tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithGenericCallSignaturesWithOptionalParameters.ts(20,15): error TS2430: Interface 'I3<T>' incorrectly extends interface 'Base<T>'.
  Types of property 'a' are incompatible.
    Type '(x: T) => T' is not assignable to type '() => T'.
tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithGenericCallSignaturesWithOptionalParameters.ts(50,15): error TS2430: Interface 'I10<T>' incorrectly extends interface 'Base<T>'.
  Types of property 'a3' are incompatible.
    Type '(x: T, y: T) => T' is not assignable to type '(x: T) => T'.
tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithGenericCallSignaturesWithOptionalParameters.ts(100,15): error TS2430: Interface 'I1<T>' incorrectly extends interface 'Base2'.
  The types returned by 'a()' are incompatible between these types.
    Type 'T' is not assignable to type 'T'. Two different types with this name exist, but they are unrelated.
      'T' could be instantiated with an arbitrary type which could be unrelated to 'T'.
tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithGenericCallSignaturesWithOptionalParameters.ts(104,15): error TS2430: Interface 'I2<T>' incorrectly extends interface 'Base2'.
  The types returned by 'a(...)' are incompatible between these types.
    Type 'T' is not assignable to type 'T'. Two different types with this name exist, but they are unrelated.
      'T' could be instantiated with an arbitrary type which could be unrelated to 'T'.
tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithGenericCallSignaturesWithOptionalParameters.ts(108,15): error TS2430: Interface 'I3<T>' incorrectly extends interface 'Base2'.
  Types of property 'a' are incompatible.
    Type '(x: T) => T' is not assignable to type '<T>() => T'.
tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithGenericCallSignaturesWithOptionalParameters.ts(113,15): error TS2430: Interface 'I4<T>' incorrectly extends interface 'Base2'.
  The types returned by 'a2(...)' are incompatible between these types.
    Type 'T' is not assignable to type 'T'. Two different types with this name exist, but they are unrelated.
      'T' could be instantiated with an arbitrary type which could be unrelated to 'T'.
tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithGenericCallSignaturesWithOptionalParameters.ts(117,15): error TS2430: Interface 'I5<T>' incorrectly extends interface 'Base2'.
  Types of property 'a2' are incompatible.
    Type '(x?: T) => T' is not assignable to type '<T>(x?: T) => T'.
      Types of parameters 'x' and 'x' are incompatible.
        Type 'T' is not assignable to type 'T'. Two different types with this name exist, but they are unrelated.
          'T' could be instantiated with an arbitrary type which could be unrelated to 'T'.
tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithGenericCallSignaturesWithOptionalParameters.ts(121,15): error TS2430: Interface 'I6<T>' incorrectly extends interface 'Base2'.
  Types of property 'a2' are incompatible.
    Type '(x: T) => T' is not assignable to type '<T>(x?: T) => T'.
      Types of parameters 'x' and 'x' are incompatible.
        Type 'T' is not assignable to type 'T'. Two different types with this name exist, but they are unrelated.
          'T' could be instantiated with an arbitrary type which could be unrelated to 'T'.
tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithGenericCallSignaturesWithOptionalParameters.ts(126,15): error TS2430: Interface 'I7<T>' incorrectly extends interface 'Base2'.
  The types returned by 'a3(...)' are incompatible between these types.
    Type 'T' is not assignable to type 'T'. Two different types with this name exist, but they are unrelated.
      'T' could be instantiated with an arbitrary type which could be unrelated to 'T'.
tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithGenericCallSignaturesWithOptionalParameters.ts(130,15): error TS2430: Interface 'I8<T>' incorrectly extends interface 'Base2'.
  Types of property 'a3' are incompatible.
    Type '(x?: T) => T' is not assignable to type '<T>(x: T) => T'.
      Types of parameters 'x' and 'x' are incompatible.
        Type 'T' is not assignable to type 'T'. Two different types with this name exist, but they are unrelated.
          'T' could be instantiated with an arbitrary type which could be unrelated to 'T'.
tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithGenericCallSignaturesWithOptionalParameters.ts(134,15): error TS2430: Interface 'I9<T>' incorrectly extends interface 'Base2'.
  Types of property 'a3' are incompatible.
    Type '(x: T) => T' is not assignable to type '<T>(x: T) => T'.
      Types of parameters 'x' and 'x' are incompatible.
        Type 'T' is not assignable to type 'T'. Two different types with this name exist, but they are unrelated.
          'T' could be instantiated with an arbitrary type which could be unrelated to 'T'.
tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithGenericCallSignaturesWithOptionalParameters.ts(138,15): error TS2430: Interface 'I10<T>' incorrectly extends interface 'Base2'.
