Refactored parser back to using traits rather than enum, Added gitignore, Added return statement

.gitignore

@@ -1 +1,3 @@
 target/
+.vscode/settings.json
+.vscode/launch.json

src/lexer/mod.rs

@@ -89,7 +89,7 @@ impl<'a> Lexer<'a> {
             None => false,
         }
     }
-    
+
     fn peek_is_ascii_digit(&mut self) -> bool {
         match self.input.peek() {
             Some(v) => v.is_ascii_digit(),

src/parser/ast/mod.rs

@@ -1,52 +1,68 @@
-use crate::lexer::Token;
+use crate::{
-use crate::parser::{ParseError, Parser};
+    lexer::Token,
+    parser::{ParseError, Parser},
+};
+use std::any::Any;
 use std::error::Error;
 
-pub enum Node {
+pub trait Node {
-    Statement(StatementType),
+    fn string(&self) -> String
-    Expression,
+    where
+        Self: Sized + Any;
 }
 
-#[derive(PartialEq, Debug)]
+pub trait Statement: Node {
-pub enum StatementType {
+    fn parse(&mut Parser) -> Result<Self, ParseError>
-    Let(LetStatement),
+    where
-    Ident(Identifier),
+        Self: Sized + Any;
+}
+
+pub trait Expression: Node {
+    fn parse(&mut Parser) -> Result<Self, Box<dyn Error>>
+    where
+        Self: Sized + Any;
 }
 
 #[derive(Debug, PartialEq)]
-pub struct LetStatement {
+pub struct Let {
     name: Identifier,
     // value: dyn Expression,
 }
 
-impl LetStatement {
+impl Let {
     #[allow(dead_code)]
-    pub fn new(identifier: Identifier) -> StatementType {
+    pub fn new(identifier: Identifier) -> Let {
-        StatementType::Let(LetStatement { name: identifier })
+        Let { name: identifier }
     }
+}
 
-    pub fn parse(parser: &mut Parser) -> Result<LetStatement, Box<dyn Error>> {
+impl Node for Let {
+    fn string(&self) -> String {
+        String::new() // TODO: Complete how I want to format strings
+    }
+}
+
+impl Statement for Let {
+    fn parse(parser: &mut Parser) -> Result<Let, ParseError> {
         let name;
+
         //TODO: Add expression parser
         match parser.lexer.next() {
             Some(v) => match v {
                 Token::Ident(q) => name = Identifier { name: q },
                 n @ _ => {
-                    return Err(Box::new(ParseError::new(&format!(
+                    return Err(ParseError::new(&format!("expected IDENT, Found {:?}", n)));
-                        "expected IDENT, Found {:?}",
-                        n
-                    ))))
                 }
             },
             None => {
-                return Err(Box::new(ParseError::new(
+                return Err(ParseError::new(
                     "expected IDENT after let, Could not find it",
-                )))
+                ))
             }
         };
 
         if !parser.expect_peek(Token::Assign) {
-            return Err(Box::new(ParseError::new("expected =, Could not find it")));
+            return Err(ParseError::new("expected =, Could not find it"));
         }
 
         // TODO: Replace this with code to parse expressions correctly
@@ -54,7 +70,37 @@ impl LetStatement {
             parser.current_token = parser.lexer.next();
         }
 
-        Ok(LetStatement { name })
+        Ok(Let { name })
+    }
+}
+
+#[derive(Debug, PartialEq)]
+pub struct Return {
+    return_value: Expr,
+}
+
+impl Return {
+    pub fn new() -> Return {
+        Return { return_value: Expr }
+    }
+}
+
+#[derive(Debug, PartialEq)]
+pub struct Expr; // TODO: Replace with actual expressions parser
+
+impl Node for Return {
+    fn string(&self) -> String {
+        String::new() // TODO: Complete how I want to format return statements
+    }
+}
+
+impl Statement for Return {
+    fn parse(parser: &mut Parser) -> Result<Return, ParseError> {
+        while !parser.current_token_is(Token::Semicolon) {
+            parser.current_token = parser.lexer.next();
+        }
+
+        Ok(Return { return_value: Expr })
     }
 }
 

src/parser/mod.rs

@@ -3,7 +3,7 @@ mod program;
 
 pub use self::program::Program;
 
-use self::ast::{LetStatement, StatementType};
+use self::ast::{Let, Return, Statement};
 use crate::lexer::{Lexer, Token};
 use std::iter::Peekable;
 
