feat: add display UI with splash screen, dashboard, and RSSI sparkline

Implement full SSD1306 OLED display support:
- Splash screen on boot (1.5s) with project name, version, board
- Dashboard showing radio state, config, counters, RSSI/SNR
- RSSI history sparkline (64-sample ring buffer, 2px-wide bars)
- DisplayOn/DisplayOff host commands routed via dedicated channel
- Pure render functions against generic DrawTarget (no hardware coupling)
- Display on/off control bypasses radio task entirely

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

vendor/basic-toml/src/error.rs

@@ -0,0 +1,54 @@
+use std::fmt::{self, Debug, Display};
+
+/// Errors that can occur when serializing or deserializing TOML.
+pub struct Error(Box<ErrorInner>);
+
+pub(crate) enum ErrorInner {
+    Ser(crate::ser::Error),
+    De(crate::de::Error),
+}
+
+impl Error {
+    /// Produces a (line, column) pair of the position of the error if
+    /// available.
+    ///
+    /// All indexes are 0-based.
+    pub fn line_col(&self) -> Option<(usize, usize)> {
+        match &*self.0 {
+            ErrorInner::Ser(_) => None,
+            ErrorInner::De(error) => error.line_col(),
+        }
+    }
+}
+
+impl From<crate::ser::Error> for Error {
+    fn from(error: crate::ser::Error) -> Self {
+        Error(Box::new(ErrorInner::Ser(error)))
+    }
+}
+
+impl From<crate::de::Error> for Error {
+    fn from(error: crate::de::Error) -> Self {
+        Error(Box::new(ErrorInner::De(error)))
+    }
+}
+
+impl Display for Error {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        match &*self.0 {
+            ErrorInner::Ser(error) => Display::fmt(error, formatter),
+            ErrorInner::De(error) => Display::fmt(error, formatter),
+        }
+    }
+}
+
+impl Debug for Error {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        match &*self.0 {
+            ErrorInner::Ser(error) => Debug::fmt(error, formatter),
+            ErrorInner::De(error) => Debug::fmt(error, formatter),
+        }
+    }
+}
+
+impl std::error::Error for Error {}

vendor/basic-toml/src/lib.rs

@@ -0,0 +1,144 @@
+//! [![github]](https://github.com/dtolnay/basic-toml) [![crates-io]](https://crates.io/crates/basic-toml) [![docs-rs]](https://docs.rs/basic-toml)
+//!
+//! [github]: https://img.shields.io/badge/github-8da0cb?style=for-the-badge&labelColor=555555&logo=github
+//! [crates-io]: https://img.shields.io/badge/crates.io-fc8d62?style=for-the-badge&labelColor=555555&logo=rust
+//! [docs-rs]: https://img.shields.io/badge/docs.rs-66c2a5?style=for-the-badge&labelColor=555555&logo=docs.rs
+//!
+//! <br>
+//!
+//! A library for parsing and producing data in [TOML] format using [Serde].
+//!
+//! TOML is designed to be "a config file format for humans": minimal and easy
+//! to read due to obvious semantics.
+//!
+//! ```toml
+//! [package]
+//! name = "basic-toml"
+#![doc = concat!("version = \"", env!("CARGO_PKG_VERSION_MAJOR"), ".", env!("CARGO_PKG_VERSION_MINOR"), ".", env!("CARGO_PKG_VERSION_PATCH"), "\"")]
+//! authors = ["Alex Crichton <alex@alexcrichton.com>"]
+//!
+//! [dependencies]
+//! serde = "1.0"
+//! ```
+//!
+//! The TOML format is widely used throughout the Rust community for
+//! configuration, notably being used by [Cargo], Rust's package manager.
+//!
+//! [TOML]: https://toml.io
+//! [Serde]: https://serde.rs
+//! [Cargo]: https://crates.io
+//!
+//! # Deserialization
+//!
+//! ```
+//! use semver::{Version, VersionReq};
+//! use serde_derive::Deserialize;
+//! use std::collections::BTreeMap as Map;
+//!
+//! #[derive(Deserialize)]
+//! struct Manifest {
+//!     package: Package,
+//!     #[serde(default)]
+//!     dependencies: Map<String, VersionReq>,
+//! }
+//!
+//! #[derive(Deserialize)]
+//! struct Package {
+//!     name: String,
+//!     version: Version,
+//!     #[serde(default)]
+//!     authors: Vec<String>,
+//! }
+//!
+//! fn main() {
+//!     let manifest: Manifest = basic_toml::from_str(r#"
+//!         [package]
+//!         name = "basic-toml"
+#![doc = concat!("        version = \"", env!("CARGO_PKG_VERSION_MAJOR"), ".", env!("CARGO_PKG_VERSION_MINOR"), ".", env!("CARGO_PKG_VERSION_PATCH"), "\"")]
+//!         authors = ["Alex Crichton <alex@alexcrichton.com>"]
+//!
+//!         [dependencies]
+//!         serde = "^1.0"
+//!     "#).unwrap();
+//!
+//!     assert_eq!(manifest.package.name, "basic-toml");
+#![doc = concat!("    assert_eq!(manifest.package.version, Version::new(", env!("CARGO_PKG_VERSION_MAJOR"), ", ", env!("CARGO_PKG_VERSION_MINOR"), ", ", env!("CARGO_PKG_VERSION_PATCH"), "));")]
+//!     assert_eq!(manifest.package.authors, ["Alex Crichton <alex@alexcrichton.com>"]);
+//!     assert_eq!(manifest.dependencies["serde"].to_string(), "^1.0");
+//! }
+//! ```
+//!
+//! # Serialization
+//!
+//! ```
+//! use semver::{Version, VersionReq};
+//! use serde_derive::Serialize;
+//! use std::collections::BTreeMap as Map;
+//!
+//! #[derive(Serialize)]
+//! struct Manifest {
+//!     package: Package,
+//!     dependencies: Map<String, VersionReq>,
+//! }
+//!
+//! #[derive(Serialize)]
+//! struct Package {
+//!     name: String,
+//!     version: Version,
+//!     authors: Vec<String>,
+//! }
+//!
