Explore higher level macros about inkwell HOT 3 OPEN

Working with heterogeneous collections is a pain in rust.. We could also provide a macro which simplifies the process for the user. (We may even want this earlier than 0.3.0)

For example,

let values = mixed_value_array!(BasicValue, [
    float_value,
    int_value,
    ...
]);

If we do end up adding this macro, I'd strongly consider switching the current homogeneous function params from say, &[&BasicValue] to &[BasicValueEnum] since the former generally requires an extra heap allocation (unless you happen to have a fixed size of values on the stack, which probably isn't realistic) for the extra trait indirection which could be avoided.

Then, this macro could expand to something like let values: Vec<BasicValueEnum> = array.iter().map(|val| val.into()).collect(). Might need associated type to derive BasicValueEnum from BasicValue, though.

from inkwell.

The example function! macro you showed above would require the power brought by proc_macro, but it can be achieved similarly using a Lisp-like syntax (like clap.rs) with the macro_rules system.

Here's an example of doing dynamic code generation using this syntax: primitives.rs (note: it's part of a legacy compiler I wrote last year, the code is ugly in some places). The macro itself is defined here.

from inkwell.

Proc macros are probably fine; I don't expect to get to this issue before Macros 2.0 lands in stable(it seems pretty close: rust-lang/rust#38356), but who knows.

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