Library defined optimizations

[Suminda Dharmasena]

Can you introduce term rewriting system to do user defined optimisations and reduction. Actually once introduced the compiler specific optimisation can be use the same framework also. Languages like Nim has this http://nim-lang.org/docs/tut2.html#templates and used for much advantage in projects like: https://github.com/unicredit/linear-algebra

[Dmitry Petrashko]

We have already plans here.
For simple declarative rule that can be context dependent and work across libraries see example here: https://github.com/dotty-linker/dotty
For complicated rules with full meta-programing we will have scala.meta: http://scalameta.org/

[Suminda Dharmasena]

Looks great.

[Suminda Dharmasena]

Can you add ability to have conditional / context based rewrites. Say rewrite only if x is annotated. Also say y is annotated and of type Y I want to change the type of y to generate type Y' and replace the type of y with Y'.