serde stuff

Cargo.toml

@@ -13,6 +13,8 @@ logos = "0.11"
 thiserror = "1.0"
 source-span = "2.2"
 memchr = "2.3.4"
+serde = "1.0"
 
 [dev-dependencies]
 maplit = "1.0.2"
+serde_derive = "1.0"

src/error.rs

@@ -70,6 +70,12 @@ pub struct SourceSpannedError<'source, T> {
     source: &'source str,
 }
 
+impl<'source, T: Error + Debug + 'static> SourceSpannedError<'source, T> {
+    pub fn spanned(self) -> SpannedError<T> {
+        SpannedError::new(self.error, self.span)
+    }
+}
+
 const METRICS: DefaultMetrics = DefaultMetrics::with_tab_stop(4);
 
 impl<'source, T: Error + Debug> Display for SourceSpannedError<'source, T> {
@@ -122,6 +128,10 @@ pub enum ParseError {
     InvalidFloatLiteral(#[from] ParseFloatError),
     #[error("Invalid string literal")]
     InvalidStringLiteral,
+    #[error("Array key not valid for this position")]
+    UnexpectedArrayKey,
+    #[error("Trailing characters after parsing")]
+    TrailingCharacters,
 }
 
 impl From<UnescapeError> for ParseError {
@@ -190,6 +200,20 @@ impl<'source> ExpectToken<'source> for Option<SpannedToken<'source>> {
     }
 }
 
+impl<'a, 'source> ExpectToken<'source> for Option<&'a SpannedToken<'source>> {
+    fn expect_token(
+        self,
+        expected: &[Token],
+    ) -> Result<SpannedToken<'source>, SpannedError<ParseError>> {
+        self.ok_or_else(|| UnexpectedTokenError {
+            expected: expected.to_vec(),
+            found: None,
+        })
+        .with_span(usize::max_value()..usize::max_value())
+        .and_then(|token| token.clone().expect_token(expected))
+    }
+}
+
 impl<'source> ExpectToken<'source> for SpannedToken<'source> {
     fn expect_token(
         self,

src/lexer.rs

@@ -166,6 +166,7 @@ fn test_lex_float() {
     assert_eq!(lex.next(), None);
 }
 
+#[derive(Clone, Debug)]
 pub struct SpannedToken<'source> {
     pub token: Token,
     pub span: Span,

src/lib.rs

@@ -23,6 +23,7 @@ mod error;
 mod lexer;
 mod num;
 mod parser;
+mod serde;
 mod string;
 
 pub use error::{ParseError, SpannedError};

src/num.rs

@@ -8,6 +8,8 @@ pub enum ParseIntError {
     InvalidDigit,
     #[error("number too large or small to fit in target type")]
     Overflow,
+    #[error("unexpected negative number")]
+    UnexpectedNegative,
 }
 
 /// Mostly copied from std

src/parser.rs

@@ -5,6 +5,7 @@ use crate::string::{is_array_key_numeric, parse_string};
 use crate::{Key, Value};
 use logos::Logos;
 use std::collections::HashMap;
+use std::iter::Peekable;
 use std::num::ParseFloatError;
 
 /// Parse a php literal
@@ -30,16 +31,24 @@ pub fn parse(source: &str) -> Result<Value, SpannedError<ParseError>> {
 }
 
 pub struct Parser<'source> {
-    tokens: TokenStream<'source>,
+    tokens: Peekable<TokenStream<'source>>,
 }
 
 impl<'source> Parser<'source> {
     pub fn new(source: &'source str) -> Self {
         Parser {
-            tokens: TokenStream::new(Token::lexer(source)),
+            tokens: TokenStream::new(Token::lexer(source)).peekable(),
         }
     }
 
+    pub fn next_token(&mut self) -> Option<SpannedToken<'source>> {
+        self.tokens.next()
+    }
+
+    pub fn eat_token(&mut self) {
+        let _ = self.tokens.next();
+    }
+
     pub fn run(&mut self) -> Result<Value, SpannedError<ParseError>> {
         let token = self.tokens.next().expect_token(&[
             Token::Bool,
@@ -55,10 +64,10 @@ impl<'source> Parser<'source> {
 
     pub fn parse_any(&mut self, token: SpannedToken) -> Result<Value, SpannedError<ParseError>> {
         let value = match token.token {
-            Token::Bool => Value::Bool(self.parse_bool(token)?),
-            Token::Integer => Value::Int(self.parse_int(token)?),
-            Token::Float => Value::Float(self.parse_float(token)?),
-            Token::LiteralString => Value::String(self.parse_string(token)?),
+            Token::Bool => Value::Bool(self.parse_bool_token(token)?),
+            Token::Integer => Value::Int(self.parse_int_token(token)?),
+            Token::Float => Value::Float(self.parse_float_token(token)?),
+            Token::LiteralString => Value::String(self.parse_string_token(token)?),
             Token::Null => Value::Null,
             Token::Array => Value::Array(self.parse_array(ArraySyntax::Long)?),
             Token::SquareOpen => Value::Array(self.parse_array(ArraySyntax::Short)?),
@@ -68,7 +77,7 @@ impl<'source> Parser<'source> {
         Ok(value)
     }
 
