Simplifies Rio error handling

src/rio/mod.rs

@@ -1,5 +1,6 @@
 use std::error::Error;
 use std::fmt;
+use std::io;
 
 pub mod ntriples;
 pub mod turtle;
@@ -22,6 +23,12 @@ impl RioError {
     }
 }
 
+impl From<io::Error> for RioError {
+    fn from(error: io::Error) -> Self {
+        RioError::new(error)
+    }
+}
+
 impl fmt::Display for RioError {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         self.error.fmt(f)

src/rio/ntriples/mod.rs

@@ -19,6 +19,6 @@ pub fn read_ntriples<'a, R: Read + 'a>(source: R) -> impl Iterator<Item = RioRes
                 Ok(triple) => Some(Ok(triple?)),
                 Err(error) => Some(Err(RioError::new(error))),
             },
-            Err(error) => Some(Err(RioError::new(error))),
+            Err(error) => Some(Err(error.into())),
         })
 }

src/rio/turtle/mod.rs

@@ -36,13 +36,13 @@ pub fn read_turtle<'a, R: Read + 'a>(
         cur_subject: Vec::default(),
         cur_predicate: Vec::default(),
     };
-    let mut string_buffer = String::default();
     let mut triple_buffer = Vec::default();
-    match BufReader::new(source).read_to_string(&mut string_buffer) {
+
-        Ok(_) => match grammar::turtleDoc(&string_buffer, &mut state, &mut triple_buffer) {
+    let mut string_buffer = String::default();
+    BufReader::new(source).read_to_string(&mut string_buffer)?;
+
+    match grammar::turtleDoc(&string_buffer, &mut state, &mut triple_buffer) {
         Ok(_) => Ok(triple_buffer.into_iter()),
         Err(error) => Err(RioError::new(error)),
-        },
-        Err(error) => Err(RioError::new(error)),
     }
 }