Using Service Properties in Service Functions

import { Context, Effect } from 'effect';

interface MathService {
  a: number;
  add: (b: number) => Effect.Effect<number>;
}

export class Math extends Context.Tag('Math')<Math, MathService>() {}

export function add(b: number) {
  return Effect.gen(function* () {
    const { a } = yield* Math; //  I know that this will never work

    return a + b;
  });
}

const program = Effect.gen(function* () {
  const { add } = yield* Math;

  return add(3);
});

Effect.provideService(program, Math, { a: 2, add });