rs-05-json-value
0.000
Challenge · difficulty 5/5
# JSON parser to a typed value
Implement the library file **`src/lib.rs`** exposing a parser for a subset of JSON:
```rust
pub fn parse(input: &str) -> Result<Value, ParseError>
pub enum Value {
Null,
Bool(bool),
Number(f64),
Str(String),
Array(Vec<Value>),
Object(Vec<(String, Value)>),
}
pub struct ParseError { /* your fields — e.g. a message and position */ }
```
Derive `Debug`, `Clone`, and `PartialEq` for `Value` so it can be compared in tests.
Parse a single JSON value from `input` and return it as a `Value`, or `Err(ParseError)` if the
input is not valid. Support:
- **Literals**: `null`, `true`, `false`.
- **Numbers**: parsed as `f64` (integers, negatives, decimals, and exponents like `1e3`).
- **Strings**: double-quoted, with the escapes `\" \\ \/ \n \t \r \b \f` and `\uXXXX`.
- **Arrays**: `[`, comma-separated values, `]`. May be empty (`[]`).
- **Objects**: `{`, comma-separated `"key": value` members, `}`. May be empty (`{}`). **Preserve
member order** exactly as it appears in the input (hence `Vec<(String, Value)>`, not a map).
- **Whitespace** (spaces, tabs, newlines, carriage returns) is allowed and ignored between tokens.
Errors (return `Err`, do not panic):
- malformed tokens, unterminated strings, missing `:`/`,`/closing brackets;
- **trailing characters** after a complete value (e.g. `"null null"` is an error).
Tests live in `tests/` and call `challenge::parse` and `challenge::Value`.
tests/json_value.rs
use challenge::{parse, Value};
#[test]
fn parses_primitives() {
assert_eq!(parse("null"), Ok(Value::Null));
assert_eq!(parse("true"), Ok(Value::Bool(true)));
assert_eq!(parse("false"), Ok(Value::Bool(false)));
assert_eq!(parse("42"), Ok(Value::Number(42.0)));
assert_eq!(parse("-3.5"), Ok(Value::Number(-3.5)));
assert_eq!(parse("1e3"), Ok(Value::Number(1000.0)));
assert_eq!(parse("\"hi\""), Ok(Value::Str("hi".to_string())));
}
#[test]
fn ignores_surrounding_whitespace() {
assert_eq!(parse(" \n true \t "), Ok(Value::Bool(true)));
}
#[test]
fn parses_string_escapes() {
assert_eq!(parse("\"a\\nb\""), Ok(Value::Str("a\nb".to_string())));
assert_eq!(parse("\"q\\\"q\""), Ok(Value::Str("q\"q".to_string())));
}
#[test]
fn parses_empty_array_and_object() {
assert_eq!(parse("[]"), Ok(Value::Array(vec![])));
assert_eq!(parse("{}"), Ok(Value::Object(vec![])));
}
#[test]
fn parses_nested_structures() {
let parsed = parse("{\"a\": [1, 2], \"b\": {\"c\": true}}").unwrap();
let expected = Value::Object(vec![
("a".to_string(), Value::Array(vec![Value::Number(1.0), Value::Number(2.0)])),
("b".to_string(), Value::Object(vec![("c".to_string(), Value::Bool(true))])),
]);
assert_eq!(parsed, expected);
}
#[test]
fn preserves_object_member_order() {
let parsed = parse("{\"z\": 1, \"a\": 2}").unwrap();
let expected = Value::Object(vec![
("z".to_string(), Value::Number(1.0)),
("a".to_string(), Value::Number(2.0)),
]);
assert_eq!(parsed, expected);
}
#[test]
fn rejects_trailing_characters() {
assert!(parse("null null").is_err());
assert!(parse("[1, 2] x").is_err());
}
#[test]
fn rejects_malformed_input() {
assert!(parse("").is_err());
assert!(parse("[1, 2").is_err());
assert!(parse("{\"a\": }").is_err());
assert!(parse("\"unterminated").is_err());
assert!(parse("{\"a\" 1}").is_err());
}
System prompt
You are an expert programmer. Solve the task exactly as specified. Output your solution as fenced code blocks using the required file name(s) and the exact function/type signatures requested. Prefer correctness; do not include prose outside code unless asked.
Proposed solution
```rust
use std::char;
use std::str::Chars;
#[derive(Debug, Clone, PartialEq)]
pub enum Value {
Null,
Bool(bool),
Number(f64),
Str(String),
Array(Vec<Value>),
Object(Vec<(String, Value)>),
}
#[derive(Debug, Clone, PartialEq)]
pub struct ParseError {
pub message: String,
pub position: usize,
}
impl std::fmt::Display for ParseError {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
write!(f, "{} at position {}", self.message, self.position)
}
}
impl std::error::Error for ParseError {}
pub fn parse(input: &str) -> Result<Value, ParseError> {
let mut parser = Parser::new(input);
let value = parser.parse_value()?;
// Check for trailing characters
parser.skip_whitespace();
if parser.peek().is_some() {
return Err(ParseError {
message: "trailing characters after complete value".to_string(),
position: parser.position,
});
}
Ok(value)
}
struct Parser<'a> {
chars: Chars<'a>,
position: usize,
current_char: Option<char>,
}
impl<'a> Parser<'a> {
fn new(input: &'a str) -> Self {
let mut chars = input.chars();
let current_char = chars.next();
Parser {
chars,
position: 0,
current_char,
}
}
fn advance(&mut self) {
if let Some(c) = self.current_char {
self.position += c.len_utf8();
}
self.current_char = self.chars.next();
}
fn peek(&self) -> Option<char> {
self.current_char
}
fn skip_whitespace(&mut self) {
while let Some(c) = self.current_char {
if c.is_whitespace() {
self.advance();
} else {
break;
}
}
}
fn parse_value(&mut self) -> Result<Value, ParseError> {
self.skip_whitespace();
match self.current_char {
Some('n') => self.parse_null(),
Some('t') => self.parse_true(),
Some('f') => self.parse_false(),
Some('"') => self.parse_string(),
Some('[') => self.parse_array(),
Some('{') => self.parse_object(),
Some(c) if c == '-' || c.is_ascii_digit() => self.parse_number(),
_ => Err(ParseError {
message: format!("unexpected character '{}'", self.current_char.unwrap_or('EOF')),
position: self.position,
}),
}
}
fn parse_null(&mut self) -> Result<Value, ParseError> {
self.expect_literal("null")?;
Ok(Value::Null)
}
fn parse_true(&mut self) -> Result<Value, ParseError> {
self.expect_literal("true")?;
Ok(Value::Bool(true))
}
fn parse_false(&mut self) -> Result<Value, ParseError> {
self.expect_literal("false")?;
Ok(Value::Bool(false))
}
fn expect_literal(&mut self, literal: &str) -> Result<(), ParseError> {
for expected in literal.chars() {
match self.current_char {
Some(c) if c == expected => self.advance(),
Some(c) => return Err(ParseError {
message: format!("expected '{}', found '{}'", expected, c),
position: self.position,
}),
None => return Err(ParseError {
message: format!("expected '{}', but input ended", expected),
position: self.position,
