Switch impl (#451)

Co-authored-by: Iban Eguia <razican@protonmail.ch>

.vscode/launch.json

@@ -36,16 +36,15 @@
       "symbolSearchPath": "https://msdl.microsoft.com/download/symbols"
     },
     {
-      "name": "(Windows) Run Test Debugger",
+      "name": "(Windows) Launch Debug",
       "type": "cppvsdbg",
       "request": "launch",
-      "program": "${workspaceFolder}/target/debug/boa-ea5ed1ef3ee0cbe1.exe",
+      "program": "${workspaceRoot}/target/debug/foo.exe",
       "args": [],
       "stopAtEntry": false,
-      "cwd": "${workspaceFolder}",
+      "cwd": "${workspaceRoot}",
       "environment": [],
-      "externalConsole": true,
+      "externalConsole": true
-      "preLaunchTask": "Cargo Test Build",
+    },
-    }
   ]
 }

boa/src/exec/block/mod.rs

@@ -1,6 +1,6 @@
 //! Block statement execution.
 
-use super::{Executable, Interpreter};
+use super::{Executable, Interpreter, InterpreterState};
 use crate::{
     builtins::value::{ResultValue, Value},
     environment::lexical_environment::new_declarative_environment,
@@ -22,9 +22,20 @@ impl Executable for Block {
         for statement in self.statements() {
             obj = statement.run(interpreter)?;
 
-            // early return
+            match interpreter.get_current_state() {
-            if interpreter.is_return {
+                InterpreterState::Return => {
-                break;
+                    // Early return.
+                    break;
+                }
+                InterpreterState::Break(_label) => {
+                    // TODO, break to a label.
+
+                    // Early break.
+                    break;
+                }
+                _ => {
+                    // Continue execution
+                }
             }
         }
 

boa/src/exec/break_node/mod.rs

@@ -0,0 +1,16 @@
+use super::{Executable, Interpreter, InterpreterState};
+use crate::{
+    builtins::value::{ResultValue, Value},
+    syntax::ast::node::Break,
+};
+
+#[cfg(test)]
+mod tests;
+
+impl Executable for Break {
+    fn run(&self, interpreter: &mut Interpreter) -> ResultValue {
+        interpreter.set_current_state(InterpreterState::Break(self.label().map(String::from)));
+
+        Ok(Value::undefined())
+    }
+}

boa/src/exec/break_node/tests.rs

@@ -0,0 +1,17 @@
+use super::{Interpreter, InterpreterState};
+use crate::{exec::Executable, syntax::ast::node::Break, Realm};
+
+#[test]
+fn check_post_state() {
+    let realm = Realm::create();
+    let mut engine = Interpreter::new(realm);
+
+    let brk: Break = Break::new("label");
+
+    brk.run(&mut engine).unwrap();
+
+    assert_eq!(
+        engine.get_current_state(),
+        &InterpreterState::Break(Some("label".to_string()))
+    );
+}

boa/src/exec/expression/mod.rs

@@ -1,6 +1,6 @@
 //! Expression execution.
 
-use super::{Executable, Interpreter};
+use super::{Executable, Interpreter, InterpreterState};
 use crate::{
     builtins::{
         object::{INSTANCE_PROTOTYPE, PROTOTYPE},
@@ -48,7 +48,7 @@ impl Executable for Call {
         let fnct_result = interpreter.call(&func, &mut this, &v_args);
 
         // unset the early return flag
-        interpreter.is_return = false;
+        interpreter.set_current_state(InterpreterState::Executing);
 
         fnct_result
     }

boa/src/exec/iteration/mod.rs

@@ -1,6 +1,6 @@
 //! Iteration node execution.
 
-use super::{Executable, Interpreter};
+use super::{Executable, Interpreter, InterpreterState};
 use crate::{
     builtins::value::{ResultValue, Value},
     environment::lexical_environment::new_declarative_environment,
@@ -9,6 +9,9 @@ use crate::{
 };
 use std::borrow::Borrow;
 
