What this snippet does
Unlike interfaces, which merge on duplicate declarations, type aliases cannot be redeclared in the same scope.
Expected output
Compile Error: Duplicate identifier 'T'.
Why practise typing this
Typing type aliases vs 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.
More TypeScript practice
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- Defining a constructable type aliasType Aliases vs Interfaces · advanced