fix corner cases in `ie8` (#3485)

fixes #3484

1 files changed, 13 insertions, 2 deletions

diff --git a/lib/compress.js b/lib/compress.js
index be9e8dc8..c903d9af 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -4167,6 +4167,15 @@ merge(Compressor.prototype, {
         }
     });
 
+    function safe_to_drop(fn, compressor) {
+        if (!fn.name || !compressor.option("ie8")) return true;
+        var def = fn.name.definition();
+        if (compressor.exposed(def)) return false;
+        return all(def.references, function(sym) {
+            return !(sym instanceof AST_SymbolRef);
+        });
+    }
+
     // drop_side_effect_free()
     // remove side-effect-free parts which only affects return value
     (function(def) {
@@ -4284,7 +4293,7 @@ merge(Compressor.prototype, {
             return expr.drop_side_effect_free(compressor, first_in_statement);
         });
         def(AST_Function, function(compressor) {
-            return this.name && compressor.option("ie8") ? this : null;
+            return safe_to_drop(this, compressor) ? null : this;
         });
         def(AST_Object, function(compressor, first_in_statement) {
             var values = trim(this.properties, compressor, first_in_statement);
@@ -5170,7 +5179,9 @@ merge(Compressor.prototype, {
                 fn._squeezed = true;
                 return make_sequence(self, flatten_fn()).optimize(compressor);
             }
-            if (compressor.option("side_effects") && all(fn.body, is_empty)) {
+            if (compressor.option("side_effects")
+                && all(fn.body, is_empty)
+                && (fn !== exp || safe_to_drop(fn, compressor))) {
                 var args = self.args.concat(make_node(AST_Undefined, self));
                 return make_sequence(self, args).optimize(compressor);
             }