  Types of property 'a3' are incompatible.
    Type '(x: T, y: T) => T' is not assignable to type '<T>(x: T) => T'.
tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithGenericCallSignaturesWithOptionalParameters.ts(143,15): error TS2430: Interface 'I11<T>' incorrectly extends interface 'Base2'.
  The types returned by 'a4(...)' are incompatible between these types.
    Type 'T' is not assignable to type 'T'. Two different types with this name exist, but they are unrelated.
      'T' could be instantiated with an arbitrary type which could be unrelated to 'T'.
tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithGenericCallSignaturesWithOptionalParameters.ts(147,15): error TS2430: Interface 'I12<T>' incorrectly extends interface 'Base2'.
  Types of property 'a4' are incompatible.
    Type '(x?: T, y?: T) => T' is not assignable to type '<T>(x: T, y?: T) => T'.
      Types of parameters 'x' and 'x' are incompatible.
        Type 'T' is not assignable to type 'T'. Two different types with this name exist, but they are unrelated.
          'T' could be instantiated with an arbitrary type which could be unrelated to 'T'.
tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithGenericCallSignaturesWithOptionalParameters.ts(151,15): error TS2430: Interface 'I13<T>' incorrectly extends interface 'Base2'.
  Types of property 'a4' are incompatible.
    Type '(x: T) => T' is not assignable to type '<T>(x: T, y?: T) => T'.
      Types of parameters 'x' and 'x' are incompatible.
        Type 'T' is not assignable to type 'T'. Two different types with this name exist, but they are unrelated.
          'T' could be instantiated with an arbitrary type which could be unrelated to 'T'.
tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithGenericCallSignaturesWithOptionalParameters.ts(155,15): error TS2430: Interface 'I14<T>' incorrectly extends interface 'Base2'.
  Types of property 'a4' are incompatible.
    Type '(x: T, y: T) => T' is not assignable to type '<T>(x: T, y?: T) => T'.
      Types of parameters 'x' and 'x' are incompatible.
        Type 'T' is not assignable to type 'T'. Two different types with this name exist, but they are unrelated.
          'T' could be instantiated with an arbitrary type which could be unrelated to 'T'.
tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithGenericCallSignaturesWithOptionalParameters.ts(160,15): error TS2430: Interface 'I15<T>' incorrectly extends interface 'Base2'.
  The types returned by 'a5(...)' are incompatible between these types.
    Type 'T' is not assignable to type 'T'. Two different types with this name exist, but they are unrelated.
      'T' could be instantiated with an arbitrary type which could be unrelated to 'T'.
tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithGenericCallSignaturesWithOptionalParameters.ts(164,15): error TS2430: Interface 'I16<T>' incorrectly extends interface 'Base2'.
  Types of property 'a5' are incompatible.
    Type '(x?: T, y?: T) => T' is not assignable to type '<T>(x?: T, y?: T) => T'.
      Types of parameters 'x' and 'x' are incompatible.
        Type 'T' is not assignable to type 'T'. Two different types with this name exist, but they are unrelated.
          'T' could be instantiated with an arbitrary type which could be unrelated to 'T'.
tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithGenericCallSignaturesWithOptionalParameters.ts(168,15): error TS2430: Interface 'I17<T>' incorrectly extends interface 'Base2'.
  Types of property 'a5' are incompatible.
    Type '(x: T) => T' is not assignable to type '<T>(x?: T, y?: T) => T'.
      Types of parameters 'x' and 'x' are incompatible.
        Type 'T' is not assignable to type 'T'. Two different types with this name exist, but they are unrelated.
          'T' could be instantiated with an arbitrary type which could be unrelated to 'T'.
tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithGenericCallSignaturesWithOptionalParameters.ts(172,15): error TS2430: Interface 'I18<T>' incorrectly extends interface 'Base2'.
  Types of property 'a5' are incompatible.
    Type '(x: T, y: T) => T' is not assignable to type '<T>(x?: T, y?: T) => T'.
      Types of parameters 'x' and 'x' are incompatible.
        Type 'T' is not assignable to type 'T'. Two different types with this name exist, but they are unrelated.
          'T' could be instantiated with an arbitrary type which could be unrelated to 'T'.
tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithGenericCallSignaturesWithOptionalParameters.ts(196,15): error TS2430: Interface 'I3' incorrectly extends interface 'Base2'.
  Types of property 'a' are incompatible.
    Type '<T>(x: T) => T' is not assignable to type '<T>() => T'.
tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithGenericCallSignaturesWithOptionalParameters.ts(226,15): error TS2430: Interface 'I10' incorrectly extends interface 'Base2'.
  Types of property 'a3' are incompatible.
    Type '<T>(x: T, y: T) => T' is not assignable to type '<T>(x: T) => T'.


==== tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithGenericCallSignaturesWithOptionalParameters.ts (22 errors) ====
    // call signatures in derived types must have the same or fewer optional parameters as the base type
    
    module ClassTypeParam {
        interface Base<T> {
            a: () => T;
            a2: (x?: T) => T;
            a3: (x: T) => T;
            a4: (x: T, y?: T) => T;
            a5: (x?: T, y?: T) => T;
        }
    
        interface I1<T> extends Base<T> {
            a: () => T; // ok, same T of required params
        }
    
        interface I2<T> extends Base<T> {
            a: (x?: T) => T; // ok, same T of required params
        }
    
        interface I3<T> extends Base<T> {
                  ~~
!!! error TS2430: Interface 'I3<T>' incorrectly extends interface 'Base<T>'.
!!! error TS2430:   Types of property 'a' are incompatible.
!!! error TS2430:     Type '(x: T) => T' is not assignable to type '() => T'.
            a: (x: T) => T; // error, too many required params
        }
    
    
        interface I4<T> extends Base<T> {
            a2: () => T; // ok, same T of required params
        }
    
        interface I5<T> extends Base<T> {
            a2: (x?: T) => T; // ok, same T of required params
        }
    
        interface I6<T> extends Base<T> {
            a2: (x: T) => T; // ok, same number of params
        }
    
    
        interface I7<T> extends Base<T> {
            a3: () => T; // ok, fewer required params
        }
    
        interface I8<T> extends Base<T> {
            a3: (x?: T) => T; // ok, fewer required params
        }
    
        interface I9<T> extends Base<T> {
            a3: (x: T) => T; // ok, same T of required params
        }
    
        interface I10<T> extends Base<T> {
                  ~~~
!!! error TS2430: Interface 'I10<T>' incorrectly extends interface 'Base<T>'.
!!! error TS2430:   Types of property 'a3' are incompatible.
!!! error TS2430:     Type '(x: T, y: T) => T' is not assignable to type '(x: T) => T'.
            a3: (x: T, y: T) => T;  // error, too many required params
        }
    
    
        interface I11<T> extends Base<T> {
            a4: () => T; // ok, fewer required params
        }
    
        interface I12<T> extends Base<T> {
            a4: (x?: T, y?: T) => T; // ok, fewer required params
        }
    
        interface I13<T> extends Base<T> {
            a4: (x: T) => T; // ok, same T of required params
        }
    
        interface I14<T> extends Base<T> {
            a4: (x: T, y: T) => T;  // ok, same number of params
        }
    
    
        interface I15<T> extends Base<T> {
            a5: () => T; // ok, fewer required params
        }
    
        interface I16<T> extends Base<T> {
            a5: (x?: T, y?: T) => T; // ok, fewer required params
        }
    
        interface I17<T> extends Base<T> {
            a5: (x: T) => T; // ok, all present params match
        }
    
