"Used before assigned" error with arrow functions and strict null checks

[Christoph-D]

TypeScript Version:

1.9.0-dev.20160627-1.0

Code

const f = () => { return f; };

Compiled with --strictNullChecks.

Expected behavior:

No errors.

Actual behavior:

foo.ts(1,26): error TS2454: Variable 'f' is used before being assigned.

It sems to be impossible to call f before f is assigned, so I don't think this should trigger an error.

[mhegazy]

The error message is a bit misleading. the message is about the type system trying to know what is the type of f and catching its own tail. so an explicit type annotation would resolve the issue. so:

const f: any = () => { return f; };

[Christoph-D]

This gives the same error, although I added an explicit type annotation.

const f: () => void = () => { f; }

But the following gives no error:

let f: () => void;
f = () => { f; }

[bolismauro]

@Christoph-D I don't receive the error if I change the definition of the function from const to let.
So basically this gives me an error

const t2 = (): number => 1 + t2();

while this does not

let t = (): number => 1 + t();

[mhegazy]

should be fixed by #10815