AI solution for TypeScript puzzle on BFE.dev
15. implement OmitThisParameter<T>

Here's the implementation of MyOmitThisParameter<T> type:

type MyOmitThisParameter<T> = T extends (this: any, ...args: infer P) => infer R
  ? (...args: P) => R
  : never;

Explanation:

• We use conditional types (T extends ... ? ... : ...) to check if T extends a function with this parameter and rest arguments.
• If it does, we use infer keyword to capture the parameter type (P) and return type (R).
• We then create a new function type with the same argument types (P) and return type (R) but omit the this parameter.
• If T doesn't extend such a function, we return never.

Testing our implementation:

function foo(this: {a: string}) {}
foo() // Error

const bar = foo.bind({a: 'BFE.dev'})
bar() // OK

type Foo = (this: {a: string}) => string
type Bar = MyOmitThisParameter<Foo> // () => string

The type Bar is correctly inferred as a function that takes no this parameter and returns a string.