entry.0, entry.1);
+        }
+
+        Ok(Value::Map(res))
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use std::str::FromStr;
+
+    use super::*;
+
+    fn eval(s: &str) -> Value {
+        s.parse().expect("Failed to parse")
+    }
+
+    #[test]
+    fn test_none() {
+        assert_eq!(eval("None"), Value::Option(None));
+    }
+
+    #[test]
+    fn test_some() {
+        assert_eq!(eval("Some(())"), Value::Option(Some(Box::new(Value::Unit))));
+        assert_eq!(
+            eval("Some  (  () )"),
+            Value::Option(Some(Box::new(Value::Unit)))
+        );
+    }
+
+    #[test]
+    fn test_tuples_basic() {
+        assert_eq!(
+            eval("(3, 4.0, 5.0)"),
+            Value::Seq(vec![
+                Value::Number(Number::new(3)),
+                Value::Number(Number::new(4.0)),
+                Value::Number(Number::new(5.0)),
+            ],),
+        );
+    }
+
+    #[test]
+    fn test_tuples_ident() {
+        assert_eq!(
+            eval("(true, 3, 4, 5.0)"),
+            Value::Seq(vec![
+                Value::Bool(true),
+                Value::Number(Number::new(3)),
+                Value::Number(Number::new(4)),
+                Value::Number(Number::new(5.0)),
+            ]),
+        );
+    }
+
+    #[test]
+    fn test_tuples_error() {
+        use crate::de::{Error, Position, SpannedError};
+
+        assert_eq!(
+            Value::from_str("Foo:").unwrap_err(),
+            SpannedError {
+                code: Error::TrailingCharacters,
+                position: Position { col: 4, line: 1 }
+            },
+        );
+    }
+
+    #[test]
+    fn test_floats() {
+        assert_eq!(
+            eval("(inf, -inf, NaN)"),
+            Value::Seq(vec![
+                Value::Number(Number::new(std::f64::INFINITY)),
+                Value::Number(Number::new(std::f64::NEG_INFINITY)),
+                Value::Number(Number::new(std::f64::NAN)),
+            ]),
+        );
+    }
+
+    #[test]
+    fn test_complex() {
+        assert_eq!(
+            eval(
+                "Some([
+    Room ( width: 20, height: 5, name: \"The Room\" ),
+
+    (
+        width: 10.0,
+        height: 10.0,
+        name: \"Another room\",
+        enemy_levels: {
+            \"Enemy1\": 3,
+            \"Enemy2\": 5,
+            \"Enemy3\": 7,
+        },
+    ),
+])"
+            ),
+            Value::Option(Some(Box::new(Value::Seq(vec![
+                Value::Map(
+                    vec![
+                        (
+                            Value::String("width".to_owned()),
+                            Value::Number(Number::new(20)),
+                        ),
+                        (
+                            Value::String("height".to_owned()),
+                            Value::Number(Number::new(5)),
+                        ),
+                        (
+                            Value::String("name".to_owned()),
+                            Value::String("The Room".to_owned()),
+                        ),
+                    ]
+                    .into_iter()
+                    .collect(),
+                ),
+                Value::Map(
+                    vec![
+                        (
+                            Value::String("width".to_owned()),
+                            Value::Number(Number::new(10.0)),
+                        ),
+                        (
+                            Value::String("height".to_owned()),
+                            Value::Number(Number::new(10.0)),
+                        ),
+                        (
+                            Value::String("name".to_owned()),
+                            Value::String("Another room".to_owned()),
+                        ),
+                        (
+                            Value::String("enemy_levels".to_owned()),
+                            Value::Map(
+                                vec![
+                                    (
+                                        Value::String("Enemy1".to_owned()),
+                                        Value::Number(Number::new(3)),
+                                    ),
+                                    (
+                                        Value::String("Enemy2".to_owned()),
+                                        Value::Number(Number::new(5)),
+                                    ),
+                                    (
+                                        Value::String("Enemy3".to_owned()),
+                                        Value::Number(Number::new(7)),
+                                    ),
+                                ]
+                                .into_iter()
+                                .collect(),
+                            ),
+                        ),
+                    ]
+                    .into_iter()
+                    .collect(),
+                ),
+            ]))))
+        );
+    }
+}
diff --git a/third_party/rust/ron/src/error.rs b/third_party/rust/ron/src/error.rs
new file mode 100644
index 0000000000..406fb058c3
--- /dev/null
+++ b/third_party/rust/ron/src/error.rs
@@ -0,0 +1,445 @@
+use std::{error::Error as StdError, fmt, io, str::Utf8Error, string::FromUtf8Error};
+
+use serde::{de, ser};
+
+use crate::parse::{is_ident_first_char, is_ident_other_char, is_ident_raw_char, BASE64_ENGINE};
+
+/// This type represents all possible errors that can occur when
+/// serializing or deserializing RON data.
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct SpannedError {
+    pub code: Error,
+    pub position: Position,
+}
+
+pub type Result<T, E = Error> = std::result::Result<T, E>;
+pub type SpannedResult<T> = std::result::Result<T, SpannedError>;
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+#[non_exhaustive]
+pub enum Error {
+    Io(String),
+    Message(String),
+    Base64Error(base64::DecodeError),
+    Eof,
+    ExpectedArray,
+    ExpectedArrayEnd,
+    ExpectedAttribute,
+    ExpectedAttributeEnd,
+    ExpectedBoolean,
+    ExpectedComma,
+    ExpectedChar,
+    ExpectedFloat,
+    FloatUnderscore,
+    ExpectedInteger,
+    ExpectedOption,
+    ExpectedOptionEnd,
+    ExpectedMap,
+    ExpectedMapColon,
+    ExpectedMapEnd,
+    ExpectedDifferentStructName {
+        expected: &'static str,
+        found: String,
+    },
+    ExpectedStructLike,
+    ExpectedNamedStructLike(&'static str),
+    ExpectedStructLikeEnd,
+    ExpectedUnit,
+    ExpectedString,
+    ExpectedStringEnd,
+    ExpectedIdentifier,
+
+    InvalidEscape(&'static str),
+
+    IntegerOutOfBounds,
+
+    NoSuchExtension(String),
+
+    UnclosedBlockComment,
+    UnderscoreAtBeginning,
+    UnexpectedByte(char),
+
+    Utf8Error(Utf8Error),
+    TrailingCharacters,
+
+    InvalidValueForType {
+        expected: String,
+        found: String,
+    },
+    ExpectedDifferentLength {
+        expected: String,
+        found: usize,
+    },
+    NoSuchEnumVariant {
+        expected: &'static [&'static str],
+        found: String,
+        outer: Option<String>,
+    },
+    NoSuchStructField {
+        expected: &'static [&'static str],
+        found: String,
+        outer: Option<String>,
+    },
+    MissingStructField {
+        field: &'static str,
+        outer: Option<String>,
+    },
+    DuplicateStructField {
+        field: &'static str,
+        outer: Option<String>,
+    },
+    InvalidIdentifier(String),
+    SuggestRawIdentifier(String),
+    ExceededRecursionLimit,
+}
+
+impl fmt::Display for SpannedError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        if (self.position == Position { line: 0, col: 0 }) {
+            write!(f, "{}", self.code)
+        } else {
+            write!(f, "{}: {}", self.position, self.code)
+        }
+    }
+}
+
+impl fmt::Display for Error {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match *self {
+            Error::Io(ref s) => f.write_str(s),
+            Error::Message(ref s) => f.write_str(s),
+            Error::Base64Error(ref e) => fmt::Display::fmt(e, f),
+            Error::Eof => f.write_str("Unexpected end of RON"),
+            Error::ExpectedArray => f.write_str("Expected opening `[`"),
+            Error::ExpectedArrayEnd => f.write_str("Expected closing `]`"),
+            Error::ExpectedAttribute => f.write_str("Expected an `#![enable(...)]` attribute"),
+            Error::ExpectedAttributeEnd => {
+                f.write_str("Expected closing `)]` after the enable attribute")
+            }
+            Error::ExpectedBoolean => f.write_str("Expected boolean"),
+            Error::ExpectedComma => f.write_str("Expected comma"),
+            Error::ExpectedChar => f.write_str("Expected char"),
+            Error::ExpectedFloat => f.write_str("Expected float"),
+            Error::FloatUnderscore => f.write_str("Unexpected underscore in float"),
+            Error::ExpectedInteger => f.write_str("Expected integer"),
+            Error::ExpectedOption => f.write_str("Expected option"),
+            Error::ExpectedOptionEnd => f.write_str("Expected closing `)`"),
+            Error::ExpectedMap => f.write_str("Expected opening `{`"),
+            Error::ExpectedMapColon => f.write_str("Expected colon"),
+            Error::ExpectedMapEnd => f.write_str("Expected closing `}`"),
+            Error::ExpectedDifferentStructName {
+                expected,
+                ref found,
+            } => write!(
+                f,
+                "Expected struct {} but found {}",
+                Identifier(expected),
+                Identifier(found)
+            ),
+            Error::ExpectedStructLike => f.write_str("Expected opening `(`"),
+            Error::ExpectedNamedStructLike(name) => {
+                if name.is_empty() {
+                    f.write_str("Expected only opening `(`, no name, for un-nameable struct")
+                } else {
+                    write!(f, "Expected opening `(` for struct {}", Identifier(name))
+                }
+            }
+            Error::ExpectedStructLikeEnd => f.write_str("Expected closing `)`"),
+            Error::ExpectedUnit => f.write_str("Expected unit"),
+            Error::ExpectedString => f.write_str("Expected string"),
+            Error::ExpectedStringEnd => f.write_str("Expected end of string"),
+            Error::ExpectedIdentifier => f.write_str("Expected identifier"),
+            Error::InvalidEscape(s) => f.write_str(s),
+            Error::IntegerOutOfBounds => f.write_str("Integer is out of bounds"),
+            Error::NoSuchExtension(ref name) => {
+                write!(f, "No RON extension named {}", Identifier(name))
+            }
+            Error::Utf8Error(ref e) => fmt::Display::fmt(e, f),
+            Error::UnclosedBlockComment => f.write_str("Unclosed block comment"),
+            Error::UnderscoreAtBeginning => {
+                f.write_str("Unexpected leading underscore in an integer")
+            }
+            Error::UnexpectedByte(ref byte) => write!(f, "Unexpected byte {:?}", byte),
+            Error::TrailingCharacters => f.write_str("Non-whitespace trailing characters"),
+            Error::InvalidValueForType {
+                ref expected,
+                ref found,
+            } => {
+                write!(f, "Expected {} but found {} instead", expected, found)
+            }
+            Error::ExpectedDifferentLength {
+                ref expected,
+                found,
+            } => {
+                write!(f, "Expected {} but found ", expected)?;
+
+                match found {
+                    0 => f.write_str("zero elements")?,
+                    1 => f.write_str("one element")?,
+                    n => write!(f, "{} elements", n)?,
+                }
+
+                f.write_str(" instead")
+            }
+            Error::NoSuchEnumVariant {
+                expected,
+                ref found,
+                ref outer,
+            } => {
+                f.write_str("Unexpected ")?;
+
+                if outer.is_none() {
+                    f.write_str("enum ")?;
+                }
+
+                write!(f, "variant named {}", Identifier(found))?;
+
+                if let Some(outer) = outer {
+                    write!(f, "in enum {}", Identifier(outer))?;
+                }
+
+                write!(
+                    f,
+                    ", {}",
+                    OneOf {
+                        alts: expected,
+                        none: "variants"
+                    }
+                )
+            }
+            Error::NoSuchStructField {
+                expected,
+                ref found,
+                ref outer,
+            } => {
+                write!(f, "Unexpected field named {}", Identifier(found))?;
+
+                if let Some(outer) = outer {
+                    write!(f, "in {}", Identifier(outer))?;
+                }
+
+                write!(
+                    f,
+                    ", {}",
+                    OneOf {
+                        alts: expected,
+                        none: "fields"
+                    }
+                )
+            }
+            Error::MissingStructField { field, ref outer } => {
+                write!(f, "Unexpected missing field {}", Identifier(field))?;
+
+                match outer {
+                    Some(outer) => write!(f, " in {}", Identifier(outer)),
+                    None => Ok(()),
+                }
+            }
+            Error::DuplicateStructField { field, ref outer } => {
+                write!(f, "Unexpected duplicate field {}", Identifier(field))?;
+
+                match outer {
+                    Some(outer) => write!(f, " in {}", Identifier(outer)),
+                    None => Ok(()),
+                }
+            }
+            Error::InvalidIdentifier(ref invalid) => write!(f, "Invalid identifier {:?}", invalid),
+            Error::SuggestRawIdentifier(ref identifier) => write!(
+                f,
+                "Found invalid std identifier `{}`, try the raw identifier `r#{}` instead",
+                identifier, identifier
+            ),
+            Error::ExceededRecursionLimit => f.write_str("Exceeded recursion limit, try increasing the limit and using `serde_stacker` to protect against a stack overflow"),
+        }
+    }
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct Position {
+    pub line: usize,
+    pub col: usize,
+}
+
+impl fmt::Display for Position {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "{}:{}", self.line, self.col)
+    }
+}
+
+impl ser::Error for Error {
+    #[cold]
+    fn custom<T: fmt::Display>(msg: T) -> Self {
+        Error::Message(msg.to_string())
+    }
+}
+
+impl de::Error for Error {
+    #[cold]
+    fn custom<T: fmt::Display>(msg: T) -> Self {
+        Error::Message(msg.to_string())
+    }
+
+    #[cold]
+    fn invalid_type(unexp: de::Unexpected, exp: &dyn de::Expected) -> Self {
+        // Invalid type and invalid value are merged given their similarity in ron
+        Self::invalid_value(unexp, exp)
+    }
+
+    #[cold]
+    fn invalid_value(unexp: de::Unexpected, exp: &dyn de::Expected) -> Self {
+        struct UnexpectedSerdeTypeValue<'a>(de::Unexpected<'a>);
+
+        impl<'a> fmt::Display for UnexpectedSerdeTypeValue<'a> {
+            fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+                use de::Unexpected::*;
+
+                match self.0 {
+                    Bool(b) => write!(f, "the boolean `{}`", b),
+                    Unsigned(i) => write!(f, "the unsigned integer `{}`", i),
+                    Signed(i) => write!(f, "the signed integer `{}`", i),
+                    Float(n) => write!(f, "the floating point number `{}`", n),
+                    Char(c) => write!(f, "the UTF-8 character `{}`", c),
+                    Str(s) => write!(f, "the string {:?}", s),
+                    Bytes(b) => write!(f, "the bytes \"{}\"", {
+                        base64::display::Base64Display::new(b, &BASE64_ENGINE)
+                    }),
+                    Unit => write!(f, "a unit value"),
+                    Option => write!(f, "an optional value"),
+                    NewtypeStruct => write!(f, "a newtype struct"),
+                    Seq => write!(f, "a sequence"),
+                    Map => write!(f, "a map"),
+                    Enum => write!(f, "an enum"),
+                    UnitVariant => write!(f, "a unit variant"),
+                    NewtypeVariant => write!(f, "a newtype variant"),
+                    TupleVariant => write!(f, "a tuple variant"),
+                    StructVariant => write!(f, "a struct variant"),
+                    Other(other) => f.write_str(other),
+                }
+            }
+        }
+
+        Error::InvalidValueForType {
+            expected: exp.to_string(),
+            found: UnexpectedSerdeTypeValue(unexp).to_string(),
+        }
+    }
+
+    #[cold]
+    fn invalid_length(len: usize, exp: &dyn de::Expected) -> Self {
+        Error::ExpectedDifferentLength {
+            expected: exp.to_string(),
+            found: len,
+        }
+    }
+
+    #[cold]
+    fn unknown_variant(variant: &str, expected: &'static [&'static str]) -> Self {
+        Error::NoSuchEnumVariant {
+            expected,
+            found: variant.to_string(),
+            outer: None,
+        }
+    }
+
+    #[cold]
+    fn unknown_field(field: &str, expected: &'static [&'static str]) -> Self {
+        Error::NoSuchStructField {
+            expected,
+            found: field.to_string(),
+            outer: None,
+        }
+    }
+
+    #[cold]
+    fn missing_field(field: &'static str) -> Self {
+        Error::MissingStructField { field, outer: None }
+    }
+
+    #[cold]
+    fn duplicate_field(field: &'static str) -> Self {
+        Error::DuplicateStructField { field, outer: None }
+    }
+}
+
+impl StdError for SpannedError {}
+impl StdError for Error {}
+
+impl From<Utf8Error> for Error {
+    fn from(e: Utf8Error) -> Self {
+        Error::Utf8Error(e)
+    }
+}
+
+impl From<FromUtf8Error> for Error {
+    fn from(e: FromUtf8Error) -> Self {
+        Error::Utf8Error(e.utf8_error())
+    }
+}
+
+impl From<io::Error> for Error {
+    fn from(e: io::Error) -> Self {
+        Error::Io(e.to_string())
+    }
+}
+
+impl From<io::Error> for SpannedError {
+    fn from(e: io::Error) -> Self {
+        SpannedError {
+            code: e.into(),
+            position: Position { line: 0, col: 0 },
+        }
+    }
+}
+
+impl From<SpannedError> for Error {
+    fn from(e: SpannedError) -> Self {
+        e.code
+    }
+}
+
+struct OneOf {
+    alts: &'static [&'static str],
+    none: &'static str,
+}
+
+impl fmt::Display for OneOf {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self.alts {
+            [] => write!(f, "there are no {}", self.none),
+            [a1] => write!(f, "expected {} instead", Identifier(a1)),
+            [a1, a2] => write!(
+                f,
+                "expected either {} or {} instead",
+                Identifier(a1),
+                Identifier(a2)
+            ),
+            [a1, ref alts @ ..] => {
+                write!(f, "expected one of {}", Identifier(a1))?;
+
+                for alt in alts {
+                    write!(f, ", {}", Identifier(alt))?;
+                }
+
+                f.write_str(" instead")
+            }
+        }
+    }
+}
+
+struct Identifier<'a>(&'a str);
+
+impl<'a> fmt::Display for Identifier<'a> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        if self.0.is_empty() || !self.0.as_bytes().iter().copied().all(is_ident_raw_char) {
+            return write!(f, "{:?}_[invalid identifier]", self.0);
+        }
+
+        let mut bytes = self.0.as_bytes().iter().copied();
+
+        if !bytes.next().map_or(false, is_ident_first_char) || !bytes.all(is_ident_other_char) {
+            write!(f, "`r#{}`", self.0)
+        } else {
+            write!(f, "`{}`", self.0)
+        }
+    }
+}
diff --git a/third_party/rust/ron/src/extensions.rs b/third_party/rust/ron/src/extensions.rs
new file mode 100644
index 0000000000..0455a34dd3
--- /dev/null
+++ b/third_party/rust/ron/src/extensions.rs
@@ -0,0 +1,55 @@
+use serde_derive::{Deserialize, Serialize};
+
+bitflags::bitflags! {
+    #[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Serialize, Deserialize)]
+    pub struct Extensions: usize {
+        const UNWRAP_NEWTYPES = 0x1;
+        const IMPLICIT_SOME = 0x2;
+        const UNWRAP_VARIANT_NEWTYPES = 0x4;
+    }
+}
+
+impl Extensions {
+    /// Creates an extension flag from an ident.