-    pub fn parse_bool(&self, token: SpannedToken) -> Result<bool, SpannedError<ParseError>> {
+    pub fn parse_bool_token(&self, token: SpannedToken) -> Result<bool, SpannedError<ParseError>> {
         token
             .slice()
             .to_ascii_lowercase()
@@ -76,15 +85,18 @@ impl<'source> Parser<'source> {
             .with_span(token.span)
     }
 
-    pub fn parse_int(&self, token: SpannedToken) -> Result<i64, SpannedError<ParseError>> {
+    pub fn parse_int_token(&self, token: SpannedToken) -> Result<i64, SpannedError<ParseError>> {
         parse_int(token.slice()).with_span(token.span)
     }
 
-    pub fn parse_float(&self, token: SpannedToken) -> Result<f64, SpannedError<ParseError>> {
+    pub fn parse_float_token(&self, token: SpannedToken) -> Result<f64, SpannedError<ParseError>> {
         parse_float(token.slice()).with_span(token.span)
     }
 
-    pub fn parse_string(&self, token: SpannedToken) -> Result<String, SpannedError<ParseError>> {
+    pub fn parse_string_token(
+        &self,
+        token: SpannedToken,
+    ) -> Result<String, SpannedError<ParseError>> {
         parse_string(token.slice()).with_span(token.span)
     }
 
@@ -192,8 +204,8 @@ fn parse_float(literal: &str) -> Result<f64, ParseFloatError> {
 
 #[derive(Default)]
 struct ArrayBuilder {
-    next_int_key: i64,
     data: HashMap<Key, Value>,
+    next_int_key: i64,
 }
 
 impl ArrayBuilder {
@@ -211,14 +223,14 @@ impl ArrayBuilder {
     }
 }
 
-#[derive(Eq, PartialEq)]
+#[derive(Eq, PartialEq, Copy, Clone)]
 pub enum ArraySyntax {
     Short,
     Long,
 }
 
 impl ArraySyntax {
-    fn close_bracket(&self) -> Token {
+    pub fn close_bracket(&self) -> Token {
         match self {
             ArraySyntax::Long => Token::BracketClose,
             ArraySyntax::Short => Token::SquareClose,

src/serde.rs

@@ -1,32 +1,78 @@
-use std::ops::{AddAssign, MulAssign, Neg};
-
 use serde::de::{
     self, DeserializeSeed, EnumAccess, IntoDeserializer, MapAccess, SeqAccess, VariantAccess,
     Visitor,
 };
 use serde::Deserialize;
 
-use crate::lexer::Token;
-use crate::parser::{SpannedToken, TokenStream};
-use crate::ParseError;
-use error::{Error, Result};
-use logos::Lexer;
-use std::iter::Peekable;
+use crate::error::{ExpectToken, ResultExt};
+use crate::lexer::{SpannedToken, Token};
+use crate::num::ParseIntError;
+use crate::parser::{ArraySyntax, Parser};
+use crate::{Key, ParseError, SpannedError};
+use serde::export::TryFrom;
+use std::error::Error;
+use std::fmt::{Display, Formatter};
 
-type Result<T> = std::error::Result<T, ParseError>;
+#[derive(Debug)]
+pub enum SerdeParseError {
+    Parse(ParseError),
+    Spanned(SpannedError<ParseError>),
+    Custom(String),
+}
+
+impl From<SpannedError<ParseError>> for SerdeParseError {
+    fn from(err: SpannedError<ParseError>) -> Self {
+        SerdeParseError::Spanned(err)
+    }
+}
+
+impl From<ParseError> for SerdeParseError {
+    fn from(err: ParseError) -> Self {
+        SerdeParseError::Parse(err)
+    }
+}
+
+impl Display for SerdeParseError {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        match self {
+            SerdeParseError::Spanned(err) => write!(f, "{}", err),
+            SerdeParseError::Parse(err) => write!(f, "{}", err),
+            SerdeParseError::Custom(err) => write!(f, "{}", err),
+        }
+    }
+}
+
+impl Error for SerdeParseError {
+    fn source(&self) -> Option<&(dyn Error + 'static)> {
+        match self {
+            SerdeParseError::Spanned(err) => Some(err),
+            SerdeParseError::Parse(err) => Some(err),
+            SerdeParseError::Custom(_) => None,
+        }
+    }
+}
+
+impl serde::de::Error for SerdeParseError {
+    fn custom<T>(msg: T) -> Self
+    where
+        T: Display,
+    {
+        SerdeParseError::Custom(msg.to_string())
+    }
+}
+
+type Result<T> = std::result::Result<T, SerdeParseError>;
 
 pub struct Deserializer<'de> {
-    input: &'de str,
-    token_stream: Peekable<TokenStream<'de>>,
+    parser: Parser<'de>,
+    peeked: Option<SpannedToken<'de>>,
 }
 
