tests/cases/conformance/types/typeRelationships/assignmentCompatibility/typeParameterAssignability3.ts(14,5): error TS2322: Type 'U' is not assignable to type 'T'. tests/cases/conformance/types/typeRelationships/assignmentCompatibility/typeParameterAssignability3.ts(15,5): error TS2322: Type 'T' is not assignable to type 'U'. tests/cases/conformance/types/typeRelationships/assignmentCompatibility/typeParameterAssignability3.ts(22,9): error TS2322: Type 'U' is not assignable to type 'T'. tests/cases/conformance/types/typeRelationships/assignmentCompatibility/typeParameterAssignability3.ts(23,9): error TS2322: Type 'T' is not assignable to type 'U'. ==== tests/cases/conformance/types/typeRelationships/assignmentCompatibility/typeParameterAssignability3.ts (4 errors) ==== // type parameters are not assignable to one another unless directly or indirectly constrained to one another class Foo { foo: string; } function foo(t: T, u: U) { var a: T; var b: U; t = a; // ok a = t; // ok b = u; // ok u = b; // ok t = u; // error ~ !!! error TS2322: Type 'U' is not assignable to type 'T'. u = t; // error ~ !!! error TS2322: Type 'T' is not assignable to type 'U'. } class C { t: T; u: U; r = () => { this.t = this.u; // error ~~~~~~ !!! error TS2322: Type 'U' is not assignable to type 'T'. this.u = this.t; // error ~~~~~~ !!! error TS2322: Type 'T' is not assignable to type 'U'. } }