+    pub fn from_ident(ident: &[u8]) -> Option<Extensions> {
+        match ident {
+            b"unwrap_newtypes" => Some(Extensions::UNWRAP_NEWTYPES),
+            b"implicit_some" => Some(Extensions::IMPLICIT_SOME),
+            b"unwrap_variant_newtypes" => Some(Extensions::UNWRAP_VARIANT_NEWTYPES),
+            _ => None,
+        }
+    }
+}
+
+impl Default for Extensions {
+    fn default() -> Self {
+        Extensions::empty()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Extensions;
+
+    fn roundtrip_extensions(ext: Extensions) {
+        let ron = crate::to_string(&ext).unwrap();
+        let ext2: Extensions = crate::from_str(&ron).unwrap();
+        assert_eq!(ext, ext2);
+    }
+
+    #[test]
+    fn test_extension_serde() {
+        roundtrip_extensions(Extensions::default());
+        roundtrip_extensions(Extensions::UNWRAP_NEWTYPES);
+        roundtrip_extensions(Extensions::IMPLICIT_SOME);
+        roundtrip_extensions(Extensions::UNWRAP_VARIANT_NEWTYPES);
+        roundtrip_extensions(Extensions::UNWRAP_NEWTYPES | Extensions::IMPLICIT_SOME);
+        roundtrip_extensions(Extensions::UNWRAP_NEWTYPES | Extensions::UNWRAP_VARIANT_NEWTYPES);
+        roundtrip_extensions(Extensions::IMPLICIT_SOME | Extensions::UNWRAP_VARIANT_NEWTYPES);
+        roundtrip_extensions(
+            Extensions::UNWRAP_NEWTYPES
+                | Extensions::IMPLICIT_SOME
+                | Extensions::UNWRAP_VARIANT_NEWTYPES,
+        );
+    }
+}
diff --git a/third_party/rust/ron/src/lib.rs b/third_party/rust/ron/src/lib.rs
new file mode 100644
index 0000000000..638af2cb07
--- /dev/null
+++ b/third_party/rust/ron/src/lib.rs
@@ -0,0 +1,20 @@
+#![doc = include_str!("../README.md")]
+#![doc(html_root_url = "https://docs.rs/ron/0.8.1")]
+
+pub mod de;
+pub mod ser;
+
+pub mod error;
+pub mod value;
+
+pub mod extensions;
+
+pub mod options;
+
+pub use de::{from_str, Deserializer};
+pub use error::{Error, Result};
+pub use options::Options;
+pub use ser::{to_string, Serializer};
+pub use value::{Map, Number, Value};
+
+mod parse;
diff --git a/third_party/rust/ron/src/options.rs b/third_party/rust/ron/src/options.rs
new file mode 100644
index 0000000000..b0c5816bd4
--- /dev/null
+++ b/third_party/rust/ron/src/options.rs
@@ -0,0 +1,215 @@
+//! Roundtrip serde Options module.
+
+use std::io;
+
+use serde::{de, ser};
+use serde_derive::{Deserialize, Serialize};
+
+use crate::{
+    de::Deserializer,
+    error::{Result, SpannedResult},
+    extensions::Extensions,
+    ser::{PrettyConfig, Serializer},
+};
+
+/// Roundtrip serde options.
+///
+/// # Examples
+///
+/// ```
+/// use ron::{Options, extensions::Extensions};
+///
+/// let ron = Options::default()
+///     .with_default_extension(Extensions::IMPLICIT_SOME);
+///
+/// let de: Option<i32> = ron.from_str("42").unwrap();
+/// let ser = ron.to_string(&de).unwrap();
+///
+/// assert_eq!(ser, "42");
+/// ```
+#[derive(Clone, Debug, Serialize, Deserialize)]
+#[serde(default)]
+#[non_exhaustive]
+pub struct Options {
+    /// Extensions that are enabled by default during serialization and
+    ///  deserialization.
+    /// During serialization, these extensions do NOT have to be explicitly
+    ///  enabled in the parsed RON.
+    /// During deserialization, these extensions are used, but their explicit
+    ///  activation is NOT included in the output RON.
+    /// No extensions are enabled by default.
+    pub default_extensions: Extensions,
+    /// Default recursion limit that is checked during serialization and
+    ///  deserialization.
+    /// If set to `None`, infinite recursion is allowed and stack overflow
+    ///  errors can crash the serialization or deserialization process.
+    /// Defaults to `Some(128)`, i.e. 128 recursive calls are allowed.
+    pub recursion_limit: Option<usize>,
+}
+
+impl Default for Options {
+    fn default() -> Self {
+        Self {
+            default_extensions: Extensions::empty(),
+            recursion_limit: Some(128),
+        }
+    }
+}
+
+impl Options {
+    #[must_use]
+    /// Enable `default_extension` by default during serialization and deserialization.
+    pub fn with_default_extension(mut self, default_extension: Extensions) -> Self {
+        self.default_extensions |= default_extension;
+        self
+    }
+
+    #[must_use]
+    /// Do NOT enable `default_extension` by default during serialization and deserialization.
+    pub fn without_default_extension(mut self, default_extension: Extensions) -> Self {
+        self.default_extensions &= !default_extension;
+        self
+    }
+
+    #[must_use]
+    /// Set a maximum recursion limit during serialization and deserialization.
+    pub fn with_recursion_limit(mut self, recursion_limit: usize) -> Self {
+        self.recursion_limit = Some(recursion_limit);
+        self
+    }
+
+    #[must_use]
+    /// Disable the recursion limit during serialization and deserialization.
+    ///
+    /// If you expect to handle highly recursive datastructures, consider wrapping
+    /// `ron` with [`serde_stacker`](https://docs.rs/serde_stacker/latest/serde_stacker/).
+    pub fn without_recursion_limit(mut self) -> Self {
+        self.recursion_limit = None;
+        self
+    }
+}
+
+impl Options {
+    /// A convenience function for building a deserializer
+    /// and deserializing a value of type `T` from a reader.
+    pub fn from_reader<R, T>(&self, mut rdr: R) -> SpannedResult<T>
+    where
+        R: io::Read,
+        T: de::DeserializeOwned,
+    {
+        let mut bytes = Vec::new();
+        rdr.read_to_end(&mut bytes)?;
+
+        self.from_bytes(&bytes)
+    }
+
+    /// A convenience function for building a deserializer
+    /// and deserializing a value of type `T` from a string.
+    pub fn from_str<'a, T>(&self, s: &'a str) -> SpannedResult<T>
+    where
+        T: de::Deserialize<'a>,
+    {
+        self.from_bytes(s.as_bytes())
+    }
+
+    /// A convenience function for building a deserializer
+    /// and deserializing a value of type `T` from bytes.
+    pub fn from_bytes<'a, T>(&self, s: &'a [u8]) -> SpannedResult<T>
+    where
+        T: de::Deserialize<'a>,
+    {
+        self.from_bytes_seed(s, std::marker::PhantomData)
+    }
+
+    /// A convenience function for building a deserializer
+    /// and deserializing a value of type `T` from a reader
+    /// and a seed.
+    pub fn from_reader_seed<R, S, T>(&self, mut rdr: R, seed: S) -> SpannedResult<T>
+    where
+        R: io::Read,
+        S: for<'a> de::DeserializeSeed<'a, Value = T>,
+    {
+        let mut bytes = Vec::new();
+        rdr.read_to_end(&mut bytes)?;
+
+        self.from_bytes_seed(&bytes, seed)
+    }
+
+    /// A convenience function for building a deserializer
+    /// and deserializing a value of type `T` from a string
+    /// and a seed.
+    pub fn from_str_seed<'a, S, T>(&self, s: &'a str, seed: S) -> SpannedResult<T>
+    where
+        S: de::DeserializeSeed<'a, Value = T>,
+    {
+        self.from_bytes_seed(s.as_bytes(), seed)
+    }
+
+    /// A convenience function for building a deserializer
+    /// and deserializing a value of type `T` from bytes
+    /// and a seed.
+    pub fn from_bytes_seed<'a, S, T>(&self, s: &'a [u8], seed: S) -> SpannedResult<T>
+    where
+        S: de::DeserializeSeed<'a, Value = T>,
+    {
+        let mut deserializer = Deserializer::from_bytes_with_options(s, self.clone())?;
+
+        let value = seed
+            .deserialize(&mut deserializer)
+            .map_err(|e| deserializer.span_error(e))?;
+
+        deserializer.end().map_err(|e| deserializer.span_error(e))?;
+
+        Ok(value)
+    }
+
+    /// Serializes `value` into `writer`.
+    ///
+    /// This function does not generate any newlines or nice formatting;
+    /// if you want that, you can use
+    /// [`to_writer_pretty`][Self::to_writer_pretty] instead.
+    pub fn to_writer<W, T>(&self, writer: W, value: &T) -> Result<()>
+    where
+        W: io::Write,
+        T: ?Sized + ser::Serialize,
+    {
+        let mut s = Serializer::with_options(writer, None, self.clone())?;
+        value.serialize(&mut s)
+    }
+
+    /// Serializes `value` into `writer` in a pretty way.
+    pub fn to_writer_pretty<W, T>(&self, writer: W, value: &T, config: PrettyConfig) -> Result<()>
+    where
+        W: io::Write,
+        T: ?Sized + ser::Serialize,
+    {
+        let mut s = Serializer::with_options(writer, Some(config), self.clone())?;
+        value.serialize(&mut s)
+    }
+
+    /// Serializes `value` and returns it as string.
+    ///
+    /// This function does not generate any newlines or nice formatting;
+    /// if you want that, you can use
+    /// [`to_string_pretty`][Self::to_string_pretty] instead.
+    pub fn to_string<T>(&self, value: &T) -> Result<String>
+    where
+        T: ?Sized + ser::Serialize,
+    {
+        let mut output = Vec::new();
+        let mut s = Serializer::with_options(&mut output, None, self.clone())?;
+        value.serialize(&mut s)?;
+        Ok(String::from_utf8(output).expect("Ron should be utf-8"))
+    }
+
+    /// Serializes `value` in the recommended RON layout in a pretty way.
+    pub fn to_string_pretty<T>(&self, value: &T, config: PrettyConfig) -> Result<String>
+    where
+        T: ?Sized + ser::Serialize,
+    {
+        let mut output = Vec::new();
+        let mut s = Serializer::with_options(&mut output, Some(config), self.clone())?;
+        value.serialize(&mut s)?;
+        Ok(String::from_utf8(output).expect("Ron should be utf-8"))
+    }
+}
diff --git a/third_party/rust/ron/src/parse.rs b/third_party/rust/ron/src/parse.rs
new file mode 100644
index 0000000000..bed7f44916
--- /dev/null
+++ b/third_party/rust/ron/src/parse.rs
@@ -0,0 +1,1008 @@
+#![allow(clippy::identity_op)]
+
+use std::{
+    char::from_u32 as char_from_u32,
+    str::{from_utf8, from_utf8_unchecked, FromStr},
+};
+
+use base64::engine::general_purpose::{GeneralPurpose, STANDARD};
+
+use crate::{
+    error::{Error, Position, Result, SpannedError, SpannedResult},
+    extensions::Extensions,
+};
+
+pub const BASE64_ENGINE: GeneralPurpose = STANDARD;
+
+// We have the following char categories.