+//! fn main() {
+//!     let manifest = Manifest {
+//!         package: Package {
+//!             name: "basic-toml".to_owned(),
+#![doc = concat!("            version: Version::new(", env!("CARGO_PKG_VERSION_MAJOR"), ", ", env!("CARGO_PKG_VERSION_MINOR"), ", ", env!("CARGO_PKG_VERSION_PATCH"), "),")]
+//!             authors: vec!["Alex Crichton <alex@alexcrichton.com>".to_owned()],
+//!         },
+//!         dependencies: {
+//!             let mut dependencies = Map::new();
+//!             dependencies.insert("serde".to_owned(), "^1.0".parse().unwrap());
+//!             dependencies
+//!         },
+//!     };
+//!
+//!     let toml = basic_toml::to_string(&manifest).unwrap();
+//!     print!("{}", toml);
+//! }
+//! ```
+//!
+//! # Spec compatibility
+//!
+//! TOML v0.5.0.
+//!
+//! TOML's date and time syntax are not supported.
+
+#![doc(html_root_url = "https://docs.rs/basic-toml/0.1.10")]
+#![deny(missing_docs)]
+#![allow(
+    clippy::bool_to_int_with_if,
+    clippy::elidable_lifetime_names,
+    clippy::let_underscore_untyped,
+    clippy::manual_let_else,
+    clippy::manual_range_contains,
+    clippy::match_like_matches_macro,
+    clippy::missing_errors_doc,
+    clippy::must_use_candidate,
+    clippy::needless_doctest_main,
+    clippy::needless_lifetimes,
+    clippy::needless_pass_by_value,
+    clippy::similar_names,
+    clippy::type_complexity,
+    clippy::uninlined_format_args,
+    clippy::unnecessary_box_returns,
+    clippy::unwrap_or_default
+)]
+
+mod de;
+mod error;
+mod ser;
+mod tokens;
+
+pub use crate::de::{from_slice, from_str};
+pub use crate::error::Error;
+pub use crate::ser::to_string;

vendor/basic-toml/src/ser.rs

@@ -0,0 +1,833 @@
+use serde::ser::{self, Serialize};
+use std::cell::Cell;
+use std::error;
+use std::fmt::{self, Display, Write};
+
+/// Serialize the given data structure as a String of TOML.
+///
+/// Serialization can fail if `T`'s implementation of `Serialize` decides to
+/// fail, if `T` contains a map with non-string keys, or if `T` attempts to
+/// serialize an unsupported datatype such as an enum, tuple, or tuple struct.
+pub fn to_string<T>(value: &T) -> Result<String, crate::Error>
+where
+    T: ?Sized + Serialize,
+{
+    let mut dst = String::with_capacity(128);
+    value.serialize(&mut Serializer::new(&mut dst))?;
+    Ok(dst)
+}
+
+#[derive(Debug)]
+pub(crate) enum Error {
+    /// Indicates that a Rust type was requested to be serialized but it was not
+    /// supported.
+    ///
+    /// Currently the TOML format does not support serializing types such as
+    /// enums, tuples and tuple structs.
+    UnsupportedType,
+
+    /// The key of all TOML maps must be strings, but serialization was
+    /// attempted where the key of a map was not a string.
+    KeyNotString,
+
+    /// All values in a TOML table must be emitted before further tables are
+    /// emitted. If a value is emitted *after* a table then this error is
+    /// generated.
+    ValueAfterTable,
+
+    /// None was attempted to be serialized, but it's not supported.
+    UnsupportedNone,
+
+    /// A custom error which could be generated when serializing a particular
+    /// type.
+    Custom(String),
+}
+
+struct Serializer<'a> {
+    dst: &'a mut String,
+    state: State<'a>,
+}
+
+#[derive(Debug, Copy, Clone)]
+enum ArrayState {
+    Started,
+    StartedAsATable,
+}
+
+#[derive(Debug, Clone)]
+enum State<'a> {
+    Table {
+        key: &'a str,
+        parent: &'a State<'a>,
+        first: &'a Cell<bool>,
+        table_emitted: &'a Cell<bool>,
+    },
+    Array {
+        parent: &'a State<'a>,
+        first: &'a Cell<bool>,
+        type_: &'a Cell<Option<ArrayState>>,
+        len: Option<usize>,
+    },
+    End,
+}
+
+struct SerializeSeq<'a, 'b> {
+    ser: &'b mut Serializer<'a>,
+    first: Cell<bool>,
+    type_: Cell<Option<ArrayState>>,
+    len: Option<usize>,
+}
+
+struct SerializeTable<'a, 'b> {
+    ser: &'b mut Serializer<'a>,
+    key: String,
+    first: Cell<bool>,
+    table_emitted: Cell<bool>,
+}
+
+impl<'a> Serializer<'a> {
+    fn new(dst: &'a mut String) -> Serializer<'a> {
+        Serializer {
+            dst,
+            state: State::End,
+        }
+    }
+
+    fn display<T: Display>(&mut self, t: T, type_: ArrayState) -> Result<(), Error> {
+        self.emit_key(type_)?;
+        write!(self.dst, "{}", t).map_err(ser::Error::custom)?;
+        if let State::Table { .. } = self.state {
+            self.dst.push('\n');
+        }
+        Ok(())
+    }
+
+    fn emit_key(&mut self, type_: ArrayState) -> Result<(), Error> {
+        self.array_type(type_);
+        let state = self.state.clone();
+        self.do_emit_key(&state)
+    }
+
+    // recursive implementation of `emit_key` above
+    fn do_emit_key(&mut self, state: &State) -> Result<(), Error> {
+        match *state {
+            State::End => Ok(()),
+            State::Array {
+                parent,
+                first,
+                type_,
+                len,
+            } => {
+                assert!(type_.get().is_some());
+                if first.get() {
+                    self.do_emit_key(parent)?;
+                }
+                self.emit_array(first, len);
+                Ok(())
+            }
+            State::Table {
+                parent,
+                first,
+                table_emitted,
+                key,
+            } => {
+                if table_emitted.get() {
+                    return Err(Error::ValueAfterTable);
+                }
+                if first.get() {
+                    self.emit_table_header(parent)?;
+                    first.set(false);
+                }
+                self.escape_key(key)?;
+                self.dst.push_str(" = ");
+                Ok(())
+            }
+        }
+    }
+
+    fn emit_array(&mut self, first: &Cell<bool>, _len: Option<usize>) {
+        if first.get() {
+            self.dst.push('[');
+        } else {
+            self.dst.push_str(", ");
+        }
+    }
+
+    fn array_type(&mut self, type_: ArrayState) {
+        let prev = match self.state {
+            State::Array { type_, .. } => type_,
+            _ => return,
+        };
+        if prev.get().is_none() {
+            prev.set(Some(type_));
+        }
+    }
+
+    fn escape_key(&mut self, key: &str) -> Result<(), Error> {
+        let ok = !key.is_empty()
+            && key.chars().all(|c| match c {
+                'a'..='z' | 'A'..='Z' | '0'..='9' | '-' | '_' => true,
+                _ => false,
+            });
+        if ok {
+            write!(self.dst, "{}", key).map_err(ser::Error::custom)?;
+        } else {
+            self.emit_str(key)?;
+        }
+        Ok(())
+    }
+
+    fn emit_str(&mut self, value: &str) -> Result<(), Error> {
+        self.dst.push('"');
+        for ch in value.chars() {
+            match ch {
+                '\u{8}' => self.dst.push_str("\\b"),
+                '\u{9}' => self.dst.push_str("\\t"),
+                '\u{a}' => self.dst.push_str("\\n"),
+                '\u{c}' => self.dst.push_str("\\f"),
+                '\u{d}' => self.dst.push_str("\\r"),
+                '\u{22}' => self.dst.push_str("\\\""),
+                '\u{5c}' => self.dst.push_str("\\\\"),
+                c if c <= '\u{1f}' || c == '\u{7f}' => {
+                    write!(self.dst, "\\u{:04X}", ch as u32).map_err(ser::Error::custom)?;
+                }
+                ch => self.dst.push(ch),
+            }
+        }
+        self.dst.push('"');
+        Ok(())
+    }
+
+    fn emit_table_header(&mut self, state: &State) -> Result<(), Error> {
+        let array_of_tables = match *state {
+            State::End => return Ok(()),
+            State::Array { .. } => true,
+            State::Table { .. } => false,
+        };
+
+        // Unlike [..]s, we can't omit [[..]] ancestors, so be sure to emit
+        // table headers for them.
