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The problem AIUI is that "const generic expressions" in full generality are as powerful as dependent types. It's not clear to me that the Rust folks will want to open that particular can of worms.

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galangalalgol 2 hours ago | parent [-]

I thought dependent types were types that depended on a value? What they are proposing are types that depend on types or compile time constants.

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zozbot234 an hour ago | parent [-]

The problem is combining the "const generic" and "expression" part. If your "compile time constants" can actually be complex expressions, you arguably end up with the same kind of generality as dependent types.

This is true even for expressions that are only evaluated in a compile-time context, since dependently-typed languages do "everything" at compile time anyway, they don't have a phase distinction where you can talk about "runtime" being separate.

	▲	galangalalgol an hour ago \| parent [-]
		Ah, yeah! I get it now. So c++ is a dependently typed language. That is hilarious. I want lisp syntax in c++29. That said, too many features are blocked on const generic expressions, so I think they are going to have to bite that off. There is already talk about migrating proceduralacros to be something more like normal rust, this moght fit in with that.