feat(parser): a rest parameter cannot have an initializer

crates/oxc_parser/src/diagnostics.rs

@@ -525,6 +525,11 @@ pub fn rest_element_property_name(span: Span) -> OxcDiagnostic {
     ts_error("2566", "A rest element cannot have a property name.").with_label(span)
 }
 
+#[cold]
+pub fn a_rest_element_cannot_have_an_initializer(span: Span) -> OxcDiagnostic {
+    OxcDiagnostic::error("A rest element cannot have an initializer.").with_label(span)
+}
+
 // ================================= MODIFIERS =================================
 
 #[cold]

crates/oxc_parser/src/js/binding.rs

@@ -123,12 +123,17 @@ impl<'a> ParserImpl<'a> {
         // The span is not extended to its type_annotation
         let type_annotation = self.parse_ts_type_annotation()?;
         let pattern = self.ast.binding_pattern(kind, type_annotation, false);
+
         // Rest element does not allow `= initializer`
+        // function foo([...x = []]) { }
+        //                    ^^^^ A rest element cannot have an initializer
         let argument = self
             .context(Context::In, Context::empty(), |p| p.parse_initializer(init_span, pattern))?;
-        let span = self.end_span(span);
+        if let BindingPatternKind::AssignmentPattern(pat) = &argument.kind {
+            self.error(diagnostics::a_rest_element_cannot_have_an_initializer(pat.span));
+        }
 
-        Ok(self.ast.binding_rest_element(span, argument))
+        Ok(self.ast.binding_rest_element(self.end_span(span), argument))
     }
 
     /// `BindingProperty`[Yield, Await] :

crates/oxc_semantic/src/checker/javascript.rs

@@ -973,28 +973,6 @@ pub fn check_object_property(prop: &ObjectProperty, ctx: &SemanticBuilder<'_>) {
     }
 }
 
-fn a_rest_parameter_cannot_have_an_initializer(span: Span) -> OxcDiagnostic {
-    OxcDiagnostic::error("A rest parameter cannot have an initializer").with_label(span)
-}
-
-pub fn check_formal_parameters(params: &FormalParameters, ctx: &SemanticBuilder<'_>) {
-    if let Some(rest) = &params.rest {
-        if let BindingPatternKind::AssignmentPattern(pat) = &rest.argument.kind {
-            ctx.error(a_rest_parameter_cannot_have_an_initializer(pat.span));
-        }
-    }
-}
-
-pub fn check_array_pattern(pattern: &ArrayPattern, ctx: &SemanticBuilder<'_>) {
-    // function foo([...x = []]) { }
-    //                    ^^^^ A rest element cannot have an initializer
-    if let Some(rest) = &pattern.rest {
-        if let BindingPatternKind::AssignmentPattern(pat) = &rest.argument.kind {
-            ctx.error(a_rest_parameter_cannot_have_an_initializer(pat.span));
-        }
-    }
-}
-
 fn assignment_is_not_simple(span: Span) -> OxcDiagnostic {
     OxcDiagnostic::error("Invalid left-hand side in assignment").with_label(span)
 }

crates/oxc_semantic/src/checker/mod.rs

@@ -96,11 +96,9 @@ pub fn check<'a>(node: &AstNode<'a>, ctx: &SemanticBuilder<'a>) {
         AstKind::Super(sup) => js::check_super(sup, node, ctx),
 
         AstKind::FormalParameters(params) => {
-            js::check_formal_parameters(params, ctx);
             ts::check_formal_parameters(params, ctx);
         }
         AstKind::ArrayPattern(pat) => {
-            js::check_array_pattern(pat, ctx);
             ts::check_array_pattern(pat, ctx);
         }
 

tasks/coverage/snapshots/estree_typescript.snap

@@ -867,7 +867,7 @@ Expect to Parse: tasks/coverage/typescript/tests/cases/compiler/restParameterNot
 A rest parameter must be last in a parameter list
 Mismatch: tasks/coverage/typescript/tests/cases/compiler/restParameterWithBindingPattern1.ts
 Expect to Parse: tasks/coverage/typescript/tests/cases/compiler/restParameterWithBindingPattern3.ts
-A rest element cannot have a property name.
+A rest element cannot have an initializer.
 tasks/coverage/typescript/tests/cases/compiler/reuseTypeAnnotationImportTypeInGlobalThisTypeArgument.ts
 Unexpected estree file content error: 2 != 4
 
