From 6a9d77808b8513246592129e8c9e154f686fa8a9 Mon Sep 17 00:00:00 2001
From: Austaras <austaras@outlook.com>
Date: Wed, 23 Feb 2022 12:08:46 +0800
Subject: [PATCH] fix(es/parser): Emit an error for non-last rest element in an
 object pattern (#3675)

---
 crates/swc_ecma_parser/src/parser/pat.rs            | 13 +++++++------
 .../tests/jsx/errors/issue-3523/input.js            |  4 ++++
 .../tests/jsx/errors/issue-3523/input.js.stderr     |  6 ++++++
 3 files changed, 17 insertions(+), 6 deletions(-)
 create mode 100644 crates/swc_ecma_parser/tests/jsx/errors/issue-3523/input.js
 create mode 100644 crates/swc_ecma_parser/tests/jsx/errors/issue-3523/input.js.stderr

diff --git a/crates/swc_ecma_parser/src/parser/pat.rs b/crates/swc_ecma_parser/src/parser/pat.rs
index d84ab7c1228..80381cdd4b7 100644
--- a/crates/swc_ecma_parser/src/parser/pat.rs
+++ b/crates/swc_ecma_parser/src/parser/pat.rs
@@ -510,11 +510,7 @@ impl<'a, I: Tokens> Parser<I> {
         self.reparse_expr_as_pat_inner(pat_ty, expr)
     }
 
-    pub(super) fn reparse_expr_as_pat_inner(
-        &mut self,
-        pat_ty: PatType,
-        expr: Box<Expr>,
-    ) -> PResult<Pat> {
+    fn reparse_expr_as_pat_inner(&mut self, pat_ty: PatType, expr: Box<Expr>) -> PResult<Pat> {
         // In dts, we do not reparse.
         debug_assert!(!self.input.syntax().dts());
 
@@ -608,11 +604,13 @@ impl<'a, I: Tokens> Parser<I> {
             }
             Expr::Object(ObjectLit { span, props }) => {
                 // {}
+                let len = props.len();
                 Ok(Pat::Object(ObjectPat {
                     span,
                     props: props
                         .into_iter()
-                        .map(|prop| {
+                        .enumerate()
+                        .map(|(idx, prop)| {
                             let span = prop.span();
                             match prop {
                                 PropOrSpread::Prop(prop) => match *prop {
@@ -643,6 +641,9 @@ impl<'a, I: Tokens> Parser<I> {
                                 },
 
                                 PropOrSpread::Spread(SpreadElement { dot3_token, expr }) => {
+                                    if idx != len - 1 {
+                                        self.emit_err(span, SyntaxError::NonLastRestParam)
+                                    };
                                     Ok(ObjectPatProp::Rest(RestPat {
                                         span,
                                         dot3_token,
diff --git a/crates/swc_ecma_parser/tests/jsx/errors/issue-3523/input.js b/crates/swc_ecma_parser/tests/jsx/errors/issue-3523/input.js
new file mode 100644
index 00000000000..1dbafa65978
--- /dev/null
+++ b/crates/swc_ecma_parser/tests/jsx/errors/issue-3523/input.js
@@ -0,0 +1,4 @@
+var rest, b;
+
+for ({...rest, b} of [{}
+]) ;
\ No newline at end of file
diff --git a/crates/swc_ecma_parser/tests/jsx/errors/issue-3523/input.js.stderr b/crates/swc_ecma_parser/tests/jsx/errors/issue-3523/input.js.stderr
new file mode 100644
index 00000000000..d678014aab3
--- /dev/null
+++ b/crates/swc_ecma_parser/tests/jsx/errors/issue-3523/input.js.stderr
@@ -0,0 +1,6 @@
+error: Rest element must be final element
+ --> $DIR/tests/jsx/errors/issue-3523/input.js:3:7
+  |
+3 | for ({...rest, b} of [{}
+  |       ^^^^^^^
+