+#[cfg(test)]
+mod tests;
+
 impl Executable for ForLoop {
     fn run(&self, interpreter: &mut Interpreter) -> ResultValue {
         // Create the block environment.
@@ -30,7 +33,23 @@ impl Executable for ForLoop {
             .transpose()?
             .unwrap_or(true)
         {
-            self.body().run(interpreter)?;
+            let result = self.body().run(interpreter)?;
+
+            match interpreter.get_current_state() {
+                InterpreterState::Break(_label) => {
+                    // TODO break to label.
+
+                    // Loops 'consume' breaks.
+                    interpreter.set_current_state(InterpreterState::Executing);
+                    break;
+                }
+                InterpreterState::Return => {
+                    return Ok(result);
+                }
+                _ => {
+                    // Continue execution.
+                }
+            }
 
             if let Some(final_expr) = self.final_expr() {
                 final_expr.run(interpreter)?;
@@ -49,6 +68,21 @@ impl Executable for WhileLoop {
         let mut result = Value::undefined();
         while self.cond().run(interpreter)?.borrow().is_true() {
             result = self.expr().run(interpreter)?;
+            match interpreter.get_current_state() {
+                InterpreterState::Break(_label) => {
+                    // TODO break to label.
+
+                    // Loops 'consume' breaks.
+                    interpreter.set_current_state(InterpreterState::Executing);
+                    break;
+                }
+                InterpreterState::Return => {
+                    return Ok(result);
+                }
+                _ => {
+                    // Continue execution.
+                }
+            }
         }
         Ok(result)
     }
@@ -57,8 +91,39 @@ impl Executable for WhileLoop {
 impl Executable for DoWhileLoop {
     fn run(&self, interpreter: &mut Interpreter) -> ResultValue {
         let mut result = self.body().run(interpreter)?;
+        match interpreter.get_current_state() {
+            InterpreterState::Break(_label) => {
+                // TODO break to label.
+
+                // Loops 'consume' breaks.
+                interpreter.set_current_state(InterpreterState::Executing);
+                return Ok(result);
+            }
+            InterpreterState::Return => {
+                return Ok(result);
+            }
+            _ => {
+                // Continue execution.
+            }
+        }
+
         while self.cond().run(interpreter)?.borrow().is_true() {
             result = self.body().run(interpreter)?;
+            match interpreter.get_current_state() {
+                InterpreterState::Break(_label) => {
+                    // TODO break to label.
+
+                    // Loops 'consume' breaks.
+                    interpreter.set_current_state(InterpreterState::Executing);
+                    break;
+                }
+                InterpreterState::Return => {
+                    return Ok(result);
+                }
+                _ => {
+                    // Continue execution.
+                }
+            }
         }
         Ok(result)
     }

boa/src/exec/iteration/tests.rs

@@ -0,0 +1,101 @@
+use crate::exec;
+
+#[test]
+fn while_loop_late_break() {
+    // Ordering with statement before the break.
+    let scenario = r#"
+        let a = 1;
+        while (a < 5) {
+            a++;
+            if (a == 3) {
+                break;
+            }
+        }
+        a;
+    "#;
+
+    assert_eq!(&exec(scenario), "3");
+}
+
+#[test]
+fn while_loop_early_break() {
+    // Ordering with statements after the break.
+    let scenario = r#"
+        let a = 1;
+        while (a < 5) {
+            if (a == 3) {
+                break;
+            }
+            a++;
+        }
+        a;
+    "#;
+
+    assert_eq!(&exec(scenario), "3");
+}
+
+#[test]
+fn for_loop_break() {
+    let scenario = r#"
+        let a = 1;
+        for (; a < 5; a++) {
+            if (a == 3) {
+                break;
+            }
+        }
+        a;
+    "#;
+
+    assert_eq!(&exec(scenario), "3");
+}
+
+#[test]
+fn for_loop_return() {
+    let scenario = r#"
+    function foo() {
+        for (let a = 1; a < 5; a++) {
+            if (a == 3) {
+                return a;
+            }
+        }
+    }
+      
+    foo();
+    "#;
+
+    assert_eq!(&exec(scenario), "3");
+}
+
+#[test]
+fn do_loop_late_break() {
+    // Ordering with statement before the break.
+    let scenario = r#"
+        let a = 1;
+        do {
+            a++;
+            if (a == 3) {
+                break;
+            }
+        } while (a < 5);
+        a;
+    "#;
+
+    assert_eq!(&exec(scenario), "3");
+}
+
+#[test]
+fn do_loop_early_break() {
+    // Ordering with statements after the break.
+    let scenario = r#"
+        let a = 1;
+        do {
+            if (a == 3) {
+                break;
+            }
+            a++;
+        } while (a < 5);
+        a;
+    "#;
+
+    assert_eq!(&exec(scenario), "3");
+}

boa/src/exec/mod.rs

@@ -2,6 +2,7 @@
 
 mod array;
 mod block;
+mod break_node;
 mod conditional;
 mod declaration;
 mod exception;
@@ -45,6 +46,12 @@ pub trait Executable {
     fn run(&self, interpreter: &mut Interpreter) -> ResultValue;
 }
 