 impl<'de> Deserializer<'de> {
     pub fn from_str(input: &'de str) -> Self {
-        let lexer = Token::lexer(source);
-        let token_stream = TokenStream::new(lexer, input);
         Deserializer {
-            input,
-            token_stream: token_stream.peekable(),
+            parser: Parser::new(input),
+            peeked: None,
         }
     }
 }
@@ -37,104 +83,108 @@ where
 {
     let mut deserializer = Deserializer::from_str(s);
     let t = T::deserialize(&mut deserializer)?;
-    if deserializer.input.is_empty() {
+    if deserializer.next_token().is_none() {
         Ok(t)
     } else {
-        Err(Error::TrailingCharacters)
+        Err(ParseError::TrailingCharacters.into())
     }
 }
 
 impl<'de> Deserializer<'de> {
-    fn parse_bool(&mut self) -> Result<bool> {
-        let token = self.token_stream.next()
-        if self.input.starts_with("true") {
-            self.input = &self.input["true".len()..];
-            Ok(true)
-        } else if self.input.starts_with("false") {
-            self.input = &self.input["false".len()..];
-            Ok(false)
-        } else {
-            Err(Error::ExpectedBoolean)
+    fn next_token(&mut self) -> Option<SpannedToken<'de>> {
+        self.peeked.take().or_else(|| self.parser.next_token())
+    }
+
+    fn peek_token(&mut self) -> Option<&SpannedToken<'de>> {
+        if self.peeked.is_none() {
+            self.peeked = self.next_token()
+        }
+        self.peeked.as_ref()
+    }
+
+    fn eat_token(&mut self) {
+        if self.peeked.take().is_none() {
+            self.parser.eat_token()
         }
     }
 
-    // Parse a group of decimal digits as an unsigned integer of type T.
-    //
-    // This implementation is a bit too lenient, for example `001` is not
-    // allowed in JSON. Also the various arithmetic operations can overflow and
-    // panic or return bogus data. But it is good enough for example code!
+    fn parse_bool(&mut self) -> Result<bool> {
+        let token = self.next_token().expect_token(&[Token::Bool])?;
+        Ok(self.parser.parse_bool_token(token)?)
+    }
+
+    fn set_peeked(&mut self, peeked: SpannedToken<'de>) {
+        self.peeked = Some(peeked)
+    }
+
     fn parse_unsigned<T>(&mut self) -> Result<T>
     where
-        T: AddAssign<T> + MulAssign<T> + From<u8>,
+        T: TryFrom<i64>,
     {
-        let mut int = match self.next_char()? {
-            ch @ '0'..='9' => T::from(ch as u8 - b'0'),
-            _ => {
-                return Err(Error::ExpectedInteger);
-            }
-        };
-        loop {
-            match self.input.chars().next() {
-                Some(ch @ '0'..='9') => {
-                    self.input = &self.input[1..];
-                    int *= T::from(10);
-                    int += T::from(ch as u8 - b'0');
-                }
-                _ => {
-                    return Ok(int);
-                }
-            }
+        let token = self.next_token().expect_token(&[Token::Integer])?;
+        let span = token.span.clone();
+        let int = self.parser.parse_int_token(token)?;
+        if int < 0 {
+            Err(SpannedError::new(
+                ParseError::InvalidIntLiteral(ParseIntError::UnexpectedNegative),
+                span,
+            )
+            .into())
+        } else {
+            Ok(T::try_from(int).map_err(|_| {
+                SpannedError::new(ParseError::InvalidIntLiteral(ParseIntError::Overflow), span)
+            })?)
         }
     }
 
-    // Parse a possible minus sign followed by a group of decimal digits as a
-    // signed integer of type T.
     fn parse_signed<T>(&mut self) -> Result<T>
     where
-        T: Neg<Output = T> + AddAssign<T> + MulAssign<T> + From<i8>,
+        T: TryFrom<i64>,
     {
-        // Optional minus sign, delegate to `parse_unsigned`, negate if negative.
-        unimplemented!()
+        let token = self.next_token().expect_token(&[Token::Integer])?;
+        let span = token.span.clone();
+        Ok(
+            T::try_from(self.parser.parse_int_token(token)?).map_err(|_| {
+                SpannedError::new(ParseError::InvalidIntLiteral(ParseIntError::Overflow), span)
+            })?,
+        )
     }
 
-    // Parse a string until the next '"' character.
-    //
-    // Makes no attempt to handle escape sequences. What did you expect? This is
-    // example code!
-    fn parse_string(&mut self) -> Result<&'de str> {
-        if self.next_char()? != '"' {
-            return Err(Error::ExpectedString);
-        }
-        match self.input.find('"') {
-            Some(len) => {
-                let s = &self.input[..len];
-                self.input = &self.input[len + 1..];
-                Ok(s)
-            }
-            None => Err(Error::Eof),
+    fn parse_float(&mut self) -> Result<f64> {
+        let token = self.next_token().expect_token(&[Token::Float])?;
+        Ok(self.parser.parse_float_token(token)?)
     }
+
+    fn parse_string(&mut self) -> Result<String> {
+        let token = self.next_token().expect_token(&[Token::LiteralString])?;
+        Ok(self.parser.parse_string_token(token)?)
     }
 }
 
 impl<'de, 'a> de::Deserializer<'de> for &'a mut Deserializer<'de> {
-    type Error = ParseError;
+    type Error = SerdeParseError;
 
