improve identifier parsing

bip/src/lib.rs

@@ -13,6 +13,7 @@ pub enum ParseError {
     ExpectedParens,
     ExpectedSym,
     ExpectedTerm,
+    BadID,
     BadInt,
     BadStr,
     BadSym(char),
@@ -25,6 +26,7 @@ impl fmt::Display for ParseError {
             Self::ExpectedParens => write!(f, "expected parenthesis"),
             Self::ExpectedSym => write!(f, "expected symbol"),
             Self::ExpectedTerm => write!(f, "expected semicolon"),
+            Self::BadID => write!(f, "invalid identifier"),
             Self::BadInt => write!(f, "invalid integer"),
             Self::BadStr => write!(f, "unterminated string"),
             Self::BadSym(c) => write!(f, "invalid symbol {c}"),
@@ -141,13 +143,12 @@ impl Symbol {
                 }
                 ' ' | '\t' | '\r' => {}
                 _ => {
-                    let err = ParseError::BadSym(c.to_owned());
-
                     if !c.is_alphanumeric() {
-                        return Err(err);
+                        return Err(ParseError::BadSym(*c));
                     }
 
-                    let v = Symbol::take(&mut it, |c| c.is_alphanumeric()).map_err(|_| err)?;
+                    let v = Symbol::take(&mut it, |c| c.is_alphanumeric())
+                        .map_err(|_| ParseError::BadID)?;
                     syms.push(Self::Id(Some(v.iter().collect())));
                     continue;
                 }