fix corner case in `collapse_vars` (#3521)

fixes #3520

1 files changed, 3 insertions, 3 deletions

diff --git a/lib/compress.js b/lib/compress.js
index 7202219a..c8eb3487 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -1128,6 +1128,8 @@ merge(Compressor.prototype, {
                 if (!stop_if_hit && in_conditional(node, parent)) {
                     stop_if_hit = parent;
                 }
+                // Skip transient nodes caused by single-use variable replacement
+                if (node.single_use && parent instanceof AST_VarDef && parent.value === node) return node;
                 // Replace variable with assignment when found
                 var hit_rhs;
                 if (can_replace
@@ -3737,9 +3739,7 @@ merge(Compressor.prototype, {
                         def.value = null;
                         head.push(def);
                     } else {
-                        var value = def.value
-                            && !def.value.single_use
-                            && def.value.drop_side_effect_free(compressor);
+                        var value = def.value && def.value.drop_side_effect_free(compressor);
                         if (value) {
                             AST_Node.warn("Side effects in initialization of unused variable {name} [{file}:{line},{col}]", template(def.name));
                             side_effects.push(value);