-
-
Notifications
You must be signed in to change notification settings - Fork 701
/
sumtype.d
2513 lines (2121 loc) · 62 KB
/
sumtype.d
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
/++
[SumType] is a generic discriminated union implementation that uses
design-by-introspection to generate safe and efficient code. Its features
include:
* [Pattern matching.][match]
* Support for self-referential types.
* Full attribute correctness (`pure`, `@safe`, `@nogc`, and `nothrow` are
inferred whenever possible).
* A type-safe and memory-safe API compatible with DIP 1000 (`scope`).
* No dependency on runtime type information (`TypeInfo`).
* Compatibility with BetterC.
License: Boost License 1.0
Authors: Paul Backus
+/
module std.sumtype;
/// $(DIVID basic-usage,$(H3 Basic usage))
version (D_BetterC) {} else
@safe unittest
{
import std.math.operations : isClose;
struct Fahrenheit { double degrees; }
struct Celsius { double degrees; }
struct Kelvin { double degrees; }
alias Temperature = SumType!(Fahrenheit, Celsius, Kelvin);
// Construct from any of the member types.
Temperature t1 = Fahrenheit(98.6);
Temperature t2 = Celsius(100);
Temperature t3 = Kelvin(273);
// Use pattern matching to access the value.
Fahrenheit toFahrenheit(Temperature t)
{
return Fahrenheit(
t.match!(
(Fahrenheit f) => f.degrees,
(Celsius c) => c.degrees * 9.0/5 + 32,
(Kelvin k) => k.degrees * 9.0/5 - 459.4
)
);
}
assert(toFahrenheit(t1).degrees.isClose(98.6));
assert(toFahrenheit(t2).degrees.isClose(212));
assert(toFahrenheit(t3).degrees.isClose(32));
// Use ref to modify the value in place.
void freeze(ref Temperature t)
{
t.match!(
(ref Fahrenheit f) => f.degrees = 32,
(ref Celsius c) => c.degrees = 0,
(ref Kelvin k) => k.degrees = 273
);
}
freeze(t1);
assert(toFahrenheit(t1).degrees.isClose(32));
// Use a catch-all handler to give a default result.
bool isFahrenheit(Temperature t)
{
return t.match!(
(Fahrenheit f) => true,
_ => false
);
}
assert(isFahrenheit(t1));
assert(!isFahrenheit(t2));
assert(!isFahrenheit(t3));
}
/** $(DIVID introspection-based-matching, $(H3 Introspection-based matching))
*
* In the `length` and `horiz` functions below, the handlers for `match` do not
* specify the types of their arguments. Instead, matching is done based on how
* the argument is used in the body of the handler: any type with `x` and `y`
* properties will be matched by the `rect` handlers, and any type with `r` and
* `theta` properties will be matched by the `polar` handlers.
*/
version (D_BetterC) {} else
@safe unittest
{
import std.math.operations : isClose;
import std.math.trigonometry : cos;
import std.math.constants : PI;
import std.math.algebraic : sqrt;
struct Rectangular { double x, y; }
struct Polar { double r, theta; }
alias Vector = SumType!(Rectangular, Polar);
double length(Vector v)
{
return v.match!(
rect => sqrt(rect.x^^2 + rect.y^^2),
polar => polar.r
);
}
double horiz(Vector v)
{
return v.match!(
rect => rect.x,
polar => polar.r * cos(polar.theta)
);
}
Vector u = Rectangular(1, 1);
Vector v = Polar(1, PI/4);
assert(length(u).isClose(sqrt(2.0)));
assert(length(v).isClose(1));
assert(horiz(u).isClose(1));
assert(horiz(v).isClose(sqrt(0.5)));
}
/** $(DIVID arithmetic-expression-evaluator, $(H3 Arithmetic expression evaluator))
*
* This example makes use of the special placeholder type `This` to define a
* [recursive data type](https://en.wikipedia.org/wiki/Recursive_data_type): an
* [abstract syntax tree](https://en.wikipedia.org/wiki/Abstract_syntax_tree) for
* representing simple arithmetic expressions.
*/
version (D_BetterC) {} else
@system unittest
{
import std.functional : partial;
import std.traits : EnumMembers;
import std.typecons : Tuple;
enum Op : string
{
Plus = "+",
Minus = "-",
Times = "*",
Div = "/"
}
// An expression is either
// - a number,
// - a variable, or
// - a binary operation combining two sub-expressions.
alias Expr = SumType!(
double,
string,
Tuple!(Op, "op", This*, "lhs", This*, "rhs")
);
// Shorthand for Tuple!(Op, "op", Expr*, "lhs", Expr*, "rhs"),
// the Tuple type above with Expr substituted for This.
