fix corner case in `inline` (#4389)

fixes #4388

2 files changed, 23 insertions, 2 deletions

diff --git a/lib/compress.js b/lib/compress.js
index ffc19b25..2c50cb37 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -8026,8 +8026,14 @@ merge(Compressor.prototype, {
                 }));
                 if (found) return false;
             }
-            var safe_to_inject = (!(scope instanceof AST_Toplevel) || compressor.toplevel.vars)
-                && (exp !== fn || fn.parent_scope.resolve() === scope);
+            var safe_to_inject = exp !== fn || fn.parent_scope.resolve() === scope;
+            if (scope instanceof AST_Toplevel) {
+                if (compressor.toplevel.vars) {
+                    defined["arguments"] = true;
+                } else {
+                    safe_to_inject = false;
+                }
+            }
             var inline = compressor.option("inline");
             var used = Object.create(defined);
             if (!can_inject_args(defined, used, inline >= 2 && safe_to_inject)) return false;
diff --git a/test/compress/arrows.js b/test/compress/arrows.js
index 02c4acde..eded9134 100644
--- a/test/compress/arrows.js
+++ b/test/compress/arrows.js
@@ -336,3 +336,18 @@ trim_body: {
     expect_stdout: "PASS undefined"
     node_version: ">=4"
 }
+
+issue_4388: {
+    options = {
+        inline: true,
+        toplevel: true,
+    }
+    input: {
+        (arguments => console.log(arguments && arguments))();
+    }
+    expect: {
+        (arguments => console.log(arguments && arguments))();
+    }
+    expect_stdout: "undefined"
+    node_version: ">=4"
+}