fix corner case in `unused` (#4557)

fixes #4556

1 files changed, 3 insertions, 0 deletions

diff --git a/lib/compress.js b/lib/compress.js
index fadd7415..01ec7e60 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -5766,6 +5766,9 @@ merge(Compressor.prototype, {
                             var write_only = def.value.write_only;
                             var value = def.value.drop_side_effect_free(compressor);
                             if (def.value !== value) {
+                                sym.references.forEach(function(node) {
+                                    if (node.fixed === sym.fixed) node.fixed = def.value;
+                                });
                                 def.value = null;
                                 if (value) {
                                     AST_Node.warn("Side effects in last use of variable {name} [{file}:{line},{col}]", template(def.name));