        interface I18<T> extends Base<T> {
            a5: (x: T, y: T) => T;  // ok, same number of params
        }
    }
    
    module GenericSignaturesInvalid {
    
        // all of these are errors
        interface Base2 {
            a: <T>() => T;
            a2: <T>(x?: T) => T;
            a3: <T>(x: T) => T;
            a4: <T>(x: T, y?: T) => T;
            a5: <T>(x?: T, y?: T) => T;
        }
    
        interface I1<T> extends Base2 {
                  ~~
!!! error TS2430: Interface 'I1<T>' incorrectly extends interface 'Base2'.
!!! error TS2430:   The types returned by 'a()' are incompatible between these types.
!!! error TS2430:     Type 'T' is not assignable to type 'T'. Two different types with this name exist, but they are unrelated.
!!! error TS2430:       'T' could be instantiated with an arbitrary type which could be unrelated to 'T'.
!!! related TS2208 tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithGenericCallSignaturesWithOptionalParameters.ts:100:18: This type parameter might need an `extends T` constraint.
            a: () => T; 
        }
    
        interface I2<T> extends Base2 {
                  ~~
!!! error TS2430: Interface 'I2<T>' incorrectly extends interface 'Base2'.
!!! error TS2430:   The types returned by 'a(...)' are incompatible between these types.
!!! error TS2430:     Type 'T' is not assignable to type 'T'. Two different types with this name exist, but they are unrelated.
!!! error TS2430:       'T' could be instantiated with an arbitrary type which could be unrelated to 'T'.
!!! related TS2208 tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithGenericCallSignaturesWithOptionalParameters.ts:104:18: This type parameter might need an `extends T` constraint.
            a: (x?: T) => T;
        }
    
        interface I3<T> extends Base2 {
                  ~~
!!! error TS2430: Interface 'I3<T>' incorrectly extends interface 'Base2'.
!!! error TS2430:   Types of property 'a' are incompatible.
!!! error TS2430:     Type '(x: T) => T' is not assignable to type '<T>() => T'.
            a: (x: T) => T; 
        }
    
    
        interface I4<T> extends Base2 {
                  ~~
!!! error TS2430: Interface 'I4<T>' incorrectly extends interface 'Base2'.
!!! error TS2430:   The types returned by 'a2(...)' are incompatible between these types.
!!! error TS2430:     Type 'T' is not assignable to type 'T'. Two different types with this name exist, but they are unrelated.
!!! error TS2430:       'T' could be instantiated with an arbitrary type which could be unrelated to 'T'.
!!! related TS2208 tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithGenericCallSignaturesWithOptionalParameters.ts:113:18: This type parameter might need an `extends T` constraint.
            a2: () => T; 
        }
    
        interface I5<T> extends Base2 {
                  ~~
!!! error TS2430: Interface 'I5<T>' incorrectly extends interface 'Base2'.
!!! error TS2430:   Types of property 'a2' are incompatible.
!!! error TS2430:     Type '(x?: T) => T' is not assignable to type '<T>(x?: T) => T'.
!!! error TS2430:       Types of parameters 'x' and 'x' are incompatible.
!!! error TS2430:         Type 'T' is not assignable to type 'T'. Two different types with this name exist, but they are unrelated.
!!! error TS2430:           'T' could be instantiated with an arbitrary type which could be unrelated to 'T'.
!!! related TS2208 tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithGenericCallSignaturesWithOptionalParameters.ts:94:14: This type parameter might need an `extends T` constraint.
            a2: (x?: T) => T
        }
    
        interface I6<T> extends Base2 {
                  ~~
!!! error TS2430: Interface 'I6<T>' incorrectly extends interface 'Base2'.
!!! error TS2430:   Types of property 'a2' are incompatible.
!!! error TS2430:     Type '(x: T) => T' is not assignable to type '<T>(x?: T) => T'.
!!! error TS2430:       Types of parameters 'x' and 'x' are incompatible.
!!! error TS2430:         Type 'T' is not assignable to type 'T'. Two different types with this name exist, but they are unrelated.
!!! error TS2430:           'T' could be instantiated with an arbitrary type which could be unrelated to 'T'.
!!! related TS2208 tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithGenericCallSignaturesWithOptionalParameters.ts:94:14: This type parameter might need an `extends T` constraint.
            a2: (x: T) => T;
        }
    