}),
}
}
Ok(())
}
fn parse_string(&mut self) -> Result<Value, ParseError> {
// Consume opening quote
match self.current_char {
Some('"') => self.advance(),
_ => unreachable!(),
}
let mut result = String::new();
loop {
match self.current_char {
None => return Err(ParseError {
message: "unterminated string".to_string(),
position: self.position,
}),
Some('"') => {
self.advance();
return Ok(Value::Str(result));
}
Some('\\') => {
self.advance(); // consume backslash
match self.current_char {
None => return Err(ParseError {
message: "unterminated escape sequence in string".to_string(),
position: self.position,
}),
Some('"') => {
result.push('"');
self.advance();
}
Some('\\') => {
result.push('\\');
self.advance();
}
Some('/') => {
result.push('/');
self.advance();
}
Some('b') => {
result.push('\x08'); // backspace
self.advance();
}
Some('f') => {
result.push('\x0c'); // form feed
self.advance();
}
Some('n') => {
result.push('\n');
self.advance();
}
Some('r') => {
result.push('\r');
self.advance();
}
Some('t') => {
result.push('\t');
self.advance();
}
Some('u') => {
self.advance(); // consume 'u'
let hex_str = self.get_hex_digits(4)?;
match char::from_u32(u32::from_str_radix(&hex_str, 16).map_err(|_| ParseError {
message: "invalid unicode escape sequence".to_string(),
position: self.position - 5,
})?) {
Some(c) => result.push(c),
None => return Err(ParseError {
message: "invalid unicode escape sequence".to_string(),
position: self.position - 5,
}),
}
}
Some(c) => return Err(ParseError {
message: format!("invalid escape character '{}'", c),
position: self.position,
}),
}
}
Some(c) => {
result.push(c);
self.advance();
}
}
}
}
fn get_hex_digits(&mut self, count: usize) -> Result<String, ParseError> {
let mut hex = String::new();
for _ in 0..count {
match self.current_char {
Some(c) if c.is_ascii_hexdigit() => {
hex.push(c);
self.advance();
}
Some(c) => return Err(ParseError {
message: format!("expected hex digit, found '{}'", c),
position: self.position,
}),
None => return Err(ParseError {
message: "unexpected end of input in unicode escape sequence".to_string(),
position: self.position,
}),
}
}
Ok(hex)
}
fn parse_number(&mut self) -> Result<Value, ParseError> {
let start_pos = self.position;
// Handle negative sign
if self.current_char == Some('-') {
self.advance();
}
// Integer part
match self.current_char {
Some('0') => {
self.advance();
// No leading zeros allowed except for "0" itself
if let Some(c) = self.current_char {
if c.is_ascii_digit() {
return Err(ParseError {
message: "invalid number: leading zeros not allowed".to_string(),
position: start_pos,
});
}
}
}
Some(c) if c.is_ascii_digit() => {
while let Some(c) = self.current_char {
if !c.is_ascii_digit() {
break;
}
self.advance();
}
}
_ => return Err(ParseError {
message: "invalid number".to_string(),
position: start_pos,
}),
}
// Fractional part
if self.current_char == Some('.') {
self.advance();
let mut has_fraction = false;
while let Some(c) = self.current_char {
if !c.is_ascii_digit() {
break;
}
has_fraction = true;
self.advance();
}
if !has_fraction {
return Err(ParseError {
message: "invalid number: decimal point without digits".to_string(),
position: start_pos,
});
}
}
// Exponent part
if self.current_char == Some('e') || self.current_char == Some('E') {
self.advance();
// Optional sign
if self.current_char == Some('+') || self.current_char == Some('-') {
self.advance();
}
let mut has_exponent = false;
while let Some(c) = self.current_char {
if !c.is_ascii_digit() {
break;
}
has_exponent = true;
self.advance();
}
if !has_exponent {
return Err(ParseError {
message: "invalid number: exponent without digits".to_string(),
position: start_pos,
});
}
}
let num_str = &input_from_position(self.position, start_pos);
match num_str.parse::<f64>() {
Ok(n) => Ok(Value::Number(n)),
Err(_) => Err(ParseError {
message: format!("invalid number: {}", num_str),
position: start_pos,
}),
}
}
fn parse_array(&mut self) -> Result<Value, ParseError> {
// Consume opening bracket
match self.current_char {
Some('[') => self.advance(),
_ => unreachable!(),
}
let mut values = Vec::new();
self.skip_whitespace();
if self.current_char == Some(']') {
self.advance();
return Ok(Value::Array(values));
}
loop {
values.push(self.parse_value()?);
self.skip_whitespace();
match self.current_char {
Some(',') => {
self.advance();
self.skip_whitespace();
}
Some(']') => {
self.advance();
return Ok(Value::Array(values));
}
None => return Err(ParseError {
message: "unterminated array".to_string(),
position: self.position,
}),
_ => return Err(ParseError {
message: format!("expected ',' or ']', found '{}'", self.current_char.unwrap_or('EOF')),
position: self.position,
}),
}
}
}
fn parse_object(&mut self) -> Result<Value, ParseError> {
// Consume opening brace
match self.current_char {
Some('{') => self.advance(),
_ => unreachable!(),
}
let mut members = Vec::new();
self.skip_whitespace();
if self.current_char == Some('}') {
self.advance();
return Ok(Value::Object(members));
}
loop {
// Parse key
match self.current_char {
Some('"') => {
let key = match self.parse_string()? {
Value::Str(s) => s,
_ => unreachable!(),
};
// Expect colon
self.skip_whitespace();
match self.current_char {
Some(':') => self.advance(),
_ => return Err(ParseError {
message: format!("expected ':' after object key, found '{}'", self.current_char.unwrap_or('EOF')),
position: self.position,
}),
}
// Parse value
self.skip_whitespace();
let value = self.parse_value()?;
members.push((key, value));
self.skip_whitespace();
match self.current_char {
Some(',') => {
self.advance();
self.skip_whitespace();
}
Some('}') => {
self.advance();
return Ok(Value::Object(members));
}
None => return Err(ParseError {
message: "unterminated object".to_string(),
position: self.position,
}),
_ => return Err(ParseError {
message: format!("expected ',' or '}}', found '{}'", self.current_char.unwrap_or('EOF')),
position: self.position,
}),
}
}
None => return Err(ParseError {
message: "unterminated object".to_string(),
position: self.position,
}),
_ => return Err(ParseError {
message: format!("expected string key in object, found '{}'", self.current_char.unwrap_or('EOF')),
position: self.position,
}),
}
}
}
}
// Helper function to extract substring from start_pos to current position
