Tree-shaking

Classes and/or methods in classes can be marked with @devsWhenUsed JSDoc attribute. This will cause them to be omitted from compilation unless they are used. In such case, care needs to be taken when using index operator (obj[some_expression]) or accessing properties through any type. You can use ds.keep() function to make sure methods are included.

/**
 * Foooooo!
 * 
 * @devsWhenUsed
 */
class Foo {
    bar() {}
}
function callBar(v: any) {
    v["bar"]()
}
callBar(new Foo())

// can be called anywhere from the reachable code
ds.keep(Foo.prototype.bar)

The @devsWhenUsed attribute is implicit when methods are defined through prototype assignments.

We may improve compiler warnings about such cases in future.

See discussion.