feat(parser): recover from const used as a BindingIdentifier

crates/oxc_parser/src/diagnostics.rs

@@ -282,6 +282,14 @@ pub fn identifier_generator(x0: &str, span1: Span) -> OxcDiagnostic {
         .with_label(span1)
 }
 
+#[cold]
+pub fn unexpected_const(span: Span) -> OxcDiagnostic {
+    OxcDiagnostic::error(
+        "Identifier expected. 'const' is a reserved word that cannot be used here.",
+    )
+    .with_label(span)
+}
+
 #[cold]
 pub fn constructor_generator(span: Span) -> OxcDiagnostic {
     OxcDiagnostic::error("Constructor can't be a generator").with_label(span)

crates/oxc_parser/src/js/expression.rs

@@ -73,7 +73,11 @@ impl<'a> ParserImpl<'a> {
     /// `BindingIdentifier` : Identifier
     pub(crate) fn parse_binding_identifier(&mut self) -> Result<BindingIdentifier<'a>> {
         if !self.cur_kind().is_binding_identifier() {
-            return Err(self.unexpected());
+            if matches!(self.cur_kind(), Kind::Const) {
+                self.error(diagnostics::unexpected_const(self.cur_token().span()));
+            } else {
+                return Err(self.unexpected());
+            }
         }
         let (span, name) = self.parse_identifier_kind(Kind::Ident);
         self.check_identifier(span, &name);

tasks/coverage/snapshots/parser_babel.snap

@@ -2669,13 +2669,20 @@ Expect to Parse: tasks/coverage/babel/packages/babel-parser/test/fixtures/typesc
    ╰────
   help: In non-strict mode code, functions can only be declared at top level, inside a block, or as the body of an if statement
 
-  × Unexpected token
+  × Identifier expected. 'const' is a reserved word that cannot be used here.
    ╭─[babel/packages/babel-parser/test/fixtures/es2015/identifiers/invalid-escape-seq-const/input.js:1:5]
  1 │ var co\u{6e}st = 123;
    ·     ──────────
  2 │ 
    ╰────
 
+  × Keywords cannot contain escape characters
+   ╭─[babel/packages/babel-parser/test/fixtures/es2015/identifiers/invalid-escape-seq-const/input.js:3:1]
+ 2 │ 
+ 3 │ co\u{6e}st x = 2;
+   · ──────────
+   ╰────
+
   × Unexpected token
    ╭─[babel/packages/babel-parser/test/fixtures/es2015/identifiers/invalid-escape-seq-export/input.js:1:5]
  1 │ var expor\u{74} = 123;

tasks/coverage/snapshots/parser_test262.snap

@@ -18317,7 +18317,7 @@ Expect to Parse: tasks/coverage/test262/test/built-ins/String/prototype/split/se
     ·     ─────
     ╰────
 
-  × Unexpected token
+  × Identifier expected. 'const' is a reserved word that cannot be used here.
     ╭─[test262/test/language/future-reserved-words/const.js:21:5]
  20 │ 
  21 │ var const = 1;
@@ -18715,21 +18715,21 @@ Expect to Parse: tasks/coverage/test262/test/built-ins/String/prototype/split/se
     ·     ─────
     ╰────
 
-  × Unexpected token
+  × Identifier expected. 'const' is a reserved word that cannot be used here.
     ╭─[test262/test/language/identifiers/val-const-via-escape-hex.js:17:5]
  16 │ 
  17 │ var co\u{6e}st = 123;
     ·     ──────────
     ╰────
 
-  × Unexpected token
+  × Identifier expected. 'const' is a reserved word that cannot be used here.
     ╭─[test262/test/language/identifiers/val-const-via-escape-hex4.js:17:5]
  16 │ 
  17 │ var co\u006est = 123;
     ·     ──────────
     ╰────
 
-  × Unexpected token
+  × Identifier expected. 'const' is a reserved word that cannot be used here.
     ╭─[test262/test/language/identifiers/val-const.js:16:5]
  15 │ 
  16 │ var const = 123;