Back to using enum in AST

src/parser/ast/mod.rs

@@ -2,27 +2,19 @@ use crate::{
     lexer::Token,
     parser::{ParseError, Parser},
 };
-use std::any::Any;
-use std::error::Error;
 
-pub trait Node {
-    fn string(&self) -> String
-    where
-        Self: Sized + Any;
+#[derive(Debug, PartialEq)]
+pub enum Statement {
+    Let(Let),
+
+    Return(Return),
+    //ExpressionStatement(ExpressionStatement),
 }
 
-pub trait Statement: Node {
-    fn parse(&mut Parser) -> Result<Self, ParseError>
-    where
-        Self: Sized + Any;
+#[derive(Debug, PartialEq)]
+pub enum Expression {
+    Ident(Identifier),
 }
-
-pub trait Expression: Node {
-    fn parse(&mut Parser) -> Result<Self, Box<dyn Error>>
-    where
-        Self: Sized + Any;
-}
-
 #[derive(Debug, PartialEq)]
 pub struct Let {
     name: Identifier,
@@ -34,16 +26,8 @@ impl Let {
     pub fn new(identifier: Identifier) -> Let {
         Let { name: identifier }
     }
-}
 
-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> {
+    pub fn parse(parser: &mut Parser) -> Result<Let, ParseError> {
         let name;
 
         //TODO: Add expression parser
@@ -74,6 +58,9 @@ impl Statement for Let {
     }
 }
 
+#[derive(Debug, PartialEq)]
+pub struct Expr;
+
 #[derive(Debug, PartialEq)]
 pub struct Return {
     return_value: Expr,
@@ -83,19 +70,8 @@ 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> {
+    pub fn parse(parser: &mut Parser) -> Result<Return, ParseError> {
         while !parser.current_token_is(Token::Semicolon) {
             parser.current_token = parser.lexer.next();
         }

src/parser/mod.rs

@@ -19,14 +19,14 @@ impl<'a> Parser<'a> {
             current_token: None,
         }
     }
-    fn parse_statement(&mut self, token: Token) -> Result<Box<dyn ast::Statement>, ParseError> {
+    fn parse_statement(&mut self, token: Token) -> Result<Statement, ParseError> {
         match token {
             Token::Let => match Let::parse(self) {
-                Ok(v) => Ok(Box::new(v)),
+                Ok(v) => Ok(Statement::Let(v)),
                 Err(e) => Err(e), //TODO: Return appropriate error
             },
             Token::Return => match Return::parse(self) {
-                Ok(v) => Ok(Box::new(v)),
+                Ok(v) => Ok(Statement::Return(v)),
                 Err(e) => Err(e),
             },
             n @ _ => {
@@ -42,8 +42,7 @@ impl<'a> Parser<'a> {
                 self.current_token = self.lexer.next();
                 true
             }
-            Some(v) => false,
-            None => false,
+            Some(_) | None => false,
         }
     }
 

src/parser/program.rs

@@ -2,7 +2,7 @@ use crate::lexer::{Lexer, Token};
 use crate::parser::{ast::Statement, Parser};
 
 pub struct Program {
-    statements: Vec<Box<dyn Statement>>,
+    statements: Vec<Statement>,
 }
 
 impl Program {
@@ -36,7 +36,7 @@ mod tests {
     use crate::lexer::Lexer;
     use crate::parser::ast::{Identifier, Let, Statement};
     use crate::parser::Program;
-    use std::any::Any;
+
     #[test]
     fn let_statements() {
         let ip = "
@@ -46,9 +46,9 @@ mod tests {
         ";
 
         let expected_out = vec![
-            Box::new(Let::new(Identifier::new("yr"))),
-            Box::new(Let::new(Identifier::new("qq"))),
-            Box::new(Let::new(Identifier::new("foobar"))),
+            Statement::Let(Let::new(Identifier::new("yr"))),
+            Statement::Let(Let::new(Identifier::new("qq"))),
+            Statement::Let(Let::new(Identifier::new("foobar"))),
         ];
         let lexer = Lexer::new(ip);
         let as_tree = Program::parse(lexer);
@@ -56,14 +56,7 @@ mod tests {
         assert_eq!(as_tree.statements.len(), 3);
 
         for (out, expected_out) in as_tree.statements.into_iter().zip(expected_out.into_iter()) {
-            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 {}
+            assert_eq!(out, expected_out);
         }
     }