@@ -1304,7 +1304,8 @@ Mismatch: tasks/coverage/typescript/tests/cases/conformance/es6/destructuring/re
 Mismatch: tasks/coverage/typescript/tests/cases/conformance/es6/destructuring/restElementWithAssignmentPattern2.ts
 Mismatch: tasks/coverage/typescript/tests/cases/conformance/es6/destructuring/restElementWithAssignmentPattern3.ts
 Mismatch: tasks/coverage/typescript/tests/cases/conformance/es6/destructuring/restElementWithAssignmentPattern4.ts
-Mismatch: tasks/coverage/typescript/tests/cases/conformance/es6/destructuring/restElementWithInitializer1.ts
+Expect to Parse: tasks/coverage/typescript/tests/cases/conformance/es6/destructuring/restElementWithInitializer1.ts
+A rest element cannot have an initializer.
 Expect to Parse: tasks/coverage/typescript/tests/cases/conformance/es6/destructuring/restElementWithInitializer2.ts
 Cannot assign to this expression
 Mismatch: tasks/coverage/typescript/tests/cases/conformance/es6/destructuring/restPropertyWithBindingPattern.ts
@@ -2257,7 +2258,8 @@ Expect to Parse: tasks/coverage/typescript/tests/cases/conformance/parser/ecmasc
 Unexpected token
 Expect to Parse: tasks/coverage/typescript/tests/cases/conformance/parser/ecmascript5/ParameterLists/parserParameterList1.ts
 A rest parameter must be last in a parameter list
-Mismatch: tasks/coverage/typescript/tests/cases/conformance/parser/ecmascript5/ParameterLists/parserParameterList10.ts
+Expect to Parse: tasks/coverage/typescript/tests/cases/conformance/parser/ecmascript5/ParameterLists/parserParameterList10.ts
+A rest element cannot have an initializer.
 Expect to Parse: tasks/coverage/typescript/tests/cases/conformance/parser/ecmascript5/ParameterLists/parserParameterList11.ts
 A rest parameter cannot be optional
 Expect to Parse: tasks/coverage/typescript/tests/cases/conformance/parser/ecmascript5/ParameterLists/parserParameterList9.ts

tasks/coverage/snapshots/parser_babel.snap

@@ -4373,6 +4373,12 @@ Expect to Parse: tasks/coverage/babel/packages/babel-parser/test/fixtures/typesc
    ·               ────
    ╰────
 
+  × A rest element cannot have an initializer.
+   ╭─[babel/packages/babel-parser/test/fixtures/es2015/uncategorised/278/input.js:1:18]
+ 1 │ function f(a, ...b = 0)
+   ·                  ─────
+   ╰────
+
   × Unexpected token
    ╭─[babel/packages/babel-parser/test/fixtures/es2015/uncategorised/278/input.js:1:24]
  1 │ function f(a, ...b = 0)
@@ -5794,13 +5800,25 @@ Expect to Parse: tasks/coverage/babel/packages/babel-parser/test/fixtures/typesc
    ·      ─────
    ╰────
 
+  × A rest element cannot have an initializer.
+   ╭─[babel/packages/babel-parser/test/fixtures/es2018/object-rest-spread/22/input.js:1:9]
+ 1 │ var {...x = 1} = {}
+   ·         ─────
+   ╰────
+
   × Invalid rest element
    ╭─[babel/packages/babel-parser/test/fixtures/es2018/object-rest-spread/22/input.js:1:9]
  1 │ var {...x = 1} = {}
    ·         ─────
    ╰────
   help: Expected identifier in rest element
 
+  × A rest element cannot have an initializer.
+   ╭─[babel/packages/babel-parser/test/fixtures/es2018/object-rest-spread/23/input.js:1:19]
+ 1 │ function test({...x = 1}) {}
+   ·                   ─────
+   ╰────
+
   × Invalid rest element
    ╭─[babel/packages/babel-parser/test/fixtures/es2018/object-rest-spread/23/input.js:1:19]
  1 │ function test({...x = 1}) {}
@@ -11225,7 +11243,7 @@ Expect to Parse: tasks/coverage/babel/packages/babel-parser/test/fixtures/typesc
    ·               ────
    ╰────
 
-  × A rest parameter cannot have an initializer
+  × A rest element cannot have an initializer.
    ╭─[babel/packages/babel-parser/test/fixtures/esprima/invalid-syntax/migrated_0260/input.js:1:15]
  1 │ function x(...a = 1){}
    ·               ─────