What prevents the use of method overloading that differs only by the return type?

Overloading methods that differ only by return type is not possible because the compiler cannot unambiguously determine which method to call based solely on the return type. When calling a method, the compiler looks at the method name and parameter types, but not at the return type.

For example, if there are two methods:

func getValue() -> Int { ... }
func getValue() -> String { ... }

When calling getValue(), the compiler cannot understand which version to invoke, as the method signatures match in name and parameters (none), and differ only in the return type.

Therefore, to overload methods, they must differ in the number or types of parameters, not in the return type.