Update current scope when visiting namespace elements

Fixes #13098

src/compiler/transformers/ts.ts

@@ -2731,7 +2731,7 @@ namespace ts {
             let blockLocation: TextRange;
             const body = node.body;
             if (body.kind === SyntaxKind.ModuleBlock) {
-                addRange(statements, visitNodes((<ModuleBlock>body).statements, namespaceElementVisitor, isStatement));
+                saveStateAndInvoke(body, body => addRange(statements, visitNodes((<ModuleBlock>body).statements, namespaceElementVisitor, isStatement)));
                 statementsLocation = (<ModuleBlock>body).statements;
                 blockLocation = body;
             }

tests/baselines/reference/metadataOfClassFromModule.js

@@ -38,7 +38,7 @@ var MyModule;
     }());
     __decorate([
         inject,
-        __metadata("design:type", Object)
+        __metadata("design:type", Leg)
     ], Person.prototype, "leftLeg", void 0);
     MyModule.Person = Person;
 })(MyModule || (MyModule = {}));