+const INT_CHAR: u8 = 1 << 0; // [0-9A-Fa-f_]
+const FLOAT_CHAR: u8 = 1 << 1; // [0-9\.Ee+-_]
+const IDENT_FIRST_CHAR: u8 = 1 << 2; // [A-Za-z_]
+const IDENT_OTHER_CHAR: u8 = 1 << 3; // [A-Za-z_0-9]
+const IDENT_RAW_CHAR: u8 = 1 << 4; // [A-Za-z_0-9\.+-]
+const WHITESPACE_CHAR: u8 = 1 << 5; // [\n\t\r ]
+
+// We encode each char as belonging to some number of these categories.
+const DIGIT: u8 = INT_CHAR | FLOAT_CHAR | IDENT_OTHER_CHAR | IDENT_RAW_CHAR; // [0-9]
+const ABCDF: u8 = INT_CHAR | IDENT_FIRST_CHAR | IDENT_OTHER_CHAR | IDENT_RAW_CHAR; // [ABCDFabcdf]
+const UNDER: u8 = INT_CHAR | FLOAT_CHAR | IDENT_FIRST_CHAR | IDENT_OTHER_CHAR | IDENT_RAW_CHAR; // [_]
+const E____: u8 = INT_CHAR | FLOAT_CHAR | IDENT_FIRST_CHAR | IDENT_OTHER_CHAR | IDENT_RAW_CHAR; // [Ee]
+const G2Z__: u8 = IDENT_FIRST_CHAR | IDENT_OTHER_CHAR | IDENT_RAW_CHAR; // [G-Zg-z]
+const PUNCT: u8 = FLOAT_CHAR | IDENT_RAW_CHAR; // [\.+-]
+const WS___: u8 = WHITESPACE_CHAR; // [\t\n\r ]
+const _____: u8 = 0; // everything else
+
+// Table of encodings, for fast predicates. (Non-ASCII and special chars are
+// shown with '·' in the comment.)
+#[rustfmt::skip]
+const ENCODINGS: [u8; 256] = [
+/*                     0      1      2      3      4      5      6      7      8      9    */
+/*   0+: ·········· */ _____, _____, _____, _____, _____, _____, _____, _____, _____, WS___,
+/*  10+: ·········· */ WS___, _____, _____, WS___, _____, _____, _____, _____, _____, _____,
+/*  20+: ·········· */ _____, _____, _____, _____, _____, _____, _____, _____, _____, _____,
+/*  30+: ·· !"#$%&' */ _____, _____, WS___, _____, _____, _____, _____, _____, _____, _____,
+/*  40+: ()*+,-./01 */ _____, _____, _____, PUNCT, _____, PUNCT, PUNCT, _____, DIGIT, DIGIT,
+/*  50+: 23456789:; */ DIGIT, DIGIT, DIGIT, DIGIT, DIGIT, DIGIT, DIGIT, DIGIT, _____, _____,
+/*  60+: <=>?@ABCDE */ _____, _____, _____, _____, _____, ABCDF, ABCDF, ABCDF, ABCDF, E____,
+/*  70+: FGHIJKLMNO */ ABCDF, G2Z__, G2Z__, G2Z__, G2Z__, G2Z__, G2Z__, G2Z__, G2Z__, G2Z__,
+/*  80+: PQRSTUVWZY */ G2Z__, G2Z__, G2Z__, G2Z__, G2Z__, G2Z__, G2Z__, G2Z__, G2Z__, G2Z__,
+/*  90+: Z[\]^_`abc */ G2Z__, _____, _____, _____, _____, UNDER, _____, ABCDF, ABCDF, ABCDF,
+/* 100+: defghijklm */ ABCDF, E____, ABCDF, G2Z__, G2Z__, G2Z__, G2Z__, G2Z__, G2Z__, G2Z__,
+/* 110+: nopqrstuvw */ G2Z__, G2Z__, G2Z__, G2Z__, G2Z__, G2Z__, G2Z__, G2Z__, G2Z__, G2Z__,
+/* 120+: xyz{|}~··· */ G2Z__, G2Z__, G2Z__, _____, _____, _____, _____, _____, _____, _____,
+/* 130+: ·········· */ _____, _____, _____, _____, _____, _____, _____, _____, _____, _____,
+/* 140+: ·········· */ _____, _____, _____, _____, _____, _____, _____, _____, _____, _____,
+/* 150+: ·········· */ _____, _____, _____, _____, _____, _____, _____, _____, _____, _____,
+/* 160+: ·········· */ _____, _____, _____, _____, _____, _____, _____, _____, _____, _____,
+/* 170+: ·········· */ _____, _____, _____, _____, _____, _____, _____, _____, _____, _____,
+/* 180+: ·········· */ _____, _____, _____, _____, _____, _____, _____, _____, _____, _____,
+/* 190+: ·········· */ _____, _____, _____, _____, _____, _____, _____, _____, _____, _____,
+/* 200+: ·········· */ _____, _____, _____, _____, _____, _____, _____, _____, _____, _____,
+/* 210+: ·········· */ _____, _____, _____, _____, _____, _____, _____, _____, _____, _____,
+/* 220+: ·········· */ _____, _____, _____, _____, _____, _____, _____, _____, _____, _____,
+/* 230+: ·········· */ _____, _____, _____, _____, _____, _____, _____, _____, _____, _____,
+/* 240+: ·········· */ _____, _____, _____, _____, _____, _____, _____, _____, _____, _____,
+/* 250+: ·········· */ _____, _____, _____, _____, _____, _____
+];
+
+const fn is_int_char(c: u8) -> bool {
+    ENCODINGS[c as usize] & INT_CHAR != 0
+}
+
+const fn is_float_char(c: u8) -> bool {
+    ENCODINGS[c as usize] & FLOAT_CHAR != 0
+}
+
+pub const fn is_ident_first_char(c: u8) -> bool {
+    ENCODINGS[c as usize] & IDENT_FIRST_CHAR != 0
+}
+
+pub const fn is_ident_other_char(c: u8) -> bool {
+    ENCODINGS[c as usize] & IDENT_OTHER_CHAR != 0
+}
+
+pub const fn is_ident_raw_char(c: u8) -> bool {
+    ENCODINGS[c as usize] & IDENT_RAW_CHAR != 0
+}
+
+const fn is_whitespace_char(c: u8) -> bool {
+    ENCODINGS[c as usize] & WHITESPACE_CHAR != 0
+}
+
+#[derive(Clone, Debug, PartialEq)]
+pub enum AnyNum {
+    F32(f32),
+    F64(f64),
+    I8(i8),
+    U8(u8),
+    I16(i16),
+    U16(u16),
+    I32(i32),
+    U32(u32),
+    I64(i64),
+    U64(u64),
+    #[cfg(feature = "integer128")]
+    I128(i128),
+    #[cfg(feature = "integer128")]
+    U128(u128),
+}
+
+#[derive(Clone, Copy, Debug)]
+pub struct Bytes<'a> {
+    /// Bits set according to the [`Extensions`] enum.
+    pub exts: Extensions,
+    bytes: &'a [u8],
+    cursor: Position,
+}
+
+#[cfg(feature = "integer128")]
+pub(crate) type LargeUInt = u128;
+#[cfg(not(feature = "integer128"))]
+pub(crate) type LargeUInt = u64;
+#[cfg(feature = "integer128")]
+pub(crate) type LargeSInt = i128;
+#[cfg(not(feature = "integer128"))]
+pub(crate) type LargeSInt = i64;
+
+impl<'a> Bytes<'a> {
+    pub fn new(bytes: &'a [u8]) -> SpannedResult<Self> {
+        let mut b = Bytes {
+            exts: Extensions::empty(),
+            bytes,
+            cursor: Position { line: 1, col: 1 },
+        };
+
+        b.skip_ws().map_err(|e| b.span_error(e))?;
+
+        // Loop over all extensions attributes
+        loop {
+            let attribute = b.extensions().map_err(|e| b.span_error(e))?;
+
+            if attribute.is_empty() {
+                break;
+            }
+
+            b.exts |= attribute;
+            b.skip_ws().map_err(|e| b.span_error(e))?;
+        }
+
+        Ok(b)
+    }
+
+    pub fn span_error(&self, code: Error) -> SpannedError {
+        SpannedError {
+            code,
+            position: self.cursor,
+        }
+    }
+
+    pub fn advance(&mut self, bytes: usize) -> Result<()> {
+        for _ in 0..bytes {
+            self.advance_single()?;
+        }
+
+        Ok(())
+    }
+
+    pub fn advance_single(&mut self) -> Result<()> {
+        if self.peek_or_eof()? == b'\n' {
+            self.cursor.line += 1;
+            self.cursor.col = 1;
+        } else {
+            self.cursor.col += 1;
+        }
+
+        self.bytes = &self.bytes[1..];
+
+        Ok(())
+    }
+
+    fn any_integer<T: Num>(&mut self, sign: i8) -> Result<T> {
+        let base = if self.peek() == Some(b'0') {
+            match self.bytes.get(1).copied() {
+                Some(b'x') => 16,
+                Some(b'b') => 2,
+                Some(b'o') => 8,
+                _ => 10,
+            }
+        } else {
+            10
+        };
+
+        if base != 10 {
+            // If we have `0x45A` for example,
+            // cut it to `45A`.
+            let _ = self.advance(2);
+        }
+
+        let num_bytes = self.next_bytes_contained_in(is_int_char);
+
+        if num_bytes == 0 {
+            return Err(Error::ExpectedInteger);
+        }
+
+        let s = unsafe { from_utf8_unchecked(&self.bytes[0..num_bytes]) };
+
+        if s.as_bytes()[0] == b'_' {
+            return Err(Error::UnderscoreAtBeginning);
+        }
+
+        fn calc_num<T: Num>(
+            bytes: &Bytes,
+            s: &str,
+            base: u8,
+            mut f: impl FnMut(&mut T, u8) -> bool,
+        ) -> Result<T> {
+            let mut num_acc = T::from_u8(0);
+
+            for &byte in s.as_bytes() {
+                if byte == b'_' {
+                    continue;
+                }
+
+                if num_acc.checked_mul_ext(base) {
+                    return Err(Error::IntegerOutOfBounds);
+                }
+
+                let digit = bytes.decode_hex(byte)?;
+
+                if digit >= base {
+                    return Err(Error::ExpectedInteger);
+                }
+
+                if f(&mut num_acc, digit) {
+                    return Err(Error::IntegerOutOfBounds);
+                }
+            }
+
+            Ok(num_acc)
+        }
+
+        let res = if sign > 0 {
+            calc_num(self, s, base, T::checked_add_ext)
+        } else {
+            calc_num(self, s, base, T::checked_sub_ext)
+        };
+
+        let _ = self.advance(num_bytes);
+
+        res
+    }
+
+    pub fn any_num(&mut self) -> Result<AnyNum> {
+        // We are not doing float comparisons here in the traditional sense.
+        // Instead, this code checks if a f64 fits inside an f32.
+        #[allow(clippy::float_cmp)]
+        fn any_float(f: f64) -> Result<AnyNum> {
+            if f == f64::from(f as f32) {
+                Ok(AnyNum::F32(f as f32))
+            } else {
+                Ok(AnyNum::F64(f))
+            }
+        }
+
+        let bytes_backup = self.bytes;
+
+        let first_byte = self.peek_or_eof()?;
+        let is_signed = first_byte == b'-' || first_byte == b'+';
+        let is_float = self.next_bytes_is_float();
+
+        if is_float {
+            let f = self.float::<f64>()?;
+
+            any_float(f)
+        } else {
+            let max_u8 = LargeUInt::from(std::u8::MAX);
+            let max_u16 = LargeUInt::from(std::u16::MAX);
+            let max_u32 = LargeUInt::from(std::u32::MAX);
+            #[cfg_attr(not(feature = "integer128"), allow(clippy::useless_conversion))]
+            let max_u64 = LargeUInt::from(std::u64::MAX);
+
+            let min_i8 = LargeSInt::from(std::i8::MIN);
+            let max_i8 = LargeSInt::from(std::i8::MAX);
+            let min_i16 = LargeSInt::from(std::i16::MIN);
+            let max_i16 = LargeSInt::from(std::i16::MAX);
+            let min_i32 = LargeSInt::from(std::i32::MIN);
+            let max_i32 = LargeSInt::from(std::i32::MAX);
+            #[cfg_attr(not(feature = "integer128"), allow(clippy::useless_conversion))]
+            let min_i64 = LargeSInt::from(std::i64::MIN);
+            #[cfg_attr(not(feature = "integer128"), allow(clippy::useless_conversion))]
+            let max_i64 = LargeSInt::from(std::i64::MAX);
+
+            if is_signed {
+                match self.signed_integer::<LargeSInt>() {
+                    Ok(x) => {
+                        if x >= min_i8 && x <= max_i8 {
+                            Ok(AnyNum::I8(x as i8))
+                        } else if x >= min_i16 && x <= max_i16 {
+                            Ok(AnyNum::I16(x as i16))
+                        } else if x >= min_i32 && x <= max_i32 {
+                            Ok(AnyNum::I32(x as i32))
+                        } else if x >= min_i64 && x <= max_i64 {
+                            Ok(AnyNum::I64(x as i64))
+                        } else {
+                            #[cfg(feature = "integer128")]
+                            {
+                                Ok(AnyNum::I128(x))
+                            }
+                            #[cfg(not(feature = "integer128"))]
+                            {
+                                Ok(AnyNum::I64(x))
+                            }
+                        }
+                    }
+                    Err(_) => {
+                        self.bytes = bytes_backup;
+
+                        any_float(self.float::<f64>()?)
+                    }
+                }
+            } else {
+                match self.unsigned_integer::<LargeUInt>() {
+                    Ok(x) => {
+                        if x <= max_u8 {
+                            Ok(AnyNum::U8(x as u8))
+                        } else if x <= max_u16 {
+                            Ok(AnyNum::U16(x as u16))
+                        } else if x <= max_u32 {
+                            Ok(AnyNum::U32(x as u32))
+                        } else if x <= max_u64 {
+                            Ok(AnyNum::U64(x as u64))
+                        } else {
+                            #[cfg(feature = "integer128")]
+                            {
+                                Ok(AnyNum::U128(x))
+                            }
+                            #[cfg(not(feature = "integer128"))]
+                            {
+                                Ok(AnyNum::U64(x))
+                            }
+                        }
+                    }
+                    Err(_) => {
+                        self.bytes = bytes_backup;
+
+                        any_float(self.float::<f64>()?)
