Arrow function name is not defined.

[mpodlasin]

Hi everyone. Afaik arrow functions should have names copied from names of variables they are assigned to at creation time.

This is a problem for example with stateless React components, where function name is a basis for component name (which now in react development tools are seen as Unknown).
Babel sets arrow function names properly.

Code

const x = (a: number, b: number) => a + b;
console.log(x.name);

Expected behavior:
Compiles to

const x = function x(a, b) { return a + b; };
console.log(x.name);

Prints "x".

Actual behavior:
Compiles to

const x = function (a, b) { return a + b; };
console.log(x.name);

Prints undefined.

[kitsonk]

Dupe of #6433

[mpodlasin]

@kitsonk thanks. could not find one.