What this snippet does
Because 'never' is absorbed by unions, returning it in conditional types effectively removes unwanted members from the union.
Expected output
a
Why practise typing this
Typing type system limits code builds muscle memory for the symbols and indentation TypeScript uses most, which prose-based typing tests never cover. DevType measures your words per minute and accuracy on this snippet and tracks the individual characters you mistype, so later lessons can target them.
More TypeScript practice
- Contrasting any, unknown, and neverType System Limits · advanced
- Assigning values to a never variableType System Limits · advanced
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- Exceeding tuple recursion limitsType System Limits · advanced
- Infinite conditional type distributionType System Limits · advanced
- Defining a circular type referenceType System Limits · advanced