fix(parser): reject trailing commas after rest elements in object patterns (#15223)

Reject codes like `({...a,} = {});` like we reject `([...a,] = []);`.

Author: sapphi-red

crates/oxc_parser/src/js/grammar.rs

@@ -187,6 +187,9 @@ impl<'a> CoverGrammar<'a, ObjectExpression<'a>> for ObjectAssignmentTarget<'a> {
                         ) {
                             p.error(diagnostics::invalid_rest_assignment_target(argument.span()));
                         }
+                        if let Some(span) = p.state.trailing_commas.get(&expr.span.start) {
+                            p.error(diagnostics::rest_element_trailing_comma(*span));
+                        }
                         let target = AssignmentTarget::cover(argument, p);
                         rest = Some(p.ast.alloc_assignment_target_rest(span, target));
                     } else {

crates/oxc_parser/src/js/object.rs

@@ -19,13 +19,16 @@ impl<'a> ParserImpl<'a> {
     pub(crate) fn parse_object_expression(&mut self) -> Box<'a, ObjectExpression<'a>> {
         let span = self.start_span();
         self.expect(Kind::LCurly);
-        let (object_expression_properties, _) = self.context_add(Context::In, |p| {
+        let (object_expression_properties, comma_span) = self.context_add(Context::In, |p| {
             p.parse_delimited_list(
                 Kind::RCurly,
                 Kind::Comma,
                 Self::parse_object_expression_property,
             )
         });
+        if let Some(comma_span) = comma_span {
+            self.state.trailing_commas.insert(span, self.end_span(comma_span));
+        }
         self.expect(Kind::RCurly);
         self.ast.alloc_object_expression(self.end_span(span), object_expression_properties)
     }

crates/oxc_parser/src/state.rs

@@ -10,9 +10,9 @@ pub struct ParserState<'a> {
     /// Keyed by `ObjectProperty`'s span.start.
     pub cover_initialized_name: FxHashMap<u32, AssignmentExpression<'a>>,
 
-    /// Trailing comma spans for `ArrayExpression`.
+    /// Trailing comma spans for `ArrayExpression` and `ObjectExpression`.
     /// Used for error reporting.
-    /// Keyed by start span of `ArrayExpression`.
+    /// Keyed by start span of `ArrayExpression` / `ObjectExpression`.
     /// Valued by position of the trailing_comma.
     pub trailing_commas: FxHashMap<u32, Span>,
 }

tasks/coverage/snapshots/parser_babel.snap

@@ -3,13 +3,7 @@ commit: 4cc3d888
 parser_babel Summary:
 AST Parsed     : 2422/2440 (99.26%)
 Positive Passed: 2395/2440 (98.16%)
-Negative Passed: 1676/1752 (95.66%)
-Expect Syntax Error: tasks/coverage/babel/packages/babel-parser/test/fixtures/es2018/object-rest-spread/comma-after-rest/input.js
-
-Expect Syntax Error: tasks/coverage/babel/packages/babel-parser/test/fixtures/es2018/object-rest-spread/comma-after-spread-for-in/input.js
-
-Expect Syntax Error: tasks/coverage/babel/packages/babel-parser/test/fixtures/es2018/object-rest-spread/comma-after-spread-nested/input.js
-
+Negative Passed: 1679/1752 (95.83%)
 Expect Syntax Error: tasks/coverage/babel/packages/babel-parser/test/fixtures/es2022/private-in/invalid-private-followed-by-in-2/input.js
 
 Expect Syntax Error: tasks/coverage/babel/packages/babel-parser/test/fixtures/es2026/async-explicit-resource-management/invalid-in-single-statement-context-async/input.js
@@ -6215,6 +6209,27 @@ Expect to Parse: tasks/coverage/babel/packages/babel-parser/test/fixtures/typesc
    ·          ────
    ╰────
 
+  × A rest parameter or binding pattern may not have a trailing comma.
+   ╭─[babel/packages/babel-parser/test/fixtures/es2018/object-rest-spread/comma-after-rest/input.js:1:7]
+ 1 │ ({...a,} = {});
+   ·       ─
+   ╰────
+  help: Remove the trailing comma here
+
+  × A rest parameter or binding pattern may not have a trailing comma.
+   ╭─[babel/packages/babel-parser/test/fixtures/es2018/object-rest-spread/comma-after-spread-for-in/input.js:1:11]
+ 1 │ for ({...a,} in []);
+   ·           ─
+   ╰────
+  help: Remove the trailing comma here
+
+  × A rest parameter or binding pattern may not have a trailing comma.
+   ╭─[babel/packages/babel-parser/test/fixtures/es2018/object-rest-spread/comma-after-spread-nested/input.js:1:7]
+ 1 │ [{...a,}] = [];
+   ·       ─
+   ╰────
+  help: Remove the trailing comma here
+
   × Spread must be last element
    ╭─[babel/packages/babel-parser/test/fixtures/es2018/object-rest-spread/expression-rest-not-last-invalid/input.js:1:3]
  1 │ ({...rest, b} = {})

tasks/coverage/snapshots/parser_typescript.snap

@@ -20165,6 +20165,15 @@ Expect to Parse: tasks/coverage/typescript/tests/cases/conformance/parser/ecmasc
    ╰────
   help: Remove the trailing comma here
 
+  × A rest parameter or binding pattern may not have a trailing comma.
+   ╭─[typescript/tests/cases/conformance/es7/trailingCommasInBindingPatterns.ts:5:7]
+ 4 │ ([...c,] = []);
+ 5 │ ({...d,} = {});
+   ·       ─
+ 6 │ 
+   ╰────
+  help: Remove the trailing comma here
+
   × A rest parameter or binding pattern may not have a trailing comma.
    ╭─[typescript/tests/cases/conformance/es7/trailingCommasInFunctionParametersAndArguments.ts:5:20]
  4 │ 

tasks/track_memory_allocations/allocs_parser.snap

@@ -1,14 +1,14 @@
 File                       | File size      || Sys allocs     | Sys reallocs   || Arena allocs   | Arena reallocs | Arena bytes    
 -------------------------------------------------------------------------------------------------------------------------------------------
-checker.ts                 | 2.92 MB        ||          10163 |             21 ||         268665 |          23341
+checker.ts                 | 2.92 MB        ||          10165 |             21 ||         268665 |          23341
 
-cal.com.tsx                | 1.06 MB        ||           2205 |             61 ||         138188 |          13712
+cal.com.tsx                | 1.06 MB        ||           2209 |             61 ||         138188 |          13712
 
 RadixUIAdoptionSection.jsx | 2.52 kB        ||              1 |              0 ||            365 |             66
 
 pdf.mjs                    | 567.30 kB      ||            701 |             75 ||          90678 |           8148
 
-antd.js                    | 6.69 MB        ||           6995 |            235 ||         528505 |          55357
+antd.js                    | 6.69 MB        ||           6997 |            235 ||         528505 |          55357
 
-binder.ts                  | 193.08 kB      ||            537 |              7 ||          16807 |           1475
+binder.ts                  | 193.08 kB      ||            538 |              7 ||          16807 |           1475