+        let mut p = state;
+        if let State::Array { first, parent, .. } = *state {
+            if first.get() {
+                p = parent;
+            }
+        }
+        while let State::Table { first, parent, .. } = *p {
+            p = parent;
+            if !first.get() {
+                break;
+            }
+            if let State::Array {
+                parent: &State::Table { .. },
+                ..
+            } = *parent
+            {
+                self.emit_table_header(parent)?;
+                break;
+            }
+        }
+
+        match *state {
+            State::Table { first, .. } => {
+                if !first.get() {
+                    // Newline if we are a table that is not the first table in
+                    // the document.
+                    self.dst.push('\n');
+                }
+            }
+            State::Array { parent, first, .. } => {
+                if !first.get() {
+                    // Always newline if we are not the first item in the
+                    // table-array
+                    self.dst.push('\n');
+                } else if let State::Table { first, .. } = *parent {
+                    if !first.get() {
+                        // Newline if we are not the first item in the document
+                        self.dst.push('\n');
+                    }
+                }
+            }
+            State::End => {}
+        }
+        self.dst.push('[');
+        if array_of_tables {
+            self.dst.push('[');
+        }
+        self.emit_key_part(state)?;
+        if array_of_tables {
+            self.dst.push(']');
+        }
+        self.dst.push_str("]\n");
+        Ok(())
+    }
+
+    fn emit_key_part(&mut self, key: &State) -> Result<bool, Error> {
+        match *key {
+            State::Array { parent, .. } => self.emit_key_part(parent),
+            State::End => Ok(true),
+            State::Table {
+                key,
+                parent,
+                table_emitted,
+                ..
+            } => {
+                table_emitted.set(true);
+                let first = self.emit_key_part(parent)?;
+                if !first {
+                    self.dst.push('.');
+                }
+                self.escape_key(key)?;
+                Ok(false)
+            }
+        }
+    }
+}
+
+macro_rules! serialize_float {
+    ($this:expr, $v:expr) => {{
+        $this.emit_key(ArrayState::Started)?;
+        match ($v.is_sign_negative(), $v.is_nan(), $v == 0.0) {
+            (_, true, _) => write!($this.dst, "nan"),
+            (true, false, true) => write!($this.dst, "-0.0"),
+            (false, false, true) => write!($this.dst, "0.0"),
+            (_, false, false) => write!($this.dst, "{}", $v).and_then(|()| {
+                if $v % 1.0 == 0.0 {
+                    write!($this.dst, ".0")
+                } else {
+                    Ok(())
+                }
+            }),
+        }
+        .map_err(ser::Error::custom)?;
+
+        if let State::Table { .. } = $this.state {
+            $this.dst.push_str("\n");
+        }
+        return Ok(());
+    }};
+}
+
+impl<'a, 'b> ser::Serializer for &'b mut Serializer<'a> {
+    type Ok = ();
+    type Error = Error;
+    type SerializeSeq = SerializeSeq<'a, 'b>;
+    type SerializeTuple = SerializeSeq<'a, 'b>;
+    type SerializeTupleStruct = SerializeSeq<'a, 'b>;
+    type SerializeTupleVariant = ser::Impossible<(), Error>;
+    type SerializeMap = SerializeTable<'a, 'b>;
+    type SerializeStruct = SerializeTable<'a, 'b>;
+    type SerializeStructVariant = ser::Impossible<(), Error>;
+
+    fn serialize_bool(self, v: bool) -> Result<(), Self::Error> {
+        self.display(v, ArrayState::Started)
+    }
+
+    fn serialize_i8(self, v: i8) -> Result<(), Self::Error> {
+        self.display(v, ArrayState::Started)
+    }
+
+    fn serialize_i16(self, v: i16) -> Result<(), Self::Error> {
+        self.display(v, ArrayState::Started)
+    }
+
+    fn serialize_i32(self, v: i32) -> Result<(), Self::Error> {
+        self.display(v, ArrayState::Started)
+    }
+
+    fn serialize_i64(self, v: i64) -> Result<(), Self::Error> {
+        self.display(v, ArrayState::Started)
+    }
+
+    fn serialize_u8(self, v: u8) -> Result<(), Self::Error> {
+        self.display(v, ArrayState::Started)
+    }
+
+    fn serialize_u16(self, v: u16) -> Result<(), Self::Error> {
+        self.display(v, ArrayState::Started)
+    }
+
+    fn serialize_u32(self, v: u32) -> Result<(), Self::Error> {
+        self.display(v, ArrayState::Started)
+    }
+
+    fn serialize_u64(self, v: u64) -> Result<(), Self::Error> {
+        self.display(v, ArrayState::Started)
+    }
+
+    fn serialize_f32(self, v: f32) -> Result<(), Self::Error> {
+        serialize_float!(self, v)
+    }
+
+    fn serialize_f64(self, v: f64) -> Result<(), Self::Error> {
+        serialize_float!(self, v)
+    }
+
+    fn serialize_char(self, v: char) -> Result<(), Self::Error> {
+        let mut buf = [0; 4];
+        self.serialize_str(v.encode_utf8(&mut buf))
+    }
+
+    fn serialize_str(self, value: &str) -> Result<(), Self::Error> {
+        self.emit_key(ArrayState::Started)?;
+        self.emit_str(value)?;
+        if let State::Table { .. } = self.state {
+            self.dst.push('\n');
+        }
+        Ok(())
+    }
+
+    fn serialize_bytes(self, value: &[u8]) -> Result<(), Self::Error> {