+                    }
+                }
+            }
+        }
+    }
+
+    pub fn bool(&mut self) -> Result<bool> {
+        if self.consume("true") {
+            Ok(true)
+        } else if self.consume("false") {
+            Ok(false)
+        } else {
+            Err(Error::ExpectedBoolean)
+        }
+    }
+
+    pub fn bytes(&self) -> &[u8] {
+        self.bytes
+    }
+
+    pub fn char(&mut self) -> Result<char> {
+        if !self.consume("'") {
+            return Err(Error::ExpectedChar);
+        }
+
+        let c = self.peek_or_eof()?;
+
+        let c = if c == b'\\' {
+            let _ = self.advance(1);
+
+            self.parse_escape()?
+        } else {
+            // Check where the end of the char (') is and try to
+            // interpret the rest as UTF-8
+
+            let max = self.bytes.len().min(5);
+            let pos: usize = self.bytes[..max]
+                .iter()
+                .position(|&x| x == b'\'')
+                .ok_or(Error::ExpectedChar)?;
+            let s = from_utf8(&self.bytes[0..pos]).map_err(Error::from)?;
+            let mut chars = s.chars();
+
+            let first = chars.next().ok_or(Error::ExpectedChar)?;
+            if chars.next().is_some() {
+                return Err(Error::ExpectedChar);
+            }
+
+            let _ = self.advance(pos);
+
+            first
+        };
+
+        if !self.consume("'") {
+            return Err(Error::ExpectedChar);
+        }
+
+        Ok(c)
+    }
+
+    pub fn comma(&mut self) -> Result<bool> {
+        self.skip_ws()?;
+
+        if self.consume(",") {
+            self.skip_ws()?;
+
+            Ok(true)
+        } else {
+            Ok(false)
+        }
+    }
+
+    /// Only returns true if the char after `ident` cannot belong
+    /// to an identifier.
+    pub fn check_ident(&mut self, ident: &str) -> bool {
+        self.test_for(ident) && !self.check_ident_other_char(ident.len())
+    }
+
+    fn check_ident_other_char(&self, index: usize) -> bool {
+        self.bytes
+            .get(index)
+            .map_or(false, |&b| is_ident_other_char(b))
+    }
+
+    /// Should only be used on a working copy
+    pub fn check_tuple_struct(mut self) -> Result<bool> {
+        if self.identifier().is_err() {
+            // if there's no field ident, this is a tuple struct
+            return Ok(true);
+        }
+
+        self.skip_ws()?;
+
+        // if there is no colon after the ident, this can only be a unit struct
+        self.eat_byte().map(|c| c != b':')
+    }
+
+    /// Only returns true if the char after `ident` cannot belong
+    /// to an identifier.
+    pub fn consume_ident(&mut self, ident: &str) -> bool {
+        if self.check_ident(ident) {
+            let _ = self.advance(ident.len());
+
+            true
+        } else {
+            false
+        }
+    }
+
+    pub fn consume_struct_name(&mut self, ident: &'static str) -> Result<bool> {
+        if self.check_ident("") {
+            return Ok(false);
+        }
+
+        let found_ident = match self.identifier() {
+            Ok(maybe_ident) => std::str::from_utf8(maybe_ident)?,
+            Err(Error::SuggestRawIdentifier(found_ident)) if found_ident == ident => {
+                return Err(Error::SuggestRawIdentifier(found_ident))
+            }
+            Err(_) => return Err(Error::ExpectedNamedStructLike(ident)),
+        };
+
+        if found_ident != ident {
+            return Err(Error::ExpectedDifferentStructName {
+                expected: ident,
+                found: String::from(found_ident),
+            });
+        }
+
+        Ok(true)
+    }
+
+    pub fn consume(&mut self, s: &str) -> bool {
+        if self.test_for(s) {
+            let _ = self.advance(s.len());
+
+            true
+        } else {
+            false
+        }
+    }
+
+    fn consume_all(&mut self, all: &[&str]) -> Result<bool> {
+        all.iter()
+            .map(|elem| {
+                if self.consume(elem) {
+                    self.skip_ws()?;
+
+                    Ok(true)
+                } else {
+                    Ok(false)
+                }
+            })
+            .fold(Ok(true), |acc, x| acc.and_then(|val| x.map(|x| x && val)))
+    }
+
+    pub fn eat_byte(&mut self) -> Result<u8> {
+        let peek = self.peek_or_eof()?;
+        let _ = self.advance_single();
+
+        Ok(peek)
+    }
+
+    pub fn expect_byte(&mut self, byte: u8, error: Error) -> Result<()> {
+        self.eat_byte()
+            .and_then(|b| if b == byte { Ok(()) } else { Err(error) })
+    }
+
+    /// Returns the extensions bit mask.
+    fn extensions(&mut self) -> Result<Extensions> {
+        if self.peek() != Some(b'#') {
+            return Ok(Extensions::empty());
+        }
+
+        if !self.consume_all(&["#", "!", "[", "enable", "("])? {
+            return Err(Error::ExpectedAttribute);
+        }
+
+        self.skip_ws()?;
+        let mut extensions = Extensions::empty();
+
+        loop {
+            let ident = self.identifier()?;
+            let extension = Extensions::from_ident(ident).ok_or_else(|| {
+                Error::NoSuchExtension(String::from_utf8_lossy(ident).into_owned())
+            })?;
+
+            extensions |= extension;
+
+            let comma = self.comma()?;
+
+            // If we have no comma but another item, return an error
+            if !comma && self.check_ident_other_char(0) {
+                return Err(Error::ExpectedComma);
+            }
+
+            // If there's no comma, assume the list ended.
+            // If there is, it might be a trailing one, thus we only
+            // continue the loop if we get an ident char.
+            if !comma || !self.check_ident_other_char(0) {
+                break;
+            }
+        }
+
+        self.skip_ws()?;
+
+        if self.consume_all(&[")", "]"])? {
+            Ok(extensions)
+        } else {
+            Err(Error::ExpectedAttributeEnd)
+        }
+    }
+
+    pub fn float<T>(&mut self) -> Result<T>
+    where
+        T: FromStr,
+    {
+        for literal in &["inf", "+inf", "-inf", "NaN", "+NaN", "-NaN"] {
+            if self.consume_ident(literal) {
+                return FromStr::from_str(literal).map_err(|_| unreachable!()); // must not fail
+            }
+        }
+
+        let num_bytes = self.next_bytes_contained_in(is_float_char);
+
+        // Since `rustc` allows `1_0.0_1`, lint against underscores in floats
+        if let Some(err_bytes) = self.bytes[0..num_bytes].iter().position(|b| *b == b'_') {
+            let _ = self.advance(err_bytes);
+
+            return Err(Error::FloatUnderscore);
+        }
+
+        let s = unsafe { from_utf8_unchecked(&self.bytes[0..num_bytes]) };
+        let res = FromStr::from_str(s).map_err(|_| Error::ExpectedFloat);
+
+        let _ = self.advance(num_bytes);
+
+        res
+    }
+
+    pub fn identifier(&mut self) -> Result<&'a [u8]> {
+        let next = self.peek_or_eof()?;
+        if !is_ident_first_char(next) {
+            if is_ident_raw_char(next) {
+                let ident_bytes = &self.bytes[..self.next_bytes_contained_in(is_ident_raw_char)];
+
+                if let Ok(ident) = std::str::from_utf8(ident_bytes) {
+                    return Err(Error::SuggestRawIdentifier(String::from(ident)));
+                }
+            }
+
+            return Err(Error::ExpectedIdentifier);
+        }
+
+        // If the next two bytes signify the start of a raw string literal,
+        // return an error.
+        let length = if next == b'r' {
+            match self.bytes.get(1).ok_or(Error::Eof)? {
+                b'"' => return Err(Error::ExpectedIdentifier),
+                b'#' => {
+                    let after_next = self.bytes.get(2).copied().unwrap_or_default();
+                    // Note: it's important to check this before advancing forward, so that
+                    // the value-type deserializer can fall back to parsing it differently.
+                    if !is_ident_raw_char(after_next) {
+                        return Err(Error::ExpectedIdentifier);
+                    }
+                    // skip "r#"
+                    let _ = self.advance(2);
+                    self.next_bytes_contained_in(is_ident_raw_char)
+                }
+                _ => {
+                    let std_ident_length = self.next_bytes_contained_in(is_ident_other_char);
+                    let raw_ident_length = self.next_bytes_contained_in(is_ident_raw_char);
+
+                    if raw_ident_length > std_ident_length {
+                        if let Ok(ident) = std::str::from_utf8(&self.bytes[..raw_ident_length]) {
+                            return Err(Error::SuggestRawIdentifier(String::from(ident)));
+                        }
+                    }
+
+                    std_ident_length
+                }
+            }
+        } else {
+            let std_ident_length = self.next_bytes_contained_in(is_ident_other_char);
+            let raw_ident_length = self.next_bytes_contained_in(is_ident_raw_char);
+
+            if raw_ident_length > std_ident_length {
+                if let Ok(ident) = std::str::from_utf8(&self.bytes[..raw_ident_length]) {
+                    return Err(Error::SuggestRawIdentifier(String::from(ident)));
+                }
+            }
+
+            std_ident_length
+        };
+
+        let ident = &self.bytes[..length];
+        let _ = self.advance(length);
+
+        Ok(ident)
+    }
+
+    pub fn next_bytes_contained_in(&self, allowed: fn(u8) -> bool) -> usize {
+        self.bytes.iter().take_while(|&&b| allowed(b)).count()
+    }
+
+    pub fn next_bytes_is_float(&self) -> bool {
+        if let Some(byte) = self.peek() {
+            let skip = match byte {
+                b'+' | b'-' => 1,
+                _ => 0,
+            };
+            let flen = self
+                .bytes
+                .iter()
+                .skip(skip)
+                .take_while(|&&b| is_float_char(b))
+                .count();
+            let ilen = self
+                .bytes
+                .iter()
+                .skip(skip)
+                .take_while(|&&b| is_int_char(b))
+                .count();
+            flen > ilen
+        } else {
+            false
+        }
+    }
+
+    pub fn skip_ws(&mut self) -> Result<()> {
+        loop {
+            while self.peek().map_or(false, is_whitespace_char) {
+                let _ = self.advance_single();
+            }
+
+            if !self.skip_comment()? {
+                return Ok(());
+            }
+        }
+    }
+
+    pub fn peek(&self) -> Option<u8> {
+        self.bytes.first().copied()
+    }
+
+    pub fn peek_or_eof(&self) -> Result<u8> {
+        self.bytes.first().copied().ok_or(Error::Eof)
+    }
+
+    pub fn signed_integer<T>(&mut self) -> Result<T>
+    where
+        T: Num,
+    {
+        match self.peek_or_eof()? {
+            b'+' => {
+                let _ = self.advance_single();
+
+                self.any_integer(1)
+            }
+            b'-' => {
+                let _ = self.advance_single();
+
+                self.any_integer(-1)
+            }
+            _ => self.any_integer(1),
+        }
+    }
+
+    pub fn string(&mut self) -> Result<ParsedStr<'a>> {
+        if self.consume("\"") {
+            self.escaped_string()
+        } else if self.consume("r") {
+            self.raw_string()
+        } else {
+            Err(Error::ExpectedString)
+        }
+    }
+
+    fn escaped_string(&mut self) -> Result<ParsedStr<'a>> {
+        use std::iter::repeat;
+
+        let (i, end_or_escape) = self
+            .bytes
+            .iter()
+            .enumerate()
+            .find(|&(_, &b)| b == b'\\' || b == b'"')
+            .ok_or(Error::ExpectedStringEnd)?;
+
+        if *end_or_escape == b'"' {
+            let s = from_utf8(&self.bytes[..i]).map_err(Error::from)?;
+
+            // Advance by the number of bytes of the string
+            // + 1 for the `"`.
+            let _ = self.advance(i + 1);
+
+            Ok(ParsedStr::Slice(s))
+        } else {
+            let mut i = i;
+            let mut s: Vec<_> = self.bytes[..i].to_vec();
+
+            loop {
+                let _ = self.advance(i + 1);
+                let character = self.parse_escape()?;
+                match character.len_utf8() {
+                    1 => s.push(character as u8),
+                    len => {
+                        let start = s.len();
+                        s.extend(repeat(0).take(len));
+                        character.encode_utf8(&mut s[start..]);
+                    }
+                }
+
+                let (new_i, end_or_escape) = self
+                    .bytes
+                    .iter()
+                    .enumerate()
+                    .find(|&(_, &b)| b == b'\\' || b == b'"')
+                    .ok_or(Error::ExpectedStringEnd)?;
+
+                i = new_i;
+                s.extend_from_slice(&self.bytes[..i]);
+
+                if *end_or_escape == b'"' {
+                    let _ = self.advance(i + 1);
+
+                    let s = String::from_utf8(s).map_err(Error::from)?;
+                    break Ok(ParsedStr::Allocated(s));
+                }
+            }
+        }
+    }
+
+    fn raw_string(&mut self) -> Result<ParsedStr<'a>> {
+        let num_hashes = self.bytes.iter().take_while(|&&b| b == b'#').count();
+        let hashes = &self.bytes[..num_hashes];
+        let _ = self.advance(num_hashes);
+
+        if !self.consume("\"") {
+            return Err(Error::ExpectedString);
+        }
+
+        let ending = [&[b'"'], hashes].concat();
+        let i = self
+            .bytes
+            .windows(num_hashes + 1)
+            .position(|window| window == ending.as_slice())
+            .ok_or(Error::ExpectedStringEnd)?;
+
+        let s = from_utf8(&self.bytes[..i]).map_err(Error::from)?;
+
+        // Advance by the number of bytes of the string
+        // + `num_hashes` + 1 for the `"`.
+        let _ = self.advance(i + num_hashes + 1);
+
+        Ok(ParsedStr::Slice(s))
+    }
+
+    fn test_for(&self, s: &str) -> bool {
+        s.bytes()
+            .enumerate()
+            .all(|(i, b)| self.bytes.get(i).map_or(false, |t| *t == b))
+    }
+
+    pub fn unsigned_integer<T: Num>(&mut self) -> Result<T> {
+        self.any_integer(1)
+    }
+
+    fn decode_ascii_escape(&mut self) -> Result<u8> {
+        let mut n = 0;
+        for _ in 0..2 {
+            n <<= 4;
+            let byte = self.eat_byte()?;
+            let decoded = self.decode_hex(byte)?;
+            n |= decoded;
+        }
+
+        Ok(n)
+    }
+
+    #[inline]
+    fn decode_hex(&self, c: u8) -> Result<u8> {
+        match c {
+            c @ b'0'..=b'9' => Ok(c - b'0'),
+            c @ b'a'..=b'f' => Ok(10 + c - b'a'),
+            c @ b'A'..=b'F' => Ok(10 + c - b'A'),
+            _ => Err(Error::InvalidEscape("Non-hex digit found")),
+        }
+    }
+
+    fn parse_escape(&mut self) -> Result<char> {
+        let c = match self.eat_byte()? {
+            b'\'' => '\'',
+            b'"' => '"',
+            b'\\' => '\\',
+            b'n' => '\n',
+            b'r' => '\r',
+            b't' => '\t',
+            b'0' => '\0',
+            b'x' => self.decode_ascii_escape()? as char,
+            b'u' => {
+                self.expect_byte(b'{', Error::InvalidEscape("Missing { in Unicode escape"))?;
+
+                let mut bytes: u32 = 0;
+                let mut num_digits = 0;
+
+                while num_digits < 6 {
+                    let byte = self.peek_or_eof()?;
+
+                    if byte == b'}' {
+                        break;
+                    } else {
+                        self.advance_single()?;
+                    }
+
+                    let byte = self.decode_hex(byte)?;
+                    bytes <<= 4;
+                    bytes |= u32::from(byte);
+
+                    num_digits += 1;
+                }
+
+                if num_digits == 0 {
+                    return Err(Error::InvalidEscape(
+                        "Expected 1-6 digits, got 0 digits in Unicode escape",
+                    ));
+                }
+
+                self.expect_byte(
+                    b'}',
+                    Error::InvalidEscape("No } at the end of Unicode escape"),
+                )?;
+                char_from_u32(bytes).ok_or(Error::InvalidEscape("Not a valid char"))?
