[parser, types] Clean up obj parsers

- Define ListParser, SymParser in their own separate modules
- Add some stuff to types to make working with them more ergonomic

parser/src/sym_parser.rs

@@ -0,0 +1,27 @@
+/* parser/src/sym_parser.rs
+ * Eryn Wells <eryn@erynwells.me>
+ */
+
+use sibillexer::{Lex, Token};
+use sibiltypes::{Obj, Sym};
+use node_parser::{NodeParser, NodeParseResult};
+
+#[derive(Debug)]
+pub struct SymParser;
+
+impl NodeParser for SymParser {
+    fn parse(&mut self, lex: Lex) -> NodeParseResult {
+        match lex.token() {
+            Token::Id => {
+                let value = String::from(lex.value());
+                // Initializing with Sym(value) caused E0423. So use this isntead.
+                let obj = Obj::new(Sym::new(value));
+                NodeParseResult::Complete { obj: obj }
+            }
+            _ => {
+                let msg = format!("Invalid token: {:?}", lex);
+                NodeParseResult::error(msg)
+            }
+        }
+    }
+}