-    // Look at the input data to decide what Serde data model type to
-    // deserialize as. Not all data formats are able to support this operation.
-    // Formats that support `deserialize_any` are known as self-describing.
     fn deserialize_any<V>(self, visitor: V) -> Result<V::Value>
     where
         V: Visitor<'de>,
     {
-        match self.peek_char()? {
-            'n' => self.deserialize_unit(visitor),
-            't' | 'f' => self.deserialize_bool(visitor),
-            '"' => self.deserialize_str(visitor),
-            '0'..='9' => self.deserialize_u64(visitor),
-            '-' => self.deserialize_i64(visitor),
-            '[' => self.deserialize_seq(visitor),
-            '{' => self.deserialize_map(visitor),
-            _ => Err(Error::Syntax),
+        let peek = self.peek_token().expect_token(&[
+            Token::Null,
+            Token::Bool,
+            Token::LiteralString,
+            Token::Integer,
+            Token::Float,
+            Token::Array,
+            Token::SquareOpen,
+        ])?;
+        match peek.token {
+            Token::Null => self.deserialize_unit(visitor),
+            Token::Bool => self.deserialize_bool(visitor),
+            Token::LiteralString => self.deserialize_string(visitor),
+            Token::Integer => self.deserialize_i64(visitor),
+            Token::Float => self.deserialize_f64(visitor),
+            Token::Array | Token::SquareOpen => self.deserialize_seq(visitor),
+            _ => unreachable!(),
         }
     }
 
@@ -203,20 +253,18 @@ impl<'de, 'a> de::Deserializer<'de> for &'a mut Deserializer<'de> {
         visitor.visit_u64(self.parse_unsigned()?)
     }
 
-    // Float parsing is stupidly hard.
-    fn deserialize_f32<V>(self, _visitor: V) -> Result<V::Value>
+    fn deserialize_f32<V>(self, visitor: V) -> Result<V::Value>
     where
         V: Visitor<'de>,
     {
-        unimplemented!()
+        visitor.visit_f32(self.parse_float()? as f32)
     }
 
-    // Float parsing is stupidly hard.
-    fn deserialize_f64<V>(self, _visitor: V) -> Result<V::Value>
+    fn deserialize_f64<V>(self, visitor: V) -> Result<V::Value>
     where
         V: Visitor<'de>,
     {
-        unimplemented!()
+        visitor.visit_f64(self.parse_float()?)
     }
 
     // The `Serializer` implementation on the previous page serialized chars as
@@ -235,14 +283,15 @@ impl<'de, 'a> de::Deserializer<'de> for &'a mut Deserializer<'de> {
     where
         V: Visitor<'de>,
     {
-        visitor.visit_borrowed_str(self.parse_string()?)
+        let str = self.parse_string()?;
+        visitor.visit_str(str.as_str())
     }
 
     fn deserialize_string<V>(self, visitor: V) -> Result<V::Value>
     where
         V: Visitor<'de>,
     {
-        self.deserialize_str(visitor)
+        visitor.visit_string(self.parse_string()?)
     }
 
     // The `Serializer` implementation on the previous page serialized byte
@@ -251,14 +300,15 @@ impl<'de, 'a> de::Deserializer<'de> for &'a mut Deserializer<'de> {
     where
         V: Visitor<'de>,
     {
-        unimplemented!()
+        todo!()
     }
 
     fn deserialize_byte_buf<V>(self, _visitor: V) -> Result<V::Value>
     where
         V: Visitor<'de>,
     {
-        unimplemented!()
+        todo!()
+        // visitor.visit_string(self.parse_string()?.to_vec())
     }
 
     // An absent optional is represented as the JSON `null` and a present
@@ -273,28 +323,31 @@ impl<'de, 'a> de::Deserializer<'de> for &'a mut Deserializer<'de> {
     where
         V: Visitor<'de>,
     {
-        if self.input.starts_with("null") {
-            self.input = &self.input["null".len()..];
+        let token = self.peek_token().expect_token(&[
+            Token::Null,
+            Token::Bool,
+            Token::LiteralString,
+            Token::Integer,
+            Token::Float,
+            Token::Array,
+            Token::SquareOpen,
+        ])?;
+        if token.token == Token::Null {
+            let _ = self.next_token();
             visitor.visit_none()
         } else {
             visitor.visit_some(self)
         }
     }
 
-    // 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.input.starts_with("null") {
-            self.input = &self.input["null".len()..];
+        self.next_token().expect_token(&[Token::Null])?;
         visitor.visit_unit()
-        } else {
-            Err(Error::ExpectedNull)
-        }
     }
 
