FnProtoOne

    pub const FnProtoOne = struct {
        /// Populated if there is exactly 1 parameter. Otherwise there are 0 parameters.
        param: OptionalIndex,
        /// Populated if align(A) is present.
        align_expr: OptionalIndex,
        /// Populated if addrspace(A) is present.
        addrspace_expr: OptionalIndex,
        /// Populated if linksection(A) is present.
        section_expr: OptionalIndex,
        /// Populated if callconv(A) is present.
        callconv_expr: OptionalIndex,
    }