fix corner case in `spread` (#4370)

1 files changed, 5 insertions, 4 deletions

diff --git a/lib/compress.js b/lib/compress.js
index cc601bfb..96589686 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -10051,13 +10051,14 @@ merge(Compressor.prototype, {
             found = true;
             var exp = prop.expression;
             if (compressor.option("spread") && exp instanceof AST_Object && all(exp.properties, function(prop) {
-                return !(prop instanceof AST_ObjectGetter
-                    || prop instanceof AST_ObjectSetter && prop.key instanceof AST_Node
-                    || prop instanceof AST_Spread);
+                return !(prop instanceof AST_ObjectGetter || prop instanceof AST_Spread);
             })) {
                 changed = true;
                 exp.properties.forEach(function(prop) {
-                    if (prop instanceof AST_ObjectKeyVal) process(prop);
+                    process(prop instanceof AST_ObjectSetter ? make_node(AST_ObjectKeyVal, prop, {
+                        key: prop.key,
+                        value: make_node(AST_Undefined, prop).optimize(compressor)
+                    }) : prop);
                 });
             } else {
                 generated = true;