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test/static/assert.ts

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+import { Static, StaticDecode, StaticEncode, TSchema } from '@sinclair/typebox'
+
+// ------------------------------------------------------------------
+// Symbols
+// ------------------------------------------------------------------
+export declare const Unsatisfiable: unique symbol
+// Warning: `never` and `any` satisfy the constraint `extends Expected<...>`
+export type Expected<_> = { [Unsatisfiable]: never }
+// ------------------------------------------------------------------
+// Gates
+// ------------------------------------------------------------------
+export type If<T, Y, N> = T extends true ? Y : N
+export type And<T, U> = If<T, U, false>
+export type Or<T, U> = If<T, true, U>
+export type Not<T> = If<T, false, true>
+// ------------------------------------------------------------------
+// Helpers
+// ------------------------------------------------------------------
+export type Extends<T, U> = [T] extends [U] ? true : false
+export type IsAny<T> = 0 extends 1 & T ? true : false
+export type IsNever<T> = Extends<T, never>
+// ------------------------------------------------------------------
+// Constraints
+// ------------------------------------------------------------------
+// See https://github.com/microsoft/TypeScript/issues/51011
+export type CircularHelper<T, U> = [T] extends U ? T : Expected<T>
+// See https://github.com/Microsoft/TypeScript/issues/27024
+export type ConstrainEqual<T, U> = (<V>() => V extends T ? 1 : 2) extends <V>() => V extends U ? 1 : 2 ? T : Expected<T>
+export type ConstraintMutuallyExtend<T, U> = CircularHelper<T, [U]>
+
+// Circular Error on TS 5.4.0
+// If U is never, there's nothing we can do
+// export type ComplexConstraint<T, U> = If<
+//   // If U is any, we can't use Expect<T> or it would satisfy the constraint
+//   And<Not<IsAny<T>>, IsAny<U>>,
+//   never,
+//   If<
+//     Or<
+//       // If they are both any we are happy
+//       And<IsAny<T>, IsAny<U>>,
+//       // If T extends U, but not because it's any, we are happy
+//       And<Extends<T, U>, Not<IsAny<T>>>
+//     >,
+//     T,
+//     Expected<T>
+//   >
+// >
+// ------------------------------------------------------------------
+// Expect
+// ------------------------------------------------------------------
+export type ExpectResult<T extends TSchema> = If<
+  IsNever<Static<T>>,
+  { ToStaticNever(): void },
+  {
+    ToStatic<U extends ConstraintMutuallyExtend<Static<T>, U>>(): void
+    ToStaticDecode<U extends ConstraintMutuallyExtend<StaticDecode<T>, U>>(): void
+    ToStaticEncode<U extends ConstraintMutuallyExtend<StaticEncode<T>, U>>(): void
+    // ToStatic<U extends Static<T>>(): void
+    // ToStaticDecode<U extends StaticDecode<T>>(): void
+    // ToStaticEncode<U extends StaticEncode<T>>(): void
+  }
+>
+export function Expect<T extends TSchema>(schema: T) {
+  return {
+    ToStatic() {},
+    ToStaticNever() {},
+    ToStaticDecode() {},
+    ToStaticEncode() {},
+  } as ExpectResult<T>
+}