fn input_from_position(current_pos: usize, start_pos: usize) -> String {
// This is a simplified approach; in practice, we'd need to track positions more carefully
// For now, we'll use a different approach by building the string as we parse
panic!("This helper function is not used in the final implementation");
}
```Errors (stderr)
nly contain one codepoint
--> src/lib.rs:94:91
|
94 | message: format!("unexpected character '{}'", self.current_char.unwrap_or('EOF')),
| ^^^^^
|
help: if you meant to write a string literal, use double quotes
|
94 - message: format!("unexpected character '{}'", self.current_char.unwrap_or('EOF')),
94 + message: format!("unexpected character '{}'", self.current_char.unwrap_or("EOF")),
|
error: character literal may only contain one codepoint
--> src/lib.rs:364:101
|
364 | message: format!("expected ',' or ']', found '{}'", self.current_char.unwrap_or('EOF')),
| ^^^^^
|
help: if you meant to write a string literal, use double quotes
|
364 - message: format!("expected ',' or ']', found '{}'", self.current_char.unwrap_or('EOF')),
364 + message: format!("expected ',' or ']', found '{}'", self.current_char.unwrap_or("EOF")),
|
error: character literal may only contain one codepoint
--> src/lib.rs:401:119
|
401 | ... message: format!("expected ':' after object key, found '{}'", self.current_char.unwrap_or('EOF')),
| ^^^^^
|
help: if you meant to write a string literal, use double quotes
|
401 - message: format!("expected ':' after object key, found '{}'", self.current_char.unwrap_or('EOF')),
401 + message: format!("expected ':' after object key, found '{}'", self.current_char.unwrap_or("EOF")),
|
error: character literal may only contain one codepoint
--> src/lib.rs:427:110
|
427 | ... message: format!("expected ',' or '}}', found '{}'", self.current_char.unwrap_or('EOF')),
| ^^^^^
|
help: if you meant to write a string literal, use double quotes
|
427 - message: format!("expected ',' or '}}', found '{}'", self.current_char.unwrap_or('EOF')),
427 + message: format!("expected ',' or '}}', found '{}'", self.current_char.unwrap_or("EOF")),
|
error: character literal may only contain one codepoint
--> src/lib.rs:437:111
|
437 | message: format!("expected string key in object, found '{}'", self.current_char.unwrap_or('EOF')),
| ^^^^^
|
help: if you meant to write a string literal, use double quotes
|
437 - message: format!("expected string key in object, found '{}'", self.current_char.unwrap_or('EOF')),
437 + message: format!("expected string key in object, found '{}'", self.current_char.unwrap_or("EOF")),
|
warning: unused variable: `current_pos`
--> src/lib.rs:446:24
|
446 | fn input_from_position(current_pos: usize, start_pos: usize) -> String {
| ^^^^^^^^^^^ help: if this is intentional, prefix it with an underscore: `_current_pos`
|
= note: `#[warn(unused_variables)]` (part of `#[warn(unused)]`) on by default
warning: unused variable: `start_pos`
--> src/lib.rs:446:44
|
446 | fn input_from_position(current_pos: usize, start_pos: usize) -> String {
| ^^^^^^^^^ help: if this is intentional, prefix it with an underscore: `_start_pos`
error: could not compile `challenge` (lib) due to 5 previous errors; 2 warnings emitted
error: could not compile `challenge` (lib test) due to 5 previous errors; 2 warnings emitted
Self-repair attempts
[
{
"total": 1,
"answer": "```rust\nuse std::char;\nuse std::str::Chars;\n\n#[derive(Debug, Clone, PartialEq)]\npub enum Value {\n Null,\n Bool(bool),\n Number(f64),\n Str(String),\n Array(Vec<Value>),\n Object(Vec<(String, Value)>),\n}\n\n#[derive(Debug, Clone, PartialEq)]\npub struct ParseError {\n pub message: String,\n pub position: usize,\n}\n\nimpl std::fmt::Display for ParseError {\n fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {\n write!(f, \"{} at position {}\", self.message, self.position)\n }\n}\n\nimpl std::error::Error for ParseError {}\n\npub fn parse(input: &str) -> Result<Value, ParseError> {\n let mut parser = Parser::new(input);\n let value = parser.parse_value()?;\n \n // Check for trailing characters\n parser.skip_whitespace();\n if parser.peek().is_some() {\n return Err(ParseError {\n message: \"trailing characters after complete value\".to_string(),\n position: parser.position,\n });\n }\n \n Ok(value)\n}\n\nstruct Parser<'a> {\n chars: Chars<'a>,\n position: usize,\n current_char: Option<char>,\n}\n\nimpl<'a> Parser<'a> {\n fn new(input: &'a str) -> Self {\n let mut chars = input.chars();\n let current_char = chars.next();\n Parser {\n chars,\n position: 0,\n current_char,\n }\n }\n\n fn advance(&mut self) {\n if let Some(c) = self.current_char {\n self.position += c.len_utf8();\n }\n self.current_char = self.chars.next();\n }\n\n fn peek(&self) -> Option<char> {\n self.current_char\n }\n\n fn skip_whitespace(&mut self) {\n while let Some(c) = self.current_char {\n if c.is_whitespace() {\n self.advance();\n } else {\n break;\n }\n }\n }\n\n fn parse_value(&mut self) -> Result<Value, ParseError> {\n self.skip_whitespace();\n \n match self.current_char {\n Some('n') => self.parse_null(),\n Some('t') => self.parse_true(),\n Some('f') => self.parse_false(),\n Some('\"') => self.parse_string(),\n Some('[') => self.parse_array(),\n Some('{') => self.parse_object(),\n Some(c) if c == '-' || c.is_ascii_digit() => self.parse_number(),\n _ => Err(ParseError {\n message: format!(\"unexpected character '{}'\", self.current_char.unwrap_or('EOF')),\n position: self.position,\n }),\n }\n }\n\n fn parse_null(&mut self) -> Result<Value, ParseError> {\n self.expect_literal(\"null\")?;\n Ok(Value::Null)\n }\n\n fn parse_true(&mut self) -> Result<Value, ParseError> {\n self.expect_literal(\"true\")?;\n Ok(Value::Bool(true))\n }\n\n fn parse_false(&mut self) -> Result<Value, ParseError> {\n self.expect_literal(\"false\")?;\n Ok(Value::Bool(false))\n }\n\n fn expect_literal(&mut self, literal: &str) -> Result<(), ParseError> {\n for expected in literal.chars() {\n match self.current_char {\n Some(c) if c == expected => self.advance(),\n Some(c) => return Err(ParseError {\n message: format!(\"expected '{}', found '{}'\", expected, c),\n position: self.position,\n }),\n None => return Err(ParseError {\n message: format!