fix corner case in `reduce_vars` (#4563)

fixes #4562

1 files changed, 19 insertions, 11 deletions

diff --git a/test/reduce.js b/test/reduce.js
index 3f24b7b4..c478da5f 100644
--- a/test/reduce.js
+++ b/test/reduce.js
@@ -104,15 +104,14 @@ module.exports = function reduce_test(testcase, minify_options, reduce_options)
 
             // quick ignores
             if (node instanceof U.AST_Accessor) return;
-            if (node instanceof U.AST_Destructured) return;
             if (node instanceof U.AST_Directive) return;
             if (!in_list && node instanceof U.AST_EmptyStatement) return;
             if (node instanceof U.AST_Label) return;
             if (node instanceof U.AST_LabelRef) return;
-            if (!in_list && node instanceof U.AST_SymbolDeclaration) return;
             if (node instanceof U.AST_Toplevel) return;
             var parent = tt.parent();
             if (node instanceof U.AST_SymbolFunarg && parent instanceof U.AST_Accessor) return;
+            if (!in_list && parent.rest !== node && node instanceof U.AST_SymbolDeclaration) return;
 
             // ensure that the _permute prop is a number.
             // can not use `node.start._permute |= 0;` as it will erase fractional part.
@@ -124,6 +123,7 @@ module.exports = function reduce_test(testcase, minify_options, reduce_options)
 
             // ignore lvalues
             if (parent instanceof U.AST_Assign && parent.left === node) return;
+            if (parent instanceof U.AST_DefaultValue && parent.name === node) return;
             if (parent instanceof U.AST_DestructuredKeyVal && parent.value === node) return;
             if (parent instanceof U.AST_Unary && parent.expression === node) switch (parent.operator) {
               case "++":
@@ -229,6 +229,23 @@ module.exports = function reduce_test(testcase, minify_options, reduce_options)
                 CHANGED = true;
                 return node.name;
             }
+            else if (node instanceof U.AST_DestructuredArray) {
+                var expr = node.elements[0];
+                if (expr && !(expr instanceof U.AST_Hole)) {
+                    node.start._permute++;
+                    CHANGED = true;
+                    return expr;
+                }
+            }
+            else if (node instanceof U.AST_DestructuredObject) {
+                // first property's value
+                var expr = node.properties[0];
+                if (expr) {
+                    node.start._permute++;
+                    CHANGED = true;
+                    return expr.value;
+                }
+            }
             else if (node instanceof U.AST_Defun) {
                 switch (((node.start._permute += step) * steps | 0) % 2) {
                   case 0:
@@ -443,15 +460,6 @@ module.exports = function reduce_test(testcase, minify_options, reduce_options)
                     CHANGED = true;
                     return List.skip;
                 }
-
-                // skip element/property from (destructured) array/object
-                if (parent instanceof U.AST_Array
-                    || parent instanceof U.AST_Destructured
-                    || parent instanceof U.AST_Object) {
-                    node.start._permute++;
-                    CHANGED = true;
-                    return List.skip;
-                }
             } else if (parent.rest === node) {
                 node.start._permute++;
                 CHANGED = true;