From 2b01ef1c2780e5a82b9660717ead021edce6e280 Mon Sep 17 00:00:00 2001
From: Haled Odat <8566042+HalidOdat@users.noreply.github.com>
Date: Sun, 30 Jul 2023 05:50:15 +0200
Subject: [PATCH] Close iterator after generator return call while array
 destructuring assignment (#3164)

* Close iterator after generator return while array destructuring

* Add MaybeException opcode and remove handler check
---
 .../declaration/declaration_pattern.rs        | 10 +++-----
 boa_engine/src/vm/code_block.rs               |  4 ++--
 boa_engine/src/vm/flowgraph/mod.rs            |  4 ++--
 .../src/vm/opcode/control_flow/throw.rs       | 24 +++++++++++++++++++
 boa_engine/src/vm/opcode/mod.rs               | 11 ++++++---
 5 files changed, 39 insertions(+), 14 deletions(-)

diff --git a/boa_engine/src/bytecompiler/declaration/declaration_pattern.rs b/boa_engine/src/bytecompiler/declaration/declaration_pattern.rs
index 17a9bd4c12..a0a34b723c 100644
--- a/boa_engine/src/bytecompiler/declaration/declaration_pattern.rs
+++ b/boa_engine/src/bytecompiler/declaration/declaration_pattern.rs
@@ -180,19 +180,15 @@ impl ByteCompiler<'_, '_> {
                 self.emit_opcode(Opcode::ValueNotNullOrUndefined);
                 self.emit_opcode(Opcode::GetIterator);
 
-                // TODO: maybe, refactor this to be more condensed.
                 let handler_index = self.push_handler();
                 for element in pattern.bindings() {
                     self.compile_array_pattern_element(element, def);
                 }
 
-                self.emit_opcode(Opcode::PushFalse);
-
-                let exit = self.jump();
                 self.patch_handler(handler_index);
-                self.emit_opcode(Opcode::Exception);
-                self.emit_opcode(Opcode::PushTrue);
-                self.patch_jump(exit);
+                self.emit_opcode(Opcode::MaybeException);
+
+                // stack: hasPending, exception?
 
                 self.current_stack_value_count += 2;
 
diff --git a/boa_engine/src/vm/code_block.rs b/boa_engine/src/vm/code_block.rs
index 1cf0bf5361..bce2c9ece8 100644
--- a/boa_engine/src/vm/code_block.rs
+++ b/boa_engine/src/vm/code_block.rs
@@ -566,6 +566,7 @@ impl CodeBlock {
             | Opcode::Throw
             | Opcode::ReThrow
             | Opcode::Exception
+            | Opcode::MaybeException
             | Opcode::This
             | Opcode::Super
             | Opcode::Return
@@ -677,8 +678,7 @@ impl CodeBlock {
             | Opcode::Reserved60
             | Opcode::Reserved61
             | Opcode::Reserved62
-            | Opcode::Reserved63
-            | Opcode::Reserved64 => unreachable!("Reserved opcodes are unrechable"),
+            | Opcode::Reserved63 => unreachable!("Reserved opcodes are unrechable"),
         }
     }
 }
diff --git a/boa_engine/src/vm/flowgraph/mod.rs b/boa_engine/src/vm/flowgraph/mod.rs
index 4499331ba2..ff210e418c 100644
--- a/boa_engine/src/vm/flowgraph/mod.rs
+++ b/boa_engine/src/vm/flowgraph/mod.rs
@@ -537,6 +537,7 @@ impl CodeBlock {
                 | Opcode::GetReturnValue
                 | Opcode::SetReturnValue
                 | Opcode::Exception
+                | Opcode::MaybeException
                 | Opcode::Nop => {
                     graph.add_node(previous_pc, NodeShape::None, label.into(), Color::None);
                     graph.add_edge(previous_pc, pc, None, Color::None, EdgeStyle::Line);
@@ -606,8 +607,7 @@ impl CodeBlock {
                 | Opcode::Reserved60
                 | Opcode::Reserved61
                 | Opcode::Reserved62
-                | Opcode::Reserved63
-                | Opcode::Reserved64 => unreachable!("Reserved opcodes are unrechable"),
+                | Opcode::Reserved63 => unreachable!("Reserved opcodes are unrechable"),
             }
         }
 
diff --git a/boa_engine/src/vm/opcode/control_flow/throw.rs b/boa_engine/src/vm/opcode/control_flow/throw.rs
index b5c31bea48..a9843ad8ec 100644
--- a/boa_engine/src/vm/opcode/control_flow/throw.rs
+++ b/boa_engine/src/vm/opcode/control_flow/throw.rs
@@ -86,6 +86,30 @@ impl Operation for Exception {
     }
 }
 
+/// `MaybeException` implements the Opcode Operation for `Opcode::MaybeException`
+///
+/// Operation:
+///  - Get the thrown pending exception if it's set and push `true`, otherwise push only `false`.
+#[derive(Debug, Clone, Copy)]
+pub(crate) struct MaybeException;
+
+impl Operation for MaybeException {
+    const NAME: &'static str = "MaybeException";
+    const INSTRUCTION: &'static str = "INST - MaybeException";
+
+    fn execute(context: &mut Context<'_>) -> JsResult<CompletionType> {
+        if let Some(error) = context.vm.pending_exception.take() {
+            let error = error.to_opaque(context);
+            context.vm.push(error);
+            context.vm.push(true);
+            return Ok(CompletionType::Normal);
+        }
+
+        context.vm.push(false);
+        Ok(CompletionType::Normal)
+    }
+}
+
 /// `ThrowNewTypeError` implements the Opcode Operation for `Opcode::ThrowNewTypeError`
 ///
 /// Operation:
diff --git a/boa_engine/src/vm/opcode/mod.rs b/boa_engine/src/vm/opcode/mod.rs
index d43841c732..f67794efa8 100644
--- a/boa_engine/src/vm/opcode/mod.rs
+++ b/boa_engine/src/vm/opcode/mod.rs
@@ -1147,7 +1147,7 @@ generate_impl! {
         /// Stack: **=>**
         ReThrow,
 
-        /// Get the thrown pending exception and push on the stack.
+        /// Get the thrown pending exception (if it's set) and push on the stack.
         ///
         /// If there is no pending exception, which can happend if we are handling `return()` call on generator,
         /// then we rethrow the empty exception. See [`Opcode::ReThrow`].
@@ -1157,6 +1157,13 @@ generate_impl! {
         /// Stack: **=>** exception
         Exception,
 
+        /// Get the thrown pending exception if it's set and push `true`, otherwise push only `false`.
+        ///
+        /// Operands:
+        ///
+        /// Stack: **=>** (`true`, exception) or `false`
+        MaybeException,
+
         /// Throw a new `TypeError` exception
         ///
         /// Operands: message: u32
@@ -1764,8 +1771,6 @@ generate_impl! {
         Reserved62 => Reserved,
         /// Reserved [`Opcode`].
         Reserved63 => Reserved,
-        /// Reserved [`Opcode`].
-        Reserved64 => Reserved,
     }
 }