go spec: Base comparison compatibility on assignment compatibility.
Specifically:
- Simplified definition of comparison compatibility and folded into
section on comparison operators since it's only used there.
This is a small language change/cleanup. As a consequence:
- An interface value may now be compared against a non-interface value.
- Channels with opposite directions cannot be compared directly anymore
(per discussion with rsc).
R=rsc, r, iant, ken2
CC=golang-dev
https://golang.org/cl/
1462041