+            }
+            _ => {
+                return Err(Error::InvalidEscape("Unknown escape character"));
+            }
+        };
+
+        Ok(c)
+    }
+
+    fn skip_comment(&mut self) -> Result<bool> {
+        if self.consume("/") {
+            match self.eat_byte()? {
+                b'/' => {
+                    let bytes = self.bytes.iter().take_while(|&&b| b != b'\n').count();
+
+                    let _ = self.advance(bytes);
+                }
+                b'*' => {
+                    let mut level = 1;
+
+                    while level > 0 {
+                        let bytes = self
+                            .bytes
+                            .iter()
+                            .take_while(|&&b| b != b'/' && b != b'*')
+                            .count();
+
+                        if self.bytes.is_empty() {
+                            return Err(Error::UnclosedBlockComment);
+                        }
+
+                        let _ = self.advance(bytes);
+
+                        // check whether / or * and take action
+                        if self.consume("/*") {
+                            level += 1;
+                        } else if self.consume("*/") {
+                            level -= 1;
+                        } else {
+                            self.eat_byte().map_err(|_| Error::UnclosedBlockComment)?;
+                        }
+                    }
+                }
+                b => return Err(Error::UnexpectedByte(b as char)),
+            }
+
+            Ok(true)
+        } else {
+            Ok(false)
+        }
+    }
+}
+
+pub trait Num {
+    fn from_u8(x: u8) -> Self;
+
+    /// Returns `true` on overflow
+    fn checked_mul_ext(&mut self, x: u8) -> bool;
+
+    /// Returns `true` on overflow
+    fn checked_add_ext(&mut self, x: u8) -> bool;
+
+    /// Returns `true` on overflow
+    fn checked_sub_ext(&mut self, x: u8) -> bool;
+}
+
+macro_rules! impl_num {
+    ($ty:ident) => {
+        impl Num for $ty {
+            fn from_u8(x: u8) -> Self {
+                x as $ty
+            }
+
+            fn checked_mul_ext(&mut self, x: u8) -> bool {
+                match self.checked_mul(Self::from_u8(x)) {
+                    Some(n) => {
+                        *self = n;
+                        false
+                    }
+                    None => true,
+                }
+            }
+
+            fn checked_add_ext(&mut self, x: u8) -> bool {
+                match self.checked_add(Self::from_u8(x)) {
+                    Some(n) => {
+                        *self = n;
+                        false
+                    }
+                    None => true,
+                }
+            }
+
+            fn checked_sub_ext(&mut self, x: u8) -> bool {
+                match self.checked_sub(Self::from_u8(x)) {
+                    Some(n) => {
+                        *self = n;
+                        false
+                    }
+                    None => true,
+                }
+            }
+        }
+    };
+    ($($tys:ident)*) => {
+        $( impl_num!($tys); )*
+    };
+}
+
+#[cfg(feature = "integer128")]
+impl_num!(u8 u16 u32 u64 u128 i8 i16 i32 i64 i128);
+#[cfg(not(feature = "integer128"))]
+impl_num!(u8 u16 u32 u64 i8 i16 i32 i64);
+
+#[derive(Clone, Debug)]
+pub enum ParsedStr<'a> {
+    Allocated(String),
+    Slice(&'a str),
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn decode_x10() {
+        let mut bytes = Bytes::new(b"10").unwrap();
+        assert_eq!(bytes.decode_ascii_escape(), Ok(0x10));
+    }
+}
diff --git a/third_party/rust/ron/src/ser/mod.rs b/third_party/rust/ron/src/ser/mod.rs
new file mode 100644
index 0000000000..b1aefbcba4
--- /dev/null
+++ b/third_party/rust/ron/src/ser/mod.rs
@@ -0,0 +1,1041 @@
+use std::io;
+
+use base64::Engine;
+use serde::{ser, ser::Serialize};
+use serde_derive::{Deserialize, Serialize};
+
+use crate::{
+    error::{Error, Result},
+    extensions::Extensions,
+    options::Options,
+    parse::{
+        is_ident_first_char, is_ident_other_char, is_ident_raw_char, LargeSInt, LargeUInt,
+        BASE64_ENGINE,
+    },
+};
+
+#[cfg(test)]
+mod tests;
+mod value;
+
+/// Serializes `value` into `writer`.
+///
+/// This function does not generate any newlines or nice formatting;
+/// if you want that, you can use [`to_writer_pretty`] instead.
+pub fn to_writer<W, T>(writer: W, value: &T) -> Result<()>
+where
+    W: io::Write,
+    T: ?Sized + Serialize,
+{
+    Options::default().to_writer(writer, value)
+}
+
+/// Serializes `value` into `writer` in a pretty way.
+pub fn to_writer_pretty<W, T>(writer: W, value: &T, config: PrettyConfig) -> Result<()>
+where
+    W: io::Write,
+    T: ?Sized + Serialize,
+{
+    Options::default().to_writer_pretty(writer, value, config)
+}
+
+/// Serializes `value` and returns it as string.
+///
+/// This function does not generate any newlines or nice formatting;
+/// if you want that, you can use [`to_string_pretty`] instead.
+pub fn to_string<T>(value: &T) -> Result<String>
+where
+    T: ?Sized + Serialize,
+{
+    Options::default().to_string(value)
+}
+
+/// Serializes `value` in the recommended RON layout in a pretty way.
+pub fn to_string_pretty<T>(value: &T, config: PrettyConfig) -> Result<String>
+where
+    T: ?Sized + Serialize,
+{
+    Options::default().to_string_pretty(value, config)
+}
+
+/// Pretty serializer state
+struct Pretty {
+    indent: usize,
+    sequence_index: Vec<usize>,
+}
+
+/// Pretty serializer configuration.
+///
+/// # Examples
+///
+/// ```
+/// use ron::ser::PrettyConfig;
+///
+/// let my_config = PrettyConfig::new()
+///     .depth_limit(4)
+///     // definitely superior (okay, just joking)
+///     .indentor("\t".to_owned());
+/// ```
+#[derive(Clone, Debug, Serialize, Deserialize)]
+#[serde(default)]
+#[non_exhaustive]
+pub struct PrettyConfig {
+    /// Limit the pretty-ness up to the given depth.
+    pub depth_limit: usize,
+    /// New line string
+    pub new_line: String,
+    /// Indentation string
+    pub indentor: String,
+    /// Separator string
+    pub separator: String,
+    // Whether to emit struct names
+    pub struct_names: bool,
+    /// Separate tuple members with indentation
+    pub separate_tuple_members: bool,
+    /// Enumerate array items in comments
+    pub enumerate_arrays: bool,
+    /// Enable extensions. Only configures 'implicit_some',
+    ///  'unwrap_newtypes', and 'unwrap_variant_newtypes' for now.
+    pub extensions: Extensions,
+    /// Enable compact arrays
+    pub compact_arrays: bool,
+}
+
+impl PrettyConfig {
+    /// Creates a default [`PrettyConfig`].
+    pub fn new() -> Self {
+        Default::default()
+    }
+
+    /// Limits the pretty-formatting based on the number of indentations.
+    /// I.e., with a depth limit of 5, starting with an element of depth
+    /// (indentation level) 6, everything will be put into the same line,
+    /// without pretty formatting.
+    ///
+    /// Default: [usize::MAX]
+    pub fn depth_limit(mut self, depth_limit: usize) -> Self {
+        self.depth_limit = depth_limit;
+
+        self
+    }
+
+    /// Configures the newlines used for serialization.
+    ///
+    /// Default: `\r\n` on Windows, `\n` otherwise
+    pub fn new_line(mut self, new_line: String) -> Self {
+        self.new_line = new_line;
+
+        self
+    }
+
+    /// Configures the string sequence used for indentation.
+    ///
+    /// Default: 4 spaces
+    pub fn indentor(mut self, indentor: String) -> Self {
+        self.indentor = indentor;
+
+        self
+    }
+
+    /// Configures the string sequence used to separate items inline.
+    ///
+    /// Default: 1 space
+    pub fn separator(mut self, separator: String) -> Self {
+        self.separator = separator;
+
+        self
+    }
+
+    /// Configures whether to emit struct names.
+    ///
+    /// Default: `false`
+    pub fn struct_names(mut self, struct_names: bool) -> Self {
+        self.struct_names = struct_names;
+
+        self
+    }
+
+    /// Configures whether tuples are single- or multi-line.
+    /// If set to `true`, tuples will have their fields indented and in new
+    /// lines. If set to `false`, tuples will be serialized without any
+    /// newlines or indentations.
+    ///
+    /// Default: `false`
+    pub fn separate_tuple_members(mut self, separate_tuple_members: bool) -> Self {
+        self.separate_tuple_members = separate_tuple_members;
+
+        self
+    }
+
+    /// Configures whether a comment shall be added to every array element,
+    /// indicating the index.
+    ///
+    /// Default: `false`
+    pub fn enumerate_arrays(mut self, enumerate_arrays: bool) -> Self {
+        self.enumerate_arrays = enumerate_arrays;
+
+        self
+    }
+
+    /// Configures whether every array should be a single line (`true`)
+    /// or a multi line one (`false`).
+    ///
+    /// When `false`, `["a","b"]` (as well as any array) will serialize to
+    /// ```
+    /// [
+    ///   "a",
+    ///   "b",
+    /// ]
+    /// # ;
+    /// ```
+    /// When `true`, `["a","b"]` (as well as any array) will serialize to
+    /// ```
+    /// ["a","b"]
+    /// # ;
+    /// ```
+    ///
+    /// Default: `false`
+    pub fn compact_arrays(mut self, compact_arrays: bool) -> Self {
+        self.compact_arrays = compact_arrays;
+
+        self
+    }
+
+    /// Configures extensions
+    ///
+    /// Default: [Extensions::empty()]
+    pub fn extensions(mut self, extensions: Extensions) -> Self {
+        self.extensions = extensions;
+
+        self
+    }
+}
+
+impl Default for PrettyConfig {
+    fn default() -> Self {
+        PrettyConfig {
+            depth_limit: usize::MAX,
+            new_line: if cfg!(not(target_os = "windows")) {
+                String::from("\n")
+            } else {
+                String::from("\r\n")
+            },
+            indentor: String::from("    "),
+            separator: String::from(" "),
+            struct_names: false,
+            separate_tuple_members: false,
+            enumerate_arrays: false,
+            extensions: Extensions::empty(),
+            compact_arrays: false,
+        }
+    }
+}
+
+/// The RON serializer.
+///
+/// You can just use [`to_string`] for deserializing a value.
+/// If you want it pretty-printed, take a look at [`to_string_pretty`].
+pub struct Serializer<W: io::Write> {
+    output: W,
+    pretty: Option<(PrettyConfig, Pretty)>,
+    default_extensions: Extensions,
+    is_empty: Option<bool>,
+    newtype_variant: bool,
+    recursion_limit: Option<usize>,
+}
+
+impl<W: io::Write> Serializer<W> {
+    /// Creates a new [`Serializer`].
+    ///
+    /// Most of the time you can just use [`to_string`] or
+    /// [`to_string_pretty`].
+    pub fn new(writer: W, config: Option<PrettyConfig>) -> Result<Self> {
+        Self::with_options(writer, config, Options::default())
+    }
+
+    /// Creates a new [`Serializer`].
+    ///
+    /// Most of the time you can just use [`to_string`] or
+    /// [`to_string_pretty`].
