From 9abf963926973304654f0a076cbc80ca7cbdc385 Mon Sep 17 00:00:00 2001
From: y21 <30553356+y21@users.noreply.github.com>
Date: Tue, 24 Dec 2024 22:09:54 +0100
Subject: [PATCH] support object rest destructuring in arrow functions

---
 crates/dash_middle/src/parser/error.rs |  4 ++--
 crates/dash_parser/src/expr.rs         | 17 +++++++++++++----
 crates/dash_parser/src/stmt.rs         |  4 ++--
 3 files changed, 17 insertions(+), 8 deletions(-)

diff --git a/crates/dash_middle/src/parser/error.rs b/crates/dash_middle/src/parser/error.rs
index 2ca10347..a86b979d 100644
--- a/crates/dash_middle/src/parser/error.rs
+++ b/crates/dash_middle/src/parser/error.rs
@@ -48,7 +48,7 @@ pub enum Error {
         expect: usize,
         token: Token,
     },
-    MultipleRestInDestructuring(Token),
+    MultipleRestInDestructuring(Span),
     RegexSyntaxError(Token, dash_regex::Error),
     IncompleteSpread(Token),
     /* Compiler */
@@ -311,7 +311,7 @@ impl fmt::Display for FormattableError<'_, '_> {
                 diag.message("incorrect number of parameters for accessor");
                 diag.span_error(span, format!("expected {expect}, got {got}"));
             }
-            Error::MultipleRestInDestructuring(Token { span, .. }) => {
+            Error::MultipleRestInDestructuring(span) => {
                 diag.message("multiple rest elements in destructuring");
                 diag.span_error(span, "second rest element defined here");
             }
diff --git a/crates/dash_parser/src/expr.rs b/crates/dash_parser/src/expr.rs
index 9e0f3e14..7caf7caf 100644
--- a/crates/dash_parser/src/expr.rs
+++ b/crates/dash_parser/src/expr.rs
@@ -911,6 +911,7 @@ impl Parser<'_, '_> {
                 ExprKind::Object(ObjectLiteral(properties)) => {
                     let destructured_id = parser.local_count.inc();
                     let mut fields = Vec::with_capacity(properties.len());
+                    let mut rest = None;
                     for (key, value) in properties {
                         match key {
                             // `x: a` aliases x to 1
@@ -926,14 +927,22 @@ impl Parser<'_, '_> {
                             ObjectMemberKind::Default(symbol) => {
                                 fields.push((parser.local_count.inc(), symbol, None, Some(value)))
                             }
+                            ObjectMemberKind::Spread => {
+                                if rest.is_none() {
+                                    if let Some(symbol) = value.kind.as_identifier() {
+                                        rest = Some(parser.create_binding(symbol));
+                                    } else {
+                                        parser.error(Error::unexpected_token(value.span, TokenType::DUMMY_IDENTIFIER));
+                                    }
+                                } else {
+                                    parser.error(Error::MultipleRestInDestructuring(value.span))
+                                }
+                            }
                             _ => parser.error(Error::unexpected_token(value.span, TokenType::DUMMY_IDENTIFIER)),
                         }
                     }
 
-                    Some(Parameter::Pattern(destructured_id, Pattern::Object {
-                        fields,
-                        rest: None,
-                    }))
+                    Some(Parameter::Pattern(destructured_id, Pattern::Object { fields, rest }))
                 }
                 _ => {
                     parser.error(Error::Unimplemented(
diff --git a/crates/dash_parser/src/stmt.rs b/crates/dash_parser/src/stmt.rs
index fc282158..0f77fb8f 100644
--- a/crates/dash_parser/src/stmt.rs
+++ b/crates/dash_parser/src/stmt.rs
@@ -588,7 +588,7 @@ impl Parser<'_, '_> {
                         if let Some(sym) = name.ty.as_identifier() {
                             if rest.is_some() {
                                 // Only allow one rest operator
-                                self.error(Error::MultipleRestInDestructuring(name));
+                                self.error(Error::MultipleRestInDestructuring(name.span));
                                 return None;
                             }
 
@@ -665,7 +665,7 @@ impl Parser<'_, '_> {
                         if let Some(sym) = name.ty.as_identifier() {
                             if rest.is_some() {
                                 // Only allow one rest operator
-                                self.error(Error::MultipleRestInDestructuring(name));
+                                self.error(Error::MultipleRestInDestructuring(name.span));
                                 return None;
                             }