fix corner case in `collapse_vars` (#3334)

fixes #3274

1 files changed, 12 insertions, 6 deletions

diff --git a/lib/compress.js b/lib/compress.js
index 2ccf330d..04adb8b2 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -1585,13 +1585,19 @@ merge(Compressor.prototype, {
                 var found = false;
                 return statements[stat_index].transform(new TreeTransformer(function(node, descend, in_list) {
                     if (found) return node;
-                    if (node === expr || node.body === expr) {
+                    if (node !== expr && node.body !== expr) return;
+                    if (node instanceof AST_VarDef) {
                         found = true;
-                        if (node instanceof AST_VarDef) {
-                            node.value = null;
-                            return node;
-                        }
-                        return in_list ? MAP.skip : null;
+                        node.value = null;
+                        return node;
+                    }
+                    if (in_list) {
+                        found = true;
+                        return MAP.skip;
+                    }
+                    if (!this.parent()) {
+                        found = true;
+                        return null;
                     }
                 }, function(node) {
                     if (node instanceof AST_Sequence) switch (node.expressions.length) {