+        value.serialize(self)
+    }
+
+    fn serialize_none(self) -> Result<(), Self::Error> {
+        Err(Error::UnsupportedNone)
+    }
+
+    fn serialize_some<T>(self, value: &T) -> Result<(), Self::Error>
+    where
+        T: ?Sized + Serialize,
+    {
+        value.serialize(self)
+    }
+
+    fn serialize_unit(self) -> Result<(), Self::Error> {
+        Err(Error::UnsupportedType)
+    }
+
+    fn serialize_unit_struct(self, _name: &'static str) -> Result<(), Self::Error> {
+        Err(Error::UnsupportedType)
+    }
+
+    fn serialize_unit_variant(
+        self,
+        _name: &'static str,
+        _variant_index: u32,
+        variant: &'static str,
+    ) -> Result<(), Self::Error> {
+        self.serialize_str(variant)
+    }
+
+    fn serialize_newtype_struct<T>(self, _name: &'static str, value: &T) -> Result<(), Self::Error>
+    where
+        T: ?Sized + Serialize,
+    {
+        value.serialize(self)
+    }
+
+    fn serialize_newtype_variant<T>(
+        self,
+        _name: &'static str,
+        _variant_index: u32,
+        _variant: &'static str,
+        _value: &T,
+    ) -> Result<(), Self::Error>
+    where
+        T: ?Sized + Serialize,
+    {
+        Err(Error::UnsupportedType)
+    }
+
+    fn serialize_seq(self, len: Option<usize>) -> Result<Self::SerializeSeq, Self::Error> {
+        self.array_type(ArrayState::Started);
+        Ok(SerializeSeq {
+            ser: self,
+            first: Cell::new(true),
+            type_: Cell::new(None),
+            len,
+        })
+    }
+
+    fn serialize_tuple(self, len: usize) -> Result<Self::SerializeTuple, Self::Error> {
+        self.serialize_seq(Some(len))
+    }
+
+    fn serialize_tuple_struct(
+        self,
+        _name: &'static str,
+        len: usize,
+    ) -> Result<Self::SerializeTupleStruct, Self::Error> {
+        self.serialize_seq(Some(len))
+    }
+
+    fn serialize_tuple_variant(
+        self,
+        _name: &'static str,
+        _variant_index: u32,
+        _variant: &'static str,
+        _len: usize,
+    ) -> Result<Self::SerializeTupleVariant, Self::Error> {
+        Err(Error::UnsupportedType)
+    }
+
+    fn serialize_map(self, _len: Option<usize>) -> Result<Self::SerializeMap, Self::Error> {
+        self.array_type(ArrayState::StartedAsATable);
+        Ok(SerializeTable {
+            ser: self,
+            key: String::new(),
+            first: Cell::new(true),
+            table_emitted: Cell::new(false),
+        })
+    }
+
+    fn serialize_struct(
+        self,
+        _name: &'static str,
+        _len: usize,
+    ) -> Result<Self::SerializeStruct, Self::Error> {
+        self.array_type(ArrayState::StartedAsATable);
+        Ok(SerializeTable {
+            ser: self,
+            key: String::new(),
+            first: Cell::new(true),
+            table_emitted: Cell::new(false),
+        })
+    }
+
+    fn serialize_struct_variant(
+        self,
+        _name: &'static str,
+        _variant_index: u32,
+        _variant: &'static str,
+        _len: usize,
+    ) -> Result<Self::SerializeStructVariant, Self::Error> {
+        Err(Error::UnsupportedType)
+    }
+}
+
+impl<'a, 'b> ser::SerializeSeq for SerializeSeq<'a, 'b> {
+    type Ok = ();
+    type Error = Error;
+
+    fn serialize_element<T>(&mut self, value: &T) -> Result<(), Error>
+    where
+        T: ?Sized + Serialize,
+    {
+        value.serialize(&mut Serializer {
+            dst: &mut *self.ser.dst,
+            state: State::Array {
+                parent: &self.ser.state,
+                first: &self.first,
+                type_: &self.type_,
+                len: self.len,
+            },
+        })?;
+        self.first.set(false);
+        Ok(())
+    }
+
+    fn end(self) -> Result<(), Error> {
+        match self.type_.get() {
+            Some(ArrayState::StartedAsATable) => return Ok(()),
+            Some(ArrayState::Started) => self.ser.dst.push(']'),
+            None => {
+                assert!(self.first.get());
+                self.ser.emit_key(ArrayState::Started)?;
+                self.ser.dst.push_str("[]");
+            }
+        }
+        if let State::Table { .. } = self.ser.state {
+            self.ser.dst.push('\n');
+        }
+        Ok(())
+    }
+}
+
+impl<'a, 'b> ser::SerializeTuple for SerializeSeq<'a, 'b> {
+    type Ok = ();
+    type Error = Error;
+
+    fn serialize_element<T>(&mut self, value: &T) -> Result<(), Error>
+    where
+        T: ?Sized + Serialize,
+    {
+        ser::SerializeSeq::serialize_element(self, value)
+    }
+
+    fn end(self) -> Result<(), Error> {
+        ser::SerializeSeq::end(self)
+    }
+}
+
+impl<'a, 'b> ser::SerializeTupleStruct for SerializeSeq<'a, 'b> {
+    type Ok = ();
+    type Error = Error;
+
+    fn serialize_field<T>(&mut self, value: &T) -> Result<(), Error>
+    where
+        T: ?Sized + Serialize,
+    {
+        ser::SerializeSeq::serialize_element(self, value)
+    }
+
+    fn end(self) -> Result<(), Error> {
+        ser::SerializeSeq::end(self)
+    }
+}
+
+impl<'a, 'b> ser::SerializeMap for SerializeTable<'a, 'b> {
+    type Ok = ();
+    type Error = Error;
+
+    fn serialize_key<T>(&mut self, input: &T) -> Result<(), Error>
+    where
+        T: ?Sized + Serialize,
+    {
+        self.key = input.serialize(StringExtractor)?;
+        Ok(())
+    }
+
+    fn serialize_value<T>(&mut self, value: &T) -> Result<(), Error>
