Weird type warning from Frog

[peter-ahe-google]

I noticed the below warning when building Frog:

leg/scanner/listener.dart:536:24: warning: type "EmptyLink$Token" is not assignable to "Link$Node"
    Link<Node> nodes = const EmptyLink<Node>();
                       ^^^^^^^^^^^^^^^^^^^^^^^

I see the following problems:

1. There should be no warning here. EmptyLink<Node> is a subtype of Link<Node>. Even if the type system was sound.
2. There are no types named EmptyLink$Token or Link$Node in the entire program. This might be as simple as a toString method that is wrong and EmptyLink$Token may mean EmptyLink<Token>, etc.
3. If my interpretation in 2. is correct, it looks like there is a problem with canonicalization of parameterized types. Type arguments should be part of the canonicalization algorithm.

[DartBot]

This comment was originally written by jimhug@google.com

---

interpretation is correct. canonicalization is ignoring type arguments when "possible" but really it should never be ignoring them.

---

Set owner to jimhug@google.com.
Added Started label.

[DartBot]

This comment was originally written by jimhug@google.com

---

http://codereview.chromium.org/8662015/

---

Added Fixed label.