Ask HN: TypeScript experts, is this a type checking issue?

The following ts code both compiles (with all checks active) and passes tslint without complaints:

  type sig = (p: number) => string;
  const x = (p: any) => p + 1;
  const y: sig = x;
  alert(typeof y(5));

Obviously the alert message will (and does) display 'number'.

IntelliJ spots the problem though ('x' should probably not be assigned to 'y').

(Apologies if this is too stackoverflow-y, but I don't expect a "solution", I'm just interested in opinions)