+    where
+        T: ?Sized + Serialize,
+    {
+        let res = value.serialize(&mut Serializer {
+            dst: &mut *self.ser.dst,
+            state: State::Table {
+                key: &self.key,
+                parent: &self.ser.state,
+                first: &self.first,
+                table_emitted: &self.table_emitted,
+            },
+        });
+        match res {
+            Ok(()) => self.first.set(false),
+            Err(Error::UnsupportedNone) => {}
+            Err(e) => return Err(e),
+        }
+        Ok(())
+    }
+
+    fn end(self) -> Result<(), Error> {
+        if self.first.get() {
+            let state = self.ser.state.clone();
+            self.ser.emit_table_header(&state)?;
+        }
+        Ok(())
+    }
+}
+
+impl<'a, 'b> ser::SerializeStruct for SerializeTable<'a, 'b> {
+    type Ok = ();
+    type Error = Error;
+
+    fn serialize_field<T>(&mut self, key: &'static str, value: &T) -> Result<(), Error>
+    where
+        T: ?Sized + Serialize,
+    {
+        let res = value.serialize(&mut Serializer {
+            dst: &mut *self.ser.dst,
+            state: State::Table {
+                key,
+                parent: &self.ser.state,
+                first: &self.first,
+                table_emitted: &self.table_emitted,
+            },
+        });
+        match res {
+            Ok(()) => self.first.set(false),
+            Err(Error::UnsupportedNone) => {}
+            Err(e) => return Err(e),
+        }
+        Ok(())
+    }
+
+    fn end(self) -> Result<(), Error> {
+        if self.first.get() {
+            let state = self.ser.state.clone();
+            self.ser.emit_table_header(&state)?;
+        }
+        Ok(())
+    }
+}
+
+struct StringExtractor;
+
+impl ser::Serializer for StringExtractor {
+    type Ok = String;
+    type Error = Error;
+    type SerializeSeq = ser::Impossible<String, Error>;
+    type SerializeTuple = ser::Impossible<String, Error>;
+    type SerializeTupleStruct = ser::Impossible<String, Error>;
+    type SerializeTupleVariant = ser::Impossible<String, Error>;
+    type SerializeMap = ser::Impossible<String, Error>;
+    type SerializeStruct = ser::Impossible<String, Error>;
+    type SerializeStructVariant = ser::Impossible<String, Error>;
+
+    fn serialize_bool(self, _v: bool) -> Result<String, Self::Error> {
+        Err(Error::KeyNotString)
+    }
+
+    fn serialize_i8(self, _v: i8) -> Result<String, Self::Error> {
+        Err(Error::KeyNotString)
+    }
+
+    fn serialize_i16(self, _v: i16) -> Result<String, Self::Error> {
+        Err(Error::KeyNotString)
+    }
+
+    fn serialize_i32(self, _v: i32) -> Result<String, Self::Error> {
+        Err(Error::KeyNotString)
+    }
+
+    fn serialize_i64(self, _v: i64) -> Result<String, Self::Error> {
+        Err(Error::KeyNotString)
+    }
+
+    fn serialize_u8(self, _v: u8) -> Result<String, Self::Error> {
+        Err(Error::KeyNotString)
+    }
+
+    fn serialize_u16(self, _v: u16) -> Result<String, Self::Error> {
+        Err(Error::KeyNotString)
+    }
+
+    fn serialize_u32(self, _v: u32) -> Result<String, Self::Error> {
+        Err(Error::KeyNotString)
+    }
+
+    fn serialize_u64(self, _v: u64) -> Result<String, Self::Error> {
+        Err(Error::KeyNotString)
+    }
+
+    fn serialize_f32(self, _v: f32) -> Result<String, Self::Error> {
+        Err(Error::KeyNotString)
+    }
+
+    fn serialize_f64(self, _v: f64) -> Result<String, Self::Error> {
+        Err(Error::KeyNotString)
+    }
+
+    fn serialize_char(self, _v: char) -> Result<String, Self::Error> {
+        Err(Error::KeyNotString)
+    }
+
+    fn serialize_str(self, value: &str) -> Result<String, Self::Error> {
+        Ok(value.to_string())
+    }
+
+    fn serialize_bytes(self, _value: &[u8]) -> Result<String, Self::Error> {
+        Err(Error::KeyNotString)
+    }
+
+    fn serialize_none(self) -> Result<String, Self::Error> {
+        Err(Error::KeyNotString)
+    }
+
+    fn serialize_some<T>(self, _value: &T) -> Result<String, Self::Error>
+    where
+        T: ?Sized + Serialize,
+    {
+        Err(Error::KeyNotString)
+    }
+
+    fn serialize_unit(self) -> Result<String, Self::Error> {
+        Err(Error::KeyNotString)
+    }
+
+    fn serialize_unit_struct(self, _name: &'static str) -> Result<String, Self::Error> {
+        Err(Error::KeyNotString)
+    }
+
+    fn serialize_unit_variant(
+        self,
+        _name: &'static str,
+        _variant_index: u32,
+        _variant: &'static str,
+    ) -> Result<String, Self::Error> {
+        Err(Error::KeyNotString)
+    }
+
+    fn serialize_newtype_struct<T>(
+        self,
+        _name: &'static str,
+        value: &T,
+    ) -> Result<String, Self::Error>
+    where
+        T: ?Sized + Serialize,
+    {
+        value.serialize(self)
+    }
+
+    fn serialize_newtype_variant<T>(
+        self,
+        _name: &'static str,
+        _variant_index: u32,
+        _variant: &'static str,
+        _value: &T,
+    ) -> Result<String, Self::Error>
+    where
+        T: ?Sized + Serialize,
+    {
+        Err(Error::KeyNotString)
+    }
+
+    fn serialize_seq(self, _len: Option<usize>) -> Result<Self::SerializeSeq, Self::Error> {
+        Err(Error::KeyNotString)
+    }
+
+    fn serialize_tuple(self, _len: usize) -> Result<Self::SerializeTuple, Self::Error> {
+        Err(Error::KeyNotString)
+    }
+
+    fn serialize_tuple_struct(