    
        interface I7<T> extends Base2 {
                  ~~
!!! error TS2430: Interface 'I7<T>' incorrectly extends interface 'Base2'.
!!! error TS2430:   The types returned by 'a3(...)' are incompatible between these types.
!!! error TS2430:     Type 'T' is not assignable to type 'T'. Two different types with this name exist, but they are unrelated.
!!! error TS2430:       'T' could be instantiated with an arbitrary type which could be unrelated to 'T'.
!!! related TS2208 tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithGenericCallSignaturesWithOptionalParameters.ts:126:18: This type parameter might need an `extends T` constraint.
            a3: () => T;
        }
    
        interface I8<T> extends Base2 {
                  ~~
!!! error TS2430: Interface 'I8<T>' incorrectly extends interface 'Base2'.
!!! error TS2430:   Types of property 'a3' are incompatible.
!!! error TS2430:     Type '(x?: T) => T' is not assignable to type '<T>(x: T) => T'.
!!! error TS2430:       Types of parameters 'x' and 'x' are incompatible.
!!! error TS2430:         Type 'T' is not assignable to type 'T'. Two different types with this name exist, but they are unrelated.
!!! error TS2430:           'T' could be instantiated with an arbitrary type which could be unrelated to 'T'.
!!! related TS2208 tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithGenericCallSignaturesWithOptionalParameters.ts:95:14: This type parameter might need an `extends T` constraint.
            a3: (x?: T) => T; 
        }
    
        interface I9<T> extends Base2 {
                  ~~
!!! error TS2430: Interface 'I9<T>' incorrectly extends interface 'Base2'.
!!! error TS2430:   Types of property 'a3' are incompatible.
!!! error TS2430:     Type '(x: T) => T' is not assignable to type '<T>(x: T) => T'.
!!! error TS2430:       Types of parameters 'x' and 'x' are incompatible.
!!! error TS2430:         Type 'T' is not assignable to type 'T'. Two different types with this name exist, but they are unrelated.
!!! error TS2430:           'T' could be instantiated with an arbitrary type which could be unrelated to 'T'.
!!! related TS2208 tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithGenericCallSignaturesWithOptionalParameters.ts:95:14: This type parameter might need an `extends T` constraint.
            a3: (x: T) => T; 
        }
    
        interface I10<T> extends Base2 {
                  ~~~
!!! error TS2430: Interface 'I10<T>' incorrectly extends interface 'Base2'.
!!! error TS2430:   Types of property 'a3' are incompatible.
!!! error TS2430:     Type '(x: T, y: T) => T' is not assignable to type '<T>(x: T) => T'.
            a3: (x: T, y: T) => T;  
        }
    
    
        interface I11<T> extends Base2 {
                  ~~~
!!! error TS2430: Interface 'I11<T>' incorrectly extends interface 'Base2'.
!!! error TS2430:   The types returned by 'a4(...)' are incompatible between these types.
!!! error TS2430:     Type 'T' is not assignable to type 'T'. Two different types with this name exist, but they are unrelated.
!!! error TS2430:       'T' could be instantiated with an arbitrary type which could be unrelated to 'T'.
!!! related TS2208 tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithGenericCallSignaturesWithOptionalParameters.ts:143:19: This type parameter might need an `extends T` constraint.
            a4: () => T; 
        }
    
        interface I12<T> extends Base2 {
                  ~~~
!!! error TS2430: Interface 'I12<T>' incorrectly extends interface 'Base2'.
!!! error TS2430:   Types of property 'a4' are incompatible.
!!! error TS2430:     Type '(x?: T, y?: T) => T' is not assignable to type '<T>(x: T, y?: T) => T'.
!!! error TS2430:       Types of parameters 'x' and 'x' are incompatible.
!!! error TS2430:         Type 'T' is not assignable to type 'T'. Two different types with this name exist, but they are unrelated.
!!! error TS2430:           'T' could be instantiated with an arbitrary type which could be unrelated to 'T'.
!!! related TS2208 tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithGenericCallSignaturesWithOptionalParameters.ts:96:14: This type parameter might need an `extends T` constraint.
            a4: (x?: T, y?: T) => T; 
        }
    