+    pub fn with_options(
+        mut writer: W,
+        config: Option<PrettyConfig>,
+        options: Options,
+    ) -> Result<Self> {
+        if let Some(conf) = &config {
+            let non_default_extensions = !options.default_extensions;
+
+            if (non_default_extensions & conf.extensions).contains(Extensions::IMPLICIT_SOME) {
+                writer.write_all(b"#![enable(implicit_some)]")?;
+                writer.write_all(conf.new_line.as_bytes())?;
+            };
+            if (non_default_extensions & conf.extensions).contains(Extensions::UNWRAP_NEWTYPES) {
+                writer.write_all(b"#![enable(unwrap_newtypes)]")?;
+                writer.write_all(conf.new_line.as_bytes())?;
+            };
+            if (non_default_extensions & conf.extensions)
+                .contains(Extensions::UNWRAP_VARIANT_NEWTYPES)
+            {
+                writer.write_all(b"#![enable(unwrap_variant_newtypes)]")?;
+                writer.write_all(conf.new_line.as_bytes())?;
+            };
+        };
+        Ok(Serializer {
+            output: writer,
+            pretty: config.map(|conf| {
+                (
+                    conf,
+                    Pretty {
+                        indent: 0,
+                        sequence_index: Vec::new(),
+                    },
+                )
+            }),
+            default_extensions: options.default_extensions,
+            is_empty: None,
+            newtype_variant: false,
+            recursion_limit: options.recursion_limit,
+        })
+    }
+
+    fn separate_tuple_members(&self) -> bool {
+        self.pretty
+            .as_ref()
+            .map_or(false, |&(ref config, _)| config.separate_tuple_members)
+    }
+
+    fn compact_arrays(&self) -> bool {
+        self.pretty
+            .as_ref()
+            .map_or(false, |&(ref config, _)| config.compact_arrays)
+    }
+
+    fn extensions(&self) -> Extensions {
+        self.default_extensions
+            | self
+                .pretty
+                .as_ref()
+                .map_or(Extensions::empty(), |&(ref config, _)| config.extensions)
+    }
+
+    fn start_indent(&mut self) -> Result<()> {
+        if let Some((ref config, ref mut pretty)) = self.pretty {
+            pretty.indent += 1;
+            if pretty.indent <= config.depth_limit {
+                let is_empty = self.is_empty.unwrap_or(false);
+
+                if !is_empty {
+                    self.output.write_all(config.new_line.as_bytes())?;
+                }
+            }
+        }
+        Ok(())
+    }
+
+    fn indent(&mut self) -> io::Result<()> {
+        if let Some((ref config, ref pretty)) = self.pretty {
+            if pretty.indent <= config.depth_limit {
+                for _ in 0..pretty.indent {
+                    self.output.write_all(config.indentor.as_bytes())?;
+                }
+            }
+        }
+        Ok(())
+    }
+
+    fn end_indent(&mut self) -> io::Result<()> {
+        if let Some((ref config, ref mut pretty)) = self.pretty {
+            if pretty.indent <= config.depth_limit {
+                let is_empty = self.is_empty.unwrap_or(false);
+
+                if !is_empty {
+                    for _ in 1..pretty.indent {
+                        self.output.write_all(config.indentor.as_bytes())?;
+                    }
+                }
+            }
+            pretty.indent -= 1;
+
+            self.is_empty = None;
+        }
+        Ok(())
+    }
+
+    fn serialize_escaped_str(&mut self, value: &str) -> io::Result<()> {
+        self.output.write_all(b"\"")?;
+        let mut scalar = [0u8; 4];
+        for c in value.chars().flat_map(|c| c.escape_debug()) {
+            self.output
+                .write_all(c.encode_utf8(&mut scalar).as_bytes())?;
+        }
+        self.output.write_all(b"\"")?;
+        Ok(())
+    }
+
+    fn serialize_sint(&mut self, value: impl Into<LargeSInt>) -> Result<()> {
+        // TODO optimize
+        write!(self.output, "{}", value.into())?;
+
+        Ok(())
+    }
+
+    fn serialize_uint(&mut self, value: impl Into<LargeUInt>) -> Result<()> {
+        // TODO optimize
+        write!(self.output, "{}", value.into())?;
+
+        Ok(())
+    }
+
+    fn write_identifier(&mut self, name: &str) -> Result<()> {
+        if name.is_empty() || !name.as_bytes().iter().copied().all(is_ident_raw_char) {
+            return Err(Error::InvalidIdentifier(name.into()));
+        }
+        let mut bytes = name.as_bytes().iter().copied();
+        if !bytes.next().map_or(false, is_ident_first_char) || !bytes.all(is_ident_other_char) {
+            self.output.write_all(b"r#")?;
+        }
+        self.output.write_all(name.as_bytes())?;
+        Ok(())
+    }
+
+    fn struct_names(&self) -> bool {
+        self.pretty
+            .as_ref()
+            .map(|(pc, _)| pc.struct_names)
+            .unwrap_or(false)
+    }
+}
+
+macro_rules! guard_recursion {
+    ($self:expr => $expr:expr) => {{
+        if let Some(limit) = &mut $self.recursion_limit {
+            if let Some(new_limit) = limit.checked_sub(1) {
+                *limit = new_limit;
+            } else {
+                return Err(Error::ExceededRecursionLimit);
+            }
+        }
+
+        let result = $expr;
+
+        if let Some(limit) = &mut $self.recursion_limit {
+            *limit = limit.saturating_add(1);
+        }
+
+        result
+    }};
+}
+
+impl<'a, W: io::Write> ser::Serializer for &'a mut Serializer<W> {
+    type Error = Error;
+    type Ok = ();
+    type SerializeMap = Compound<'a, W>;
+    type SerializeSeq = Compound<'a, W>;
+    type SerializeStruct = Compound<'a, W>;
+    type SerializeStructVariant = Compound<'a, W>;
+    type SerializeTuple = Compound<'a, W>;
+    type SerializeTupleStruct = Compound<'a, W>;
+    type SerializeTupleVariant = Compound<'a, W>;
+
+    fn serialize_bool(self, v: bool) -> Result<()> {
+        self.output.write_all(if v { b"true" } else { b"false" })?;
+        Ok(())
+    }
+
+    fn serialize_i8(self, v: i8) -> Result<()> {
+        self.serialize_sint(v)
+    }
+
+    fn serialize_i16(self, v: i16) -> Result<()> {
+        self.serialize_sint(v)
+    }
+
+    fn serialize_i32(self, v: i32) -> Result<()> {
+        self.serialize_sint(v)
+    }
+
+    fn serialize_i64(self, v: i64) -> Result<()> {
+        self.serialize_sint(v)
+    }
+
+    #[cfg(feature = "integer128")]
+    fn serialize_i128(self, v: i128) -> Result<()> {
+        self.serialize_sint(v)
+    }
+
+    fn serialize_u8(self, v: u8) -> Result<()> {
+        self.serialize_uint(v)
+    }
+
+    fn serialize_u16(self, v: u16) -> Result<()> {
+        self.serialize_uint(v)
+    }
+
+    fn serialize_u32(self, v: u32) -> Result<()> {
+        self.serialize_uint(v)
+    }
+
+    fn serialize_u64(self, v: u64) -> Result<()> {
+        self.serialize_uint(v)
+    }
+
+    #[cfg(feature = "integer128")]
+    fn serialize_u128(self, v: u128) -> Result<()> {
+        self.serialize_uint(v)
+    }
+
+    fn serialize_f32(self, v: f32) -> Result<()> {
+        write!(self.output, "{}", v)?;
+        if v.fract() == 0.0 {
+            write!(self.output, ".0")?;
+        }
+        Ok(())
+    }
+
+    fn serialize_f64(self, v: f64) -> Result<()> {
+        write!(self.output, "{}", v)?;
+        if v.fract() == 0.0 {
+            write!(self.output, ".0")?;
+        }
+        Ok(())
+    }
+
+    fn serialize_char(self, v: char) -> Result<()> {
+        self.output.write_all(b"'")?;
+        if v == '\\' || v == '\'' {
+            self.output.write_all(b"\\")?;
+        }
+        write!(self.output, "{}", v)?;
+        self.output.write_all(b"'")?;
+        Ok(())
+    }
+
+    fn serialize_str(self, v: &str) -> Result<()> {
+        self.serialize_escaped_str(v)?;
+
+        Ok(())
+    }
+
+    fn serialize_bytes(self, v: &[u8]) -> Result<()> {
+        self.serialize_str(BASE64_ENGINE.encode(v).as_str())
+    }
+
+    fn serialize_none(self) -> Result<()> {
+        self.output.write_all(b"None")?;
+
+        Ok(())
+    }
+
+    fn serialize_some<T>(self, value: &T) -> Result<()>
+    where
+        T: ?Sized + Serialize,
+    {
+        let implicit_some = self.extensions().contains(Extensions::IMPLICIT_SOME);
+        if !implicit_some {
+            self.output.write_all(b"Some(")?;
+        }
+        guard_recursion! { self => value.serialize(&mut *self)? };
+        if !implicit_some {
+            self.output.write_all(b")")?;
+        }
+
+        Ok(())
+    }
+
+    fn serialize_unit(self) -> Result<()> {
+        if !self.newtype_variant {
+            self.output.write_all(b"()")?;
+        }
+
+        self.newtype_variant = false;
+
+        Ok(())
+    }
+
+    fn serialize_unit_struct(self, name: &'static str) -> Result<()> {
+        if self.struct_names() && !self.newtype_variant {
+            self.write_identifier(name)?;
+
+            Ok(())
+        } else {
+            self.serialize_unit()
+        }
+    }
+
+    fn serialize_unit_variant(self, _: &'static str, _: u32, variant: &'static str) -> Result<()> {
+        self.write_identifier(variant)?;
+
+        Ok(())
+    }
+
+    fn serialize_newtype_struct<T>(self, name: &'static str, value: &T) -> Result<()>
+    where
+        T: ?Sized + Serialize,
+    {
+        if self.extensions().contains(Extensions::UNWRAP_NEWTYPES) || self.newtype_variant {
+            self.newtype_variant = false;
+
+            return guard_recursion! { self => value.serialize(&mut *self) };
+        }
+
+        if self.struct_names() {
+            self.write_identifier(name)?;
+        }
+
+        self.output.write_all(b"(")?;
+        guard_recursion! { self => value.serialize(&mut *self)? };
+        self.output.write_all(b")")?;
+        Ok(())
+    }
+
+    fn serialize_newtype_variant<T>(
+        self,
+        _: &'static str,
+        _: u32,
+        variant: &'static str,
+        value: &T,
+    ) -> Result<()>
+    where
+        T: ?Sized + Serialize,
+    {
+        self.write_identifier(variant)?;
+        self.output.write_all(b"(")?;
+
+        self.newtype_variant = self
+            .extensions()
+            .contains(Extensions::UNWRAP_VARIANT_NEWTYPES);
+
+        guard_recursion! { self => value.serialize(&mut *self)? };
+
+        self.newtype_variant = false;
+
+        self.output.write_all(b")")?;
+        Ok(())
+    }
+
+    fn serialize_seq(self, len: Option<usize>) -> Result<Self::SerializeSeq> {
+        self.newtype_variant = false;
+
+        self.output.write_all(b"[")?;
+
+        if let Some(len) = len {
+            self.is_empty = Some(len == 0);
+        }
+
+        if !self.compact_arrays() {
+            self.start_indent()?;
+        }
+
+        if let Some((_, ref mut pretty)) = self.pretty {
+            pretty.sequence_index.push(0);
+        }
+
+        Compound::try_new(self, false)
+    }
+
+    fn serialize_tuple(self, len: usize) -> Result<Self::SerializeTuple> {
+        let old_newtype_variant = self.newtype_variant;
+        self.newtype_variant = false;
+
+        if !old_newtype_variant {
+            self.output.write_all(b"(")?;
+        }
+
+        if self.separate_tuple_members() {
+            self.is_empty = Some(len == 0);
+
+            self.start_indent()?;
+        }
+
+        Compound::try_new(self, old_newtype_variant)
+    }
+
+    fn serialize_tuple_struct(
+        self,
+        name: &'static str,
+        len: usize,
+    ) -> Result<Self::SerializeTupleStruct> {
+        if self.struct_names() && !self.newtype_variant {
+            self.write_identifier(name)?;
+        }
+
+        self.serialize_tuple(len)
+    }
+
+    fn serialize_tuple_variant(
+        self,
+        _: &'static str,
+        _: u32,
+        variant: &'static str,
+        len: usize,
+    ) -> Result<Self::SerializeTupleVariant> {
+        self.newtype_variant = false;
+
+        self.write_identifier(variant)?;
+        self.output.write_all(b"(")?;
+
+        if self.separate_tuple_members() {
+            self.is_empty = Some(len == 0);
+
+            self.start_indent()?;
+        }
+
+        Compound::try_new(self, false)
+    }
+
+    fn serialize_map(self, len: Option<usize>) -> Result<Self::SerializeMap> {
+        self.newtype_variant = false;
+
+        self.output.write_all(b"{")?;
+
+        if let Some(len) = len {
+            self.is_empty = Some(len == 0);
+        }
+
+        self.start_indent()?;
+
+        Compound::try_new(self, false)
+    }
+
+    fn serialize_struct(self, name: &'static str, len: usize) -> Result<Self::SerializeStruct> {
+        let old_newtype_variant = self.newtype_variant;
+        self.newtype_variant = false;
+
+        if !old_newtype_variant {
+            if self.struct_names() {
+                self.write_identifier(name)?;
+            }
+            self.output.write_all(b"(")?;
+        }
+
+        self.is_empty = Some(len == 0);
+        self.start_indent()?;
+
+        Compound::try_new(self, old_newtype_variant)
+    }
+
+    fn serialize_struct_variant(
+        self,
+        _: &'static str,
+        _: u32,
+        variant: &'static str,
+        len: usize,
+    ) -> Result<Self::SerializeStructVariant> {
+        self.newtype_variant = false;
+
+        self.write_identifier(variant)?;
+        self.output.write_all(b"(")?;
+
+        self.is_empty = Some(len == 0);
+        self.start_indent()?;
+
+        Compound::try_new(self, false)
+    }
+}
+
+enum State {
+    First,
+    Rest,
+}
+
+#[doc(hidden)]
+pub struct Compound<'a, W: io::Write> {
+    ser: &'a mut Serializer<W>,
+    state: State,
+    newtype_variant: bool,
+}
+
+impl<'a, W: io::Write> Compound<'a, W> {
+    fn try_new(ser: &'a mut Serializer<W>, newtype_variant: bool) -> Result<Self> {
+        if let Some(limit) = &mut ser.recursion_limit {
+            if let Some(new_limit) = limit.checked_sub(1) {
+                *limit = new_limit;
+            } else {
+                return Err(Error::ExceededRecursionLimit);
+            }
+        }
+
+        Ok(Compound {
+            ser,
+            state: State::First,
+            newtype_variant,
+        })
+    }
+}
+
+impl<'a, W: io::Write> Drop for Compound<'a, W> {
+    fn drop(&mut self) {
+        if let Some(limit) = &mut self.ser.recursion_limit {
+            *limit = limit.saturating_add(1);
+        }
+    }
+}
+
+impl<'a, W: io::Write> ser::SerializeSeq for Compound<'a, W> {
+    type Error = Error;
+    type Ok = ();
+
+    fn serialize_element<T>(&mut self, value: &T) -> Result<()>
+    where
+        T: ?Sized + Serialize,
+    {
+        if let State::First = self.state {
+            self.state = State::Rest;
+        } else {
+            self.ser.output.write_all(b",")?;
+            if let Some((ref config, ref mut pretty)) = self.ser.pretty {
+                if pretty.indent <= config.depth_limit && !config.compact_arrays {
+                    self.ser.output.write_all(config.new_line.as_bytes())?;
+                } else {
+                    self.ser.output.write_all(config.separator.as_bytes())?;
+                }
+            }
+        }
+
+        if !self.ser.compact_arrays() {
+            self.ser.indent()?;
+        }
+
+        if let Some((ref mut config, ref mut pretty)) = self.ser.pretty {
+            if pretty.indent <= config.depth_limit && config.enumerate_arrays {
+                let index = pretty.sequence_index.last_mut().unwrap();
+                write!(self.ser.output, "/*[{}]*/ ", index)?;
+                *index += 1;
+            }
+        }
+
+        guard_recursion! { self.ser => value.serialize(&mut *self.ser)? };
+
+        Ok(())
+    }
+
+    fn end(self) -> Result<()> {
+        if let State::Rest = self.state {
+            if let Some((ref config, ref mut pretty)) = self.ser.pretty {
+                if pretty.indent <= config.depth_limit && !config.compact_arrays {
+                    self.ser.output.write_all(b",")?;
+                    self.ser.output.write_all(config.new_line.as_bytes())?;
+                }
+            }
+        }
+
+        if !self.ser.compact_arrays() {
+            self.ser.end_indent()?;
+        }
+
+        if let Some((_, ref mut pretty)) = self.ser.pretty {
+            pretty.sequence_index.pop();
+        }
+
+        // seq always disables `self.newtype_variant`
+        self.ser.output.write_all(b"]")?;
+        Ok(())
+    }
+}
+
+impl<'a, W: io::Write> ser::SerializeTuple for Compound<'a, W> {
+    type Error = Error;
+    type Ok = ();
+
+    fn serialize_element<T>(&mut self, value: &T) -> Result<()>
+    where
+        T: ?Sized + Serialize,
+    {
+        if let State::First = self.state {
+            self.state = State::Rest;
+        } else {
+            self.ser.output.write_all(b",")?;
+            if let Some((ref config, ref pretty)) = self.ser.pretty {
+                if pretty.indent <= config.depth_limit && self.ser.separate_tuple_members() {
+                    self.ser.output.write_all(config.new_line.as_bytes())?;
+                } else {
+                    self.ser.output.write_all(config.separator.as_bytes())?;
+                }
+            }
+        }
+
+        if self.ser.separate_tuple_members() {
+            self.ser.indent()?;
+        }
+
+        guard_recursion! { self.ser => value.serialize(&mut *self.ser)? };
+
+        Ok(())
+    }
+
+    fn end(self) -> Result<()> {
+        if let State::Rest = self.state {
+            if let Some((ref config, ref pretty)) = self.ser.pretty {
+                if self.ser.separate_tuple_members() && pretty.indent <= config.depth_limit {
+                    self.ser.output.write_all(b",")?;
+                    self.ser.output.write_all(config.new_line.as_bytes())?;
+                }
+            }
+        }
+        if self.ser.separate_tuple_members() {
+            self.ser.end_indent()?;
+        }
+
+        if !self.newtype_variant {
+            self.ser.output.write_all(b")")?;
+        }
+
+        Ok(())
+    }
+}
+
+// Same thing but for tuple structs.
