=== tests/cases/compiler/genericFunctionsWithOptionalParameters3.ts ===
class Collection<T> {
>Collection : Symbol(Collection, Decl(genericFunctionsWithOptionalParameters3.ts, 0, 0))
>T : Symbol(T, Decl(genericFunctionsWithOptionalParameters3.ts, 0, 17))

    public add(x: T) { }
>add : Symbol(add, Decl(genericFunctionsWithOptionalParameters3.ts, 0, 21))
>x : Symbol(x, Decl(genericFunctionsWithOptionalParameters3.ts, 1, 15))
>T : Symbol(T, Decl(genericFunctionsWithOptionalParameters3.ts, 0, 17))
}
interface Utils {
>Utils : Symbol(Utils, Decl(genericFunctionsWithOptionalParameters3.ts, 2, 1))

    fold<T, S>(c?: Collection<T>, folder?: (s: S, t: T) => T, init?: S): T;
>fold : Symbol(fold, Decl(genericFunctionsWithOptionalParameters3.ts, 3, 17))
>T : Symbol(T, Decl(genericFunctionsWithOptionalParameters3.ts, 4, 9))
>S : Symbol(S, Decl(genericFunctionsWithOptionalParameters3.ts, 4, 11))
>c : Symbol(c, Decl(genericFunctionsWithOptionalParameters3.ts, 4, 15))
>Collection : Symbol(Collection, Decl(genericFunctionsWithOptionalParameters3.ts, 0, 0))
>T : Symbol(T, Decl(genericFunctionsWithOptionalParameters3.ts, 4, 9))
>folder : Symbol(folder, Decl(genericFunctionsWithOptionalParameters3.ts, 4, 33))
>s : Symbol(s, Decl(genericFunctionsWithOptionalParameters3.ts, 4, 44))
>S : Symbol(S, Decl(genericFunctionsWithOptionalParameters3.ts, 4, 11))
>t : Symbol(t, Decl(genericFunctionsWithOptionalParameters3.ts, 4, 49))
>T : Symbol(T, Decl(genericFunctionsWithOptionalParameters3.ts, 4, 9))
>T : Symbol(T, Decl(genericFunctionsWithOptionalParameters3.ts, 4, 9))
>init : Symbol(init, Decl(genericFunctionsWithOptionalParameters3.ts, 4, 61))
>S : Symbol(S, Decl(genericFunctionsWithOptionalParameters3.ts, 4, 11))
>T : Symbol(T, Decl(genericFunctionsWithOptionalParameters3.ts, 4, 9))

    mapReduce<T, U, V>(c: Collection<T>, mapper: (x: T) => U, reducer: (y: U) => V): Collection<V>;
>mapReduce : Symbol(mapReduce, Decl(genericFunctionsWithOptionalParameters3.ts, 4, 75))
>T : Symbol(T, Decl(genericFunctionsWithOptionalParameters3.ts, 5, 14))
>U : Symbol(U, Decl(genericFunctionsWithOptionalParameters3.ts, 5, 16))
>V : Symbol(V, Decl(genericFunctionsWithOptionalParameters3.ts, 5, 19))
>c : Symbol(c, Decl(genericFunctionsWithOptionalParameters3.ts, 5, 23))
>Collection : Symbol(Collection, Decl(genericFunctionsWithOptionalParameters3.ts, 0, 0))
>T : Symbol(T, Decl(genericFunctionsWithOptionalParameters3.ts, 5, 14))
>mapper : Symbol(mapper, Decl(genericFunctionsWithOptionalParameters3.ts, 5, 40))
>x : Symbol(x, Decl(genericFunctionsWithOptionalParameters3.ts, 5, 50))
>T : Symbol(T, Decl(genericFunctionsWithOptionalParameters3.ts, 5, 14))
>U : Symbol(U, Decl(genericFunctionsWithOptionalParameters3.ts, 5, 16))
>reducer : Symbol(reducer, Decl(genericFunctionsWithOptionalParameters3.ts, 5, 61))
>y : Symbol(y, Decl(genericFunctionsWithOptionalParameters3.ts, 5, 72))
>U : Symbol(U, Decl(genericFunctionsWithOptionalParameters3.ts, 5, 16))
>V : Symbol(V, Decl(genericFunctionsWithOptionalParameters3.ts, 5, 19))
>Collection : Symbol(Collection, Decl(genericFunctionsWithOptionalParameters3.ts, 0, 0))
>V : Symbol(V, Decl(genericFunctionsWithOptionalParameters3.ts, 5, 19))
}
var utils: Utils;
>utils : Symbol(utils, Decl(genericFunctionsWithOptionalParameters3.ts, 7, 3))
>Utils : Symbol(Utils, Decl(genericFunctionsWithOptionalParameters3.ts, 2, 1))

