Updated arrow_function to make it more clear that the (expr) case sho…

…uld have already been handled

boa/src/syntax/parser/expression/assignment/arrow_function.rs

@@ -88,16 +88,9 @@ where
 
         cursor.peek_expect_no_lineterminator(0)?;
 
-        if cursor
-            .next_if(TokenKind::Punctuator(Punctuator::Arrow))?
-            .is_some()
-        {
-            let body = ConciseBody::new(self.allow_in).parse(cursor)?;
-            Ok(ArrowFunctionDecl::new(params, body))
-        } else {
-            // This might actually be an expresison.
-            unimplemented!("Todo handle this might be an expression");
-        }
+        cursor.expect(TokenKind::Punctuator(Punctuator::Arrow), "arrow function")?;
+        let body = ConciseBody::new(self.allow_in).parse(cursor)?;
+        Ok(ArrowFunctionDecl::new(params, body))
     }
 }
 

boa/src/syntax/parser/tests.rs

@@ -3,8 +3,9 @@
 use super::Parser;
 use crate::syntax::ast::{
     node::{
-        field::GetConstField, Assign, BinOp, Call, FunctionDecl, Identifier, LetDecl, LetDeclList,
-        New, Node, Return, StatementList, UnaryOp, VarDecl, VarDeclList,
+        field::GetConstField, ArrowFunctionDecl, Assign, BinOp, Call, FormalParameter,
+        FunctionDecl, Identifier, LetDecl, LetDeclList, New, Node, Return, StatementList, UnaryOp,
+        VarDecl, VarDeclList,
     },
     op::{self, CompOp, LogOp, NumOp},
     Const,
@@ -288,3 +289,23 @@ fn increment_in_comma_op() {
         .into()],
     );
 }
+
+#[test]
+fn spread_in_arrow_function() {
+    let s = r#"
+    (...b) => {
+        b
+    }
+    "#;
+
+    check_parser(
+        s,
+        vec![
+            ArrowFunctionDecl::new::<Box<[FormalParameter]>, StatementList>(
+                Box::new([FormalParameter::new("b", None, true)]),
+                vec![Identifier::from("b").into()].into(),
+            )
+            .into(),
+        ],
+    );
+}