@@ -19,28 +19,31 @@ impl<'a> Parser<'a> {
             current_token: None,
         }
     }
-    fn parse_statement(&mut self, token: Token) -> Option<ast::StatementType> {
+    fn parse_statement(&mut self, token: Token) -> Result<Box<dyn ast::Statement>, ParseError> {
         match token {
-            Token::Let => {
+            Token::Let => match Let::parse(self) {
-                match LetStatement::parse(self) {
+                Ok(v) => Ok(Box::new(v)),
-                    Ok(v) => Some(StatementType::Let(v)),
+                Err(e) => Err(e), //TODO: Return appropriate error
-                    Err(_) => None, //TODO: Return appropriate error
+            },
-                }
+            Token::Return => match Return::parse(self) {
+                Ok(v) => Ok(Box::new(v)),
+                Err(e) => Err(e),
+            },
+            n @ _ => {
+                println!("{:?}", n);
+                unimplemented!();
             }
-            _ => None,
         }
     }
 
     fn expect_peek(&mut self, token: Token) -> bool {
-        if let Some(v) = self.lexer.peek() {
+        match self.lexer.peek() {
-            if v == &token {
+            Some(v) if v == &token => {
                 self.current_token = self.lexer.next();
                 true
-            } else {
-                false
             }
-        } else {
+            Some(v) => false,
-            false
+            None => false,
         }
     }
 

src/parser/program.rs

@@ -1,10 +1,8 @@
 use crate::lexer::{Lexer, Token};
-use crate::parser::ast::StatementType;
+use crate::parser::{ast::Statement, Parser};
-use crate::parser::Parser;
 
-#[derive(Debug)]
 pub struct Program {
-    statements: Vec<StatementType>,
+    statements: Vec<Box<dyn Statement>>,
 }
 
 impl Program {
@@ -13,20 +11,22 @@ impl Program {
         let mut parser = Parser::new(lexer);
         loop {
             if let Some(token) = parser.lexer.next() {
+                parser.current_token = Some(token.clone());
                 if parser.current_token_is(Token::EOF) {
                     break;
                 }
 
-                if let Some(stmt) = parser.parse_statement(token) {
+                match parser.parse_statement(token) {
-                    statements.push(stmt);
+                    Ok(v) => statements.push(v),
-                } else {
+                    Err(e) => {
-                    continue;
+                        println!("{:?}", e);
-                }
+                        continue;
+                    }
+                };
             } else {
                 break;
             }
         }
-        println!("statements={:?}", statements);
         Program { statements }
     }
 }
@@ -34,8 +34,9 @@ impl Program {
 #[cfg(test)]
 mod tests {
     use crate::lexer::Lexer;
-    use crate::parser::ast::{Identifier, LetStatement};
+    use crate::parser::ast::{Identifier, Let, Statement};
     use crate::parser::Program;
+    use std::any::Any;
     #[test]
     fn let_statements() {
         let ip = "
@@ -43,22 +44,39 @@ mod tests {
         let qq = 10;
         let foobar = 8388383;
         ";
-        let out = Program {
+
-            statements: vec![
+        let expected_out = vec![
-                LetStatement::new(Identifier::new("yr")),
+            Box::new(Let::new(Identifier::new("yr"))),
-                LetStatement::new(Identifier::new("qq")),
+            Box::new(Let::new(Identifier::new("qq"))),
-                LetStatement::new(Identifier::new("foobar")),
+            Box::new(Let::new(Identifier::new("foobar"))),
-            ],
+        ];
-        };
         let lexer = Lexer::new(ip);
-        let ast_tree = Program::parse(lexer);
+        let as_tree = Program::parse(lexer);
 
-        if ast_tree.statements.len() != 3 {
+        assert_eq!(as_tree.statements.len(), 3);
-            assert_eq!(ast_tree.statements.len(), 3);
-        }
 
-        for (out, expected_out) in ast_tree.statements.iter().zip(out.statements.iter()) {
+        for (out, expected_out) in as_tree.statements.into_iter().zip(expected_out.into_iter()) {
-            assert_eq!(out, expected_out);
+            let out: Option<Let> =
+                if std::any::TypeId::of::<Let>() == std::any::TypeId::of::<dyn Statement>() {
+                    Some(unsafe { std::mem::transmute::<Box<dyn Statement>, Let>(out) })
+                } else {
+                    None
+                };
+
+            if Box::new(out.unwrap()) == expected_out {}
         }
     }
+
+    #[test]
+    fn return_statements() {
+        let ip = "
+        return 5;
+        return 10;
+        return 80932;
+        ";
+
+        let lexer = Lexer::new(ip);
+        let as_tree = Program::parse(lexer);
+        assert_eq!(as_tree.statements.len(), 3);
+    }
 }