// void returning call signatures can be assigned a non-void returning call signature that otherwise matches interface T { f: new (x: number) => void; } var t: T; var a: { f: new (x: number) => void }; t = a; a = t; interface S { f: new (x: number) => string; } var s: S; var a2: { f: new (x: number) => string }; t = s; t = a2; a = s; a = a2; // errors t = () => 1; t = function (x: number) { return ''; } a = () => 1; a = function (x: number) { return ''; } interface S2 { f(x: string): void; } var s2: S2; var a3: { f(x: string): void }; // these are errors t = s2; t = a3; t = (x: string) => 1; t = function (x: string) { return ''; } a = s2; a = a3; a = (x: string) => 1; a = function (x: string) { return ''; }