+impl<'a, W: io::Write> ser::SerializeTupleStruct for Compound<'a, W> {
+    type Error = Error;
+    type Ok = ();
+
+    fn serialize_field<T>(&mut self, value: &T) -> Result<()>
+    where
+        T: ?Sized + Serialize,
+    {
+        ser::SerializeTuple::serialize_element(self, value)
+    }
+
+    fn end(self) -> Result<()> {
+        ser::SerializeTuple::end(self)
+    }
+}
+
+impl<'a, W: io::Write> ser::SerializeTupleVariant for Compound<'a, W> {
+    type Error = Error;
+    type Ok = ();
+
+    fn serialize_field<T>(&mut self, value: &T) -> Result<()>
+    where
+        T: ?Sized + Serialize,
+    {
+        ser::SerializeTuple::serialize_element(self, value)
+    }
+
+    fn end(self) -> Result<()> {
+        ser::SerializeTuple::end(self)
+    }
+}
+
+impl<'a, W: io::Write> ser::SerializeMap for Compound<'a, W> {
+    type Error = Error;
+    type Ok = ();
+
+    fn serialize_key<T>(&mut self, key: &T) -> Result<()>
+    where
+        T: ?Sized + Serialize,
+    {
+        if let State::First = self.state {
+            self.state = State::Rest;
+        } else {
+            self.ser.output.write_all(b",")?;
+
+            if let Some((ref config, ref pretty)) = self.ser.pretty {
+                if pretty.indent <= config.depth_limit {
+                    self.ser.output.write_all(config.new_line.as_bytes())?;
+                } else {
+                    self.ser.output.write_all(config.separator.as_bytes())?;
+                }
+            }
+        }
+        self.ser.indent()?;
+        guard_recursion! { self.ser => key.serialize(&mut *self.ser) }
+    }
+
+    fn serialize_value<T>(&mut self, value: &T) -> Result<()>
+    where
+        T: ?Sized + Serialize,
+    {
+        self.ser.output.write_all(b":")?;
+
+        if let Some((ref config, _)) = self.ser.pretty {
+            self.ser.output.write_all(config.separator.as_bytes())?;
+        }
+
+        guard_recursion! { self.ser => value.serialize(&mut *self.ser)? };
+
+        Ok(())
+    }
+
+    fn end(self) -> Result<()> {
+        if let State::Rest = self.state {
+            if let Some((ref config, ref pretty)) = self.ser.pretty {
+                if pretty.indent <= config.depth_limit {
+                    self.ser.output.write_all(b",")?;
+                    self.ser.output.write_all(config.new_line.as_bytes())?;
+                }
+            }
+        }
+        self.ser.end_indent()?;
+        // map always disables `self.newtype_variant`
+        self.ser.output.write_all(b"}")?;
+        Ok(())
+    }
+}
+
+impl<'a, W: io::Write> ser::SerializeStruct for Compound<'a, W> {
+    type Error = Error;
+    type Ok = ();
+
+    fn serialize_field<T>(&mut self, key: &'static str, value: &T) -> Result<()>
+    where
+        T: ?Sized + Serialize,
+    {
+        if let State::First = self.state {
+            self.state = State::Rest;
+        } else {
+            self.ser.output.write_all(b",")?;
+
+            if let Some((ref config, ref pretty)) = self.ser.pretty {
+                if pretty.indent <= config.depth_limit {
+                    self.ser.output.write_all(config.new_line.as_bytes())?;
+                } else {
+                    self.ser.output.write_all(config.separator.as_bytes())?;
+                }
+            }
+        }
+        self.ser.indent()?;
+        self.ser.write_identifier(key)?;
+        self.ser.output.write_all(b":")?;
+
+        if let Some((ref config, _)) = self.ser.pretty {
+            self.ser.output.write_all(config.separator.as_bytes())?;
+        }
+
+        guard_recursion! { self.ser => value.serialize(&mut *self.ser)? };
+
+        Ok(())
+    }
+
+    fn end(self) -> Result<()> {
+        if let State::Rest = self.state {
+            if let Some((ref config, ref pretty)) = self.ser.pretty {
+                if pretty.indent <= config.depth_limit {
+                    self.ser.output.write_all(b",")?;
+                    self.ser.output.write_all(config.new_line.as_bytes())?;
+                }
+            }
+        }
+        self.ser.end_indent()?;
+        if !self.newtype_variant {
+            self.ser.output.write_all(b")")?;
+        }
+        Ok(())
+    }
+}
+
+impl<'a, W: io::Write> ser::SerializeStructVariant for Compound<'a, W> {
+    type Error = Error;
+    type Ok = ();
+
+    fn serialize_field<T>(&mut self, key: &'static str, value: &T) -> Result<()>
+    where
+        T: ?Sized + Serialize,
+    {
+        ser::SerializeStruct::serialize_field(self, key, value)
+    }
+
+    fn end(self) -> Result<()> {
+        ser::SerializeStruct::end(self)
+    }
+}
diff --git a/third_party/rust/ron/src/ser/tests.rs b/third_party/rust/ron/src/ser/tests.rs
new file mode 100644
index 0000000000..fce7f00710
--- /dev/null
+++ b/third_party/rust/ron/src/ser/tests.rs
@@ -0,0 +1,147 @@
+use serde_derive::Serialize;
+
+use super::to_string;
+
+#[derive(Serialize)]
+struct EmptyStruct1;
+
+#[derive(Serialize)]
+struct EmptyStruct2 {}
+
+#[derive(Serialize)]
+struct MyStruct {
+    x: f32,
+    y: f32,
+}
+
+#[derive(Serialize)]
+enum MyEnum {
+    A,
+    B(bool),
+    C(bool, f32),
+    D { a: i32, b: i32 },
+}
+
+#[test]
+fn test_empty_struct() {
+    assert_eq!(to_string(&EmptyStruct1).unwrap(), "()");
+    assert_eq!(to_string(&EmptyStruct2 {}).unwrap(), "()");
+}
+
+#[test]
+fn test_struct() {
+    let my_struct = MyStruct { x: 4.0, y: 7.0 };
+
+    assert_eq!(to_string(&my_struct).unwrap(), "(x:4.0,y:7.0)");
+
+    #[derive(Serialize)]
+    struct NewType(i32);
+
+    assert_eq!(to_string(&NewType(42)).unwrap(), "(42)");
+
+    #[derive(Serialize)]
+    struct TupleStruct(f32, f32);
+
+    assert_eq!(to_string(&TupleStruct(2.0, 5.0)).unwrap(), "(2.0,5.0)");
+}
+
+#[test]
+fn test_option() {
+    assert_eq!(to_string(&Some(1u8)).unwrap(), "Some(1)");
+    assert_eq!(to_string(&None::<u8>).unwrap(), "None");
+}
+
+#[test]
+fn test_enum() {
+    assert_eq!(to_string(&MyEnum::A).unwrap(), "A");
+    assert_eq!(to_string(&MyEnum::B(true)).unwrap(), "B(true)");
+    assert_eq!(to_string(&MyEnum::C(true, 3.5)).unwrap(), "C(true,3.5)");
+    assert_eq!(to_string(&MyEnum::D { a: 2, b: 3 }).unwrap(), "D(a:2,b:3)");
+}
+
+#[test]
+fn test_array() {
+    let empty: [i32; 0] = [];
+    assert_eq!(to_string(&empty).unwrap(), "()");
+    let empty_ref: &[i32] = &empty;
+    assert_eq!(to_string(&empty_ref).unwrap(), "[]");
+
+    assert_eq!(to_string(&[2, 3, 4i32]).unwrap(), "(2,3,4)");
+    assert_eq!(to_string(&(&[2, 3, 4i32] as &[i32])).unwrap(), "[2,3,4]");
+}
+
+#[test]
+fn test_slice() {
+    assert_eq!(to_string(&[0, 1, 2, 3, 4, 5][..]).unwrap(), "[0,1,2,3,4,5]");
+    assert_eq!(to_string(&[0, 1, 2, 3, 4, 5][1..4]).unwrap(), "[1,2,3]");
+}
+
+#[test]
+fn test_vec() {
+    assert_eq!(to_string(&vec![0, 1, 2, 3, 4, 5]).unwrap(), "[0,1,2,3,4,5]");
+}
+
+#[test]
+fn test_map() {
+    use std::collections::HashMap;
+
+    let mut map = HashMap::new();
+    map.insert((true, false), 4);
+    map.insert((false, false), 123);
+
+    let s = to_string(&map).unwrap();
+    s.starts_with('{');
+    s.contains("(true,false):4");
+    s.contains("(false,false):123");
+    s.ends_with('}');
+}
+
+#[test]
+fn test_string() {
+    assert_eq!(to_string(&"Some string").unwrap(), "\"Some string\"");
+}
+
+#[test]
+fn test_char() {
+    assert_eq!(to_string(&'c').unwrap(), "'c'");
+}
+
+#[test]
+fn test_escape() {
+    assert_eq!(to_string(&r#""Quoted""#).unwrap(), r#""\"Quoted\"""#);
+}
+
+#[test]
+fn test_byte_stream() {
+    use serde_bytes;
+
+    let small: [u8; 16] = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15];
+    assert_eq!(
+        to_string(&small).unwrap(),
+        "(0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15)"
+    );
+
+    let large = vec![255u8; 64];
+    let large = serde_bytes::Bytes::new(&large);
+    assert_eq!(
+        to_string(&large).unwrap(),
+        concat!(
+            "\"/////////////////////////////////////////",
+            "////////////////////////////////////////////w==\""
+        )
+    );
+}
+
+#[test]
+fn rename() {
+    #[derive(Serialize, Debug, PartialEq)]
+    enum Foo {
+        #[serde(rename = "2d")]
+        D2,
+        #[serde(rename = "triangle-list")]
+        TriangleList,
+    }
+
+    assert_eq!(to_string(&Foo::D2).unwrap(), "r#2d");
+    assert_eq!(to_string(&Foo::TriangleList).unwrap(), "r#triangle-list");
+}
diff --git a/third_party/rust/ron/src/ser/value.rs b/third_party/rust/ron/src/ser/value.rs
new file mode 100644
index 0000000000..1a47758986
--- /dev/null
+++ b/third_party/rust/ron/src/ser/value.rs
@@ -0,0 +1,23 @@
+use serde::ser::{Serialize, Serializer};
+
+use crate::value::{Number, Value};
+
+impl Serialize for Value {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        match *self {
+            Value::Bool(b) => serializer.serialize_bool(b),
+            Value::Char(c) => serializer.serialize_char(c),
+            Value::Map(ref m) => Serialize::serialize(m, serializer),
+            Value::Number(Number::Float(ref f)) => serializer.serialize_f64(f.get()),
+            Value::Number(Number::Integer(i)) => serializer.serialize_i64(i),
+            Value::Option(Some(ref o)) => serializer.serialize_some(o.as_ref()),
+            Value::Option(None) => serializer.serialize_none(),
+            Value::String(ref s) => serializer.serialize_str(s),
+            Value::Seq(ref s) => Serialize::serialize(s, serializer),
+            Value::Unit => serializer.serialize_unit(),
+        }
+    }
+}
diff --git a/third_party/rust/ron/src/value.rs b/third_party/rust/ron/src/value.rs
new file mode 100644
index 0000000000..ba843bc16a
--- /dev/null
+++ b/third_party/rust/ron/src/value.rs
@@ -0,0 +1,619 @@
+//! Value module.
+
+use std::{
+    cmp::{Eq, Ordering},
+    hash::{Hash, Hasher},
+    iter::FromIterator,
+    ops::{Index, IndexMut},
+};
+
+use serde::{
+    de::{DeserializeOwned, DeserializeSeed, Deserializer, MapAccess, SeqAccess, Visitor},
+    forward_to_deserialize_any,
+};
+use serde_derive::{Deserialize, Serialize};
+
+use crate::{de::Error, error::Result};
+
+/// A [`Value`] to [`Value`] map.
+///
+/// This structure either uses a [BTreeMap](std::collections::BTreeMap) or the
+/// [IndexMap](indexmap::IndexMap) internally.
+/// The latter can be used by enabling the `indexmap` feature. This can be used
+/// to preserve the order of the parsed map.
+#[derive(Clone, Debug, Default, Deserialize, Serialize)]
+#[serde(transparent)]
+pub struct Map(MapInner);
+
+impl Map {
+    /// Creates a new, empty [`Map`].
+    pub fn new() -> Map {
+        Default::default()
+    }
+
+    /// Returns the number of elements in the map.
+    pub fn len(&self) -> usize {
+        self.0.len()
+    }
+
+    /// Returns `true` if `self.len() == 0`, `false` otherwise.
+    pub fn is_empty(&self) -> bool {
+        self.0.len() == 0
+    }
+
+    /// Inserts a new element, returning the previous element with this `key` if
+    /// there was any.
+    pub fn insert(&mut self, key: Value, value: Value) -> Option<Value> {
+        self.0.insert(key, value)
+    }
+
+    /// Removes an element by its `key`.
+    pub fn remove(&mut self, key: &Value) -> Option<Value> {
+        self.0.remove(key)
+    }
+
+    /// Iterate all key-value pairs.
+    pub fn iter(&self) -> impl Iterator<Item = (&Value, &Value)> + DoubleEndedIterator {
+        self.0.iter()
+    }
+
+    /// Iterate all key-value pairs mutably.
+    pub fn iter_mut(&mut self) -> impl Iterator<Item = (&Value, &mut Value)> + DoubleEndedIterator {
+        self.0.iter_mut()
+    }
+
+    /// Iterate all keys.
+    pub fn keys(&self) -> impl Iterator<Item = &Value> + DoubleEndedIterator {
+        self.0.keys()
+    }
+
+    /// Iterate all values.
+    pub fn values(&self) -> impl Iterator<Item = &Value> + DoubleEndedIterator {
+        self.0.values()
+    }
+
+    /// Iterate all values mutably.
+    pub fn values_mut(&mut self) -> impl Iterator<Item = &mut Value> + DoubleEndedIterator {
+        self.0.values_mut()
+    }
+
+    /// Retains only the elements specified by the `keep` predicate.
