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Template `std.conv.castFrom`

A wrapper on top of the built-in cast operator that allows one to restrict casting of the original type of the value.


						
				template castFrom(From)
				;

A common issue with using a raw cast is that it may silently continue to compile even if the value's type has changed during refactoring, which breaks the initial assumption about the cast.

Contained Functions

Name	Description
to

Parameters

Name	Description
From	The type to cast from. The programmer must ensure it is legal to make this cast.

Example

// Regular cast, which has been verified to be legal by the programmer:
{
    long x;
    auto y = cast(int) x;
}

// However this will still compile if 'x' is changed to be a pointer:
{
    long* x;
    auto y = cast(int) x;
}

// castFrom provides a more reliable alternative to casting:
{
    long x;
    auto y = castFrom!long.to!int(x);
}

// Changing the type of 'x' will now issue a compiler error,
// allowing bad casts to be caught before it's too late:
{
    long* x;
    static assert(
        !__traits(compiles, castFrom!long.to!int(x))
    );

    // if cast is still needed, must be changed to:
    auto y = castFrom!(long*).to!int(x);
}

Authors

Walter Bright, Andrei Alexandrescu, Shin Fujishiro, Adam D. Ruppe, Kenji Hara

License

Boost License 1.0.