Exhaustive Handling and never Checks
Exhaustive handling is a crucial concept when working with discriminated unions in TypeScript. Discriminated unions allow you to model data that can take on several related shapes, each distinguished by a common property called the discriminant. This discriminant property—often named something like kind, type, or status—lets you write code that checks for each possible case in a safe and predictable way. By using exhaustive handling, you ensure that every possible variant of your union type is accounted for, which prevents runtime errors if new cases are added in the future.
When you use a switch statement or a series of if checks on the discriminant property, TypeScript can verify that you have covered all possible cases. If you miss a case, TypeScript can warn you—especially when you use the never type as a safety net. This connection between discriminated unions and the need for never checks is what makes TypeScript's type system so powerful for modeling and maintaining complex codebases. By enforcing exhaustive handling, you make your code more robust and future-proof, catching mistakes at compile time rather than at runtime.
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Can you give an example of exhaustive handling with discriminated unions in TypeScript?
How does the `never` type help ensure exhaustive checks?
What happens if I miss a case in a discriminated union?
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Exhaustive handling is a crucial concept when working with discriminated unions in TypeScript. Discriminated unions allow you to model data that can take on several related shapes, each distinguished by a common property called the discriminant. This discriminant property—often named something like kind, type, or status—lets you write code that checks for each possible case in a safe and predictable way. By using exhaustive handling, you ensure that every possible variant of your union type is accounted for, which prevents runtime errors if new cases are added in the future.
When you use a switch statement or a series of if checks on the discriminant property, TypeScript can verify that you have covered all possible cases. If you miss a case, TypeScript can warn you—especially when you use the never type as a safety net. This connection between discriminated unions and the need for never checks is what makes TypeScript's type system so powerful for modeling and maintaining complex codebases. By enforcing exhaustive handling, you make your code more robust and future-proof, catching mistakes at compile time rather than at runtime.
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