tests/cases/conformance/types/typeRelationships/assignmentCompatibility/typeParameterAssignability.ts(4,5): error TS2322: Type 'U' is not assignable to type 'T'. tests/cases/conformance/types/typeRelationships/assignmentCompatibility/typeParameterAssignability.ts(5,5): error TS2322: Type 'T' is not assignable to type 'U'. ==== tests/cases/conformance/types/typeRelationships/assignmentCompatibility/typeParameterAssignability.ts (2 errors) ==== // type parameters are not assignable to one another unless directly or indirectly constrained to one another function foo(t: T, u: U) { 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'. }