print out error message and add peek error

src/parser/mod.rs

@@ -117,7 +117,7 @@ impl Parser {
         self.peek_token = self.lexer.next_token();
     }
 
-    fn parse_program(&mut self) -> ast::Program {
+    pub fn parse_program(&mut self) -> ast::Program {
         let mut program = ast::Program {
             statements: Vec::new(),
         };
@@ -151,6 +151,7 @@ impl Parser {
             self.next_token();
             true
         } else {
+            self.peek_error(t);
             false
         }
     }
@@ -439,7 +440,7 @@ impl Parser {
         Some(args)
     }
 
-    fn errors(&self) -> &Vec<String> {
+    pub fn errors(&self) -> &Vec<String> {
         &self.errors
     }
 

src/repl/mod.rs

@@ -1,7 +1,6 @@
 use crate::ast::NodeTrait;
 use crate::lexer::new;
 use crate::parser::Parser;
-use crate::parser::ParserTrait;
 use crate::parser::new_parser;
 
 const PROMPT: &str = ">> ";
@@ -21,6 +20,11 @@ pub fn start_repl() {
         let lexer = new(input.to_string());
         let mut parser: Parser = new_parser(lexer);
         let program = parser.parse_program();
+
+        for err in parser.errors() {
+            eprintln!("ERROR: {}", err);
+        }
+
         println!("{}", program.string());
     }
 }