+    ///
+    /// In other words, remove all pairs `(k, v)` for which `keep(&k, &mut v)`
+    /// returns `false`.
+    ///
+    /// The elements are visited in iteration order.
+    pub fn retain<F>(&mut self, keep: F)
+    where
+        F: FnMut(&Value, &mut Value) -> bool,
+    {
+        self.0.retain(keep);
+    }
+}
+
+impl FromIterator<(Value, Value)> for Map {
+    fn from_iter<T: IntoIterator<Item = (Value, Value)>>(iter: T) -> Self {
+        Map(MapInner::from_iter(iter))
+    }
+}
+
+impl IntoIterator for Map {
+    type Item = (Value, Value);
+
+    type IntoIter = <MapInner as IntoIterator>::IntoIter;
+
+    fn into_iter(self) -> Self::IntoIter {
+        self.0.into_iter()
+    }
+}
+
+/// Note: equality is only given if both values and order of values match
+impl Eq for Map {}
+
+impl Hash for Map {
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        self.iter().for_each(|x| x.hash(state));
+    }
+}
+
+impl Index<&Value> for Map {
+    type Output = Value;
+
+    fn index(&self, index: &Value) -> &Self::Output {
+        &self.0[index]
+    }
+}
+
+impl IndexMut<&Value> for Map {
+    fn index_mut(&mut self, index: &Value) -> &mut Self::Output {
+        self.0.get_mut(index).expect("no entry found for key")
+    }
+}
+
+impl Ord for Map {
+    fn cmp(&self, other: &Map) -> Ordering {
+        self.iter().cmp(other.iter())
+    }
+}
+
+/// Note: equality is only given if both values and order of values match
+impl PartialEq for Map {
+    fn eq(&self, other: &Map) -> bool {
+        self.iter().zip(other.iter()).all(|(a, b)| a == b)
+    }
+}
+
+impl PartialOrd for Map {
+    fn partial_cmp(&self, other: &Map) -> Option<Ordering> {
+        self.iter().partial_cmp(other.iter())
+    }
+}
+
+#[cfg(not(feature = "indexmap"))]
+type MapInner = std::collections::BTreeMap<Value, Value>;
+#[cfg(feature = "indexmap")]
+type MapInner = indexmap::IndexMap<Value, Value>;
+
+/// A wrapper for a number, which can be either [`f64`] or [`i64`].
+#[derive(Copy, Clone, Debug, PartialEq, PartialOrd, Eq, Hash, Ord)]
+pub enum Number {
+    Integer(i64),
+    Float(Float),
+}
+
+/// A wrapper for [`f64`], which guarantees that the inner value
+/// is finite and thus implements [`Eq`], [`Hash`] and [`Ord`].
+#[derive(Copy, Clone, Debug)]
+pub struct Float(f64);
+
+impl Float {
+    /// Construct a new [`Float`].
+    pub fn new(v: f64) -> Self {
+        Float(v)
+    }
+
+    /// Returns the wrapped float.
+    pub fn get(self) -> f64 {
+        self.0
+    }
+}
+
+impl Number {
+    /// Construct a new number.
+    pub fn new(v: impl Into<Number>) -> Self {
+        v.into()
+    }
+
+    /// Returns the [`f64`] representation of the [`Number`] regardless of
+    /// whether the number is stored as a float or integer.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// # use ron::value::Number;
+    /// let i = Number::new(5);
+    /// let f = Number::new(2.0);
+    /// assert_eq!(i.into_f64(), 5.0);
+    /// assert_eq!(f.into_f64(), 2.0);
+    /// ```
+    pub fn into_f64(self) -> f64 {
+        self.map_to(|i| i as f64, |f| f)
+    }
+
+    /// If the [`Number`] is a float, return it. Otherwise return [`None`].
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// # use ron::value::Number;
+    /// let i = Number::new(5);
+    /// let f = Number::new(2.0);
+    /// assert_eq!(i.as_f64(), None);
+    /// assert_eq!(f.as_f64(), Some(2.0));
+    /// ```
+    pub fn as_f64(self) -> Option<f64> {
+        self.map_to(|_| None, Some)
+    }
+
+    /// If the [`Number`] is an integer, return it. Otherwise return [`None`].
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// # use ron::value::Number;
+    /// let i = Number::new(5);
+    /// let f = Number::new(2.0);
+    /// assert_eq!(i.as_i64(), Some(5));
+    /// assert_eq!(f.as_i64(), None);
+    /// ```
+    pub fn as_i64(self) -> Option<i64> {
+        self.map_to(Some, |_| None)
+    }
+
+    /// Map this number to a single type using the appropriate closure.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// # use ron::value::Number;
+    /// let i = Number::new(5);
+    /// let f = Number::new(2.0);
+    /// assert!(i.map_to(|i| i > 3, |f| f > 3.0));
+    /// assert!(!f.map_to(|i| i > 3, |f| f > 3.0));
+    /// ```
+    pub fn map_to<T>(
+        self,
+        integer_fn: impl FnOnce(i64) -> T,
+        float_fn: impl FnOnce(f64) -> T,
+    ) -> T {
+        match self {
+            Number::Integer(i) => integer_fn(i),
+            Number::Float(Float(f)) => float_fn(f),
+        }
+    }
+}
+
+impl From<f64> for Number {
+    fn from(f: f64) -> Number {
+        Number::Float(Float(f))
+    }
+}
+
+impl From<i64> for Number {
+    fn from(i: i64) -> Number {
+        Number::Integer(i)
+    }
+}
+
+impl From<i32> for Number {
+    fn from(i: i32) -> Number {
+        Number::Integer(i64::from(i))
+    }
+}
+
+/// The following [`Number`] conversion checks if the integer fits losslessly
+/// into an [`i64`], before constructing a [`Number::Integer`] variant.
+/// If not, the conversion defaults to [`Number::Float`].
+
+impl From<u64> for Number {
+    fn from(i: u64) -> Number {
+        if i <= std::i64::MAX as u64 {
+            Number::Integer(i as i64)
+        } else {
+            Number::new(i as f64)
+        }
+    }
+}
+
+/// Partial equality comparison
+/// In order to be able to use [`Number`] as a mapping key, NaN floating values
+/// wrapped in [`Float`] are equal to each other. It is not the case for
+/// underlying [`f64`] values itself.
+impl PartialEq for Float {
+    fn eq(&self, other: &Self) -> bool {
+        self.0.is_nan() && other.0.is_nan() || self.0 == other.0
+    }
+}
+
+/// Equality comparison
+/// In order to be able to use [`Float`] as a mapping key, NaN floating values
+/// wrapped in [`Float`] are equal to each other. It is not the case for
+/// underlying [`f64`] values itself.
+impl Eq for Float {}
+
+impl Hash for Float {
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        state.write_u64(self.0.to_bits());
+    }
+}
+
+/// Partial ordering comparison
+/// In order to be able to use [`Number`] as a mapping key, NaN floating values
+/// wrapped in [`Number`] are equal to each other and are less then any other
+/// floating value. It is not the case for the underlying [`f64`] values
+/// themselves.
+///
+/// ```
+/// use ron::value::Number;
+/// assert!(Number::new(std::f64::NAN) < Number::new(std::f64::NEG_INFINITY));
+/// assert_eq!(Number::new(std::f64::NAN), Number::new(std::f64::NAN));
+/// ```
+impl PartialOrd for Float {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        match (self.0.is_nan(), other.0.is_nan()) {
+            (true, true) => Some(Ordering::Equal),
+            (true, false) => Some(Ordering::Less),
+            (false, true) => Some(Ordering::Greater),
+            _ => self.0.partial_cmp(&other.0),
+        }
+    }
+}
+
+/// Ordering comparison
+/// In order to be able to use [`Float`] as a mapping key, NaN floating values
+/// wrapped in [`Float`] are equal to each other and are less then any other
+/// floating value. It is not the case for underlying [`f64`] values itself.
+/// See the [`PartialEq`] implementation.
+impl Ord for Float {
+    fn cmp(&self, other: &Self) -> Ordering {
+        self.partial_cmp(other).expect("Bug: Contract violation")
+    }
+}
+
+#[derive(Clone, Debug, Eq, Hash, Ord, PartialEq, PartialOrd)]
+pub enum Value {
+    Bool(bool),
+    Char(char),
+    Map(Map),
+    Number(Number),
+    Option(Option<Box<Value>>),
+    String(String),
+    Seq(Vec<Value>),
+    Unit,
+}
+
+impl Value {
+    /// Tries to deserialize this [`Value`] into `T`.
+    pub fn into_rust<T>(self) -> Result<T>
+    where
+        T: DeserializeOwned,
+    {
+        T::deserialize(self)
+    }
+}
+
+/// Deserializer implementation for RON [`Value`].
+/// This does not support enums (because [`Value`] does not store them).
+impl<'de> Deserializer<'de> for Value {
+    type Error = Error;
+
+    forward_to_deserialize_any! {
+        bool f32 f64 char str string bytes
+        byte_buf option unit unit_struct newtype_struct seq tuple
+        tuple_struct map struct enum identifier ignored_any
+    }
+
+    fn deserialize_any<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'de>,
+    {
+        match self {
+            Value::Bool(b) => visitor.visit_bool(b),
+            Value::Char(c) => visitor.visit_char(c),
+            Value::Map(m) => {
+                let old_len = m.len();
+
+                let mut items: Vec<(Value, Value)> = m.into_iter().collect();
+                items.reverse();
+
+                let value = visitor.visit_map(MapAccessor {
+                    items: &mut items,
+                    value: None,
+                })?;
+
+                if items.is_empty() {
+                    Ok(value)
+                } else {
+                    Err(Error::ExpectedDifferentLength {
+                        expected: format!("a map of length {}", old_len - items.len()),
+                        found: old_len,
+                    })
+                }
+            }
+            Value::Number(Number::Float(ref f)) => visitor.visit_f64(f.get()),
+            Value::Number(Number::Integer(i)) => visitor.visit_i64(i),
+            Value::Option(Some(o)) => visitor.visit_some(*o),
+            Value::Option(None) => visitor.visit_none(),
+            Value::String(s) => visitor.visit_string(s),
+            Value::Seq(mut seq) => {
+                let old_len = seq.len();
+
+                seq.reverse();
+                let value = visitor.visit_seq(Seq { seq: &mut seq })?;
+
+                if seq.is_empty() {
+                    Ok(value)
+                } else {
+                    Err(Error::ExpectedDifferentLength {
+                        expected: format!("a sequence of length {}", old_len - seq.len()),
+                        found: old_len,
+                    })
+                }
+            }
+            Value::Unit => visitor.visit_unit(),
+        }
+    }
+
+    fn deserialize_i8<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'de>,
+    {
+        self.deserialize_i64(visitor)
+    }
+
+    fn deserialize_i16<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'de>,
+    {
+        self.deserialize_i64(visitor)
+    }
+
+    fn deserialize_i32<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'de>,
+    {
+        self.deserialize_i64(visitor)
+    }
+
+    fn deserialize_i64<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'de>,
+    {
+        match self {
+            Value::Number(Number::Integer(i)) => visitor.visit_i64(i),
+            v => Err(Error::Message(format!("Expected a number, got {:?}", v))),
+        }
+    }
+
+    fn deserialize_u8<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'de>,
+    {
+        self.deserialize_u64(visitor)
+    }
+
+    fn deserialize_u16<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'de>,
+    {
+        self.deserialize_u64(visitor)
+    }
+
+    fn deserialize_u32<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'de>,
+    {
+        self.deserialize_u64(visitor)
+    }
+
+    fn deserialize_u64<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'de>,
+    {
+        match self {
+            Value::Number(Number::Integer(i)) => visitor.visit_u64(i as u64),
+            v => Err(Error::Message(format!("Expected a number, got {:?}", v))),
+        }
+    }
+}
+
+struct MapAccessor<'a> {
+    items: &'a mut Vec<(Value, Value)>,
+    value: Option<Value>,
+}
+
+impl<'a, 'de> MapAccess<'de> for MapAccessor<'a> {
+    type Error = Error;
+
+    fn next_key_seed<K>(&mut self, seed: K) -> Result<Option<K::Value>>
+    where
+        K: DeserializeSeed<'de>,
+    {
+        // The `Vec` is reversed, so we can pop to get the originally first element
+        match self.items.pop() {
+            Some((key, value)) => {
+                self.value = Some(value);
+                seed.deserialize(key).map(Some)
+            }
+            None => Ok(None),
+        }
+    }
+
+    fn next_value_seed<V>(&mut self, seed: V) -> Result<V::Value>
+    where
+        V: DeserializeSeed<'de>,
+    {
+        match self.value.take() {
+            Some(value) => seed.deserialize(value),
+            None => panic!("Contract violation: value before key"),
+        }
+    }
+
+    fn size_hint(&self) -> Option<usize> {
+        Some(self.items.len())
+    }
+}
+
+struct Seq<'a> {
+    seq: &'a mut Vec<Value>,
+}
+
+impl<'a, 'de> SeqAccess<'de> for Seq<'a> {
+    type Error = Error;
+
+    fn next_element_seed<T>(&mut self, seed: T) -> Result<Option<T::Value>>
+    where
+        T: DeserializeSeed<'de>,
+    {
+        // The `Vec` is reversed, so we can pop to get the originally first element
+        self.seq
+            .pop()
+            .map_or(Ok(None), |v| seed.deserialize(v).map(Some))
+    }
+
+    fn size_hint(&self) -> Option<usize> {
+        Some(self.seq.len())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use std::{collections::BTreeMap, fmt::Debug};
+
+    use serde::Deserialize;
+
+    use super::*;
+
+    fn assert_same<'de, T>(s: &'de str)
+    where
+        T: Debug + Deserialize<'de> + PartialEq,
+    {
+        use crate::de::from_str;
+
+        let direct: T = from_str(s).unwrap();
+        let value: Value = from_str(s).unwrap();
+        let value = T::deserialize(value).unwrap();
+
+        assert_eq!(direct, value, "Deserialization for {:?} is not the same", s);
+    }
+
+    #[test]
+    fn boolean() {
+        assert_same::<bool>("true");
+        assert_same::<bool>("false");
+    }
+
+    #[test]
+    fn float() {
+        assert_same::<f64>("0.123");
+        assert_same::<f64>("-4.19");
+    }
+
+    #[test]
+    fn int() {
+        assert_same::<u32>("626");
+        assert_same::<i32>("-50");
+    }
+
+    #[test]
+    fn char() {
+        assert_same::<char>("'4'");
+        assert_same::<char>("'c'");
+    }
+
+    #[test]
+    fn map() {
+        assert_same::<BTreeMap<char, String>>(
+            "{
+'a': \"Hello\",
+'b': \"Bye\",
+        }",
+        );
+    }
+
+    #[test]
+    fn option() {
+        assert_same::<Option<char>>("Some('a')");
+        assert_same::<Option<char>>("None");
+    }
+
+    #[test]
+    fn seq() {
+        assert_same::<Vec<f64>>("[1.0, 2.0, 3.0, 4.0]");
+    }
+
+    #[test]
+    fn unit() {
+        assert_same::<()>("()");
+    }
+}