-    // Unit struct means a named value containing no data.
     fn deserialize_unit_struct<V>(self, _name: &'static str, visitor: V) -> Result<V::Value>
     where
         V: Visitor<'de>,
@@ -302,9 +355,6 @@ impl<'de, 'a> de::Deserializer<'de> for &'a mut Deserializer<'de> {
         self.deserialize_unit(visitor)
     }
 
-    // As is done here, serializers are encouraged to treat newtype structs as
-    // insignificant wrappers around the data they contain. That means not
-    // parsing anything other than the contained value.
     fn deserialize_newtype_struct<V>(self, _name: &'static str, visitor: V) -> Result<V::Value>
     where
         V: Visitor<'de>,
@@ -312,34 +362,23 @@ impl<'de, 'a> de::Deserializer<'de> for &'a mut Deserializer<'de> {
         visitor.visit_newtype_struct(self)
     }
 
-    // Deserialization of compound types like sequences and maps happens by
-    // passing the visitor an "Access" object that gives it the ability to
-    // iterate through the data contained in the sequence.
     fn deserialize_seq<V>(mut self, visitor: V) -> Result<V::Value>
     where
         V: Visitor<'de>,
     {
-        // Parse the opening bracket of the sequence.
-        if self.next_char()? == '[' {
-            // Give the visitor access to each element of the sequence.
-            let value = visitor.visit_seq(CommaSeparated::new(&mut self))?;
-            // Parse the closing bracket of the sequence.
-            if self.next_char()? == ']' {
+        let token = self
+            .next_token()
+            .expect_token(&[Token::Array, Token::SquareOpen])?;
+        let syntax = match token.token {
+            Token::Array => ArraySyntax::Long,
+            Token::SquareOpen => ArraySyntax::Short,
+            _ => unreachable!(),
+        };
+
+        let value = visitor.visit_seq(ArrayWalker::new(&mut self, syntax))?;
         Ok(value)
-            } else {
-                Err(Error::ExpectedArrayEnd)
-            }
-        } else {
-            Err(Error::ExpectedArray)
-        }
     }
 
-    // Tuples look just like sequences in JSON. Some formats may be able to
-    // represent tuples more efficiently.
-    //
-    // As indicated by the length parameter, the `Deserialize` implementation
-    // for a tuple in the Serde data model is required to know the length of the
-    // tuple before even looking at the input data.
     fn deserialize_tuple<V>(self, _len: usize, visitor: V) -> Result<V::Value>
     where
         V: Visitor<'de>,
@@ -347,7 +386,6 @@ impl<'de, 'a> de::Deserializer<'de> for &'a mut Deserializer<'de> {
         self.deserialize_seq(visitor)
     }
 
-    // Tuple structs look just like sequences in JSON.
     fn deserialize_tuple_struct<V>(
         self,
         _name: &'static str,
@@ -360,34 +398,23 @@ impl<'de, 'a> de::Deserializer<'de> for &'a mut Deserializer<'de> {
         self.deserialize_seq(visitor)
     }
 
-    // Much like `deserialize_seq` but calls the visitors `visit_map` method
-    // with a `MapAccess` implementation, rather than the visitor's `visit_seq`
-    // method with a `SeqAccess` implementation.
     fn deserialize_map<V>(mut self, visitor: V) -> Result<V::Value>
     where
         V: Visitor<'de>,
     {
-        // Parse the opening brace of the map.
-        if self.next_char()? == '{' {
-            // Give the visitor access to each entry of the map.
-            let value = visitor.visit_map(CommaSeparated::new(&mut self))?;
-            // Parse the closing brace of the map.
-            if self.next_char()? == '}' {
+        let token = self
+            .next_token()
+            .expect_token(&[Token::Array, Token::SquareOpen])?;
+        let syntax = match token.token {
+            Token::Array => ArraySyntax::Long,
+            Token::SquareOpen => ArraySyntax::Short,
+            _ => unreachable!(),
+        };
+
+        let value = visitor.visit_map(ArrayWalker::new(&mut self, syntax))?;
         Ok(value)
-            } else {
-                Err(Error::ExpectedMapEnd)
-            }
-        } else {
-            Err(Error::ExpectedMap)
-        }
     }
 
