What this snippet does
When extending, you cannot override a property with a type that is not assignable to the base property type.
Expected output
Compile Error: Interface 'B' incorrectly extends interface 'A'.
Why practise typing this
Typing objects and interfaces 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.
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