Destructors

A destructor is a special method that allows to perform some actions during struct or class instance destruction. It’s needed in order to free some resources that are belong to the object - deallocate memory, close a file, close a network connection, etc.

A destructor is a method with special name destructor. It’s possible to avoid specifying of this parameter, in such case implicit this will be created. A destructor must have only single parameter - this, other parameters are not allowed. this in a destructor can’t be declared as byval. It’s not possible to overload destructors.

A destructor is called always when a struct or class instance should be destroyed:

• When leaving a scope (for local variables)

• When returning from a function (for arguments)

• In a destructor of other struct/class (for fields)

• During destruction of a temporary variable

• In operations with containers

Destructors for local variables in a single scope and for arguments are called in order reverse to creation order. A destructor of a struct or class calls field destructors implicitly.

struct T {}

struct S
{
    fn destructor()
    {
    } // The "t" destructor will be called

    T t;
}

fn Foo( S s0 )
{
    var S s1;
    var S s2;
    {
         var S s3;
    } // A destructor for "s3" will be called
    // Destructors for "s2" and "s1" will be called
} // A destructor for "s0" will be called

Destructors generation

If a struct or a class has no explicit destructor it will be generated by the compiler automatically. A generated destructor does nothing except calling destructors of fields.

If there is no necessity no destructor should be defined explicitly. Explicit destructor existence may prevent a struct to be constexpr.