+        self,
+        _name: &'static str,
+        _len: usize,
+    ) -> Result<Self::SerializeTupleStruct, Self::Error> {
+        Err(Error::KeyNotString)
+    }
+
+    fn serialize_tuple_variant(
+        self,
+        _name: &'static str,
+        _variant_index: u32,
+        _variant: &'static str,
+        _len: usize,
+    ) -> Result<Self::SerializeTupleVariant, Self::Error> {
+        Err(Error::KeyNotString)
+    }
+
+    fn serialize_map(self, _len: Option<usize>) -> Result<Self::SerializeMap, Self::Error> {
+        Err(Error::KeyNotString)
+    }
+
+    fn serialize_struct(
+        self,
+        _name: &'static str,
+        _len: usize,
+    ) -> Result<Self::SerializeStruct, Self::Error> {
+        Err(Error::KeyNotString)
+    }
+
+    fn serialize_struct_variant(
+        self,
+        _name: &'static str,
+        _variant_index: u32,
+        _variant: &'static str,
+        _len: usize,
+    ) -> Result<Self::SerializeStructVariant, Self::Error> {
+        Err(Error::KeyNotString)
+    }
+}
+
+impl Display for Error {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match *self {
+            Error::UnsupportedType => "unsupported Rust type".fmt(f),
+            Error::KeyNotString => "map key was not a string".fmt(f),
+            Error::ValueAfterTable => "values must be emitted before tables".fmt(f),
+            Error::UnsupportedNone => "unsupported None value".fmt(f),
+            Error::Custom(ref s) => s.fmt(f),
+        }
+    }
+}
+
+impl error::Error for Error {}
+
+impl ser::Error for Error {
+    fn custom<T: Display>(msg: T) -> Error {
+        Error::Custom(msg.to_string())
+    }
+}

vendor/basic-toml/src/tokens.rs

@@ -0,0 +1,545 @@
+use std::borrow::Cow;
+use std::char;
+use std::str;
+
+/// A span, designating a range of bytes where a token is located.
+#[derive(Eq, PartialEq, Debug, Clone, Copy)]
+pub struct Span {
+    /// The start of the range.
+    pub start: usize,
+    /// The end of the range (exclusive).
+    pub end: usize,
+}
+
+impl From<Span> for (usize, usize) {
+    fn from(Span { start, end }: Span) -> (usize, usize) {
+        (start, end)
+    }
+}
+
+#[derive(Eq, PartialEq, Debug)]
+pub enum Token<'a> {
+    Whitespace(&'a str),
+    Newline,
+    Comment(&'a str),
+
+    Equals,
+    Period,
+    Comma,
+    Colon,
+    Plus,
+    LeftBrace,
+    RightBrace,
+    LeftBracket,
+    RightBracket,
+
+    Keylike(&'a str),
+    String {
+        src: &'a str,
+        val: Cow<'a, str>,
+        multiline: bool,
+    },
+}
+
+#[derive(Eq, PartialEq, Debug)]
+pub enum Error {
+    InvalidCharInString(usize, char),
+    InvalidEscape(usize, char),
+    InvalidHexEscape(usize, char),
+    InvalidEscapeValue(usize, u32),
+    NewlineInString(usize),
+    Unexpected(usize, char),
+    UnterminatedString(usize),
+    NewlineInTableKey(usize),
+    MultilineStringKey(usize),
+    Wanted {
+        at: usize,
+        expected: &'static str,
+        found: &'static str,
+    },
+}
+
+#[derive(Clone)]
+pub struct Tokenizer<'a> {
+    input: &'a str,
+    chars: CrlfFold<'a>,
+}
+
+#[derive(Clone)]
+struct CrlfFold<'a> {
+    chars: str::CharIndices<'a>,
+}
+
+#[derive(Debug)]
+enum MaybeString {
+    NotEscaped(usize),
+    Owned(String),
+}
+
+impl<'a> Tokenizer<'a> {
+    pub fn new(input: &'a str) -> Tokenizer<'a> {
+        let mut t = Tokenizer {
+            input,
+            chars: CrlfFold {
+                chars: input.char_indices(),
+            },
+        };
+        // Eat utf-8 BOM
+        t.eatc('\u{feff}');
+        t
+    }
+
+    pub fn next(&mut self) -> Result<Option<(Span, Token<'a>)>, Error> {
+        let (start, token) = match self.one() {
+            Some((start, '\n')) => (start, Token::Newline),
+            Some((start, ' ' | '\t')) => (start, self.whitespace_token(start)),
+            Some((start, '#')) => (start, self.comment_token(start)),
+            Some((start, '=')) => (start, Token::Equals),
+            Some((start, '.')) => (start, Token::Period),
+            Some((start, ',')) => (start, Token::Comma),
+            Some((start, ':')) => (start, Token::Colon),
+            Some((start, '+')) => (start, Token::Plus),
+            Some((start, '{')) => (start, Token::LeftBrace),
+            Some((start, '}')) => (start, Token::RightBrace),
+            Some((start, '[')) => (start, Token::LeftBracket),
+            Some((start, ']')) => (start, Token::RightBracket),
+            Some((start, '\'')) => {
+                return self
+                    .literal_string(start)
+                    .map(|t| Some((self.step_span(start), t)))
+            }
+            Some((start, '"')) => {
+                return self
+                    .basic_string(start)
+                    .map(|t| Some((self.step_span(start), t)))
+            }
+            Some((start, ch)) if is_keylike(ch) => (start, self.keylike(start)),
+
+            Some((start, ch)) => return Err(Error::Unexpected(start, ch)),
+            None => return Ok(None),
+        };
+
+        let span = self.step_span(start);
+        Ok(Some((span, token)))
+    }
+
+    pub fn peek(&mut self) -> Result<Option<(Span, Token<'a>)>, Error> {
+        self.clone().next()
+    }
+
+    pub fn eat(&mut self, expected: Token<'a>) -> Result<bool, Error> {
+        self.eat_spanned(expected).map(|s| s.is_some())
+    }
+
+    /// Eat a value, returning it's span if it was consumed.
