Unsure how to use prototypes and parameters together

[nblei]

I am unsure how to actually use these features:

/// BinaryReductionProto
///
/// Performs a binary operation on two arguments of type `logic<WIDTH>`
proto module BinaryReductionProto #(
    param WIDTH: u32 = 1,
) (
    i_a: input  logic<WIDTH>,
    i_b: input  logic<WIDTH>,
    o_r: output logic<WIDTH>,
);
/// Performs binary reduction via addition
module add_reduce for BinaryReductionProto #(
    param WIDTH: u32 = 1,
) (
    i_a: input  logic<WIDTH>,
    i_b: input  logic<WIDTH>,
    o_r: output logic<WIDTH>,
) {
    assign o_r = i_a + i_b;
}

I have a binary operator proto module, and an implementation of that prototype which does addition.

module binary_reduction::<M: BinaryReductionProto> #(
    param WIDTH     : u32   = 1                                                     ,
    param COUNT     : u32   = 8                                                     ,
    param SCALAR    : logic = 1                                                     ,
    const INPUT_TYPE: type  = if SCALAR ? logic<WIDTH * COUNT> : logic<WIDTH, COUNT>,
) (
    i_a: input  INPUT_TYPE       ,
    o_r: output logic     <WIDTH>,

) {

    if COUNT == 1 :gen_base_case {
        if SCALAR :gen_base_case_scalar {
            assign o_r = i_a;
        } else :gen_base_case_array {
            assign o_r = i_a[0];
        }
    } else :gen_rec_case {
        const TOP_HALF: u32              = COUNT / 2;
        const BOT_HALF: u32              = COUNT - TOP_HALF;
        var partials: logic<WIDTH> [2];
        inst u_merge: M #(
            WIDTH  ,
        ) (
            i_a: partials[0],
            i_b: partials[1],
            o_r             ,
        );

        if SCALAR :gen_rec_case_scalar {
            const MID_POINT: u32 = BOT_HALF * WIDTH;

            inst u_top: BinaryReduction::<M> #(
                WIDTH : WIDTH   ,
                COUNT : TOP_HALF,
                SCALAR: SCALAR  ,
            ) (
                i_a: i_a[COUNT * WIDTH - 1:MID_POINT],
                o_r: partials[0]                     ,
            );

            inst u_bot: BinaryReduction::<M> #(
                WIDTH : WIDTH   ,
                COUNT : BOT_HALF,
                SCALAR: SCALAR  ,
            ) (
                i_a: i_a[MID_POINT - 1:0],
                o_r: partials[1]         ,
            );
        } else :gen_rec_case_array {
            const MID_POINT: u32 = BOT_HALF;

            inst u_top: BinaryReduction::<M> #(
                WIDTH : WIDTH   ,
                COUNT : TOP_HALF,
                SCALAR: SCALAR  ,
            ) (
                i_a: i_a[COUNT - 1:MID_POINT],
                o_r: partials[0]             ,
            );

            inst u_bot: BinaryReduction::<M> #(
                WIDTH : WIDTH   ,
                COUNT : BOT_HALF,
                SCALAR: SCALAR  ,
            ) (
                i_a: i_a[MID_POINT - 1:0],
                o_r: partials[1]         ,
            );

        }
    }

}

Next, I have a binary reduction module which takes generic binary operator prototype module, as well as some parameters.

And, finally

module adder_tree #(
    param WIDTH: u32 = 1,
    param COUNT: u32 = 8,
) (
    i_a: input  logic<WIDTH, COUNT>,
    o_r: output logic<WIDTH>       ,
) {
    inst u_br: binary_reduction::<add_reduce> #(WIDTH: WIDTH, COUNT: COUNT, SCALAR: 1'b0)(
        i_a: i_a,
        o_r: o_r,
    );
}

An adder tree which is just a wrapper around a binaryh_reduction with the add_reduce prototype implementation. However, this will not build. I have, for example, a Syntax Error: Unexpected token '#' when creating instance u_br.