(\"expected '{}', but input ended\", expected),\n position: self.position,\n }),\n }\n }\n Ok(())\n }\n\n fn parse_string(&mut self) -> Result<Value, ParseError> {\n // Consume opening quote\n match self.current_char {\n Some('\"') => self.advance(),\n _ => unreachable!(),\n }\n\n let mut result = String::new();\n \n loop {\n match self.current_char {\n None => return Err(ParseError {\n message: \"unterminated string\".to_string(),\n position: self.position,\n }),\n Some('\"') => {\n self.advance();\n return Ok(Value::Str(result));\n }\n Some('\\\\') => {\n self.advance(); // consume backslash\n match self.current_char {\n None => return Err(ParseError {\n message: \"unterminated escape sequence in string\".to_string(),\n position: self.position,\n }),\n Some('\"') => {\n result.push('\"');\n self.advance();\n }\n Some('\\\\') => {\n result.push('\\\\');\n self.advance();\n }\n Some('/') => {\n result.push('/');\n self.advance();\n }\n Some('b') => {\n result.push('\\x08'); // backspace\n self.advance();\n }\n Some('f') => {\n result.push('\\x0c'); // form feed\n self.advance();\n }\n Some('n') => {\n result.push('\\n');\n self.advance();\n }\n Some('r') => {\n result.push('\\r');\n self.advance();\n }\n Some('t') => {\n result.push('\\t');\n self.advance();\n }\n Some('u') => {\n self.advance(); // consume 'u'\n let hex_str = self.get_hex_digits(4)?;\n match char::from_u32(u32::from_str_radix(&hex_str, 16).map_err(|_| ParseError {\n message: \"invalid unicode escape sequence\".to_string(),\n position: self.position - 5,\n })?) {\n Some(c) => result.push(c),\n None => return Err(ParseError {\n message: \"invalid unicode escape sequence\".to_string(),\n position: self.position - 5,\n }),\n }\n }\n Some(c) => return Err(ParseError {\n message: format!(\"invalid escape character '{}'\", c),\n position: self.position,\n }),\n }\n }\n Some(c) => {\n result.push(c);\n self.advance();\n }\n }\n }\n }\n\n fn get_hex_digits(&mut self, count: usize) -> Result<String, ParseError> {\n let mut hex = String::new();\n for _ in 0..count {\n match self.current_char {\n Some(c) if c.is_ascii_hexdigit() => {\n hex.push(c);\n self.advance();\n }\n Some(c) => return Err(ParseError {\n message: format!(\"expected hex digit, found '{}'\", c),\n position: self.position,\n }),\n None => return Err(ParseError {\n message: \"unexpected end of input in unicode escape sequence\".to_string(),\n position: self.position,\n }),\n }\n }\n Ok(hex)\n }\n\n fn parse_number(&mut self) -> Result<Value, ParseError> {\n let start_pos = self.position;\n \n // Handle negative sign\n if self.current_char == Some('-') {\n self.advance();\n }\n\n // Integer part\n match self.current_char {\n Some('0') => {\n self.advance();\n // No leading zeros allowed except for \"0\" itself\n if let Some(c) = self.current_char {\n if c.is_ascii_digit() {\n return Err(ParseError {\n message: \"invalid number: leading zeros not allowed\".to_string(),\n position: start_pos,\n });\n }\n }\n }\n Some(c) if c.is_ascii_digit() => {\n while let Some(c) = self.current_char {\n if !c.is_ascii_digit() {\n break;\n }\n self.advance();\n }\n }\n _ => return Err(ParseError {\n message: \"invalid number\".to_string(),\n position: start_pos,\n }),\n }\n\n // Fractional part\n if self.current_char == Some('.') {\n self.advance();\n let mut has_fraction = false;\n while let Some(c) = self.current_char {\n if !c.is_ascii_digit() {\n break;\n }\n has_fraction = true;\n self.advance();\n }\n if !has_fraction {\n return Err(ParseError {\n message: \"invalid number: decimal point without digits\".to_string(),\n position: start_pos,\n });\n }\n }\n\n // Exponent part\n if self.current_char == Some('e') || self.current_char == Some('E') {\n self.advance();\n \n // Optional sign\n if self.current_char == Some('+') || self.current_char == Some('-') {\n self.advance();\n }\n \n let mut has_exponent = false;\n while let Some(c) = self.current_char {\n if !c.is_ascii_digit() {\n break;\n }\n has_exponent = true;\n self.advance();\n }\n if !has_exponent {\n return Err(ParseError {\n message: \"invalid number: exponent without digits\".to_string(),\n position: start_pos,\n });\n }\n }\n\n let num_str = &input_from_position(self.position, start_pos);\n match num_str.parse::<f64>() {\n Ok(n) => Ok(Value::Number(n)),\n Err(_) => Err(ParseError {\n message: format!(\"invalid number: {}\", num_str),\n position: start_pos,\n }),\n }\n }\n\n fn parse_array(&mut self) -> Result<Value, ParseError> {\n // Consume opening bracket\n match self.current_char {\n Some('[') => self.advance(),\n _ => unreachable!(),\n }\n\n let mut values = Vec::new();\n \n self.skip_whitespace();\n \n if self.current_char == Some(']') {\n self.advance();\n return Ok(Value::Array(values));\n }\n\n loop {\n values.push(self.parse_value()?);\n \n self.skip_whitespace();\n \n match self.current_char {\n Some(',') => {\n self.advance();\n self.skip_whitespace();\n }\n Some(']') => {\n self.advance();\n return Ok(Value::Array(values));\n }\n None => return Err(ParseError {\n message: \"unterminated array\".to_string(),\n position: self.position,\n }),\n _ => return Err(ParseError {\n message: format!(\"expected ',' or ']', found '{}'\", self.current_char.unwrap_or('EOF')),\n position: self.position,\n }),\n }\n }\n }\n\n fn parse_object(&mut self) -> Result<Value, ParseError> {\n // Consume opening brace\n match self.current_char {\n Some('{') => self.advance(),\n _ => unreachable!(),\n }\n\n let mut members = Vec::new();\n \n self.skip_whitespace();\n \n if self.current_char == Some('}') {\n self.advance();\n return Ok(Value::Object(members));\n }\n\n loop {\n // Parse key\n match self.current_char {\n Some('\"') => {\n let key = match self.parse_string()? {\n Value::Str(s) => s,\n _ => unreachable!(),\n };\n \n // Expect colon\n self.skip_whitespace();\n match self.current_char {\n Some(':') => self.advance(),\n _ => return Err(ParseError {\n message: format!(\"expected ':' after object key, found '{}'\", self.current_char.unwrap_or('EOF')),\n position: self.position,\n }),\n }\n \n // Parse value\n self.skip_whitespace();\n let value = self.parse_value()?;\n members.push((key, value));\n \n self.skip_whitespace();\n \n match self.current_char {\n Some(',') => {\n self.advance();\n self.skip_whitespace();\n }\n Some('}') => {\n self.advance();\n return Ok(Value::Object(members));\n }\n None => return Err(ParseError {\n message: \"unterminated object\".to_string(),\n position: self.position,\n }),\n _ => return Err(ParseError {\n message: format!