-    // Structs look just like maps in JSON.
-    //
-    // Notice the `fields` parameter - a "struct" in the Serde data model means
-    // that the `Deserialize` implementation is required to know what the fields
-    // are before even looking at the input data. Any key-value pairing in which
-    // the fields cannot be known ahead of time is probably a map.
     fn deserialize_struct<V>(
         self,
         _name: &'static str,
@@ -409,27 +436,31 @@ impl<'de, 'a> de::Deserializer<'de> for &'a mut Deserializer<'de> {
     where
         V: Visitor<'de>,
     {
-        if self.peek_char()? == '"' {
-            // Visit a unit variant.
-            visitor.visit_enum(self.parse_string()?.into_deserializer())
-        } else if self.next_char()? == '{' {
-            // Visit a newtype variant, tuple variant, or struct variant.
+        // panic!("a");
+        let token = self.peek_token().expect_token(&[
+            Token::LiteralString,
+            Token::Array,
+            Token::SquareOpen,
+        ])?;
+        match token.token {
+            Token::LiteralString => visitor.visit_enum(self.parse_string()?.into_deserializer()),
+            Token::Array | Token::SquareOpen => {
+                self.eat_token();
+                let syntax = if token.token == Token::Array {
+                    self.next_token().expect_token(&[Token::BracketOpen])?;
+                    ArraySyntax::Long
+                } else {
+                    ArraySyntax::Short
+                };
+
                 let value = visitor.visit_enum(Enum::new(self))?;
-            // Parse the matching close brace.
-            if self.next_char()? == '}' {
+                self.next_token().expect_token(&[syntax.close_bracket()])?;
                 Ok(value)
-            } else {
-                Err(Error::ExpectedMapEnd)
             }
-        } else {
-            Err(Error::ExpectedEnum)
+            _ => unreachable!(),
         }
     }
 
-    // An identifier in Serde is the type that identifies a field of a struct or
-    // the variant of an enum. In JSON, struct fields and enum variants are
-    // represented as strings. In other formats they may be represented as
-    // numeric indices.
     fn deserialize_identifier<V>(self, visitor: V) -> Result<V::Value>
     where
         V: Visitor<'de>,
@@ -437,17 +468,6 @@ impl<'de, 'a> de::Deserializer<'de> for &'a mut Deserializer<'de> {
         self.deserialize_str(visitor)
     }
 
-    // Like `deserialize_any` but indicates to the `Deserializer` that it makes
-    // no difference which `Visitor` method is called because the data is
-    // ignored.
-    //
-    // Some deserializers are able to implement this more efficiently than
-    // `deserialize_any`, for example by rapidly skipping over matched
-    // delimiters without paying close attention to the data in between.
-    //
-    // Some formats are not able to implement this at all. Formats that can
-    // implement `deserialize_any` and `deserialize_ignored_any` are known as
-    // self-describing.
     fn deserialize_ignored_any<V>(self, visitor: V) -> Result<V::Value>
     where
         V: Visitor<'de>,
@@ -456,62 +476,116 @@ impl<'de, 'a> de::Deserializer<'de> for &'a mut Deserializer<'de> {
     }
 }
 
-// In order to handle commas correctly when deserializing a JSON array or map,
-// we need to track whether we are on the first element or past the first
-// element.
-struct CommaSeparated<'a, 'de: 'a> {
-    de: &'a mut Deserializer<'de>,
-    first: bool,
+struct ArrayWalker<'source, 'a> {
+    de: &'a mut Deserializer<'source>,
+    next_int_key: i64,
+    syntax: ArraySyntax,
+    done: bool,
 }
 
-impl<'a, 'de> CommaSeparated<'a, 'de> {
-    fn new(de: &'a mut Deserializer<'de>) -> Self {
-        CommaSeparated { de, first: true }
+impl<'source, 'a> ArrayWalker<'source, 'a> {
+    pub fn new(de: &'a mut Deserializer<'source>, syntax: ArraySyntax) -> Self {
+        ArrayWalker {
+            de,
+            next_int_key: 0,
+            syntax,
+            done: false,
+        }
     }
 }
 
-// `SeqAccess` is provided to the `Visitor` to give it the ability to iterate
-// through elements of the sequence.
-impl<'de, 'a> SeqAccess<'de> for CommaSeparated<'a, 'de> {
-    type Error = Error;
+impl<'de, 'a> SeqAccess<'de> for ArrayWalker<'de, 'a> {
+    type Error = SerdeParseError;
 
     fn next_element_seed<T>(&mut self, seed: T) -> Result<Option<T::Value>>
     where
         T: DeserializeSeed<'de>,
     {
-        // Check if there are no more elements.
-        if self.de.peek_char()? == ']' {
+        if self.done {
             return Ok(None);
         }
-        // Comma is required before every element except the first.
-        if !self.first && self.de.next_char()? != ',' {
-            return Err(Error::ExpectedArrayComma);
+
+        let token = self.de.next_token().expect_token(&[
+            Token::Bool,
+            Token::Integer,
+            Token::Float,
+            Token::LiteralString,
+            Token::Null,
+            Token::Array,
+            Token::SquareOpen,
+        ])?;
+
+        let next = self.de.next_token().expect_token(&[
+            self.syntax.close_bracket(),
+            Token::Comma,
+            Token::Arrow,
+        ])?;
+
+        let value_token = match next.token.clone() {
+            Token::Comma => token,
+            Token::Arrow => {
+                let span = token.span.clone();
+                let key = self.de.parser.parse_array_key(token)?;
+                match key {
+                    Key::Int(key) if key == self.next_int_key => Ok(()),
+                    _ => Err(ParseError::UnexpectedArrayKey).with_span(span),
+                }?;
+                self.next_int_key += 1;
+                let value = self.de.next_token().expect_token(&[
+                    Token::Bool,
+                    Token::Integer,
+                    Token::Float,
+                    Token::LiteralString,
+                    Token::Null,
+                    Token::Array,
+                    Token::SquareOpen,
+                ])?;
+                let next = self
+                    .de
+                    .next_token()
+                    .expect_token(&[Token::Comma, self.syntax.close_bracket()])?;
+                if next.token == self.syntax.close_bracket() {
+                    self.done = true;
                 }
-        self.first = false;
+                value
+            }
+            peeked_token if peeked_token == self.syntax.close_bracket() => {
+                self.done = true;
+                token
+            }
+            _ => unreachable!(),
+        };
+
+        dbg!(value_token.slice());
         // Deserialize an array element.
+        self.de.set_peeked(value_token);
         seed.deserialize(&mut *self.de).map(Some)
     }
 }
 
