contextualTypeWithUnionTypeCallSignatures.ts(33,54): error TS7006: Parameter 'a' implicitly has an 'any' type.
contextualTypeWithUnionTypeCallSignatures.ts(36,54): error TS7006: Parameter 'a' implicitly has an 'any' type.


==== contextualTypeWithUnionTypeCallSignatures.ts (2 errors) ====
    //When used as a contextual type, a union type U has those members that are present in any of 
    // its constituent types, with types that are unions of the respective members in the constituent types. 
    
    // Let S be the set of types in U that have call signatures.
    // If S is not empty and the sets of call signatures of the types in S are identical ignoring return types,
    // U has the same set of call signatures, but with return types that are unions of the return types of the respective call signatures from each type in S.
    
    interface IWithNoCallSignatures {
        foo: string;
    }
    interface IWithCallSignatures {
        (a: number): string;
    }
    interface IWithCallSignatures2 {
        (a: number): number;
    }
    interface IWithCallSignatures3 {
        (b: string): number;
    }
    interface IWithCallSignatures4 {
        (a: number): string;
        (a: string, b: number): number;
    }
    
    // With no call signature | callSignatures
    var x: IWithNoCallSignatures | IWithCallSignatures = a => a.toString();
    
    // With call signatures with different return type
    var x2: IWithCallSignatures | IWithCallSignatures2 = a => a.toString(); // Like iWithCallSignatures
    var x2: IWithCallSignatures | IWithCallSignatures2 = a => a; // Like iWithCallSignatures2
    
    // With call signatures of mismatching parameter type
    var x3: IWithCallSignatures | IWithCallSignatures3 = a => /*here a should be any*/ a.toString();
                                                         ~
!!! error TS7006: Parameter 'a' implicitly has an 'any' type.
    
    // With call signature count mismatch
    var x4: IWithCallSignatures | IWithCallSignatures4 = a => /*here a should be any*/ a.toString();
                                                         ~
!!! error TS7006: Parameter 'a' implicitly has an 'any' type.