undefined namespace property will compile to "error" code since typescript v2.9.1

[linxiaowu66]

Hi guys,
A "error" will be happened when there is have a undefined namespace property, for example, I have such a namespace definition, but lack of some property:

export namespace com {
     export namespace alibaba {
         export namespace constant{
             export interface Constant{}
         }
     } 
}

above example I am forgetting to define a namespace test and the interface demo.

Then I use the v2.9.1 to compile this segment code:

function A(a: com.alibaba.test.demo) {}

Ts will generate the "error" code,

var _a, _b, _c, _d, _e, _f, _g, _h, _j, _k, _l;
function A([typeof (_e = ((_c = ((_d = (typeof com !== "undefined" && com).alibaba) && _d).test) && _c).demo)) === "function" && _e || Object)

the above code can not run.

I test other versions, only the version which > 2.9.0 will compile to this style.

< 2.9.1, eg, 2.9.0, will compile to :

function A(Object)

Any guys who know this compile rule is based on which feature, I read the changeLog but can not find any change which is related to this.

Thanks in advance.

[DanielRosenwasser]

It doesn't seem like you're giving us something we can compile that has the same issue; for example, running in our code playground doesn't seem to exhibit the problem you're running into.

What compiler options are you running, and do you have something closer to the original code you wrote?

[linxiaowu66]

@DanielRosenwasser

tsconfig.json as fowllowing:

{
  "compilerOptions": {
    "target": "es6",
    "lib": ["es6"],
    "typeRoots": ["./types", "node_modules/@types"],
    "outDir": "./dist",
    "sourceMap": true,
    "module": "commonjs",
    "moduleResolution": "node",
    "isolatedModules": false,
    "experimentalDecorators": true,
    "emitDecoratorMetadata": true,
    "noImplicitAny": true,
    "preserveConstEnums": true,
    "suppressImplicitAnyIndexErrors": true,
    "allowJs": true,
    "baseUrl": ".",
    "paths": {
      "ali-oss": ["./types/ali-oss.d.ts"]
    }
  },
  "include": ["lib"]
}

[linxiaowu66]

@DanielRosenwasser
original code is more complex, the main problem is why the ts will compile a value which type is not defined to such this format: typeof (_e = ((_c = ((_d = (typeof com !== "undefined" && com).alibaba) && _d).test) && _c).demo)) === "function" && _e

How can i switch off this feature if the function is feature

[linxiaowu66]

@DanielRosenwasser

I create a repo for this problem, https://github.com/linxiaowu66/typescript-issue-25391

In the dist/index.js, you can find the code I mentioned above.

Thanks a lot