refactor(policy): drop try_consume helper

Author: febyeji

src/policy/semantic.rs

@@ -387,17 +387,9 @@ impl<'a> MathParser<'a> {
         }
     }
 
-    fn try_consume(&mut self, want: char) -> bool {
+    fn expect(&mut self, want: char) -> Result<(), Error> {
         if self.peek() == Some(want) {
             self.next();
-            true
-        } else {
-            false
-        }
-    }
-
-    fn expect(&mut self, want: char) -> Result<(), Error> {
-        if self.try_consume(want) {
             Ok(())
         } else {
             Err(malformed_math(&format!("expected '{}'", want)))
@@ -468,6 +460,10 @@ impl<'a> MathParser<'a> {
                         parser.expect('{')?;
                         frames.push(Frame { subs: Vec::new(), kind: Kind::Thresh });
                     }
+                    '∧' | '∨' | ',' => {
+                        return Err(malformed_math("missing sub-expression before operator"))
+                    }
+                    ')' | '}' => return Err(malformed_math("empty group or threshold")),
                     _ => cur = Some(Arc::new(parser.parse_terminal()?)),
                 }
                 continue;
@@ -549,7 +545,7 @@ impl<'a> MathParser<'a> {
             return Err(malformed_math("unclosed group or threshold"));
         }
         let root = cur.ok_or_else(|| malformed_math("empty input"))?;
-        Ok(Arc::try_unwrap(root).unwrap_or_else(|arc| (*arc).clone()))
+        Ok(Arc::try_unwrap(root).expect("root Arc is uniquely owned"))
     }
 
     fn parse_terminal<Pk: FromStrKey>(&mut self) -> Result<Policy<Pk>, Error> {
@@ -558,15 +554,17 @@ impl<'a> MathParser<'a> {
             return Err(malformed_math("expected terminal name"));
         }
 
-        if !self.try_consume('(') {
+        self.skip_ws();
+        if self.peek() != Some('(') {
             return match name {
                 "UNSATISFIABLE" => Ok(Policy::Unsatisfiable),
                 "TRIVIAL" => Ok(Policy::Trivial),
                 _ => Err(malformed_math("unknown nullary terminal")),
             };
         }
+        self.next();
 
-        let arg = self.consume_while(|c| c != ')');
+        let arg = self.consume_while(|c| c != ')').trim();
         self.expect(')')?;
 
         Ok(match name {