+#[derive(Debug, Eq, PartialEq)]
+pub(crate) enum InterpreterState {
+    Executing,
+    Return,
+    Break(Option<String>),
+}
 #[derive(Clone, Copy, Debug, PartialEq)]
 pub enum PreferredType {
     String,
@@ -55,8 +62,8 @@ pub enum PreferredType {
 /// A Javascript intepreter
 #[derive(Debug)]
 pub struct Interpreter {
-    /// Wether it's running a return statement.
+    current_state: InterpreterState,
-    is_return: bool,
+
     /// realm holds both the global object and the environment
     pub realm: Realm,
 }
@@ -65,8 +72,8 @@ impl Interpreter {
     /// Creates a new interpreter.
     pub fn new(realm: Realm) -> Self {
         Self {
+            current_state: InterpreterState::Executing,
             realm,
-            is_return: false,
         }
     }
 
@@ -485,6 +492,14 @@ impl Interpreter {
             _ => panic!("TypeError: invalid assignment to {}", node),
         }
     }
+
+    pub(crate) fn set_current_state(&mut self, new_state: InterpreterState) {
+        self.current_state = new_state
+    }
+
+    pub(crate) fn get_current_state(&self) -> &InterpreterState {
+        &self.current_state
+    }
 }
 
 impl Executable for Node {
@@ -539,6 +554,7 @@ impl Executable for Node {
                 Ok(interpreter.realm().environment.get_this_binding())
             }
             Node::Try(ref try_node) => try_node.run(interpreter),
+            Node::Break(ref break_node) => break_node.run(interpreter),
             ref i => unimplemented!("{:?}", i),
         }
     }

boa/src/exec/return_smt/mod.rs

@@ -1,4 +1,4 @@
-use super::{Executable, Interpreter};
+use super::{Executable, Interpreter, InterpreterState};
 use crate::{
     builtins::value::{ResultValue, Value},
     syntax::ast::node::Return,
@@ -11,7 +11,7 @@ impl Executable for Return {
             None => Ok(Value::undefined()),
         };
         // Set flag for return
-        interpreter.is_return = true;
+        interpreter.set_current_state(InterpreterState::Return);
         result
     }
 }

boa/src/exec/statement_list.rs

@@ -1,6 +1,6 @@
 //! Statement list execution.
 
-use super::{Executable, Interpreter};
+use super::{Executable, Interpreter, InterpreterState};
 use crate::{
     builtins::value::{ResultValue, Value},
     syntax::ast::node::StatementList,
@@ -11,12 +11,24 @@ impl Executable for StatementList {
     fn run(&self, interpreter: &mut Interpreter) -> ResultValue {
         let _timer = BoaProfiler::global().start_event("StatementList", "exec");
         let mut obj = Value::null();
+        interpreter.set_current_state(InterpreterState::Executing);
         for (i, item) in self.statements().iter().enumerate() {
             let val = item.run(interpreter)?;
-            // early return
+            match interpreter.get_current_state() {
-            if interpreter.is_return {
+                InterpreterState::Return => {
-                obj = val;
+                    // Early return.
-                break;
+                    obj = val;
+                    break;
+                }
+                InterpreterState::Break(_label) => {
+                    // TODO, break to a label.
+
+                    // Early break.
+                    break;
+                }
+                _ => {
+                    // Continue execution
+                }
             }
             if i + 1 == self.statements().len() {
                 obj = val;

boa/src/exec/switch/mod.rs

@@ -1,24 +1,46 @@
-use super::{Executable, Interpreter};
+use super::{Executable, Interpreter, InterpreterState};
 use crate::{
     builtins::value::{ResultValue, Value},
     syntax::ast::node::Switch,
 };
 
