Theme

import type { Theme } from '@dr.pogodin/react-themes';

type Theme<KeyT extends string>
  = string extends KeyT ? never : ThemeI & Partial<Record<KeyT, string>>;

Theme generic type helps to define custom theme types. You call it with a union of string literals representing valid keys for your theme; e.g. if your theme has two valid keys, "container" and "content" (corresponding to .container and .content class names in SCSS code) you should define your theme type as

type MyTheme = Theme<'container' | 'content'>;

// the result will be equivalent to:

type MyTheme = {
  // These fields are provided by the base "ThemeI" interface:
  ad: string;
  hoc: string;
  context: string;

  // These come from the string literal union you provided:
  container?: string;
  content?: string;
};

As mentioned in the example, ThemeI interface includes into the result obligatory key names ad, hoc, context. Also Theme generic has a safeguard turning the result into never if given argument, by mistake, evaluates the general string type.