(\"expected ',' or '}}', found '{}'\", self.current_char.unwrap_or('EOF')),\n position: self.position,\n }),\n }\n }\n None => return Err(ParseError {\n message: \"unterminated object\".to_string(),\n position: self.position,\n }),\n _ => return Err(ParseError {\n message: format!(\"expected string key in object, found '{}'\", self.current_char.unwrap_or('EOF')),\n position: self.position,\n }),\n }\n }\n }\n}\n\n// Helper function to extract substring from start_pos to current position\nfn input_from_position(current_pos: usize, start_pos: usize) -> String {\n // This is a simplified approach; in practice, we'd need to track positions more carefully\n // For now, we'll use a different approach by building the string as we parse\n panic!(\"This helper function is not used in the final implementation\");\n}\n```",
"passed": 0,
"test_error": " ^^^^^\n |\nhelp: if you meant to write a string literal, use double quotes\n |\n401 - message: format!(\"expected ':' after object key, found '{}'\", self.current_char.unwrap_or('EOF')),\n401 + message: format!(\"expected ':' after object key, found '{}'\", self.current_char.unwrap_or(\"EOF\")),\n |\n\nerror: character literal may only contain one codepoint\n --> src/lib.rs:427:110\n |\n427 | ... message: format!(\"expected ',' or '}}', found '{}'\", self.current_char.unwrap_or('EOF')),\n | ^^^^^\n |\nhelp: if you meant to write a string literal, use double quotes\n |\n427 - message: format!(\"expected ',' or '}}', found '{}'\", self.current_char.unwrap_or('EOF')),\n427 + message: format!(\"expected ',' or '}}', found '{}'\", self.current_char.unwrap_or(\"EOF\")),\n |\n\nerror: character literal may only contain one codepoint\n --> src/lib.rs:437:111\n |\n437 | message: format!(\"expected string key in object, found '{}'\", self.current_char.unwrap_or('EOF')),\n | ^^^^^\n |\nhelp: if you meant to write a string literal, use double quotes\n |\n437 - message: format!(\"expected string key in object, found '{}'\", self.current_char.unwrap_or('EOF')),\n437 + message: format!(\"expected string key in object, found '{}'\", self.current_char.unwrap_or(\"EOF\")),\n |\n\nwarning: unused variable: `current_pos`\n --> src/lib.rs:446:24\n |\n446 | fn input_from_position(current_pos: usize, start_pos: usize) -> String {\n | ^^^^^^^^^^^ help: if this is intentional, prefix it with an underscore: `_current_pos`\n |\n = note: `#[warn(unused_variables)]` (part of `#[warn(unused)]`) on by default\n\nwarning: unused variable: `start_pos`\n --> src/lib.rs:446:44\n |\n446 | fn input_from_position(current_pos: usize, start_pos: usize) -> String {\n | ^^^^^^^^^ help: if this is intentional, prefix it with an underscore: `_start_pos`\n\nerror: could not compile `challenge` (lib) due to 5 previous errors; 2 warnings emitted\nerror: could not compile `challenge` (lib test) due to 5 previous errors; 2 warnings emitted"
},
{
"total": 1,
"answer": "Looking at the compilation errors, I need to fix several issues:\n\n1. Character literals vs string literals in `unwrap_or()` calls (should use `\"EOF\"` instead of `'EOF'`)\n2. Remove the unused helper function `input_from_position`\n3. Fix the number parsing logic to properly extract the substring\n\nLet me rewrite the solution with these fixes:\n\n```rust\nuse std::char;\n\n#[derive(Debug, Clone, PartialEq)]\npub enum Value {\n Null,\n Bool(bool),\n Number(f64),\n Str(String),\n Array(Vec<Value>),\n Object(Vec<(String, Value)>),\n}\n\n#[derive(Debug, Clone, PartialEq)]\npub struct ParseError {\n pub message: String,\n pub position: usize,\n}\n\nimpl std::fmt::Display for ParseError {\n fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {\n write!(f, \"{} at position {}\", self.message, self.position)\n }\n}\n\nimpl std::error::Error for ParseError {}\n\npub fn parse(input: &str) -> Result<Value, ParseError> {\n let mut parser = Parser::new(input);\n let value = parser.parse_value()?;\n \n // Check for trailing characters\n parser.skip_whitespace();\n if parser.peek().is_some() {\n return Err(ParseError {\n message: \"trailing characters after complete value\".to_string(),\n position: parser.position,\n });\n }\n \n Ok(value)\n}\n\nstruct Parser<'a> {\n input: &'a str,\n position: usize,\n}\n\nimpl<'a> Parser<'a> {\n fn new(input: &'a str) -> Self {\n Parser { input, position: 0 }\n }\n\n fn peek(&self) -> Option<char> {\n if self.position >= self.input.len() {\n None\n } else {\n Some(self.input[self.position..].chars().next().unwrap())\n }\n }\n\n fn advance(&mut self) {\n if self.position < self.input.len() {\n let c = self.input[self.position..].chars().next().unwrap();\n self.position += c.len_utf8();\n }\n }\n\n fn skip_whitespace(&mut self) {\n while let Some(c) = self.peek() {\n if c.is_whitespace() {\n self.advance();\n } else {\n break;\n }\n }\n }\n\n fn parse_value(&mut self) -> Result<Value, ParseError> {\n self.skip_whitespace();\n \n match self.peek() {\n Some('n') => self.parse_null(),\n Some('t') => self.parse_true(),\n Some('f') => self.parse_false(),\n Some('\"') => self.parse_string(),\n Some('[') => self.parse_array(),\n Some('{') => self.parse_object(),\n Some(c) if c == '-' || c.is_ascii_digit() => self.parse_number(),\n None => Err(ParseError {\n message: \"unexpected end of input\".to_string(),\n position: self.position,\n }),\n Some(c) => Err(ParseError {\n message: format!(\"unexpected character '{}'\", c),\n position: self.position,\n }),\n }\n }\n\n fn parse_null(&mut self) -> Result<Value, ParseError> {\n self.expect_literal(\"null\")?;\n Ok(Value::Null)\n }\n\n fn parse_true(&mut self) -> Result<Value, ParseError> {\n self.expect_literal(\"true\")?;\n Ok(Value::Bool(true))\n }\n\n fn parse_false(&mut self) -> Result<Value, ParseError> {\n self.expect_literal(\"false\")?;\n Ok(Value::Bool(false))\n }\n\n fn expect_literal(&mut self, literal: &str) -> Result<(), ParseError> {\n let start_pos = self.position;\n for expected in literal.chars() {\n match self.peek() {\n Some(c) if c == expected => self.advance(),\n Some(c) => return Err(ParseError {\n message: format!