+    pub fn eat_spanned(&mut self, expected: Token<'a>) -> Result<Option<Span>, Error> {
+        let span = match self.peek()? {
+            Some((span, ref found)) if expected == *found => span,
+            Some(_) | None => return Ok(None),
+        };
+
+        drop(self.next());
+        Ok(Some(span))
+    }
+
+    pub fn expect(&mut self, expected: Token<'a>) -> Result<(), Error> {
+        // ignore span
+        let _ = self.expect_spanned(expected)?;
+        Ok(())
+    }
+
+    /// Expect the given token returning its span.
+    pub fn expect_spanned(&mut self, expected: Token<'a>) -> Result<Span, Error> {
+        let current = self.current();
+        match self.next()? {
+            Some((span, found)) => {
+                if expected == found {
+                    Ok(span)
+                } else {
+                    Err(Error::Wanted {
+                        at: current,
+                        expected: expected.describe(),
+                        found: found.describe(),
+                    })
+                }
+            }
+            None => Err(Error::Wanted {
+                at: self.input.len(),
+                expected: expected.describe(),
+                found: "eof",
+            }),
+        }
+    }
+
+    pub fn table_key(&mut self) -> Result<(Span, Cow<'a, str>), Error> {
+        let current = self.current();
+        match self.next()? {
+            Some((span, Token::Keylike(k))) => Ok((span, k.into())),
+            Some((
+                span,
+                Token::String {
+                    src,
+                    val,
+                    multiline,
+                },
+            )) => {
+                let offset = self.substr_offset(src);
+                if multiline {
+                    return Err(Error::MultilineStringKey(offset));
+                }
+                match src.find('\n') {
+                    None => Ok((span, val)),
+                    Some(i) => Err(Error::NewlineInTableKey(offset + i)),
+                }
+            }
+            Some((_, other)) => Err(Error::Wanted {
+                at: current,
+                expected: "a table key",
+                found: other.describe(),
+            }),
+            None => Err(Error::Wanted {
+                at: self.input.len(),
+                expected: "a table key",
+                found: "eof",
+            }),
+        }
+    }
+
+    pub fn eat_whitespace(&mut self) {
+        while self.eatc(' ') || self.eatc('\t') {
+            // ...
+        }
+    }
+
+    pub fn eat_comment(&mut self) -> Result<bool, Error> {
+        if !self.eatc('#') {
+            return Ok(false);
+        }
+        drop(self.comment_token(0));
+        self.eat_newline_or_eof().map(|()| true)
+    }
+
+    pub fn eat_newline_or_eof(&mut self) -> Result<(), Error> {
+        let current = self.current();
+        match self.next()? {
+            None | Some((_, Token::Newline)) => Ok(()),
+            Some((_, other)) => Err(Error::Wanted {
+                at: current,
+                expected: "newline",
+                found: other.describe(),
+            }),
+        }
+    }
+
+    pub fn skip_to_newline(&mut self) {
+        loop {
+            match self.one() {
+                Some((_, '\n')) | None => break,
+                _ => {}
+            }
+        }
+    }
+
+    fn eatc(&mut self, ch: char) -> bool {
+        match self.chars.clone().next() {
+            Some((_, ch2)) if ch == ch2 => {
+                self.one();
+                true
+            }
+            _ => false,
+        }
+    }
+
+    pub fn current(&mut self) -> usize {
+        match self.chars.clone().next() {
+            Some(i) => i.0,
+            None => self.input.len(),
+        }
+    }
+
+    fn whitespace_token(&mut self, start: usize) -> Token<'a> {
+        while self.eatc(' ') || self.eatc('\t') {
+            // ...
+        }
+        Token::Whitespace(&self.input[start..self.current()])
+    }
+
+    fn comment_token(&mut self, start: usize) -> Token<'a> {
+        while let Some((_, ch)) = self.chars.clone().next() {
+            if ch != '\t' && (ch < '\u{20}' || ch > '\u{10ffff}') {
+                break;
+            }
+            self.one();
+        }
+        Token::Comment(&self.input[start..self.current()])
+    }
+
+    fn read_string(
+        &mut self,
+        delim: char,
+        start: usize,
+        new_ch: &mut dyn FnMut(
+            &mut Tokenizer,
+            &mut MaybeString,
+            bool,
+            usize,
+            char,
+        ) -> Result<(), Error>,
+    ) -> Result<Token<'a>, Error> {
+        let mut multiline = false;
+        if self.eatc(delim) {
+            if self.eatc(delim) {
+                multiline = true;
+            } else {
+                return Ok(Token::String {
+                    src: &self.input[start..start + 2],
+                    val: Cow::Borrowed(""),
+                    multiline: false,
+                });
+            }
+        }
+        let mut val = MaybeString::NotEscaped(self.current());
+        let mut n = 0;
+        loop {
+            n += 1;
+            match self.one() {
+                Some((i, '\n')) => {
+                    if multiline {
+                        if self.input.as_bytes()[i] == b'\r' {
+                            val.make_owned(&self.input[..i]);
+                        }
+                        if n == 1 {
+                            val = MaybeString::NotEscaped(self.current());
+                        } else {
+                            val.push('\n');
+                        }
+                    } else {
+                        return Err(Error::NewlineInString(i));
+                    }
+                }
+                Some((mut i, ch)) if ch == delim => {
+                    if multiline {
+                        if !self.eatc(delim) {
+                            val.push(delim);
+                            continue;
+                        }
+                        if !self.eatc(delim) {
+                            val.push(delim);
+                            val.push(delim);
+                            continue;
+                        }
+                        if self.eatc(delim) {
+                            val.push(delim);
+                            i += 1;
+                        }
+                        if self.eatc(delim) {
+                            val.push(delim);
+                            i += 1;
+                        }
+                    }
+                    return Ok(Token::String {
+                        src: &self.input[start..self.current()],
+                        val: val.into_cow(&self.input[..i]),
+                        multiline,
+                    });
+                }
+                Some((i, c)) => new_ch(self, &mut val, multiline, i, c)?,