+#[cfg(test)]
+mod tests;
+
 impl Executable for Switch {
     fn run(&self, interpreter: &mut Interpreter) -> ResultValue {
         let default = self.default();
         let val = self.val().run(interpreter)?;
         let mut result = Value::null();
         let mut matched = false;
+        interpreter.set_current_state(InterpreterState::Executing);
+
+        // If a case block does not end with a break statement then subsequent cases will be run without
+        // checking their conditions until a break is encountered.
+        let mut fall_through: bool = false;
+
         for case in self.cases().iter() {
             let cond = case.condition();
             let block = case.body();
-            if val.strict_equals(&cond.run(interpreter)?) {
+            if fall_through || val.strict_equals(&cond.run(interpreter)?) {
                 matched = true;
-                block.run(interpreter)?;
+                let result = block.run(interpreter)?;
+                match interpreter.get_current_state() {
+                    InterpreterState::Return => {
+                        // Early return.
+                        return Ok(result);
+                    }
+                    InterpreterState::Break(_label) => {
+                        // Break statement encountered so therefore end switch statement.
+                        interpreter.set_current_state(InterpreterState::Executing);
+                        break;
+                    }
+                    _ => {
+                        // Continuing execution / falling through to next case statement(s).
+                        fall_through = true;
+                    }
+                }
             }
-
-            // TODO: break out of switch on a break statement.
         }
         if !matched {
             if let Some(default) = default {

boa/src/exec/switch/tests.rs

@@ -0,0 +1,200 @@
+use crate::exec;
+
+#[test]
+fn single_case_switch() {
+    let scenario = r#"
+        let a = 10;
+        switch (a) {
+            case 10:
+                a = 20;
+                break;
+        }
+        
+        a;
+    "#;
+    assert_eq!(&exec(scenario), "20");
+}
+
+#[test]
+fn no_cases_switch() {
+    let scenario = r#"
+        let a = 10;
+        switch (a) {
+        }
+        
+        a;
+    "#;
+    assert_eq!(&exec(scenario), "10");
+}
+
+#[test]
+fn no_true_case_switch() {
+    let scenario = r#"
+        let a = 10;
+        switch (a) {
+            case 5:
+                a = 15;
+                break;
+        }
+        
+        a;
+    "#;
+    assert_eq!(&exec(scenario), "10");
+}
+
+#[test]
+fn two_case_switch() {
+    let scenario = r#"
+        let a = 10;
+        switch (a) {
+            case 5:
+                a = 15;
+                break;
+            case 10:
+                a = 20;
+                break;
+        }
+        
+        a;
+    "#;
+    assert_eq!(&exec(scenario), "20");
+}
+
+#[test]
+fn two_case_no_break_switch() {
+    let scenario = r#"
+        let a = 10;
+        let b = 10;
+
+        switch (a) {
+            case 10:
+                a = 150;
+            case 20:
+                b = 150;
+                break;
+        }
+        
+        a + b;
+    "#;
+    assert_eq!(&exec(scenario), "300");
+}
+
+#[test]
+fn three_case_partial_fallthrough() {
+    let scenario = r#"
+        let a = 10;
+        let b = 10;
+
+        switch (a) {
+            case 10:
+                a = 150;
+            case 20:
+                b = 150;
+                break;
+            case 15:
+                b = 1000;
+                break;
+        }
+        
+        a + b;
+    "#;
+    assert_eq!(&exec(scenario), "300");
+}
+
+#[test]
+fn default_taken_switch() {
+    let scenario = r#"
+        let a = 10;
+
+        switch (a) {
+            case 5:
+                a = 150;
+                break;
+            default:
+                a = 70;
+        }
+        
+        a;
+    "#;
+    assert_eq!(&exec(scenario), "70");
+}
+
+#[test]
+fn default_not_taken_switch() {
+    let scenario = r#"
+        let a = 5;
+
+        switch (a) {
+            case 5:
+                a = 150;
+                break;
+            default:
+                a = 70;
+        }
+        
+        a;
+    "#;
+    assert_eq!(&exec(scenario), "150");
+}
+
+#[test]
+fn string_switch() {
+    let scenario = r#"
+        let a = "hello";
+
+        switch (a) {
+            case "hello":
+                a = "world";
+                break;
+            default:
+                a = "hi";
+        }
+        
+        a;
+    "#;
+    assert_eq!(&exec(scenario), "world");
+}
+
+#[test]
+fn bigger_switch_example() {
+    let expected = ["Mon", "Tue", "Wed", "Thurs", "Fri", "Sat", "Sun"];
+
+    for (i, val) in expected.iter().enumerate() {
+        let scenario = format!(
+            r#"
+            let a = {};
+            let b = "unknown";
+
+            switch (a) {{
+                case 0:
+                    b = "Mon";
+                    break;
+                case 1:
+                    b = "Tue";
+                    break;
+                case 2:
+                    b = "Wed";
+                    break;
+                case 3:
+                    b = "Thurs";
+                    break;
+                case 4:
+                    b = "Fri";
+                    break;
+                case 5:
+                    b = "Sat";
+                    break;
+                case 6:
+                    b = "Sun";
+                    break; 
+            }}
+
+            b;
+
+            "#,
+            i
+        );
+
+        assert_eq!(&exec(&scenario), val);
+    }
+}