(\"expected '{}', found '{}'\", expected, c),\n position: self.position,\n }),\n None => return Err(ParseError {\n message: format!(\"expected '{}', but input ended\", expected),\n position: self.position,\n }),\n }\n }\n Ok(())\n }\n\n fn parse_string(&mut self) -> Result<Value, ParseError> {\n // Consume opening quote\n match self.peek() {\n Some('\"') => self.advance(),\n _ => unreachable!(),\n }\n\n let mut result = String::new();\n \n loop {\n match self.peek() {\n None => return Err(ParseError {\n message: \"unterminated string\".to_string(),\n position: self.position,\n }),\n Some('\"') => {\n self.advance();\n return Ok(Value::Str(result));\n }\n Some('\\\\') => {\n self.advance(); // consume backslash\n match self.peek() {\n None => return Err(ParseError {\n message: \"unterminated escape sequence in string\".to_string(),\n position: self.position,\n }),\n Some('\"') => {\n result.push('\"');\n self.advance();\n }\n Some('\\\\') => {\n result.push('\\\\');\n self.advance();\n }\n Some('/') => {\n result.push('/');\n self.advance();\n }\n Some('b') => {\n result.push('\\x08'); // backspace\n self.advance();\n }\n Some('f') => {\n result.push('\\x0c'); // form feed\n self.advance();\n }\n Some('n') => {\n result.push('\\n');\n self.advance();\n }\n Some('r') => {\n result.push('\\r');\n self.advance();\n }\n Some('t') => {\n result.push('\\t');\n self.advance();\n }\n Some('u') => {\n self.advance(); // consume 'u'\n let hex_str = self.get_hex_digits(4)?;\n match char::from_u32(u32::from_str_radix(&hex_str, 16).map_err(|_| ParseError {\n message: \"invalid unicode escape sequence\".to_string(),\n position: self.position - 5,\n })?) {\n Some(c) => result.push(c),\n None => return Err(ParseError {\n message: \"invalid unicode escape sequence\".to_string(),\n position: self.position - 5,\n }),\n }\n }\n Some(c) => return Err(ParseError {\n message: format!(\"invalid escape character '{}'\", c),\n position: self.position,\n }),\n }\n }\n Some(c) => {\n result.push(c);\n self.advance();\n }\n }\n }\n }\n\n fn get_hex_digits(&mut self, count: usize) -> Result<String, ParseError> {\n let mut hex = String::new();\n for _ in 0..count {\n match self.peek() {\n Some(c) if c.is_ascii_hexdigit() => {\n hex.push(c);\n self.advance();\n }\n Some(c) => return Err(ParseError {\n message: format!(\"expected hex digit, found '{}'\", c),\n position: self.position,\n }),\n None => return Err(ParseError {\n message: \"unexpected end of input in unicode escape sequence\".to_string(),\n position: self.position,\n }),\n }\n }\n Ok(hex)\n }\n\n fn parse_number(&mut self) -> Result<Value, ParseError> {\n let start_pos = self.position;\n \n // Handle negative sign\n if self.peek() == Some('-') {\n self.advance();\n }\n\n // Integer part\n match self.peek() {\n Some('0') => {\n self.advance();\n // No leading zeros allowed except for \"0\" itself\n if let Some(c) = self.peek() {\n if c.is_ascii_digit() {\n return Err(ParseError {\n message: \"invalid number: leading zeros not allowed\".to_string(),\n position: start_pos,\n });\n }\n }\n }\n Some(c) if c.is_ascii_digit() => {\n while let Some(c) = self.peek() {\n if !c.is_ascii_digit() {\n break;\n }\n self.advance();\n }\n }\n _ => return Err(ParseError {\n message: \"invalid number\".to_string(),\n position: start_pos,\n }),\n }\n\n // Fractional part\n if self.peek() == Some('.') {\n self.advance();\n let mut has_fraction = false;\n while let Some(c) = self.peek() {\n if !c.is_ascii_digit() {\n break;\n }\n has_fraction = true;\n self.advance();\n }\n if !has_fraction {\n return Err(ParseError {\n message: \"invalid number: decimal point without digits\".to_string(),\n position: start_pos,\n });\n }\n }\n\n // Exponent part\n if self.peek() == Some('e') || self.peek() == Some('E') {\n self.advance();\n \n // Optional sign\n if self.peek() == Some('+') || self.peek() == Some('-') {\n self.advance();\n }\n \n let mut has_exponent = false;\n while let Some(c) = self.peek() {\n if !c.is_ascii_digit() {\n break;\n }\n has_exponent = true;\n self.advance();\n }\n if !has_exponent {\n return Err(ParseError {\n message: \"invalid number: exponent without digits\".to_string(),\n position: start_pos,\n });\n }\n }\n\n let num_str = &self.input[start_pos..self.position];\n match num_str.parse::<f64>() {\n Ok(n) => Ok(Value::Number(n)),\n Err(_) => Err(ParseError {\n message: format!(\"invalid number: {}\", num_str),\n position: start_pos,\n }),\n }\n }\n\n fn parse_array(&mut self) -> Result<Value, ParseError> {\n // Consume opening bracket\n match self.peek() {\n Some('[') => self.advance(),\n _ => unreachable!(),\n }\n\n let mut values = Vec::new();\n \n self.skip_whitespace();\n \n if self.peek() == Some(']') {\n self.advance();\n return Ok(Value::Array(values));\n }\n\n loop {\n values.push(self.parse_value()?);\n \n self.skip_whitespace();\n \n match self.peek() {\n Some(',') => {\n self.advance();\n self.skip_whitespace();\n }\n Some(']') => {\n self.advance();\n return Ok(Value::Array(values));\n }\n None => return Err(ParseError {\n message: \"unterminated array\".to_string(),\n position: self.position,\n }),\n _ => return Err(ParseError {\n message: format!(\"expected ',' or ']', found '{}'\", self.peek().unwrap_or(\"EOF\")),\n position: self.position,\n }),\n }\n }\n }\n\n fn parse_object(&mut self) -> Result<Value, ParseError> {\n // Consume opening brace\n match self.peek() {\n Some('{') => self.advance(),\n _ => unreachable!(),\n }\n\n let mut members = Vec::new();\n \n self.skip_whitespace();\n \n if self.peek() == Some('}') {\n self.advance();\n return Ok(Value::Object(members));\n }\n\n loop {\n // Parse key\n match self.peek() {\n Some('\"') => {\n let key = match self.parse_string()? {\n Value::Str(s) => s,\n _ => unreachable!(),\n };\n \n // Expect colon\n self.skip_whitespace();\n match self.peek() {\n Some(':') => self.advance(),\n _ => return Err(ParseError {\n message: format!(\"expected ':' after object key, found '{}'\", self.peek().unwrap_or(\"EOF\")),\n position: self.position,\n }),\n }\n \n // Parse value\n self.skip_whitespace();\n let value = self.parse_value()?;\n members.push((key, value));\n \n self.skip_whitespace();\n \n match self.peek() {\n Some(',') => {\n self.advance();\n self.skip_whitespace();\n }\n Some('}') => {\n self.advance();\n return Ok(Value::Object(members));\n }\n None => return Err(ParseError {\n message: \"unterminated object\".to_string(),\n position: self.position,\n }),\n _ => return Err(ParseError {\n message: format!(\"expected ',' or '}}', found '{}'\", self.peek().unwrap_or(\"EOF\")),\n position: self.position,\n }),\n }\n }\n None => return Err(ParseError {\n message: \"unterminated object\".to_string(),\n position: self.position,\n }),\n _ => return Err(ParseError {\n message: format!(\"expected string key in object, found '{}'\", self.peek().unwrap_or(\"EOF\")),\n position: self.position,\n }),\n }\n }\n }\n}\n```",
