fix mangle on export (#2133)

- `export default ...`
- `export` with `AST_Destructuring`

fixes #2129

lib/scope.js

@@ -234,8 +234,14 @@ AST_Toplevel.DEFMETHOD("figure_out_scope", function(options){
         }
 
         function mark_export(def, level) {
+            if (in_destructuring) {
+                var i = 0;
+                do {
+                    level++;
+                } while (tw.parent(i++) !== in_destructuring);
+            }
             var node = tw.parent(level);
-            def.export = node instanceof AST_Export && !node.is_default;
+            def.export = node instanceof AST_Export;
         }
     });
     self.walk(tw);

test/compress/export.js

@@ -95,3 +95,15 @@ issue_2131: {
         };
     }
 }
+
+issue_2129: {
+    mangle = {
+        toplevel: true,
+    }
+    input: {
+        export const { keys } = Object;
+    }
+    expect: {
+        export const { keys } = Object;
+    }
+}

test/compress/issue-2001.js

@@ -171,7 +171,7 @@ export_mangle_2: {
             return one - two;
         };
     }
-    expect_exact: "export default function n(n,r){return n-r};"
+    expect_exact: "export default function foo(n,o){return n-o};"
 }
 
 export_mangle_3: {
@@ -207,7 +207,7 @@ export_mangle_4: {
             }
         };
     }
-    expect_exact: "export default class n{go(n,r){return n-r+n}};"
+    expect_exact: "export default class C{go(n,r){return n-r+n}};"
 }
 
 export_mangle_5: {