# Type.Index

The Index function performs a indexed access lookup on a type.

## Example

Example usage is shown below.

    const T = Type.Object({
      x: Type.Literal(1),
      y: Type.Literal(2),
      z: Type.Literal(3)
    })

    const S = Type.Index(T, Type.Union([                // const S: TUnion<[
      Type.Literal('x'),                                //   TLiteral<1>,
      Type.Literal('y')                                 //   TLiteral<2>
    ]))                                                 // ]>