From cd232b18f9e789acca56344503559daf9692e755 Mon Sep 17 00:00:00 2001
From: raskad <32105367+raskad@users.noreply.github.com>
Date: Fri, 11 Aug 2023 11:42:09 +0200
Subject: [PATCH] Fix switch statement `break` and `continue` return values
 (#3205)

* Fix switch statement early return values

* Remove unused control flow
---
 boa_engine/src/bytecompiler/mod.rs           | 11 ------
 boa_engine/src/bytecompiler/statement/try.rs | 38 ++++++++++++++++++--
 2 files changed, 35 insertions(+), 14 deletions(-)

diff --git a/boa_engine/src/bytecompiler/mod.rs b/boa_engine/src/bytecompiler/mod.rs
index 1973d3d76b..b0364f9f36 100644
--- a/boa_engine/src/bytecompiler/mod.rs
+++ b/boa_engine/src/bytecompiler/mod.rs
@@ -843,15 +843,10 @@ impl<'ctx, 'host> ByteCompiler<'ctx, 'host> {
     /// Compile a [`StatementList`].
     pub fn compile_statement_list(&mut self, list: &StatementList, use_expr: bool, block: bool) {
         if use_expr || self.jump_control_info_has_use_expr() {
-            let mut has_returns_value = false;
             let mut use_expr_index = 0;
-            let mut first_return_is_abrupt = false;
             for (i, statement) in list.statements().iter().enumerate() {
                 match statement {
                     StatementListItem::Statement(Statement::Break(_) | Statement::Continue(_)) => {
-                        if !has_returns_value {
-                            first_return_is_abrupt = true;
-                        }
                         break;
                     }
                     StatementListItem::Statement(Statement::Empty | Statement::Var(_))
@@ -859,17 +854,11 @@ impl<'ctx, 'host> ByteCompiler<'ctx, 'host> {
                     StatementListItem::Statement(Statement::Block(block))
                         if !returns_value(block) => {}
                     StatementListItem::Statement(_) => {
-                        has_returns_value = true;
                         use_expr_index = i;
                     }
                 }
             }
 
-            if first_return_is_abrupt {
-                self.emit_opcode(Opcode::PushUndefined);
-                self.emit_opcode(Opcode::SetReturnValue);
-            }
-
             for (i, item) in list.statements().iter().enumerate() {
                 self.compile_stmt_list_item(item, i == use_expr_index, block);
             }
diff --git a/boa_engine/src/bytecompiler/statement/try.rs b/boa_engine/src/bytecompiler/statement/try.rs
index d05501d177..fcaffc4d08 100644
--- a/boa_engine/src/bytecompiler/statement/try.rs
+++ b/boa_engine/src/bytecompiler/statement/try.rs
@@ -5,7 +5,8 @@ use crate::{
 use boa_ast::{
     declaration::Binding,
     operations::bound_names,
-    statement::{Catch, Finally, Try},
+    statement::{Block, Catch, Finally, Try},
+    Statement, StatementListItem,
 };
 
 impl ByteCompiler<'_, '_> {
@@ -130,7 +131,7 @@ impl ByteCompiler<'_, '_> {
             self.emit_opcode(Opcode::Pop);
         }
 
-        self.compile_block(catch.block(), use_expr);
+        self.compile_catch_finally_block(catch.block(), use_expr);
 
         let env_index = self.pop_compile_environment();
         self.patch_jump_with_target(push_env, env_index);
@@ -141,7 +142,7 @@ impl ByteCompiler<'_, '_> {
         // TODO: We could probably remove the Get/SetReturnValue if we check that there is no break/continues statements.
         self.current_stack_value_count += 1;
         self.emit_opcode(Opcode::GetReturnValue);
-        self.compile_block(finally.block(), true);
+        self.compile_catch_finally_block(finally.block(), true);
         self.emit_opcode(Opcode::SetReturnValue);
         self.current_stack_value_count -= 1;
 
@@ -162,4 +163,35 @@ impl ByteCompiler<'_, '_> {
 
         self.patch_jump(do_not_throw_exit);
     }
+
+    /// Compile a catch or finally block.
+    ///
+    /// If the block contains a break or continue as the first statement,
+    /// the return value is set to undefined.
+    /// See the [ECMAScript reference][spec] for more information.
+    ///
+    /// [spec]: https://tc39.es/ecma262/#sec-try-statement-runtime-semantics-evaluation
+    fn compile_catch_finally_block(&mut self, block: &Block, use_expr: bool) {
+        let mut b = block;
+
+        loop {
+            match b.statement_list().first() {
+                Some(StatementListItem::Statement(
+                    Statement::Break(_) | Statement::Continue(_),
+                )) => {
+                    self.emit_opcode(Opcode::PushUndefined);
+                    self.emit_opcode(Opcode::SetReturnValue);
+                    break;
+                }
+                Some(StatementListItem::Statement(Statement::Block(block))) => {
+                    b = block;
+                }
+                _ => {
+                    break;
+                }
+            }
+        }
+
+        self.compile_block(block, use_expr);
+    }
 }