Using dynamic function for computed annotations results in warning

[nazar-pc]

Description

The feature requested in #3299 and implemented in #3358 has minor issue in 2.x, it results in warning:

method `xyz` not defined

Even though it works fine eventually.

Live Demo

http://jsbin.com/feberifezo/1/edit?html,console,output

Steps to Reproduce

1. Define computed property with type Function and another simple property with type String (Number should work as well)
2. Use it in element's template with another element's property as argument
3. Add element to the document with another property as it's attribute

Expected Results

No warning

Actual Results

Warning:

method `xyz` not defined

Browsers Affected

Only tested in these:

• Chromium nightly
• Firefox

Versions

Polymer: 2.0-preview

[dfreedm]

Seems like this line should block printing that warning: https://github.com/Polymer/polymer/blob/master/lib/mixins/property-effects.html#L769

@kevinpschaaf is dynamicFn set later?