'this' implicitly has type 'any' because it does not have a type annotation

Question

When I enable noImplicitThis in tsconfig.json, I get this error for the following code:

\'this\' implicitly has type \         


        

Answer 1

The error is indeed fixed by inserting this with a type annotation as the first callback parameter. My attempt to do that was botched by simultaneously changing the callback into an arrow-function:

foo.on('error', (this: Foo, err: any) => { // DON'T DO THIS

It should've been this:

foo.on('error', function(this: Foo, err: any) {

or this:

foo.on('error', function(this: typeof foo, err: any) {

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A GitHub issue was created to improve the compiler's error message and highlight the actual grammar error with this and arrow-functions.