Type Alias CastedPattern<T>

CastedPattern: Pattern & { "Symbol(castedType)"?: T }

A pattern carrying an unchecked static type assertion. The runtime pattern still validates the structural shape it always did; the T parameter is a developer claim that values matched by this pattern inhabit T — typically narrower than what the structural shape can recover (e.g., a discriminated union, a branded type, or a template literal).

Like a TypeScript as cast, CastedPattern<T> is trusted by the type system but unverifiable at runtime. If the pattern matches a value that doesn't actually satisfy T, downstream code may misbehave with no runtime error.

TypeFromPattern<CastedPattern<T>> resolves to T, bypassing the normal structural inference.

Type Parameters

Example

// structural pattern with a discriminated-union static claim
  const AmountShape = harden({
    brand: BrandShape,
    value: AmountValueShape,
  });
  // The structural inference would yield the cross-product
  // `{ brand: Brand, value: NatValue | SetValue | ... }`. The cast
  // unifies brand and value through the discriminated union.
  export const AmountPattern =
    ({brand: BrandShape, value: AmountValueShape});

Type Alias CastedPattern<T>

Type Parameters

Example

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