Address PR comments

crates/syntax/src/lib.rs

@@ -187,6 +187,25 @@ impl SourceFile {
     }
 }
 
+impl ast::Literal {
+    pub fn parse(text: &str) -> Parse<ast::Literal> {
+        let lexed = parser::LexedStr::new(text);
+        let parser_input = lexed.to_input();
+        let parser_output = parser::TopEntryPoint::Expr.parse(&parser_input);
+        let (green, mut errors, _) = parsing::build_tree(lexed, parser_output);
+        let root = SyntaxNode::new_root(green.clone());
+
+        errors.extend(validation::validate(&root));
+
+        assert_eq!(root.kind(), SyntaxKind::LITERAL);
+        Parse {
+            green,
+            errors: if errors.is_empty() { None } else { Some(errors.into()) },
+            _ty: PhantomData,
+        }
+    }
+}
+
 impl ast::TokenTree {
     pub fn reparse_as_comma_separated_expr(self) -> Parse<ast::MacroEagerInput> {
         let tokens = self.syntax().descendants_with_tokens().filter_map(NodeOrToken::into_token);