Function overloaded with different string literals causes duplicate function

[epabst]

Example:

declare function foo(s: "number"): number;
declare function foo(s: "string"): string;

results in:

external fun foo(s: String /* "number" */): Number = definedExternally
external fun foo(s: String /* "string" */): String = definedExternally

but it should be:

external fun foo(s: String /* "number" | "string" */): dynamic = definedExternally