"passed": 0,
"test_error": "b.rs:428:82\n |\n428 | ... message: format!(\"expected ',' or '}}', found '{}'\", self.peek().unwrap_or(\"EOF\")),\n | ^^^^^^^^^^^^^^^^^^^^^^-----^\n | |\n | this argument influences the return type of `unwrap_or`\nnote: method defined here\n --> /rustc/ac68faa20c58cbccd01ee7208bf3b6e93a7d7f96/library/core/src/option.rs:1038:17\n\nerror[E0308]: mismatched types\n --> src/lib.rs:438:105\n |\n438 | message: format!(\"expected string key in object, found '{}'\", self.peek().unwrap_or(\"EOF\")),\n | --------- ^^^^^ expected `char`, found `&str`\n | |\n | arguments to this method are incorrect\n |\nhelp: the return type of this call is `&'static str` due to the type of the argument passed\n --> src/lib.rs:438:83\n |\n438 | message: format!(\"expected string key in object, found '{}'\", self.peek().unwrap_or(\"EOF\")),\n | ^^^^^^^^^^^^^^^^^^^^^^-----^\n | |\n | this argument influences the return type of `unwrap_or`\nnote: method defined here\n --> /rustc/ac68faa20c58cbccd01ee7208bf3b6e93a7d7f96/library/core/src/option.rs:1038:17\n\nwarning: unused variable: `start_pos`\n --> src/lib.rs:116:13\n |\n116 | let start_pos = self.position;\n | ^^^^^^^^^ help: if this is intentional, prefix it with an underscore: `_start_pos`\n |\n = note: `#[warn(unused_variables)]` (part of `#[warn(unused)]`) on by default\n\nFor more information about this error, try `rustc --explain E0308`.\nerror: could not compile `challenge` (lib test) due to 4 previous errors; 1 warning emitted\nerror: could not compile `challenge` (lib) due to 4 previous errors; 1 warning emitted"
},
{
"total": 8,
"answer": "Looking at the compilation errors, I need to fix the type mismatch in `unwrap_or()` calls. The issue is that `peek()` returns `Option<char>`, but I'm trying to use `\"EOF\"` (a string) as the default value. I should use `' '` (space) or handle it differently.\n\nAlso, I notice there's an unused variable warning for `start_pos` in `parse_null`, `parse_true`, and `parse_false`. Let me fix all these issues:\n\n```rust\nuse std::char;\n\n#[derive(Debug, Clone, PartialEq)]\npub enum Value {\n Null,\n Bool(bool),\n Number(f64),\n Str(String),\n Array(Vec<Value>),\n Object(Vec<(String, Value)>),\n}\n\n#[derive(Debug, Clone, PartialEq)]\npub struct ParseError {\n pub message: String,\n pub position: usize,\n}\n\nimpl std::fmt::Display for ParseError {\n fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {\n write!(f, \"{} at position {}\", self.message, self.position)\n }\n}\n\nimpl std::error::Error for ParseError {}\n\npub fn parse(input: &str) -> Result<Value, ParseError> {\n let mut parser = Parser::new(input);\n let value = parser.parse_value()?;\n \n // Check for trailing characters\n parser.skip_whitespace();\n if parser.peek().is_some() {\n return Err(ParseError {\n message: \"trailing characters after complete value\".to_string(),\n position: parser.position,\n });\n }\n \n Ok(value)\n}\n\nstruct Parser<'a> {\n input: &'a str,\n position: usize,\n}\n\nimpl<'a> Parser<'a> {\n fn new(input: &'a str) -> Self {\n Parser { input, position: 0 }\n }\n\n fn peek(&self) -> Option<char> {\n if self.position >= self.input.len() {\n None\n } else {\n Some(self.input[self.position..].chars().next().unwrap())\n }\n }\n\n fn advance(&mut self) {\n if self.position < self.input.len() {\n let c = self.input[self.position..].chars().next().unwrap();\n self.position += c.len_utf8();\n }\n }\n\n fn skip_whitespace(&mut self) {\n while let Some(c) = self.peek() {\n if c.is_whitespace() {\n self.advance();\n } else {\n break;\n }\n }\n }\n\n fn parse_value(&mut self) -> Result<Value, ParseError> {\n self.skip_whitespace();\n \n match self.peek() {\n Some('n') => self.parse_null(),\n Some('t') => self.parse_true(),\n Some('f') => self.parse_false(),\n Some('\"') => self.parse_string(),\n Some('[') => self.parse_array(),\n Some('{') => self.parse_object(),\n Some(c) if c == '-' || c.is_ascii_digit() => self.parse_number(),\n None => Err(ParseError {\n message: \"unexpected end of input\".to_string(),\n position: self.position,\n }),\n Some(c) => Err(ParseError {\n message: format!(\"unexpected character '{}'\", c),\n position: self.position,\n }),\n }\n }\n\n fn parse_null(&mut self) -> Result<Value, ParseError> {\n self.expect_literal(\"null\")?;\n Ok(Value::Null)\n }\n\n fn parse_true(&mut self) -> Result<Value, ParseError> {\n self.expect_literal(\"true\")?;\n Ok(Value::Bool(true))\n }\n\n fn parse_false(&mut self) -> Result<Value, ParseError> {\n self.expect_literal(\"false\")?;\n Ok(Value::Bool(false))\n }\n\n fn expect_literal(&mut self, literal: &str) -> Result<(), ParseError> {\n for expected in literal.chars() {\n match self.peek() {\n Some(c) if c == expected => self.advance(),\n Some(c) => return Err(ParseError {\n message: format!(\"expected '{}', found '{}'\", expected, c),\n position: self.position,\n }),\n None => return Err(ParseError {\n message: format!(\"expected '{}', but input ended\", expected),\n position: self.position,\n }),\n }\n }\n Ok(())\n }\n\n fn parse_string(&mut self) -> Result<Value, ParseError> {\n // Consume opening quote\n match self.peek() {\n Some('\"') => self.advance(),\n _ => unreachable!