Context type parameter disallows subtyping

[equaa]

it's impossible as-is to make a helper function that requires only one variable in the Env, and then pass to it one with several (i.e. because the route using the function has additional middleware).

import { Context } from 'hono';

type FooEnv = {
        Variables: {
                foo: string;
        }
};

type BarEnv = {
        Variables: {
                boo: string;
        }
};

async function util(c: Context<FooEnv>) {
        return
}

var c: Context<FooEnv & BarEnv>;

util(c);

test.ts:21:6 - error TS2345: Argument of type 'Context<FooEnv & BarEnv, any, {}>' is not assignable to parameter of type 'Context<FooEnv, any, {}>'.
  Type 'FooEnv' is not assignable to type 'FooEnv & BarEnv'.
    Type 'FooEnv' is not assignable to type 'BarEnv'.
      Types of property 'Variables' are incompatible.
        Property 'boo' is missing in type '{ foo: string; }' but required in type '{ boo: string; }'.

I believe the problem is the way set's arguments are contravariant; it is a little more apparent when you imagine two environments which provide the same variable like type FooVars = { foo: A | B }; type BarVars = { foo: B | C }. (I'm not sure when this case would happen, however.)

Is there a recommended way to provide helper functions that are capable of receiving subtyped Contexts?