[dfreeman]

One of the pending items from #283 is providing projects using native imports and signatures with a way to describe the type of yielded components, as @glint/environment-ember-loose's ComponentLike currently does. This is a vital piece for describing the signature of components that do things like:

{{yield (hash
  Input=(component "our-special-input" thing=this.defaultThingValue}}
)}}

Now that signature formats have been more or less standardized across the board, we can expose standardized ComponentLike, HelperLike and ModifierLike types from @glint/template itself rather than homing them in an environment-specific location. Subclasses of Component, Helper and Modifier are respectively assignable to their corresponding *Like types, as are the return values from helper() and modifier().

Each of these types is compatible as the first argument of a new WithBoundArgs helper, which will return an equivalent type except for any named args mentioned in the second argument being made optional. Capturing the above template example in a signature:

interface TheSignature {
  Blocks: {
    default: [{
      Input: WithBoundArgs<typeof OurSpecialInput, 'thing'>
    }];
  };
}

The @glint/template package is a types-only package that provides the baseline type declarations that all Glint environments are based on, and as such is something that addons can declare a dependency on without having any (even theoretical) runtime impact on their consumers.