-// `MapAccess` is provided to the `Visitor` to give it the ability to iterate
-// through entries of the map.
-impl<'de, 'a> MapAccess<'de> for CommaSeparated<'a, 'de> {
-    type Error = Error;
+impl<'de, 'a> MapAccess<'de> for ArrayWalker<'de, 'a> {
+    type Error = SerdeParseError;
 
     fn next_key_seed<K>(&mut self, seed: K) -> Result<Option<K::Value>>
     where
         K: DeserializeSeed<'de>,
     {
-        // Check if there are no more entries.
-        if self.de.peek_char()? == '}' {
+        if self.done {
             return Ok(None);
         }
-        // Comma is required before every entry except the first.
-        if !self.first && self.de.next_char()? != ',' {
-            return Err(Error::ExpectedMapComma);
-        }
-        self.first = false;
+
+        let token = self.de.next_token().expect_token(&[
+            Token::Bool,
+            Token::Integer,
+            Token::Float,
+            Token::LiteralString,
+            Token::Null,
+        ])?;
+
+        self.de.next_token().expect_token(&[Token::Arrow])?;
+
         // Deserialize a map key.
+        self.de.set_peeked(token);
         seed.deserialize(&mut *self.de).map(Some)
     }
 
@@ -519,14 +593,29 @@ impl<'de, 'a> MapAccess<'de> for CommaSeparated<'a, 'de> {
     where
         V: DeserializeSeed<'de>,
     {
-        // It doesn't make a difference whether the colon is parsed at the end
-        // of `next_key_seed` or at the beginning of `next_value_seed`. In this
-        // case the code is a bit simpler having it here.
-        if self.de.next_char()? != ':' {
-            return Err(Error::ExpectedMapColon);
+        let token = self.de.next_token().expect_token(&[
+            Token::Bool,
+            Token::Integer,
+            Token::Float,
+            Token::LiteralString,
+            Token::Null,
+            Token::Array,
+            Token::SquareOpen,
+        ])?;
+
+        // Deserialize a map key.
+        self.de.set_peeked(token);
+        let value = seed.deserialize(&mut *self.de)?;
+
+        let next = self
+            .de
+            .next_token()
+            .expect_token(&[Token::Comma, self.syntax.close_bracket()])?;
+
+        if next.token == self.syntax.close_bracket() {
+            self.done = true;
         }
-        // Deserialize a map value.
-        seed.deserialize(&mut *self.de)
+        Ok(value)
     }
 }
 
@@ -546,39 +635,29 @@ impl<'a, 'de> Enum<'a, 'de> {
 // Note that all enum deserialization methods in Serde refer exclusively to the
 // "externally tagged" enum representation.
 impl<'de, 'a> EnumAccess<'de> for Enum<'a, 'de> {
-    type Error = Error;
+    type Error = SerdeParseError;
     type Variant = Self;
 
     fn variant_seed<V>(self, seed: V) -> Result<(V::Value, Self::Variant)>
     where
         V: DeserializeSeed<'de>,
     {
-        // The `deserialize_enum` method parsed a `{` character so we are
-        // currently inside of a map. The seed will be deserializing itself from
-        // the key of the map.
         let val = seed.deserialize(&mut *self.de)?;
-        // Parse the colon separating map key from value.
-        if self.de.next_char()? == ':' {
+        self.de.next_token().expect_token(&[Token::Arrow])?;
         Ok((val, self))
-        } else {
-            Err(Error::ExpectedMapColon)
-        }
     }
 }
 
 // `VariantAccess` is provided to the `Visitor` to give it the ability to see
 // the content of the single variant that it decided to deserialize.
 impl<'de, 'a> VariantAccess<'de> for Enum<'a, 'de> {
-    type Error = Error;
+    type Error = SerdeParseError;
 
-    // If the `Visitor` expected this variant to be a unit variant, the input
-    // should have been the plain string case handled in `deserialize_enum`.
     fn unit_variant(self) -> Result<()> {
-        Err(Error::ExpectedString)
+        self.de.next_token().expect_token(&[Token::LiteralString])?;
+        Ok(())
     }
 
