issue 2316 mangle and reserved

lib/scope.js

@@ -549,6 +549,9 @@ AST_Toplevel.DEFMETHOD("mangle_names", function(options){
         var mangle_with_block_scope =
             (!options.ie8 && node instanceof AST_SymbolCatch) ||
             node instanceof AST_SymbolBlockDeclaration;
+        if (options.reserved.indexOf(node.name) >= 0) {
+            mangle_with_block_scope = false;
+        }
         if (mangle_with_block_scope) {
             to_mangle.push(node.definition());
             return;

test/compress/harmony.js

@@ -804,3 +804,21 @@ object_spread_of_sequence: {
         console.log({ ...o || o });
     }
 }
+
+// issue 2316
+class_name_can_be_preserved_with_reserved: {
+    mangle = {
+        reserved: ['Foo']
+    }
+    input: {
+        function x() {
+            class Foo {};
+            Foo.bar;
+            class Bar {};
+            Bar.foo;
+        }
+    }
+    expect: {
+        function x(){class Foo{}Foo.bar;class o{}o.foo}
+    }
+}