Overrided interface properties does not inherit type information

[liolick]

I have followed code:

/**
 * @interface
 */
var Itf = function(){};

/** @type {boolean} */
Itf.prototype.prop;

/**
 * @constructor
 * @implements  {Itf}
 */
var Cls = function(){}

/** @override */
Cls.prototype.prop;

Compiling it with "--compilation_level ADVANCED_OPTIMIZATIONS --jscomp_warning reportUnknownTypes --warning_level VERBOSE" I get a warning:

test.js:17: WARNING - could not determine the type of this expression
Cls.prototype.prop;
^

If I add @type {boolean} to Cls.prototype.prop all is fine. It seems compiler is unable to infer type from Itf.prototype.prop.

Initializing overrided property resolves a problem, but in my case it should be uninitialized (it's type actually {(boolean|undefined)}).

See discussion: https://groups.google.com/forum/#!topic/closure-compiler-discuss/gdKj25kAWeg

[dimvar]

Thanks for the report. We will fix this in the new type checker.

[dimvar]

Btw, if you want the type to be (boolean|undefined), you should declare that type on the interface instead of just boolean.

[liolick]

Thanks, Dimitris! Yes, it's (boolean|undefined) on interface, I just shortened an example here.

Are there any plans on new type checker? Can we try it on latest (v20140407) compiler via Java API? What is a suitable workaround for a while?

[dimvar]

You can try it by setting this option https://github.com/google/closure-compiler/blob/4b3d5e471b410e552ca17d7bc39dcb5d4cdf21f7/src/com/google/javascript/jscomp/CompilerOptions.java#L1760

But it's still experimental and not stable. We hope to land it in the next 2-3 months.