Generic types for es6 classes and getters

I am trying to annotate a getter on an es6 class with a generic type, but I can’t seem to get it working. A simplified example of the problem is:

// ==ClosureCompiler==
// @compilation_level ADVANCED_OPTIMIZATIONS
// @output_file_name default.js
// @language_out ES5
// ==/ClosureCompiler==

/** @template T */
class X {
  
  /** @param {T} x */
  constructor(x) {
    this.x = x;
  }

  /** @return {T} */
  get foo() {
    return this.x;
  }
}

Produces:

JSC_TYPE_PARSE_ERROR: Bad type annotation. Unknown type T at line 9 character 15
  /** @return {T} */

which is the annotation on the foo getter (the constructor seems to work fine)

(Checked with https://closure-compiler.appspot.com)

[lauraharker]

This is fixed now

[MatrixFrog]

I think I promised someone I would fix this a while back, and then it turned out to be harder than I thought. I believe the @template annotation on the class gets copied as you’d expect, but the problem is that the getter lives outside of the class in the transpiled output:

/** @constructor @template T */
function X() {}

Object.defineProperties(X.prototype, {
  foo: {
    /** @return {T} */    // <- The compiler doesn't know what you mean by "T" here.
    get: function() { return this.x; }
  }
});

I suspect this will ultimately be fixed by having the typechecker understand ES6 classes (including getters and setters) directly instead of typechecking the output of the 6-to-5 conversion 😦