Fix unreachable code panic on scan error

src/de.rs

@@ -101,17 +101,20 @@ impl<'de> Deserializer<'de> {
         let mut pos = 0;
         let mut jumpcount = 0;
 
-        match &self.progress {
+        match self.progress {
             Progress::Iterable(_) => return Err(error::new(ErrorImpl::MoreThanOneDocument)),
             Progress::Document(document) => {
                 let t = f(&mut DeserializerFromEvents {
-                    document,
+                    document: &document,
                     pos: &mut pos,
                     jumpcount: &mut jumpcount,
                     path: Path::Root,
                     remaining_depth: 128,
                     current_enum: None,
                 })?;
+                if let Some(parse_error) = document.error {
+                    return Err(error::shared(parse_error));
+                }
                 return Ok(t);
             }
             _ => {}
@@ -130,6 +133,9 @@ impl<'de> Deserializer<'de> {
             remaining_depth: 128,
             current_enum: None,
         })?;
+        if let Some(parse_error) = document.error {
+            return Err(error::shared(parse_error));
+        }
         if loader.next_document().is_none() {
             Ok(t)
         } else {

src/libyaml/parser.rs

@@ -84,6 +84,9 @@ impl<'input> Parser<'input> {
         let mut event = MaybeUninit::<sys::yaml_event_t>::uninit();
         unsafe {
             let parser = addr_of_mut!((*self.pin.ptr).sys);
+            if (*parser).error != sys::YAML_NO_ERROR {
+                return Err(Error::parse_error(parser));
+            }
             let event = event.as_mut_ptr();
             if sys::yaml_parser_parse(parser, event).fail {
                 return Err(Error::parse_error(parser));

tests/test_error.rs

@@ -3,7 +3,7 @@
 use indoc::indoc;
 use serde::de::{Deserialize, SeqAccess, Visitor};
 use serde_derive::{Deserialize, Serialize};
-use serde_yaml::Deserializer;
+use serde_yaml::{Deserializer, Value};
 use std::collections::BTreeMap;
 use std::fmt::{self, Debug};
 
@@ -15,6 +15,13 @@ where
     assert_eq!(expected, result.unwrap_err().to_string());
 }
 
+#[test]
+fn test_scan_error() {
+    let yaml = ">\n@";
+    let expected = "found character that cannot start any token at line 2 column 1, while scanning for the next token";
+    test_error::<Value>(yaml, expected);
+}
+
 #[test]
 fn test_incorrect_type() {
     let yaml = indoc! {"