boa/src/syntax/ast/node/return_smt.rs

@@ -24,25 +24,31 @@ use serde::{Deserialize, Serialize};
 /// [spec]: https://tc39.es/ecma262/#prod-ReturnStatement
 /// [mdn]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/return
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
-#[cfg_attr(feature = "serde", serde(transparent))]
 #[derive(Clone, Debug, Trace, Finalize, PartialEq)]
 pub struct Return {
     expr: Option<Box<Node>>,
+    label: Option<Box<str>>,
 }
 
 impl Return {
+    pub fn label(&self) -> Option<&str> {
+        self.label.as_ref().map(Box::as_ref)
+    }
+
     pub fn expr(&self) -> Option<&Node> {
         self.expr.as_ref().map(Box::as_ref)
     }
 
     /// Creates a `Return` AST node.
-    pub fn new<E, OE>(expr: OE) -> Self
+    pub fn new<E, OE, L>(expr: OE, label: L) -> Self
     where
         E: Into<Node>,
         OE: Into<Option<E>>,
+        L: Into<Option<Box<str>>>,
     {
         Self {
             expr: expr.into().map(E::into).map(Box::new),
+            label: label.into(),
         }
     }
 }

boa/src/syntax/ast/node/switch.rs

@@ -24,6 +24,18 @@ impl Case {
     pub fn body(&self) -> &StatementList {
         &self.body
     }
+
+    /// Creates a `Case` AST node.
+    pub fn new<C, B>(condition: C, body: B) -> Self
+    where
+        C: Into<Node>,
+        B: Into<StatementList>,
+    {
+        Self {
+            condition: condition.into(),
+            body: body.into(),
+        }
+    }
 }
 
 /// The `switch` statement evaluates an expression, matching the expression's value to a case

boa/src/syntax/ast/token.rs

@@ -31,7 +31,7 @@ pub struct Token {
     /// The token kind, which contains the actual data of the token.
     pub(crate) kind: TokenKind,
     /// The token position in the original source code.
-    span: Span,
+    pub(crate) span: Span,
 }
 
 impl Token {

boa/src/syntax/parser/expression/assignment/arrow_function.rs

@@ -119,6 +119,7 @@ impl TokenParser for ConciseBody {
             }
             _ => Ok(StatementList::from(vec![Return::new(
                 ExpressionBody::new(self.allow_in, false).parse(cursor)?,
+                None,
             )
             .into()])),
         }

