Fix: destructuring assignment with an empty array in object (#5000)

* destructuring assignment with empty array in object

* improvements

lib/coffeescript/nodes.js

@@ -2179,7 +2179,7 @@
       }
 
       isAssignable() {
-        var j, len1, message, prop, ref1;
+        var j, len1, message, prop, ref1, ref2;
         ref1 = this.properties;
         for (j = 0, len1 = ref1.length; j < len1; j++) {
           prop = ref1[j];
@@ -2188,7 +2188,7 @@
           if (message) {
             prop.error(message);
           }
-          if (prop instanceof Assign && prop.context === 'object') {
+          if (prop instanceof Assign && prop.context === 'object' && !(((ref2 = prop.value) != null ? ref2.base : void 0) instanceof Arr)) {
             prop = prop.value;
           }
           if (!prop.isAssignable()) {

src/nodes.coffee

@@ -1477,7 +1477,9 @@ exports.Obj = class Obj extends Base
       message = isUnassignable prop.unwrapAll().value
       prop.error message if message
 
-      prop = prop.value if prop instanceof Assign and prop.context is 'object'
+      prop = prop.value if prop instanceof Assign and
+        prop.context is 'object' and
+        prop.value?.base not instanceof Arr
       return no unless prop.isAssignable()
     yes
 

test/assignment.coffee

@@ -986,6 +986,23 @@ test "#4878: Compile error when using destructuring with a splat or expansion in
 
   arrayEq bar(arr), ['a', ['b', 'c', 'd']]
 
+test "destructuring assignment with an empty array in object", ->
+  obj =
+    a1: [1, 2]
+    b1: 3
+
+  {a1:[], b1} = obj
+  eq 'undefined', typeof a1
+  eq b1, 3
+
+  obj =
+    a2:
+      b2: [1, 2]
+    c2: 3
+
+  {a2: {b2:[]}, c2} = obj
+  eq 'undefined', typeof b2
+  eq c2, 3
 
 test "#5004: array destructuring with accessors", ->
   obj =