SumType

A tagged union that can hold a single value from any of a specified set of types.

The value in a SumType can be operated on using pattern matching.

The special type This can be used as a placeholder to create self-referential types, just like with Algebraic. See the "Arithmetic expression evaluator" example for usage.

A SumType is initialized by default to hold the .init value of its first member type, just like a regular union. The version identifier SumTypeNoDefaultCtor can be used to disable this behavior.

To avoid ambiguity, duplicate types are not allowed (but see the "basic usage" example for a workaround).

struct SumType (

TypeArgs...

) if (

is(NoDuplicates!TypeArgs == TypeArgs) &&

TypeArgs.length > 0

) {

import std.meta : AliasSeq, Filter, anySatisfy, allSatisfy;;

import std.traits : hasElaborateCopyConstructor, hasElaborateDestructor, isAssignable, isCopyable;;

import std.typecons : ReplaceType;;

alias Types = AliasSeq!(ReplaceType!(This, typeof(this), TypeArgs));

this(T val);

this(const(T) val);

this(immutable(T) val);

this(const(T) val);

this(immutable(T) val);

this();

static if(isAssignable!T)

void opAssign(T rhs);

bool opEquals(SumType rhs);

~this();

this(this);

static if(allSatisfy!(isCopyable, Types))

string toString();

}

Constructors

this this(T val)
this(const(T) val)
this(immutable(T) val): Constructs a SumType holding a specific value.
this this(const(T) val): Undocumented in source.
this this(immutable(T) val): Undocumented in source.
this this(): Undocumented in source.

Destructor

~this ~this(): Calls the destructor of the SumType's current value.

Postblit

this(this) this(this): Calls the postblit of the SumType's current value.

Members

Aliases

Types alias Types = AliasSeq!(ReplaceType!(This, typeof(this), TypeArgs)): The types a SumType can hold.

Functions

opAssign void opAssign(T rhs): Assigns a value to a SumType.
opEquals bool opEquals(SumType rhs): Compares two SumTypes for equality.
toString string toString(): Returns a string representation of a SumType's value.

Bugs

Types with @disabled opEquals overloads cannot be members of a SumType.