boa/src/syntax/parser/expression/left_hand_side/call.rs

@@ -8,6 +8,7 @@
 //! [spec]: https://tc39.es/ecma262/#prod-CallExpression
 
 use super::arguments::Arguments;
+
 use crate::{
     syntax::{
         ast::{

boa/src/syntax/parser/expression/left_hand_side/member.rs

@@ -6,6 +6,7 @@
 //! [spec]: https://tc39.es/ecma262/#prod-MemberExpression
 
 use super::arguments::Arguments;
+
 use crate::{
     syntax::{
         ast::{

boa/src/syntax/parser/function/tests.rs

@@ -14,7 +14,7 @@ fn check_basic() {
         vec![FunctionDecl::new(
             Box::from("foo"),
             vec![FormalParameter::new("a", None, false)],
-            vec![Return::new(Identifier::from("a")).into()],
+            vec![Return::new(Identifier::from("a"), None).into()],
         )
         .into()],
     );
@@ -28,7 +28,7 @@ fn check_basic_semicolon_insertion() {
         vec![FunctionDecl::new(
             Box::from("foo"),
             vec![FormalParameter::new("a", None, false)],
-            vec![Return::new(Identifier::from("a")).into()],
+            vec![Return::new(Identifier::from("a"), None).into()],
         )
         .into()],
     );
@@ -42,7 +42,7 @@ fn check_empty_return() {
         vec![FunctionDecl::new(
             Box::from("foo"),
             vec![FormalParameter::new("a", None, false)],
-            vec![Return::new::<Node, Option<Node>>(None).into()],
+            vec![Return::new::<Node, Option<Node>, Option<_>>(None, None).into()],
         )
         .into()],
     );
@@ -56,7 +56,7 @@ fn check_empty_return_semicolon_insertion() {
         vec![FunctionDecl::new(
             Box::from("foo"),
             vec![FormalParameter::new("a", None, false)],
-            vec![Return::new::<Node, Option<Node>>(None).into()],
+            vec![Return::new::<Node, Option<Node>, Option<_>>(None, None).into()],
         )
         .into()],
     );
@@ -115,11 +115,10 @@ fn check_arrow() {
                 FormalParameter::new("a", None, false),
                 FormalParameter::new("b", None, false),
             ],
-            vec![Return::new(BinOp::new(
+            vec![Return::new(
-                NumOp::Add,
+                BinOp::new(NumOp::Add, Identifier::from("a"), Identifier::from("b")),
-                Identifier::from("a"),
+                None,
-                Identifier::from("b"),
+            )
-            ))
             .into()],
         )
         .into()],
@@ -136,11 +135,10 @@ fn check_arrow_semicolon_insertion() {
                 FormalParameter::new("a", None, false),
                 FormalParameter::new("b", None, false),
             ],
-            vec![Return::new(BinOp::new(
+            vec![Return::new(
-                NumOp::Add,
+                BinOp::new(NumOp::Add, Identifier::from("a"), Identifier::from("b")),
-                Identifier::from("a"),
+                None,
-                Identifier::from("b"),
+            )
-            ))
             .into()],
         )
         .into()],
@@ -157,7 +155,7 @@ fn check_arrow_epty_return() {
                 FormalParameter::new("a", None, false),
                 FormalParameter::new("b", None, false),
             ],
-            vec![Return::new::<Node, Option<_>>(None).into()],
+            vec![Return::new::<Node, Option<_>, Option<_>>(None, None).into()],
         )
         .into()],
     );
@@ -173,7 +171,7 @@ fn check_arrow_empty_return_semicolon_insertion() {
                 FormalParameter::new("a", None, false),
                 FormalParameter::new("b", None, false),
             ],
-            vec![Return::new::<Node, Option<_>>(None).into()],
+            vec![Return::new::<Node, Option<_>, Option<_>>(None, None).into()],
         )
         .into()],
     );

boa/src/syntax/parser/statement/block/tests.rs

@@ -51,7 +51,7 @@ fn non_empty() {
             FunctionDecl::new(
                 "hello".to_owned().into_boxed_str(),
                 vec![],
-                vec![Return::new(Const::from(10)).into()],
+                vec![Return::new(Const::from(10), None).into()],
             )
             .into(),
             VarDeclList::from(vec![VarDecl::new(
@@ -77,7 +77,7 @@ fn hoisting() {
             FunctionDecl::new(
                 "hello".to_owned().into_boxed_str(),
                 vec![],
-                vec![Return::new(Const::from(10)).into()],
+                vec![Return::new(Const::from(10), None).into()],
             )
             .into(),
             VarDeclList::from(vec![VarDecl::new(

boa/src/syntax/parser/statement/mod.rs

@@ -57,6 +57,7 @@ use crate::{
 ///  - `WithStatement`
 ///  - `LabelledStatement`
 ///  - `ThrowStatement`
+///  - `SwitchStatement`
 ///  - `TryStatement`
 ///  - `DebuggerStatement`
 ///
@@ -184,7 +185,7 @@ pub(super) struct StatementList {
     allow_yield: AllowYield,
     allow_await: AllowAwait,
     allow_return: AllowReturn,
-    break_when_closingbrase: bool,
+    break_when_closingbraces: bool,
 }
 
