Luke Champine

I want a language where I can "zoom in" on any expression and provide a custom implementation using a lower-level language (and zoom in on expressions in that language, and so on, all the way down to asm). Practical? Perhaps not. But it sounds super fun.

Thinking about this more: "zoom in" would actually mean running the compiler on some highlighted section of code, expanding it into the lower-level code that the compiler would normally generate (but wrapped in an "asm" block, or equivalent)

An inescapable downside of such a language would be that it would severely limit the compiler's ability to do whole-program optimization. E.g. you might think you're helping by writing inline asm, but actually the compiler could have proven that that block was unreachable anyway.

So it's certainly possible that such a language would typically result in slower programs. Compilers work best when given full reign with total context, and this language deprives them of that.