(),\n }\n\n let mut result = String::new();\n \n loop {\n match self.peek() {\n None => return Err(ParseError {\n message: \"unterminated string\".to_string(),\n position: self.position,\n }),\n Some('\"') => {\n self.advance();\n return Ok(Value::Str(result));\n }\n Some('\\\\') => {\n self.advance(); // consume backslash\n match self.peek() {\n None => return Err(ParseError {\n message: \"unterminated escape sequence in string\".to_string(),\n position: self.position,\n }),\n Some('\"') => {\n result.push('\"');\n self.advance();\n }\n Some('\\\\') => {\n result.push('\\\\');\n self.advance();\n }\n Some('/') => {\n result.push('/');\n self.advance();\n }\n Some('b') => {\n result.push('\\x08'); // backspace\n self.advance();\n }\n Some('f') => {\n result.push('\\x0c'); // form feed\n self.advance();\n }\n Some('n') => {\n result.push('\\n');\n self.advance();\n }\n Some('r') => {\n result.push('\\r');\n self.advance();\n }\n Some('t') => {\n result.push('\\t');\n self.advance();\n }\n Some('u') => {\n self.advance(); // consume 'u'\n let hex_str = self.get_hex_digits(4)?;\n match char::from_u32(u32::from_str_radix(&hex_str, 16).map_err(|_| ParseError {\n message: \"invalid unicode escape sequence\".to_string(),\n position: self.position - 5,\n })?) {\n Some(c) => result.push(c),\n None => return Err(ParseError {\n message: \"invalid unicode escape sequence\".to_string(),\n position: self.position - 5,\n }),\n }\n }\n Some(c) => return Err(ParseError {\n message: format!(\"invalid escape character '{}'\", c),\n position: self.position,\n }),\n }\n }\n Some(c) => {\n result.push(c);\n self.advance();\n }\n }\n }\n }\n\n fn get_hex_digits(&mut self, count: usize) -> Result<String, ParseError> {\n let mut hex = String::new();\n for _ in 0..count {\n match self.peek() {\n Some(c) if c.is_ascii_hexdigit() => {\n hex.push(c);\n self.advance();\n }\n Some(c) => return Err(ParseError {\n message: format!(\"expected hex digit, found '{}'\", c),\n position: self.position,\n }),\n None => return Err(ParseError {\n message: \"unexpected end of input in unicode escape sequence\".to_string(),\n position: self.position,\n }),\n }\n }\n Ok(hex)\n }\n\n fn parse_number(&mut self) -> Result<Value, ParseError> {\n let start_pos = self.position;\n \n // Handle negative sign\n if self.peek() == Some('-') {\n self.advance();\n }\n\n // Integer part\n match self.peek() {\n Some('0') => {\n self.advance();\n // No leading zeros allowed except for \"0\" itself\n if let Some(c) = self.peek() {\n if c.is_ascii_digit() {\n return Err(ParseError {\n message: \"invalid number: leading zeros not allowed\".to_string(),\n position: start_pos,\n });\n }\n }\n }\n Some(c) if c.is_ascii_digit() => {\n while let Some(c) = self.peek() {\n if !c.is_ascii_digit() {\n break;\n }\n self.advance();\n }\n }\n _ => return Err(ParseError {\n message: \"invalid number\".to_string(),\n position: start_pos,\n }),\n }\n\n // Fractional part\n if self.peek() == Some('.') {\n self.advance();\n let mut has_fraction = false;\n while let Some(c) = self.peek() {\n if !c.is_ascii_digit() {\n break;\n }\n has_fraction = true;\n self.advance();\n }\n if !has_fraction {\n return Err(ParseError {\n message: \"invalid number: decimal point without digits\".to_string(),\n position: start_pos,\n });\n }\n }\n\n // Exponent part\n if self.peek() == Some('e') || self.peek() == Some('E') {\n self.advance();\n \n // Optional sign\n if self.peek() == Some('+') || self.peek() == Some('-') {\n self.advance();\n }\n \n let mut has_exponent = false;\n while let Some(c) = self.peek() {\n if !c.is_ascii_digit() {\n break;\n }\n has_exponent = true;\n self.advance();\n }\n if !has_exponent {\n return Err(ParseError {\n message: \"invalid number: exponent without digits\".to_string(),\n position: start_pos,\n });\n }\n }\n\n let num_str = &self.input[start_pos..self.position];\n match num_str.parse::<f64>() {\n Ok(n) => Ok(Value::Number(n)),\n Err(_) => Err(ParseError {\n message: format!(\"invalid number: {}\", num_str),\n position: start_pos,\n }),\n }\n }\n\n fn parse_array(&mut self) -> Result<Value, ParseError> {\n // Consume opening bracket\n match self.peek() {\n Some('[') => self.advance(),\n _ => unreachable!(),\n }\n\n let mut values = Vec::new();\n \n self.skip_whitespace();\n \n if self.peek() == Some(']') {\n self.advance();\n return Ok(Value::Array(values));\n }\n\n loop {\n values.push(self.parse_value()?);\n \n self.skip_whitespace();\n \n match self.peek() {\n Some(',') => {\n self.advance();\n self.skip_whitespace();\n }\n Some(']') => {\n self.advance();\n return Ok(Value::Array(values));\n }\n None => return Err(ParseError {\n message: \"unterminated array\".to_string(),\n position: self.position,\n }),\n _ => return Err(ParseError {\n message: format!(\"expected ',' or ']', found '{}'\", self.peek().unwrap_or(' ')),\n position: self.position,\n }),\n }\n }\n }\n\n fn parse_object(&mut self) -> Result<Value, ParseError> {\n // Consume opening brace\n match self.peek() {\n Some('{') => self.advance(),\n _ => unreachable!(),\n }\n\n let mut members = Vec::new();\n \n self.skip_whitespace();\n \n if self.peek() == Some('}') {\n self.advance();\n return Ok(Value::Object(members));\n }\n\n loop {\n // Parse key\n match self.peek() {\n Some('\"') => {\n let key = match self.parse_string()? {\n Value::Str(s) => s,\n _ => unreachable!(),\n };\n \n // Expect colon\n self.skip_whitespace();\n match self.peek() {\n Some(':') => self.advance(),\n _ => return Err(ParseError {\n message: format!(\"expected ':' after object key, found '{}'\", self.peek().unwrap_or(' ')),\n position: self.position,\n }),\n }\n \n // Parse value\n self.skip_whitespace();\n let value = self.parse_value()?;\n members.push((key, value));\n \n self.skip_whitespace();\n \n match self.peek() {\n Some(',') => {\n self.advance();\n self.skip_whitespace();\n }\n Some('}') => {\n self.advance();\n return Ok(Value::Object(members));\n }\n None => return Err(ParseError {\n message: \"unterminated object\".to_string(),\n position: self.position,\n }),\n _ => return Err(ParseError {\n message: format!(\"expected ',' or '}}', found '{}'\", self.peek().unwrap_or(' ')),\n position: self.position,\n }),\n }\n }\n None => return Err(ParseError {\n message: \"unterminated object\".to_string(),\n position: self.position,\n }),\n _ => return Err(ParseError {\n message: format!(\"expected string key in object, found '{}'\", self.peek().unwrap_or(' ')),\n position: self.position,\n }),\n }\n }\n }\n}\n```",
"passed": 8,
"test_error": ""
}
]