From 2880ba81ab76c5df0618c197058771d69dcbdb92 Mon Sep 17 00:00:00 2001
From: Daniel M <daniel.q.mueller@stud.h-da.de>
Date: Thu, 10 Feb 2022 13:13:15 +0100
Subject: [PATCH] Implement break & continue

- Fix return propagation inside loops
---
 src/ast.rs          |  2 ++
 src/astoptimizer.rs |  1 +
 src/interpreter.rs  | 29 +++++++++++++++++++++++------
 src/lexer.rs        |  2 ++
 src/parser.rs       | 16 ++++++++++++++++
 src/token.rs        | 12 ++++++++++++
 6 files changed, 56 insertions(+), 6 deletions(-)

diff --git a/src/ast.rs b/src/ast.rs
index 2443161..042e80e 100644
--- a/src/ast.rs
+++ b/src/ast.rs
@@ -129,6 +129,8 @@ pub struct FunDecl {
 #[derive(Debug, PartialEq, Eq, Clone)]
 pub enum Statement {
     Return(Expression),
+    Break,
+    Continue,
     Declaration(Sid, usize, Expression),
     FunDeclare(FunDecl),
     Expr(Expression),
diff --git a/src/astoptimizer.rs b/src/astoptimizer.rs
index 5017083..71fe509 100644
--- a/src/astoptimizer.rs
+++ b/src/astoptimizer.rs
@@ -43,6 +43,7 @@ impl SimpleAstOptimizer {
                 Statement::Declaration(_, _, expr) => Self::optimize_expr(expr),
                 Statement::FunDeclare(_) => (),
                 Statement::Return(expr) => Self::optimize_expr(expr),
+                Statement::Break | Statement::Continue => (),
             }
         }
     }
diff --git a/src/interpreter.rs b/src/interpreter.rs
index c088370..0726ab2 100644
--- a/src/interpreter.rs
+++ b/src/interpreter.rs
@@ -48,6 +48,8 @@ pub enum Value {
 #[derive(Debug, PartialEq, Eq, Clone)]
 pub enum BlockExit {
     Normal,
+    Break,
+    Continue,
     Return(Value),
 }
 
@@ -139,6 +141,9 @@ impl Interpreter {
 
         for stmt in prog {
             match stmt {
+                Statement::Break => return Ok(BlockExit::Break),
+                Statement::Continue => return Ok(BlockExit::Continue),
+
                 Statement::Return(expr) => {
                     let val = self.resolve_expr(expr)?;
 
@@ -156,9 +161,10 @@ impl Interpreter {
                 }
 
                 Statement::Block(block) => match self.run_block(block)? {
-                    BlockExit::Return(val) => {
+                    // Propagate return, continue and break
+                    be @ (BlockExit::Return(_) | BlockExit::Continue | BlockExit::Break) => {
                         self.vartable.truncate(framepointer);
-                        return Ok(BlockExit::Return(val));
+                        return Ok(be);
                     }
                     _ => (),
                 },
@@ -170,7 +176,16 @@ impl Interpreter {
                             break;
                         }
 
-                        self.run_block(&looop.body)?;
+                        let be = self.run_block(&looop.body)?;
+                        match be {
+                            // Propagate return
+                            be @ BlockExit::Return(_) => {
+                                self.vartable.truncate(framepointer);
+                                return Ok(be);
+                            }
+                            BlockExit::Break => break,
+                            BlockExit::Continue | BlockExit::Normal => (),
+                        }
 
                         if let Some(adv) = &looop.advancement {
                             self.resolve_expr(&adv)?;
@@ -198,10 +213,12 @@ impl Interpreter {
                     } else {
                         self.run_block(body_true)?
                     };
+
                     match exit {
-                        BlockExit::Return(val) => {
+                        // Propagate return, continue and break
+                        be @ (BlockExit::Return(_) | BlockExit::Continue | BlockExit::Break) => {
                             self.vartable.truncate(framepointer);
-                            return Ok(BlockExit::Return(val));
+                            return Ok(be);
                         }
                         _ => (),
                     }
@@ -269,7 +286,7 @@ impl Interpreter {
                     &Rc::clone(&self.funtable.get(*fun_stackpos).unwrap().body),
                     expected_num_args,
                 )? {
-                    BlockExit::Normal => Value::Void,
+                    BlockExit::Normal | BlockExit::Continue | BlockExit::Break => Value::Void,
                     BlockExit::Return(val) => val,
                 }
             }
diff --git a/src/lexer.rs b/src/lexer.rs
index 9c592cc..2dd491d 100644
--- a/src/lexer.rs
+++ b/src/lexer.rs
@@ -202,6 +202,8 @@ impl<'a> Lexer<'a> {
             "else" => T![else],
             "fun" => T![fun],
             "return" => T![return],
+            "break" => T![break],
+            "continue" => T![continue],
 
             // If it doesn't match a keyword, it is a normal identifier
             _ => T![ident(ident)],
diff --git a/src/parser.rs b/src/parser.rs
index 906ad6b..2bbc6ef 100644
--- a/src/parser.rs
+++ b/src/parser.rs
@@ -107,6 +107,22 @@ impl<T: Iterator<Item = Token>> Parser<T> {
     /// Parse a single statement from the tokens.
     fn parse_stmt(&mut self) -> ResPE<Statement> {
         let stmt = match self.peek() {
+            T![break] => {
+                self.next();
+
+                validate_next!(self, T![;], ";");
+
+                Statement::Break
+            }
+
+            T![continue] => {
+                self.next();
+
+                validate_next!(self, T![;], ";");
+
+                Statement::Continue
+            }
+
             T![loop] => Statement::Loop(self.parse_loop()?),
 
             T![print] => {
diff --git a/src/token.rs b/src/token.rs
index add510c..0fadc77 100644
--- a/src/token.rs
+++ b/src/token.rs
@@ -18,6 +18,10 @@ pub enum Keyword {
     Fun,
     /// Return keyword ("return")
     Return,
+    /// Break keyword ("break")
+    Break,
+    /// Continue keyword ("continue")
+    Continue,
 }
 
 /// Literal values
@@ -217,6 +221,14 @@ macro_rules! T {
         crate::token::Token::Keyword(crate::token::Keyword::Return)
     };
 
+    [break] => {
+        crate::token::Token::Keyword(crate::token::Keyword::Break)
+    };
+
+    [continue] => {
+        crate::token::Token::Keyword(crate::token::Keyword::Continue)
+    };
+
     // Literals
     [i64($($val:tt)*)] => {
         crate::token::Token::Literal(crate::token::Literal::I64($($val)*))