fix corner case in pure_getters (#4441)

fixes #4440

lib/compress.js

@@ -3237,7 +3237,8 @@ merge(Compressor.prototype, {
             if (!is_strict(compressor)) return false;
             if (is_undeclared_ref(this) && this.is_declared(compressor)) return false;
             if (this.is_immutable()) return false;
-            if (is_arguments(this.definition())) return false;
+            var def = this.definition();
+            if (is_arguments(def)) return def.scope.uses_arguments > 2;
             var fixed = this.fixed_value();
             if (!fixed) return true;
             this._dot_throw = return_true;

test/compress/pure_getters.js

@@ -1208,3 +1208,32 @@ issue_3427: {
     expect: {}
     expect_stdout: true
 }
+
+issue_4440: {
+    options = {
+        pure_getters: "strict",
+        side_effects: true,
+        unused: true,
+    }
+    input: {
+        try {
+            (function() {
+                arguments = null;
+                console.log(arguments.p = "FAIL");
+            })();
+        } catch (e) {
+            console.log("PASS");
+        }
+    }
+    expect: {
+        try {
+            (function() {
+                arguments = null;
+                console.log(arguments.p = "FAIL");
+            })();
+        } catch (e) {
+            console.log("PASS");
+        }
+    }
+    expect_stdout: "PASS"
+}