==== tests/cases/compiler/subtypingWithGenericCallSignaturesWithOptionalParameters.ts (6 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> {
                  ~~
!!! subtypingWithGenericCallSignaturesWithOptionalParameters.ts(20,15): error TS2143: Interface 'ClassTypeParam.I3<T>' cannot extend interface 'ClassTypeParam.Base<T>':
!!! 	Types of property 'a' of types 'I3<T>' and 'Base<T>' are incompatible:
!!! 		Call signatures of types '(x: T) => T' and '() => T' are incompatible:
!!! 			Call signature expects 0 or fewer parameters.
            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> {
                  ~~~
!!! subtypingWithGenericCallSignaturesWithOptionalParameters.ts(50,15): error TS2143: Interface 'ClassTypeParam.I10<T>' cannot extend interface 'ClassTypeParam.Base<T>':
!!! 	Types of property 'a3' of types 'I10<T>' and 'Base<T>' are incompatible:
!!! 		Call signatures of types '(x: T, y: T) => T' and '(x: T) => T' are incompatible:
!!! 			Call signature expects 1 or fewer parameters.
            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 {
            a: () => T; 
        }
    
        interface I2<T> extends Base2 {
            a: (x?: T) => T;
        }
    
        interface I3<T> extends Base2 {
                  ~~
!!! subtypingWithGenericCallSignaturesWithOptionalParameters.ts(108,15): error TS2143: Interface 'GenericSignaturesInvalid.I3<T>' cannot extend interface 'GenericSignaturesInvalid.Base2':
!!! 	Types of property 'a' of types 'I3<T>' and 'Base2' are incompatible:
!!! 		Call signatures of types '(x: T) => T' and '<T>() => T' are incompatible:
!!! 			Call signature expects 0 or fewer parameters.
            a: (x: T) => T; 
        }
    
    
        interface I4<T> extends Base2 {
            a2: () => T; 
        }
    
        interface I5<T> extends Base2 {
            a2: (x?: T) => T
        }
    
        interface I6<T> extends Base2 {
            a2: (x: T) => T;
        }
    
    
        interface I7<T> extends Base2 {
            a3: () => T;
        }
    
        interface I8<T> extends Base2 {
            a3: (x?: T) => T; 
        }
    
        interface I9<T> extends Base2 {
            a3: (x: T) => T; 
        }
    
        interface I10<T> extends Base2 {
                  ~~~
!!! subtypingWithGenericCallSignaturesWithOptionalParameters.ts(138,15): error TS2143: Interface 'GenericSignaturesInvalid.I10<T>' cannot extend interface 'GenericSignaturesInvalid.Base2':
!!! 	Types of property 'a3' of types 'I10<T>' and 'Base2' are incompatible:
!!! 		Call signatures of types '(x: T, y: T) => T' and '<T>(x: T) => T' are incompatible:
!!! 			Call signature expects 1 or fewer parameters.
            a3: (x: T, y: T) => T;  
        }
    
    
        interface I11<T> extends Base2 {
            a4: () => T; 
        }
    
        interface I12<T> extends Base2 {
            a4: (x?: T, y?: T) => T; 
        }
    
        interface I13<T> extends Base2 {
            a4: (x: T) => T; 
        }
    
        interface I14<T> extends Base2 {
            a4: (x: T, y: T) => T; 
        }
    
    
        interface I15<T> extends Base2 {
            a5: () => T; 
        }
    
        interface I16<T> extends Base2 {
            a5: (x?: T, y?: T) => T; 
        }
    
        interface I17<T> extends Base2 {
            a5: (x: T) => T;
        }
    
        interface I18<T> extends Base2 {
            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 {
                  ~~
!!! subtypingWithGenericCallSignaturesWithOptionalParameters.ts(196,15): error TS2143: Interface 'GenericSignaturesValid.I3' cannot extend interface 'GenericSignaturesValid.Base2':
!!! 	Types of property 'a' of types 'I3' and 'Base2' are incompatible:
!!! 		Call signatures of types '<T>(x: T) => T' and '<T>() => T' are incompatible:
!!! 			Call signature expects 0 or fewer parameters.
            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 {
                  ~~~
!!! subtypingWithGenericCallSignaturesWithOptionalParameters.ts(226,15): error TS2143: Interface 'GenericSignaturesValid.I10' cannot extend interface 'GenericSignaturesValid.Base2':
!!! 	Types of property 'a3' of types 'I10' and 'Base2' are incompatible:
!!! 		Call signatures of types '<T>(x: T, y: T) => T' and '<T>(x: T) => T' are incompatible:
!!! 			Call signature expects 1 or fewer parameters.
            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
        }
    }