Incorrect error message when overloaded function is called with invalid parameter

[bjouhier]

TypeScript Version: 2.0.3

Code

function foo(x: 'a'): void;
function foo(x: 'b'): void;
function foo(x: 'c'): void;
function foo(x: 'a' | 'b' | 'c') {}

foo('d');

Expected behavior:

Error: Argument of type '"d"' is not assignable to parameter of type '"a" | "b" | "c"'

Actual behavior:

Error: Argument of type '"d"' is not assignable to parameter of type '"c"'

[RyanCavanaugh]

The implementation signature is not part of the type. If this function were in a declaration file you'd just see

function foo(x: 'a'): void;
function foo(x: 'b'): void;
function foo(x: 'c'): void;

It wouldn't be feasible to show a synthesized union type of all the possible first argument types -- some functions have dozens of overloads and that type would be huge (not to mention not even correct)

[bjouhier]

Would be nice to have an indication that the parameter has overloads. Something like:

Error: Argument of type '"d"' is not assignable to parameter of type '"c"', nor to any of its overloads.