Rewrite byte parser without macros

Author: dtolnay

src/fallback.rs

@@ -1125,13 +1125,13 @@ fn raw_string(input: Cursor) -> PResult<()> {
     Err(LexError)
 }
 
-named!(byte -> (), do_parse!(
-    punct!("b") >>
-    tag!("'") >>
-    cooked_byte >>
-    tag!("'") >>
-    (())
-));
+fn byte(input: Cursor) -> PResult<()> {
+    let input = skip_whitespace(input);
+    let input = input.expect("b'")?;
+    let (input, ()) = cooked_byte(input)?;
+    let input = input.expect("'")?;
+    Ok((input, ()))
+}
 
 fn cooked_byte(input: Cursor) -> PResult<()> {
     let mut bytes = input.bytes().enumerate();

src/strnom.rs

@@ -57,6 +57,14 @@ impl<'a> Cursor<'a> {
     pub fn char_indices(&self) -> CharIndices<'a> {
         self.rest.char_indices()
     }
+
+    pub fn expect(&self, tag: &str) -> Result<Cursor<'a>, LexError> {
+        if self.starts_with(tag) {
+            Ok(self.advance(tag.len()))
+        } else {
+            Err(LexError)
+        }
+    }
 }
 
 pub(crate) type PResult<'a, O> = Result<(Cursor<'a>, O), LexError>;