 impl StatementList {
@@ -193,7 +194,7 @@ impl StatementList {
         allow_yield: Y,
         allow_await: A,
         allow_return: R,
-        break_when_closingbrase: bool,
+        break_when_closingbraces: bool,
     ) -> Self
     where
         Y: Into<AllowYield>,
@@ -204,9 +205,48 @@ impl StatementList {
             allow_yield: allow_yield.into(),
             allow_await: allow_await.into(),
             allow_return: allow_return.into(),
-            break_when_closingbrase,
+            break_when_closingbraces,
         }
     }
+
+    /// The function parses a node::StatementList using the given break_nodes to know when to terminate.
+    ///
+    /// This ignores the break_when_closingbraces flag.
+    ///
+    /// Returns a ParseError::AbruptEnd if end of stream is reached before a break token.
+    ///
+    /// This is a more general version of the TokenParser parse function for StatementList which can exit based on multiple
+    /// different tokens. This may eventually replace the parse() function but is currently seperate to allow testing the
+    /// performance impact of this more general mechanism.
+    ///
+    /// Note that the last token which causes the parse to finish is not consumed.
+    pub(crate) fn parse_generalised(
+        self,
+        cursor: &mut Cursor<'_>,
+        break_nodes: &[TokenKind],
+    ) -> Result<node::StatementList, ParseError> {
+        let mut items = Vec::new();
+
+        loop {
+            match cursor.peek(0) {
+                Some(token) if break_nodes.contains(&token.kind) => break,
+                None => return Err(ParseError::AbruptEnd),
+                _ => {}
+            }
+
+            let item =
+                StatementListItem::new(self.allow_yield, self.allow_await, self.allow_return)
+                    .parse(cursor)?;
+            items.push(item);
+
+            // move the cursor forward for any consecutive semicolon.
+            while cursor.next_if(Punctuator::Semicolon).is_some() {}
+        }
+
+        items.sort_by(Node::hoistable_order);
+
+        Ok(items.into())
+    }
 }
 
 impl TokenParser for StatementList {
@@ -219,14 +259,14 @@ impl TokenParser for StatementList {
         loop {
             match cursor.peek(0) {
                 Some(token) if token.kind == TokenKind::Punctuator(Punctuator::CloseBlock) => {
-                    if self.break_when_closingbrase {
+                    if self.break_when_closingbraces {
                         break;
                     } else {
                         return Err(ParseError::unexpected(token.clone(), None));
                     }
                 }
                 None => {
-                    if self.break_when_closingbrase {
+                    if self.break_when_closingbraces {
                         return Err(ParseError::AbruptEnd);
                     } else {
                         break;

boa/src/syntax/parser/statement/return_stm/mod.rs

@@ -55,13 +55,13 @@ impl TokenParser for ReturnStatement {
                 _ => {}
             }
 
-            return Ok(Return::new::<Node, Option<_>>(None));
+            return Ok(Return::new::<Node, Option<_>, Option<_>>(None, None));
         }
 
         let expr = Expression::new(true, self.allow_yield, self.allow_await).parse(cursor)?;
 
         cursor.expect_semicolon(false, "return statement")?;
 
-        Ok(Return::new(expr))
+        Ok(Return::new(expr, None))
     }
 }

boa/src/syntax/parser/statement/switch/mod.rs

@@ -3,18 +3,22 @@ mod tests;
 
 use crate::{
     syntax::{
-        ast::{
+        ast::{node, node::Switch, Keyword, Node, Punctuator, TokenKind},
-            node::{Case, Switch},
-            Keyword, Node, Punctuator,
-        },
         parser::{
-            expression::Expression, AllowAwait, AllowReturn, AllowYield, Cursor, ParseError,
+            expression::Expression, statement::StatementList, AllowAwait, AllowReturn, AllowYield,
-            TokenParser,
+            Cursor, ParseError, Token, TokenParser,
         },
     },
     BoaProfiler,
 };
 
+/// The possible TokenKind which indicate the end of a case statement.
+const CASE_BREAK_TOKENS: [TokenKind; 3] = [
+    TokenKind::Punctuator(Punctuator::CloseBlock),
+    TokenKind::Keyword(Keyword::Case),
+    TokenKind::Keyword(Keyword::Default),
+];
+
 /// Switch statement parsing.
 ///
 /// More information:
@@ -95,14 +99,81 @@ impl CaseBlock {
 }
 
 impl TokenParser for CaseBlock {
-    type Output = (Box<[Case]>, Option<Node>);
+    type Output = (Box<[node::Case]>, Option<Node>);
 
     fn parse(self, cursor: &mut Cursor<'_>) -> Result<Self::Output, ParseError> {
-        cursor.expect(Punctuator::OpenBlock, "switch case block")?;
+        let mut cases = Vec::<node::Case>::new();
+        let mut default: Option<Node> = None;
+
+        cursor.expect(Punctuator::OpenBlock, "switch start case block")?;
+
+        loop {
+            match cursor.expect(Keyword::Case, "switch case: block") {
+                Ok(_) => {
+                    // Case statement.
+                    let cond =
+                        Expression::new(true, self.allow_yield, self.allow_await).parse(cursor)?;
+
+                    cursor.expect(Punctuator::Colon, "switch case block start")?;
 