-    // Newtype variants are represented in JSON as `{ NAME: VALUE }` so
-    // deserialize the value here.
     fn newtype_variant_seed<T>(self, seed: T) -> Result<T::Value>
     where
         T: DeserializeSeed<'de>,
@@ -586,8 +665,6 @@ impl<'de, 'a> VariantAccess<'de> for Enum<'a, 'de> {
         seed.deserialize(self.de)
     }
 
-    // Tuple variants are represented in JSON as `{ NAME: [DATA...] }` so
-    // deserialize the sequence of data here.
     fn tuple_variant<V>(self, _len: usize, visitor: V) -> Result<V::Value>
     where
         V: Visitor<'de>,
@@ -595,8 +672,6 @@ impl<'de, 'a> VariantAccess<'de> for Enum<'a, 'de> {
         de::Deserializer::deserialize_seq(self.de, visitor)
     }
 
-    // Struct variants are represented in JSON as `{ NAME: { K: V, ... } }` so
-    // deserialize the inner map here.
     fn struct_variant<V>(self, _fields: &'static [&'static str], visitor: V) -> Result<V::Value>
     where
         V: Visitor<'de>,
@@ -607,6 +682,42 @@ impl<'de, 'a> VariantAccess<'de> for Enum<'a, 'de> {
 
 ////////////////////////////////////////////////////////////////////////////////
 
+#[cfg(test)]
+mod tests {
+    use serde_derive::Deserialize;
+
+    fn from_str<'a, T>(source: &'a str) -> super::Result<T>
+    where
+        T: serde::Deserialize<'a>,
+    {
+        match super::from_str(source) {
+            Ok(res) => Ok(res),
+            Err(super::SerdeParseError::Spanned(err)) => {
+                let with_source = err.with_source(source);
+                eprintln!("{}", with_source);
+                Err(super::SerdeParseError::Spanned(with_source.spanned()))
+            }
+            Err(err) => {
+                eprintln!("{}", err);
+                Err(err)
+            }
+        }
+    }
+
+    #[test]
+    fn test_vec() {
+        let j = r#"["a","b"]"#;
+        let expected: Vec<String> = vec!["a".to_string(), "b".to_string()];
+        assert_eq!(expected, from_str::<Vec<String>>(j).unwrap());
+    }
+
+    #[test]
+    fn test_vec_explicit_keys() {
+        let j = r#"[0=>"a", 1=>"b"]"#;
+        let expected: Vec<String> = vec!["a".to_string(), "b".to_string()];
+        assert_eq!(expected, from_str::<Vec<String>>(j).unwrap());
+    }
+
     #[test]
     fn test_struct() {
         #[derive(Deserialize, PartialEq, Debug)]
@@ -615,7 +726,7 @@ fn test_struct() {
             seq: Vec<String>,
         }
 
-    let j = r#"{"int":1,"seq":["a","b"]}"#;
+        let j = r#"["int"=>1,"seq"=>["a","b"]]"#;
         let expected = Test {
             int: 1,
             seq: vec!["a".to_owned(), "b".to_owned()],
@@ -623,12 +734,35 @@ fn test_struct() {
         assert_eq!(expected, from_str(j).unwrap());
     }
 
+    #[test]
+    fn test_struct_nested() {
+        #[derive(Deserialize, PartialEq, Debug)]
+        struct Inner {
+            a: f32,
+            b: bool,
+        }
+
+        #[derive(Deserialize, PartialEq, Debug)]
+        struct Test {
+            int: u32,
+            nested: Inner,
+        }
+
+        let j = r#"["int"=>1,"nested"=>["a" => 1.0, "b" => false]]"#;
+        let expected = Test {
+            int: 1,
+            nested: Inner { a: 1.0, b: false },
+        };
+        assert_eq!(expected, from_str(j).unwrap());
+    }
+
     #[test]
     fn test_enum() {
         #[derive(Deserialize, PartialEq, Debug)]
         enum E {
             Unit,
-        Newtype(u32),
+            Newtype1(u32),
+            Newtype2(u32),
             Tuple(u32, u32),
             Struct { a: u32 },
         }
@@ -637,15 +771,20 @@ fn test_enum() {
         let expected = E::Unit;
         assert_eq!(expected, from_str(j).unwrap());
 
-    let j = r#"{"Newtype":1}"#;
-    let expected = E::Newtype(1);
+        let j = r#"["Newtype1"=>1]"#;
+        let expected = E::Newtype1(1);
         assert_eq!(expected, from_str(j).unwrap());
 
-    let j = r#"{"Tuple":[1,2]}"#;
+        let j = r#"["Newtype2"=>1]"#;
+        let expected = E::Newtype2(1);
+        assert_eq!(expected, from_str(j).unwrap());
+
+        let j = r#"["Tuple"=>[1,2]]"#;
         let expected = E::Tuple(1, 2);
         assert_eq!(expected, from_str(j).unwrap());
 
-    let j = r#"{"Struct":{"a":1}}"#;
+        let j = r#"["Struct"=>["a"=>1]]"#;
         let expected = E::Struct { a: 1 };
         assert_eq!(expected, from_str(j).unwrap());
     }
+}