feat: finish challenge #3 of ch9

src/ast.rs

@@ -40,6 +40,7 @@ pub enum Stmt {
     Block {
         statements: Vec<Stmt>,
     },
+    Break,
     Expression {
         expression: Expr,
     },

src/interpreter.rs

@@ -1,8 +1,9 @@
+use core::panic;
 use std::{cell::RefCell, rc::Rc};
 
 use crate::{
     ast::{Expr, Stmt},
-    environment::{self, Environment},
+    environment::Environment,
     token::{LiteralType, Token, TokenType},
 };
 
@@ -21,10 +22,30 @@ impl RuntimeError {
     }
 }
 
+pub enum InterpreterError {
+    RuntimeError(RuntimeError),
+    BreakSignal,
+}
+
+impl From<RuntimeError> for InterpreterError {
+    fn from(value: RuntimeError) -> Self {
+        Self::RuntimeError(value)
+    }
+}
+
+impl From<InterpreterError> for RuntimeError {
+    fn from(value: InterpreterError) -> Self {
+        match value {
+            InterpreterError::RuntimeError(runtime_error) => runtime_error,
+            InterpreterError::BreakSignal => panic!("Not a runtime error"),
+        }
+    }
+}
+
 pub fn interpret(
     statements: &Vec<Stmt>,
     environment: &Rc<RefCell<Environment>>,
-) -> Result<(), RuntimeError> {
+) -> Result<(), InterpreterError> {
     for statement in statements {
         execute(statement, environment)?;
     }
@@ -32,7 +53,10 @@ pub fn interpret(
     Ok(())
 }
 
-fn execute(statement: &Stmt, environment: &Rc<RefCell<Environment>>) -> Result<(), RuntimeError> {
+fn execute(
+    statement: &Stmt,
+    environment: &Rc<RefCell<Environment>>,
+) -> Result<(), InterpreterError> {
     match statement {
         Stmt::Expression { expression } => {
             evaluate(expression, &mut environment.borrow_mut())?;
@@ -65,10 +89,14 @@ fn execute(statement: &Stmt, environment: &Rc<RefCell<Environment>>) -> Result<(
         }
         Stmt::While { condition, body } => {
             while is_truthy(&evaluate(condition, &mut environment.borrow_mut())?) {
-                execute(body, environment)?;
+                let result = execute(body, environment);
+                if result.is_err() {
+                    break;
                 }
             }
         }
+        Stmt::Break => Err(InterpreterError::BreakSignal)?,
+    }
 
     Ok(())
 }
@@ -76,7 +104,7 @@ fn execute(statement: &Stmt, environment: &Rc<RefCell<Environment>>) -> Result<(
 fn execute_block(
     statements: &Vec<Stmt>,
     environment: &Rc<RefCell<Environment>>,
-) -> Result<(), RuntimeError> {
+) -> Result<(), InterpreterError> {
     let block_enviroment = Rc::new(RefCell::new(Environment::with_enclosing(environment)));
     for stmt in statements {
         execute(stmt, &block_enviroment)?;
@@ -85,7 +113,7 @@ fn execute_block(
     Ok(())
 }
 
-fn evaluate(expr: &Expr, environment: &mut Environment) -> Result<LiteralType, RuntimeError> {
+fn evaluate(expr: &Expr, environment: &mut Environment) -> Result<LiteralType, InterpreterError> {
     match expr {
         Expr::Ternary {
             first,
@@ -112,7 +140,8 @@ fn evaluate(expr: &Expr, environment: &mut Environment) -> Result<LiteralType, R
                     token: name.clone(),
                     message: format!("Uninitialized variable {}.", name.lexeme),
                 })
-            }),
+            })
+            .map_err(InterpreterError::RuntimeError),
         Expr::Assign { name, value } => {
             let value = evaluate(value, environment)?;
             environment
@@ -145,7 +174,7 @@ fn ternary(
     second: &Expr,
     third: &Expr,
     environment: &mut Environment,
-) -> Result<LiteralType, RuntimeError> {
+) -> Result<LiteralType, InterpreterError> {
     let first = evaluate(first, environment)?;
     if is_truthy(&first) {
         return evaluate(second, environment);
@@ -157,7 +186,7 @@ fn binary(
     left: &LiteralType,
     right: &LiteralType,
     op: &Token,
-) -> Result<LiteralType, RuntimeError> {
+) -> Result<LiteralType, InterpreterError> {
     use LiteralType::{Bool, Number, String};
     use TokenType::{
         BangEqual, Comma, EqualEqual, Greater, GreaterEqual, Less, LessEqual, Minus, Plus, Slash,
@@ -180,8 +209,8 @@ fn binary(
         (Star, Number(left), Number(right)) => Ok(Number(left * right)),
         /* comma operator discard the left operand, so we just return the evaluation of the right operand */
         (Comma, _,_) => Ok(right.clone()),
-        (Greater | GreaterEqual | Less | LessEqual | Minus | Slash | Star, _, _) => Err(RuntimeError::new(op, "Operands must be numbers")),
-        (Plus, _, _) => Err(RuntimeError::new(op, "Operands must be two numbers or two strings")),
+        (Greater | GreaterEqual | Less | LessEqual | Minus | Slash | Star, _, _) => Err(RuntimeError::new(op, "Operands must be numbers"))?,
+        (Plus, _, _) => Err(RuntimeError::new(op, "Operands must be two numbers or two strings"))?,
 
