TypeScript

Polymorphic this breaking type inference when extracted in TypeScript

TypeScriptAdvanced Classes & OOPPolymorphic thisadvanced

What this snippet does

When extracting methods that use 'this' types, the contextual 'this' is lost, making it difficult to type the standalone function.

Expected output

Compile Error: The 'this' context of type 'typeof C' is not assignable to method's 'this'.

Why practise typing this

Typing advanced classes & oop 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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