tests/cases/compiler/typeParameterArgumentEquivalence4.ts(4,5): error TS2322: Type '(item: any) => T' is not assignable to type '(item: any) => U'.
  Type 'T' is not assignable to type 'U'.
    'T' is assignable to the constraint of type 'U', but 'U' could be instantiated with a different subtype of constraint '{}'.
tests/cases/compiler/typeParameterArgumentEquivalence4.ts(5,5): error TS2322: Type '(item: any) => U' is not assignable to type '(item: any) => T'.
  Type 'U' is not assignable to type 'T'.
    'U' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.


==== tests/cases/compiler/typeParameterArgumentEquivalence4.ts (2 errors) ====
    function foo<T,U>() {
        var x: (item) => U;
        var y: (item) => T;
        x = y;  // Should be an error
        ~
!!! error TS2322: Type '(item: any) => T' is not assignable to type '(item: any) => U'.
!!! error TS2322:   Type 'T' is not assignable to type 'U'.
!!! error TS2322:     'T' is assignable to the constraint of type 'U', but 'U' could be instantiated with a different subtype of constraint '{}'.
        y = x;  // Shound be an error
        ~
!!! error TS2322: Type '(item: any) => U' is not assignable to type '(item: any) => T'.
!!! error TS2322:   Type 'U' is not assignable to type 'T'.
!!! error TS2322:     'U' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
    }
    