Avoid parens around spread arguments

Reviewed By: tmikov

Differential Revision: D33072069

fbshipit-source-id: 2dfcd20c7f82c4f717a6c5b23a4efc6abc34159c

Author: avp

unsupported/juno/crates/juno/src/gen_js.rs

@@ -919,7 +919,12 @@ impl<W: Write> GenJS<W> {
                     if i > 0 {
                         self.comma();
                     }
-                    self.print_comma_expression(ctx, *arg, Path::new(node, NodeField::arguments));
+                    self.print_child(
+                        ctx,
+                        Some(*arg),
+                        Path::new(node, NodeField::arguments),
+                        ChildPos::Anywhere,
+                    );
                 }
                 out!(self, ")");
             }
@@ -948,7 +953,12 @@ impl<W: Write> GenJS<W> {
                     if i > 0 {
                         self.comma();
                     }
-                    self.print_comma_expression(ctx, *arg, Path::new(node, NodeField::arguments));
+                    self.print_child(
+                        ctx,
+                        Some(*arg),
+                        Path::new(node, NodeField::arguments),
+                        ChildPos::Anywhere,
+                    );
                 }
                 out!(self, ")");
             }
@@ -3556,6 +3566,13 @@ impl<W: Write> GenJS<W> {
             // Nullish coalescing always requires parens when mixed with any
             // other logical operations.
             return NeedParens::Yes;
+        } else if matches!(
+            path.parent,
+            Node::CallExpression(_) | Node::OptionalCallExpression(_)
+        ) && matches!(child, Node::SpreadElement(_))
+        {
+            // It's illegal to place parens around spread arguments.
+            return NeedParens::No;
         }
 
         let (child_prec, _child_assoc) = self.get_precedence(child);

unsupported/juno/crates/juno/tests/gen_js/mod.rs

@@ -199,8 +199,10 @@ fn test_calls() {
     test_roundtrip("f();");
     test_roundtrip("f(1);");
     test_roundtrip("f(1, 2);");
+    test_roundtrip("f(1, (2,3), 4);");
     test_roundtrip("(f?.(1, 2))(3);");
     test_roundtrip("f?.(1, 2)?.(3)(5);");
+    test_roundtrip("f(...x)");
     test_roundtrip("new f();");
     test_roundtrip("new f(1);");
     test_roundtrip("new(a.b);");