+                None => return Err(Error::UnterminatedString(start)),
+            }
+        }
+    }
+
+    fn literal_string(&mut self, start: usize) -> Result<Token<'a>, Error> {
+        self.read_string('\'', start, &mut |_me, val, _multi, i, ch| {
+            if ch == '\u{09}' || ('\u{20}' <= ch && ch <= '\u{10ffff}' && ch != '\u{7f}') {
+                val.push(ch);
+                Ok(())
+            } else {
+                Err(Error::InvalidCharInString(i, ch))
+            }
+        })
+    }
+
+    fn basic_string(&mut self, start: usize) -> Result<Token<'a>, Error> {
+        self.read_string('"', start, &mut |me, val, multi, i, ch| match ch {
+            '\\' => {
+                val.make_owned(&me.input[..i]);
+                match me.chars.next() {
+                    Some((_, '"')) => val.push('"'),
+                    Some((_, '\\')) => val.push('\\'),
+                    Some((_, 'b')) => val.push('\u{8}'),
+                    Some((_, 'f')) => val.push('\u{c}'),
+                    Some((_, 'n')) => val.push('\n'),
+                    Some((_, 'r')) => val.push('\r'),
+                    Some((_, 't')) => val.push('\t'),
+                    Some((i, c @ ('u' | 'U'))) => {
+                        let len = if c == 'u' { 4 } else { 8 };
+                        val.push(me.hex(start, i, len)?);
+                    }
+                    Some((i, c @ (' ' | '\t' | '\n'))) if multi => {
+                        if c != '\n' {
+                            while let Some((_, ch)) = me.chars.clone().next() {
+                                match ch {
+                                    ' ' | '\t' => {
+                                        me.chars.next();
+                                    }
+                                    '\n' => {
+                                        me.chars.next();
+                                        break;
+                                    }
+                                    _ => return Err(Error::InvalidEscape(i, c)),
+                                }
+                            }
+                        }
+                        while let Some((_, ch)) = me.chars.clone().next() {
+                            match ch {
+                                ' ' | '\t' | '\n' => {
+                                    me.chars.next();
+                                }
+                                _ => break,
+                            }
+                        }
+                    }
+                    Some((i, c)) => return Err(Error::InvalidEscape(i, c)),
+                    None => return Err(Error::UnterminatedString(start)),
+                }
+                Ok(())
+            }
+            ch if ch == '\u{09}' || ('\u{20}' <= ch && ch <= '\u{10ffff}' && ch != '\u{7f}') => {
+                val.push(ch);
+                Ok(())
+            }
+            _ => Err(Error::InvalidCharInString(i, ch)),
+        })
+    }
+
+    fn hex(&mut self, start: usize, i: usize, len: usize) -> Result<char, Error> {
+        let mut buf = String::with_capacity(len);
+        for _ in 0..len {
+            match self.one() {
+                Some((_, ch)) if ch as u32 <= 0x7F && ch.is_ascii_hexdigit() => buf.push(ch),
+                Some((i, ch)) => return Err(Error::InvalidHexEscape(i, ch)),
+                None => return Err(Error::UnterminatedString(start)),
+            }
+        }
+        let val = u32::from_str_radix(&buf, 16).unwrap();
+        match char::from_u32(val) {
+            Some(ch) => Ok(ch),
+            None => Err(Error::InvalidEscapeValue(i, val)),
+        }
+    }
+
+    fn keylike(&mut self, start: usize) -> Token<'a> {
+        while let Some((_, ch)) = self.peek_one() {
+            if !is_keylike(ch) {
+                break;
+            }
+            self.one();
+        }
+        Token::Keylike(&self.input[start..self.current()])
+    }
+
+    pub fn substr_offset(&self, s: &'a str) -> usize {
+        assert!(s.len() <= self.input.len());
+        let a = self.input.as_ptr() as usize;
+        let b = s.as_ptr() as usize;
+        assert!(a <= b);
+        b - a
+    }
+
+    /// Calculate the span of a single character.
+    fn step_span(&mut self, start: usize) -> Span {
+        let end = match self.peek_one() {
+            Some(t) => t.0,
+            None => self.input.len(),
+        };
+        Span { start, end }
+    }
+
+    /// Peek one char without consuming it.
+    fn peek_one(&mut self) -> Option<(usize, char)> {
+        self.chars.clone().next()
+    }
+
+    /// Take one char.
+    pub fn one(&mut self) -> Option<(usize, char)> {
+        self.chars.next()
+    }
+}
+
+impl<'a> Iterator for CrlfFold<'a> {
+    type Item = (usize, char);
+
+    fn next(&mut self) -> Option<(usize, char)> {
+        self.chars.next().map(|(i, c)| {
+            if c == '\r' {
+                let mut attempt = self.chars.clone();
+                if let Some((_, '\n')) = attempt.next() {
+                    self.chars = attempt;
+                    return (i, '\n');
+                }
+            }
+            (i, c)
+        })
+    }
+}
+
+impl MaybeString {
+    fn push(&mut self, ch: char) {
+        match *self {
+            MaybeString::NotEscaped(..) => {}
+            MaybeString::Owned(ref mut s) => s.push(ch),
+        }
+    }
+
+    fn make_owned(&mut self, input: &str) {
+        match *self {
+            MaybeString::NotEscaped(start) => {
+                *self = MaybeString::Owned(input[start..].to_owned());
+            }
+            MaybeString::Owned(..) => {}
+        }
+    }
+
+    fn into_cow(self, input: &str) -> Cow<str> {
+        match self {
+            MaybeString::NotEscaped(start) => Cow::Borrowed(&input[start..]),
+            MaybeString::Owned(s) => Cow::Owned(s),
+        }
+    }
+}
+
+fn is_keylike(ch: char) -> bool {
+    ('A' <= ch && ch <= 'Z')
+        || ('a' <= ch && ch <= 'z')
+        || ('0' <= ch && ch <= '9')
+        || ch == '-'
+        || ch == '_'
+}
+
+impl<'a> Token<'a> {
+    pub fn describe(&self) -> &'static str {
+        match *self {
+            Token::Keylike(_) => "an identifier",
+            Token::Equals => "an equals",
+            Token::Period => "a period",
+            Token::Comment(_) => "a comment",
+            Token::Newline => "a newline",
+            Token::Whitespace(_) => "whitespace",
+            Token::Comma => "a comma",
+            Token::RightBrace => "a right brace",
+            Token::LeftBrace => "a left brace",
+            Token::RightBracket => "a right bracket",
+            Token::LeftBracket => "a left bracket",
+            Token::String { multiline, .. } => {
+                if multiline {
+                    "a multiline string"
+                } else {
+                    "a string"
+                }
+            }
+            Token::Colon => "a colon",
+            Token::Plus => "a plus",
+        }
+    }
+}