From eac71e7c641c8e0079d6ef7470953db1fe344719 Mon Sep 17 00:00:00 2001
From: raskad <32105367+raskad@users.noreply.github.com>
Date: Wed, 13 Mar 2024 03:34:36 +0100
Subject: [PATCH] Add default value for descructing property access arrays

---
 core/ast/src/expression/literal/array.rs      |  2 +
 core/ast/src/pattern.rs                       | 39 ++++++++++++++++---
 .../declaration/declaration_pattern.rs        | 11 +++++-
 3 files changed, 45 insertions(+), 7 deletions(-)

diff --git a/core/ast/src/expression/literal/array.rs b/core/ast/src/expression/literal/array.rs
index 21f99fa195a..1cadeb08ae9 100644
--- a/core/ast/src/expression/literal/array.rs
+++ b/core/ast/src/expression/literal/array.rs
@@ -109,6 +109,7 @@ impl ArrayLiteral {
                     AssignTarget::Access(access) => {
                         bindings.push(ArrayPatternElement::PropertyAccess {
                             access: access.clone(),
+                            default_init: Some(assign.rhs().clone()),
                         });
                     }
                     AssignTarget::Pattern(pattern) => match pattern {
@@ -143,6 +144,7 @@ impl ArrayLiteral {
                 Expression::PropertyAccess(access) => {
                     bindings.push(ArrayPatternElement::PropertyAccess {
                         access: access.clone(),
+                        default_init: None,
                     });
                 }
                 _ => return None,
diff --git a/core/ast/src/pattern.rs b/core/ast/src/pattern.rs
index 4cfc4b50be2..8a6b19da46e 100644
--- a/core/ast/src/pattern.rs
+++ b/core/ast/src/pattern.rs
@@ -612,6 +612,8 @@ pub enum ArrayPatternElement {
     PropertyAccess {
         /// The property access where the index element will be stored.
         access: PropertyAccess,
+        /// An optional default value for the variable, in case the index element doesn't exist.
+        default_init: Option<Expression>,
     },
 
     /// Pattern represents a `Pattern` in an `Element` of an array pattern.
@@ -680,8 +682,15 @@ impl ToInternedString for ArrayPatternElement {
                 }
                 buf
             }
-            Self::PropertyAccess { access } => {
-                format!(" {}", access.to_interned_string(interner))
+            Self::PropertyAccess {
+                access,
+                default_init,
+            } => {
+                let mut buf = format!(" {}", access.to_interned_string(interner));
+                if let Some(init) = default_init {
+                    buf.push_str(&format!(" = {}", init.to_interned_string(interner)));
+                }
+                buf
             }
             Self::Pattern {
                 pattern,
@@ -723,9 +732,18 @@ impl VisitWith for ArrayPatternElement {
                     ControlFlow::Continue(())
                 }
             }
-            Self::PropertyAccess { access } | Self::PropertyAccessRest { access } => {
-                visitor.visit_property_access(access)
+            Self::PropertyAccess {
+                access,
+                default_init,
+            } => {
+                try_break!(visitor.visit_property_access(access));
+                if let Some(expr) = default_init {
+                    visitor.visit_expression(expr)
+                } else {
+                    ControlFlow::Continue(())
+                }
             }
+            Self::PropertyAccessRest { access } => visitor.visit_property_access(access),
             Self::Pattern {
                 pattern,
                 default_init,
@@ -762,9 +780,18 @@ impl VisitWith for ArrayPatternElement {
                     ControlFlow::Continue(())
                 }
             }
-            Self::PropertyAccess { access } | Self::PropertyAccessRest { access } => {
-                visitor.visit_property_access_mut(access)
+            Self::PropertyAccess {
+                access,
+                default_init,
+            } => {
+                try_break!(visitor.visit_property_access_mut(access));
+                if let Some(expr) = default_init {
+                    visitor.visit_expression_mut(expr)
+                } else {
+                    ControlFlow::Continue(())
+                }
             }
+            Self::PropertyAccessRest { access } => visitor.visit_property_access_mut(access),
             Self::Pattern {
                 pattern,
                 default_init,
diff --git a/core/engine/src/bytecompiler/declaration/declaration_pattern.rs b/core/engine/src/bytecompiler/declaration/declaration_pattern.rs
index a01b6417828..e7b7928f59a 100644
--- a/core/engine/src/bytecompiler/declaration/declaration_pattern.rs
+++ b/core/engine/src/bytecompiler/declaration/declaration_pattern.rs
@@ -240,10 +240,19 @@ impl ByteCompiler<'_> {
                 }
                 self.emit_binding(def, ident.to_js_string(self.interner()));
             }
-            PropertyAccess { access } => {
+            PropertyAccess {
+                access,
+                default_init,
+            } => {
                 self.access_set(Access::Property { access }, false, |compiler, _level| {
                     compiler.emit_opcode(Opcode::IteratorNextWithoutPop);
                     compiler.emit_opcode(Opcode::IteratorValueWithoutPop);
+
+                    if let Some(init) = default_init {
+                        let skip = compiler.emit_opcode_with_operand(Opcode::JumpIfNotUndefined);
+                        compiler.compile_expr(init, true);
+                        compiler.patch_jump(skip);
+                    }
                 });
             }
             // BindingElement : BindingPattern Initializer[opt]