        interface I13<T> extends Base2 {
                  ~~~
!!! error TS2430: Interface 'I13<T>' incorrectly extends interface 'Base2'.
!!! error TS2430:   Types of property 'a4' are incompatible.
!!! error TS2430:     Type '(x: T) => T' is not assignable to type '<T>(x: T, y?: T) => T'.
!!! error TS2430:       Types of parameters 'x' and 'x' are incompatible.
!!! error TS2430:         Type 'T' is not assignable to type 'T'. Two different types with this name exist, but they are unrelated.
!!! error TS2430:           'T' could be instantiated with an arbitrary type which could be unrelated to 'T'.
!!! related TS2208 tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithGenericCallSignaturesWithOptionalParameters.ts:96:14: This type parameter might need an `extends T` constraint.
            a4: (x: T) => T; 
        }
    
        interface I14<T> extends Base2 {
                  ~~~
!!! error TS2430: Interface 'I14<T>' incorrectly extends interface 'Base2'.
!!! error TS2430:   Types of property 'a4' are incompatible.
!!! error TS2430:     Type '(x: T, y: T) => T' is not assignable to type '<T>(x: T, y?: T) => T'.
!!! error TS2430:       Types of parameters 'x' and 'x' are incompatible.
!!! error TS2430:         Type 'T' is not assignable to type 'T'. Two different types with this name exist, but they are unrelated.
!!! error TS2430:           'T' could be instantiated with an arbitrary type which could be unrelated to 'T'.
!!! related TS2208 tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithGenericCallSignaturesWithOptionalParameters.ts:96:14: This type parameter might need an `extends T` constraint.
            a4: (x: T, y: T) => T; 
        }
    
    
        interface I15<T> extends Base2 {
                  ~~~
!!! error TS2430: Interface 'I15<T>' incorrectly extends interface 'Base2'.
!!! error TS2430:   The types returned by 'a5(...)' are incompatible between these types.
!!! error TS2430:     Type 'T' is not assignable to type 'T'. Two different types with this name exist, but they are unrelated.
!!! error TS2430:       'T' could be instantiated with an arbitrary type which could be unrelated to 'T'.
!!! related TS2208 tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithGenericCallSignaturesWithOptionalParameters.ts:160:19: This type parameter might need an `extends T` constraint.
            a5: () => T; 
        }
    
        interface I16<T> extends Base2 {
                  ~~~
!!! error TS2430: Interface 'I16<T>' incorrectly extends interface 'Base2'.
!!! error TS2430:   Types of property 'a5' are incompatible.
!!! error TS2430:     Type '(x?: T, y?: T) => T' is not assignable to type '<T>(x?: T, y?: T) => T'.
!!! error TS2430:       Types of parameters 'x' and 'x' are incompatible.
!!! error TS2430:         Type 'T' is not assignable to type 'T'. Two different types with this name exist, but they are unrelated.
!!! error TS2430:           'T' could be instantiated with an arbitrary type which could be unrelated to 'T'.
!!! related TS2208 tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithGenericCallSignaturesWithOptionalParameters.ts:97:14: This type parameter might need an `extends T` constraint.
            a5: (x?: T, y?: T) => T; 
        }
    
        interface I17<T> extends Base2 {
                  ~~~
!!! error TS2430: Interface 'I17<T>' incorrectly extends interface 'Base2'.
!!! error TS2430:   Types of property 'a5' are incompatible.
!!! error TS2430:     Type '(x: T) => T' is not assignable to type '<T>(x?: T, y?: T) => T'.
!!! error TS2430:       Types of parameters 'x' and 'x' are incompatible.
!!! error TS2430:         Type 'T' is not assignable to type 'T'. Two different types with this name exist, but they are unrelated.
!!! error TS2430:           'T' could be instantiated with an arbitrary type which could be unrelated to 'T'.
!!! related TS2208 tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithGenericCallSignaturesWithOptionalParameters.ts:97:14: This type parameter might need an `extends T` constraint.
            a5: (x: T) => T;
        }
    
