Fix multibyte char after value

fuzz/.gitignore

@@ -0,0 +1,4 @@
+target
+corpus
+artifacts
+coverage

fuzz/Cargo.toml

@@ -0,0 +1,21 @@
+[package]
+name = "json-five-fuzz"
+version = "0.0.0"
+publish = false
+edition = "2024"
+
+[package.metadata]
+cargo-fuzz = true
+
+[dependencies]
+libfuzzer-sys = "0.4"
+
+[dependencies.json-five]
+path = ".."
+
+[[bin]]
+name = "fuzz_target_1"
+path = "fuzz_targets/fuzz_target_1.rs"
+test = false
+doc = false
+bench = false

fuzz/fuzz_targets/fuzz_target_1.rs

@@ -0,0 +1,11 @@
+#![no_main]
+
+use libfuzzer_sys::fuzz_target;
+use json_five::tokenize::tokenize_bytes;
+use json_five::parser::from_tokens;
+fuzz_target!(|data: &[u8]| {
+    let result = tokenize_bytes(data);
+    if let Ok(tokens) = result {
+        let _ = from_tokens(&tokens);
+    }
+});

src/parser.rs

@@ -538,7 +538,7 @@ impl<'toks, 'input> JSON5Parser<'toks, 'input> {
             None => {}
             Some(span) => {
                 if span.1 != TokType::EOF {
-                    return Err(self.make_error(format!("Unexpected {:?} token after value", span.1), span.0 - 1))
+                    return Err(self.make_error(format!("Unexpected {:?} token after value", span.1), span.0))
                 }
             }
         }
@@ -600,6 +600,12 @@ mod tests {
     use crate::parser::JSONValue::*;
     use super::*;
 
+        #[test]
+    fn test_fuzz_1() {
+        let res = from_str("0xA18 {9");
+        assert!(res.is_err());
+    }
+
     #[test]
     fn test_from_bytes() {
         let res = from_bytes(b"{}").unwrap();

src/rt/parser.rs

@@ -656,7 +656,7 @@ impl<'toks, 'input> JSON5Parser<'toks, 'input> {
             None => {}
             Some(span) => {
                 if span.1 != TokType::EOF {
-                    return Err(self.make_error(format!("Unexpected {:?} token after value", span.1), span.0 - 1))
+                    return Err(self.make_error(format!("Unexpected {:?} token after value", span.1), span.0))
                 }
             }
         }
@@ -704,7 +704,15 @@ pub fn from_str(source: &str) -> Result<JSONText, ParsingError> {
 #[cfg(test)]
 mod tests {
     use crate::tokenize::Tokenizer;
+
     use super::*;
+
+    #[test]
+    fn test_fuzz_1() {
+        let res = from_str("0xA18 {9");
+        assert!(res.is_err());
+    }
+
     #[test]
     fn test_foo() {
         let res = from_str("{}").unwrap();