[kernel] Incomplete global type propagation.

To make this more digestible, a lot of things are intentionally left
out from the implementation:
 - Some AST nodes, like super calls and await
 - Handling of externals
 - Avoidance of redundant variables in the constraint system

The solver is currently field-based, which is also something I plan to
change.

Suggested reading order:
- constraints.dart
- solver.dart
- canonicalizer.dart
- builder.dart
- visualizer.dart

R=kasperl@google.com

Review URL: https://chromereviews.googleplex.com/442937013 .
7 files changed
tree: 415ca8b3e88574cd53f6955f4927015473728419
  1. pkg/