var c = new Collection<string>();
>c : Symbol(c, Decl(genericFunctionsWithOptionalParameters3.ts, 8, 3))
>Collection : Symbol(Collection, Decl(genericFunctionsWithOptionalParameters3.ts, 0, 0))

var r3 = utils.mapReduce(c, (x) => { return 1 }, (y) => { return new Date() });
>r3 : Symbol(r3, Decl(genericFunctionsWithOptionalParameters3.ts, 9, 3))
>utils.mapReduce : Symbol(Utils.mapReduce, Decl(genericFunctionsWithOptionalParameters3.ts, 4, 75))
>utils : Symbol(utils, Decl(genericFunctionsWithOptionalParameters3.ts, 7, 3))
>mapReduce : Symbol(Utils.mapReduce, Decl(genericFunctionsWithOptionalParameters3.ts, 4, 75))
>c : Symbol(c, Decl(genericFunctionsWithOptionalParameters3.ts, 8, 3))
>x : Symbol(x, Decl(genericFunctionsWithOptionalParameters3.ts, 9, 29))
>y : Symbol(y, Decl(genericFunctionsWithOptionalParameters3.ts, 9, 50))
>Date : Symbol(Date, Decl(lib.d.ts, 633, 23), Decl(lib.d.ts, 815, 11))

var r4 = utils.mapReduce(c, (x: string) => { return 1 }, (y: number) => { return new Date() });
>r4 : Symbol(r4, Decl(genericFunctionsWithOptionalParameters3.ts, 10, 3))
>utils.mapReduce : Symbol(Utils.mapReduce, Decl(genericFunctionsWithOptionalParameters3.ts, 4, 75))
>utils : Symbol(utils, Decl(genericFunctionsWithOptionalParameters3.ts, 7, 3))
>mapReduce : Symbol(Utils.mapReduce, Decl(genericFunctionsWithOptionalParameters3.ts, 4, 75))
>c : Symbol(c, Decl(genericFunctionsWithOptionalParameters3.ts, 8, 3))
>x : Symbol(x, Decl(genericFunctionsWithOptionalParameters3.ts, 10, 29))
>y : Symbol(y, Decl(genericFunctionsWithOptionalParameters3.ts, 10, 58))
>Date : Symbol(Date, Decl(lib.d.ts, 633, 23), Decl(lib.d.ts, 815, 11))

var f1 = (x: string) => { return 1 };
>f1 : Symbol(f1, Decl(genericFunctionsWithOptionalParameters3.ts, 11, 3))
>x : Symbol(x, Decl(genericFunctionsWithOptionalParameters3.ts, 11, 10))

var f2 = (y: number) => { return new Date() };
>f2 : Symbol(f2, Decl(genericFunctionsWithOptionalParameters3.ts, 12, 3))
>y : Symbol(y, Decl(genericFunctionsWithOptionalParameters3.ts, 12, 10))
>Date : Symbol(Date, Decl(lib.d.ts, 633, 23), Decl(lib.d.ts, 815, 11))

var r5 = utils.mapReduce(c, f1, f2);
>r5 : Symbol(r5, Decl(genericFunctionsWithOptionalParameters3.ts, 13, 3))
>utils.mapReduce : Symbol(Utils.mapReduce, Decl(genericFunctionsWithOptionalParameters3.ts, 4, 75))
>utils : Symbol(utils, Decl(genericFunctionsWithOptionalParameters3.ts, 7, 3))
>mapReduce : Symbol(Utils.mapReduce, Decl(genericFunctionsWithOptionalParameters3.ts, 4, 75))
>c : Symbol(c, Decl(genericFunctionsWithOptionalParameters3.ts, 8, 3))
>f1 : Symbol(f1, Decl(genericFunctionsWithOptionalParameters3.ts, 11, 3))
>f2 : Symbol(f2, Decl(genericFunctionsWithOptionalParameters3.ts, 12, 3))