        interface I18<T> extends Base2 {
                  ~~~
!!! error TS2430: Interface 'I18<T>' incorrectly extends interface 'Base2'.
!!! error TS2430:   Types of property 'a5' are incompatible.
!!! error TS2430:     Type '(x: T, y: T) => T' is not assignable to type '<T>(x?: T, y?: T) => T'.
!!! error TS2430:       Types of parameters 'x' and 'x' are incompatible.
!!! error TS2430:         Type 'T' is not assignable to type 'T'. Two different types with this name exist, but they are unrelated.
!!! error TS2430:           'T' could be instantiated with an arbitrary type which could be unrelated to 'T'.
!!! related TS2208 tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypingWithGenericCallSignaturesWithOptionalParameters.ts:97:14: This type parameter might need an `extends T` constraint.
            a5: (x: T, y: T) => T; 
        }
    }
    
    module GenericSignaturesValid {
    
        interface Base2 {
            a: <T>() => T;
            a2: <T>(x?: T) => T;
            a3: <T>(x: T) => T;
            a4: <T>(x: T, y?: T) => T;
            a5: <T>(x?: T, y?: T) => T;
        }
    
        // BUG 833350
        interface I1 extends Base2 {
            a: <T>() => T; // ok, same number of required params
        }
    
        interface I2 extends Base2 {
            a: <T>(x?: T) => T; // error, not identical and contextual signature instatiation can't make inference from T to T
        }
    
        interface I3 extends Base2 {
                  ~~
!!! error TS2430: Interface 'I3' incorrectly extends interface 'Base2'.
!!! error TS2430:   Types of property 'a' are incompatible.
!!! error TS2430:     Type '<T>(x: T) => T' is not assignable to type '<T>() => T'.
            a: <T>(x: T) => T; // error, not identical and contextual signature instatiation can't make inference from T to T
        }
    
    
        interface I4 extends Base2 {
            a2: <T>() => T; // error, not identical and contextual signature instatiation can't make inference from T to T
        }
    
        interface I5 extends Base2 {
            a2: <T>(x?: T) => T; // ok, identical
        }
    
        interface I6 extends Base2 {
            a2: <T>(x: T) => T; // ok, same number of params
        }
    
    
        interface I7 extends Base2 {
            a3: <T>() => T; // error, no inferences for T so {} not assignable to {} in return type
        }
    
        interface I8 extends Base2 {
            a3: <T>(x?: T) => T; // ok, fewer required params
        }
    
        interface I9 extends Base2 {
            a3: <T>(x: T) => T; // ok, identical, same number of required params
        }
    
        interface I10 extends Base2 {
                  ~~~
!!! error TS2430: Interface 'I10' incorrectly extends interface 'Base2'.
!!! error TS2430:   Types of property 'a3' are incompatible.
!!! error TS2430:     Type '<T>(x: T, y: T) => T' is not assignable to type '<T>(x: T) => T'.
            a3: <T>(x: T, y: T) => T;  // error, too many required params
        }
    
    
        interface I11 extends Base2 {
            a4: <T>() => T; // error, not identical and contextual signature instatiation can't make inference from T to T
        }
    
        interface I12 extends Base2 {
            a4: <T>(x?: T, y?: T) => T; // ok, fewer required params
        }
    
        interface I13 extends Base2 {
            a4: <T>(x: T) => T; // ok, same T of required params
        }
    
        interface I14 extends Base2 {
            a4: <T>(x: T, y: T) => T;  // error, too many required params
        }
    
    
        interface I15 extends Base2 {
            a5: <T>() => T; // error, not identical and contextual signature instatiation can't make inference from T to T
        }
    
        interface I16 extends Base2 {
            a5: <T>(x?: T, y?: T) => T; // ok, fewer required params
        }
    
        interface I17 extends Base2 {
            a5: <T>(x: T) => T; // ok, all present params match
        }
    
        interface I18 extends Base2 {
            a5: <T>(x: T, y: T) => T;  // ok, same number of params
        }
    }