Underlying schema language parsed from arktype syntax.

UNDER DEVELOPMENT

The parts of ArkType's type system that exist in TS (i.e. not runtime-only constraints like bounds, divisors, custom predicates, morphs etc.) are structured like this:

• Union: a set of intersections
• Intersection: a set of a basis and constraints
• Basis: this is the base type to which refinements like props are applied. It is one of three things, getting narrower as you move down the list:
  • Domain: "string" | "number" | "bigint" | "object" | "symbol" parallels built-in TS keywords for non-enumerable value sets
  • Proto: Must be an instanceof some class (implies domain "object")
  • Unit: Must === some value (can be intersected with any other constraint and reduced to itself or a disjoint)
• Constraint: an individual condition that must be satisfied:
  • Required: must have a specified literal string or symbol key and a value that conforms to a specified union or intersection
  • Optional: Required conditions met or the specified key is not present
  • Index: all keys that satisfy an index type must have values satisfying the corresponding value type

In this system, L extends/subtypes/is assignable to R if and only if the intersection L & R is equal to L.