         _ => unreachable!("Shouldn't happen. Expr::Binary for evaluate. Some case is a binary operation that wasn't matched")
     }

src/lib.rs

@@ -10,7 +10,7 @@ use environment::Environment;
 use interpreter::RuntimeError;
 use parser::{ParseError, Parser};
 use scanner::Scanner;
-use token::{Token, TokenType};
+use token::TokenType;
 
 mod ast;
 mod environment;
@@ -68,6 +68,7 @@ pub fn run(src: &str, environment: &Rc<RefCell<Environment>>) -> Result<(), RunE
     let statements = statements.into_iter().flatten().collect();
 
     interpreter::interpret(&statements, environment)
+        .map_err(|x| x.into())
         .inspect_err(runtime_error)
         .map_err(RunError::RuntimeError)?;
 

src/parser.rs

@@ -3,11 +3,13 @@ use std::fmt::Display;
 use crate::{
     ast::{Expr, Stmt},
     token::{LiteralType, Token, TokenType},
+    utils::{defer, expr, ScopeCall},
 };
 
 pub struct Parser<'a> {
     tokens: &'a Vec<Token>,
     current: usize,
+    loop_depth: u32,
 }
 
 #[derive(Debug)]
@@ -26,7 +28,15 @@ impl std::error::Error for ParseError {}
 
 impl Parser<'_> {
     pub fn new(tokens: &Vec<Token>) -> Parser<'_> {
-        Parser { tokens, current: 0 }
+        Parser {
+            tokens,
+            current: 0,
+            loop_depth: 0,
+        }
+    }
+
+    pub fn loop_depth(&mut self) -> &mut u32 {
+        &mut self.loop_depth
     }
 
     //pub fn parse(&mut self) -> Result<Expr, ParseError> {
@@ -84,6 +94,10 @@ impl Parser<'_> {
             return self.while_statement();
         }
 
+        if self.match_token(&[TokenType::Break]) {
+            return self.break_statement();
+        }
+
         if self.match_token(&[TokenType::LeftBrace]) {
             return Ok(Stmt::Block {
                 statements: self.block()?,
@@ -105,6 +119,18 @@ impl Parser<'_> {
         Ok(statements)
     }
 
+    fn break_statement(&mut self) -> Result<Stmt, ParseError> {
+        if *self.loop_depth() == 0 {
+            return Err(ParseError {
+                token: self.previous().clone(),
+                msg: "Must be inside a loop to use 'break'".to_string(),
+            });
+        }
+        self.consume(TokenType::Semicolon, "Expect ';' after 'break'")?;
+
+        Ok(Stmt::Break)
+    }
+
     fn if_statement(&mut self) -> Result<Stmt, ParseError> {
         self.consume(TokenType::LeftParen, "Expect '(' after 'if'.")?;
         let condition = self.expression()?;
@@ -125,15 +151,20 @@ impl Parser<'_> {
     }
 
     fn while_statement(&mut self) -> Result<Stmt, ParseError> {
+        self.loop_depth += 1;
         self.consume(TokenType::LeftParen, "Expect '(' after 'while'.")?;
         let condition = self.expression()?;
         self.consume(TokenType::RightParen, "Expect ')' after while condition.")?;
         let body = Box::new(self.statement()?);
+        defer! {
+            *self.loop_depth() += 1;
+        }
 
         Ok(Stmt::While { condition, body })
     }
 
     fn for_statement(&mut self) -> Result<Stmt, ParseError> {
+        self.loop_depth += 1;
         self.consume(TokenType::LeftParen, "Expect '(' after 'for'.")?;
         let initializer = if self.match_token(&[TokenType::Semicolon]) {
             None
@@ -182,6 +213,10 @@ impl Parser<'_> {
             None => body,
         };
 
+        defer! {
+            *self.loop_depth() -= 1;
+        }
+
         Ok(body)
     }
 

src/scanner.rs

@@ -266,6 +266,7 @@ fn get_identified_keyword(identifier: &str) -> Option<TokenType> {
         "true" => Some(TokenType::True),
         "var" => Some(TokenType::Var),
         "while" => Some(TokenType::While),
+        "break" => Some(TokenType::Break),
         _ => None,
     }
 }

src/token.rs

@@ -30,6 +30,7 @@ pub enum TokenType {
     Number,
 
     And,
+    Break,
     Class,
     Else,
     False,

src/utils.rs

@@ -50,3 +50,30 @@ impl StringUtils for String {
         self.substring(start, len)
     }
 }
+
+pub struct ScopeCall<F: FnMut()> {
+    pub c: Option<F>,
+}
+
+impl<F: FnMut()> Drop for ScopeCall<F> {
+    fn drop(&mut self) {
+        self.c.take().unwrap()()
+    }
+}
+
+macro_rules! expr {
+    ($e: expr) => {
+        $e
+    };
+}
+
+macro_rules! defer {
+    ($($data: tt)*) => (
+        let _scope_call = ScopeCall {
+            c: Some(|| -> () { expr!({ $($data)* }) })
+        };
+    )
+}
+
+pub(crate) use defer;
+pub(crate) use expr;