> Crystal is the closest I've seen to match that
And it's 20 times faster than MRI Ruby JIT 3.0, see http://software.rochus-keller.ch/are-we-fast-yet_crystal_rub.... It's a pity Ruby typing went in another direction.
> The trade off for that powerful type inference is a slow compiler.
When run in the default (i.e. no release, debug) mode, build time is ok, especially for rebuilds when only one file has changed which is less than a second. Release builds are slow (see my PDF).
The trade off for that powerful type inference is a slow compiler.