44 lines
1.3 KiB
TypeScript
44 lines
1.3 KiB
TypeScript
/**
|
|
* Error class for exhaustive type checking in switch statements and
|
|
* conditionals.
|
|
*
|
|
* Ensures at compile-time that all possible cases of a union type are handled.
|
|
* When TypeScript's type system proves all cases are covered, the variable in
|
|
* the default case has type `never`, making this error theoretically
|
|
* unreachable in correctly typed code.
|
|
*
|
|
* This pattern is crucial for maintaining type safety when adding new options
|
|
* to existing types - TypeScript will error if a new case isn't handled.
|
|
*
|
|
* @example
|
|
*
|
|
* ```ts
|
|
* // Exhaustive handling of sorting types
|
|
* function getSortingAlgorithm(
|
|
* type: 'alphabetical' | 'natural' | 'custom',
|
|
* ) {
|
|
* switch (type) {
|
|
* case 'alphabetical':
|
|
* return alphabeticalSort
|
|
* case 'natural':
|
|
* return naturalSort
|
|
* case 'custom':
|
|
* return customSort
|
|
* default:
|
|
* throw new UnreachableCaseError(type)
|
|
* // TypeScript ensures 'type' is 'never' here
|
|
* }
|
|
* }
|
|
* ```
|
|
*/
|
|
export declare class UnreachableCaseError extends Error {
|
|
/**
|
|
* Creates an error indicating that an supposedly unreachable case was
|
|
* reached.
|
|
*
|
|
* @param value - The value that should have type `never` if all cases are
|
|
* handled. In practice, this will contain the unhandled case value.
|
|
*/
|
|
constructor(value: never)
|
|
}
|