tests/cases/compiler/overload1.ts(27,5): error TS2322: Type 'C' is not assignable to type 'string'. tests/cases/compiler/overload1.ts(29,1): error TS2322: Type 'number' is not assignable to type 'string'. tests/cases/compiler/overload1.ts(31,3): error TS2346: Supplied parameters do not match any signature of call target. tests/cases/compiler/overload1.ts(32,3): error TS2346: Supplied parameters do not match any signature of call target. tests/cases/compiler/overload1.ts(33,1): error TS2322: Type 'C' is not assignable to type 'string'. tests/cases/compiler/overload1.ts(34,9): error TS2345: Argument of type 'number' is not assignable to parameter of type 'string'. ==== tests/cases/compiler/overload1.ts (6 errors) ==== module O { export class A { } export class B extends A { } export class C extends B { } export interface I { f(s:string):number; f(n:number):string; g(n1:number,n2:number):number; g(n:number):string; g(a:A):C; g(c:C):string; h(s1:string,s2:number):string; h(s1:number,s2:string):number; } } declare var x:O.I; var e:string=x.g(new O.A()); // matches overload but bad assignment ~ !!! error TS2322: Type 'C' is not assignable to type 'string'. var y:string=x.f(3); // good y=x.f("nope"); // can't assign number to string ~ !!! error TS2322: Type 'number' is not assignable to type 'string'. var z:string=x.g(x.g(3,3)); // good z=x.g(2,2,2); // no match ~~~~~~~~~~ !!! error TS2346: Supplied parameters do not match any signature of call target. z=x.g(); // no match ~~~~~ !!! error TS2346: Supplied parameters do not match any signature of call target. z=x.g(new O.B()); // ambiguous (up and down conversion) ~ !!! error TS2322: Type 'C' is not assignable to type 'string'. z=x.h(2,2); // no match ~ !!! error TS2345: Argument of type 'number' is not assignable to parameter of type 'string'. z=x.h("hello",0); // good var v=x.g;