Consider struct syntax instead of assignment syntax.

[kitlith]

Currently:

use derive_more::From;
use typemap_core::typemap;

#[derive(From)]
struct ContextA(u8);
#[derive(From)]
struct ContextB(u16);

typemap!(ContextA = 0u8, ContextB = 10u16, ..typemap!(/* whatever */));

Consider:

use derive_more::From;
use typemap_core::typemap;

#[derive(From)]
struct ContextA(u8);
#[derive(From)]
struct ContextB(u16);

typemap! { ContextA: 0u8, ContextB: 10u16, ..typemap! {/* whatever */} };