5.3.1
- Revised handling of `Any` exported to untyped code
- Added `cast`
- Correctly compute variance of polymorphic type application
5.3
- Keyword and optional arguments
- Faster startup
- Random testing of the numeric tower
5.2.1
- Inference of functions with keyword arguments
- `typecheck-fail' for explicit creation of type errors
- Extensive documentation of typed numeric tower
5.2
- Performance work: delayed environment evaluation
- Support `racket'-style optional arguments
- Changes to support new-style keyword argument expansion