-        // CaseClauses[?Yield, ?Await, ?Return]opt
+                    let statement_list = StatementList::new(
-        // CaseClauses[?Yield, ?Await, ?Return]optDefaultClause[?Yield, ?Await, ?Return]CaseClauses[?Yield, ?Await, ?Return]opt
+                        self.allow_yield,
+                        self.allow_await,
+                        self.allow_return,
+                        true,
+                    )
+                    .parse_generalised(cursor, &CASE_BREAK_TOKENS)?;
+
+                    cases.push(node::Case::new(cond, statement_list));
+                }
+                Err(ParseError::Expected {
+                    expected: _,
+                    found:
+                        Token {
+                            kind: TokenKind::Keyword(Keyword::Default),
+                            span: s,
+                        },
+                    context: _,
+                }) => {
+                    // Default statement.
+                    if default.is_some() {
+                        // If default has already been defined then it cannot be defined again and to do so is an error.
+                        return Err(ParseError::unexpected(
+                            Token::new(TokenKind::Keyword(Keyword::Default), s),
+                            Some("Second default clause found in switch statement"),
+                        ));
+                    }
+
+                    cursor.expect(Punctuator::Colon, "switch default case block start")?;
+                    let statement_list = StatementList::new(
+                        self.allow_yield,
+                        self.allow_await,
+                        self.allow_return,
+                        true,
+                    )
+                    .parse_generalised(cursor, &CASE_BREAK_TOKENS)?;
+
+                    default = Some(node::Block::from(statement_list).into());
+                }
+                Err(ParseError::Expected {
+                    expected: _,
+                    found:
+                        Token {
+                            kind: TokenKind::Punctuator(Punctuator::CloseBlock),
+                            span: _,
+                        },
+                    context: _,
+                }) => {
+                    // End of switch block.
+                    break;
+                }
+                Err(e) => {
+                    // Unexpected statement.
+                    return Err(e);
+                }
+            }
+        }
 
-        unimplemented!("switch case block parsing")
+        Ok((cases.into_boxed_slice(), default))
     }
 }

boa/src/syntax/parser/statement/switch/tests.rs

@@ -1 +1,99 @@
+use crate::syntax::parser::tests::check_invalid;
 
+/// Checks parsing malformed switch with no closeblock.
+#[test]
+fn check_switch_no_closeblock() {
+    check_invalid(
+        r#"
+        let a = 10;
+        switch (a) {
+            case 10:
+                a = 20;
+                break;
+        
+        "#,
+    );
+}
+
+/// Checks parsing malformed switch in which a case is started but not finished.
+#[test]
+fn check_switch_case_unclosed() {
+    check_invalid(
+        r#"
+        let a = 10;
+        switch (a) {
+            case 10:
+                a = 20;
+        
+        "#,
+    );
+}
+
+/// Checks parsing malformed switch with 2 defaults.
+#[test]
+fn check_switch_two_default() {
+    check_invalid(
+        r#"
+        let a = 10;
+        switch (a) {
+            default:
+                a = 20;
+                break;
+            default:
+                a = 30;
+                break;
+        }
+        "#,
+    );
+}
+
+/// Checks parsing malformed switch with no expression.
+#[test]
+fn check_switch_no_expr() {
+    check_invalid(
+        r#"
+        let a = 10;
+        switch {
+            default:
+                a = 20;
+                break;
+        }
+        "#,
+    );
+}
+
+/// Checks parsing malformed switch with an unknown label.
+#[test]
+fn check_switch_unknown_label() {
+    check_invalid(
+        r#"
+        let a = 10;
+        switch (a) {
+            fake:
+                a = 20;
+                break;
+        }
+        "#,
+    );
+}
+
+/// Checks parsing malformed switch with two defaults that are seperated by cases.
+#[test]
+fn check_switch_seperated_defaults() {
+    check_invalid(
+        r#"
+        let a = 10;
+        switch (a) {
+            default:
+                a = 20;
+                break;
+            case 10:
+                a = 60;
+                break;
+            default:
+                a = 30;
+                break;
+        }
+        "#,
+    );
+}

boa/src/syntax/parser/tests.rs

@@ -79,7 +79,7 @@ fn hoisting() {
             FunctionDecl::new(
                 Box::from("hello"),
                 vec![],
-                vec![Return::new(Const::from(10)).into()],
+                vec![Return::new(Const::from(10), None).into()],
             )
             .into(),
             VarDeclList::from(vec![VarDecl::new(