alias BinOp = Expr.Types[2];
// Factory function for number expressions
Expr* num(double value)
{
return new Expr(value);
}
// Factory function for variable expressions
Expr* var(string name)
{
return new Expr(name);
}
// Factory function for binary operation expressions
Expr* binOp(Op op, Expr* lhs, Expr* rhs)
{
return new Expr(BinOp(op, lhs, rhs));
}
// Convenience wrappers for creating BinOp expressions
alias sum = partial!(binOp, Op.Plus);
alias diff = partial!(binOp, Op.Minus);
alias prod = partial!(binOp, Op.Times);
alias quot = partial!(binOp, Op.Div);
// Evaluate expr, looking up variables in env
double eval(Expr expr, double[string] env)
{
return expr.match!(
(double num) => num,
(string var) => env[var],
(BinOp bop)
{
double lhs = eval(*bop.lhs, env);
double rhs = eval(*bop.rhs, env);
final switch (bop.op)
{
static foreach (op; EnumMembers!Op)
{
case op:
return mixin("lhs" ~ op ~ "rhs");
}
}
}
);
}
// Return a "pretty-printed" representation of expr
string pprint(Expr expr)
{
import std.format : format;
return expr.match!(
(double num) => "%g".format(num),
(string var) => var,
(BinOp bop) => "(%s %s %s)".format(
pprint(*bop.lhs),
cast(string) bop.op,
pprint(*bop.rhs)
)
);
}
Expr* myExpr = sum(var("a"), prod(num(2), var("b")));
double[string] myEnv = ["a":3, "b":4, "c":7];
assert(eval(*myExpr, myEnv) == 11);
assert(pprint(*myExpr) == "(a + (2 * b))");
}
import std.format.spec : FormatSpec, singleSpec;
import std.meta : AliasSeq, Filter, IndexOf = staticIndexOf, Map = staticMap;
import std.meta : NoDuplicates;
import std.meta : anySatisfy, allSatisfy;
import std.traits : hasElaborateCopyConstructor, hasElaborateDestructor;
import std.traits : isAssignable, isCopyable, isStaticArray, isRvalueAssignable;
import std.traits : ConstOf, ImmutableOf, InoutOf, TemplateArgsOf;
import std.traits : CommonType;
import std.typecons : ReplaceTypeUnless;
import std.typecons : Flag;
/// Placeholder used to refer to the enclosing [SumType].
struct This {}
// Converts an unsigned integer to a compile-time string constant.
private enum toCtString(ulong n) = n.stringof[0 .. $ - "LU".length];
// Check that .stringof does what we expect, since it's not guaranteed by the
// language spec.
@safe unittest
{
assert(toCtString!0 == "0");
assert(toCtString!123456 == "123456");
}
// True if a variable of type T can appear on the lhs of an assignment
private enum isAssignableTo(T) =
isAssignable!T || (!isCopyable!T && isRvalueAssignable!T);
// toHash is required by the language spec to be nothrow and @safe
private enum isHashable(T) = __traits(compiles,
() nothrow @safe { hashOf(T.init); }
);
private enum hasPostblit(T) = __traits(hasPostblit, T);
/**
* A [tagged union](https://en.wikipedia.org/wiki/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][match].
*
* To avoid ambiguity, duplicate types are not allowed (but see the
* ["basic usage" example](#basic-usage) for a workaround).
*
* 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](#arithmetic-expression-evaluator) 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.
*
* See_Also: $(REF Algebraic, std,variant)
*/
struct SumType(Types...)
if (is(NoDuplicates!Types == Types) && Types.length > 0)
{
/// The types a `SumType` can hold.
alias Types = AliasSeq!(
ReplaceTypeUnless!(isSumTypeInstance, This, typeof(this), TemplateArgsOf!SumType)
);
private:
enum bool canHoldTag(T) = Types.length <= T.max;
alias unsignedInts = AliasSeq!(ubyte, ushort, uint, ulong);
alias Tag = Filter!(canHoldTag, unsignedInts)[0];
union Storage
{
// Workaround for https://issues.dlang.org/show_bug.cgi?id=20068
template memberName(T)
if (IndexOf!(T, Types) >= 0)
{
enum tid = IndexOf!(T, Types);
mixin("enum memberName = `values_", toCtString!tid, "`;");
}
static foreach (T; Types)
{
mixin("T ", memberName!T, ";");
}
}
Storage storage;
Tag tag;
/* Accesses the value stored in a SumType.
*
* This method is memory-safe, provided that:
*
* 1. A SumType's tag is always accurate.
* 2. A SumType cannot be assigned to in @safe code if that assignment
* could cause unsafe aliasing.
*
* All code that accesses a SumType's tag or storage directly, including
* @safe code in this module, must be manually checked to ensure that it
* does not violate either of the above requirements.
*/
@trusted
ref inout(T) get(T)() inout
if (IndexOf!(T, Types) >= 0)
{
enum tid = IndexOf!(T, Types);
assert(tag == tid,
"This `" ~ SumType.stringof ~
"` does not contain a(n) `" ~ T.stringof ~ "`"
);
return __traits(getMember, storage, Storage.memberName!T);
}
public:
// Workaround for https://issues.dlang.org/show_bug.cgi?id=21399
version (StdDdoc)
{
// Dummy type to stand in for loop variable
private struct T;
/// Constructs a `SumType` holding a specific value.
this(T value);
/// ditto
this(const(T) value) const;
/// ditto
this(immutable(T) value) immutable;
}
static foreach (tid, T; Types)
{
/// Constructs a `SumType` holding a specific value.
this(T value)
{
import core.lifetime : forward;
storage = ()
{
static if (isCopyable!T)
{
mixin("Storage newStorage = { ",
// Workaround for https://issues.dlang.org/show_bug.cgi?id=21542
Storage.memberName!T, ": (__ctfe ? value : forward!value)",
" };");
}
else
{
mixin("Storage newStorage = { ",
Storage.memberName!T, " : forward!value",
" };");
}
return newStorage;
}();
tag = tid;
}
static if (isCopyable!(const(T)))
{
static if (IndexOf!(const(T), Map!(ConstOf, Types)) == tid)
{
/// ditto
this(const(T) value) const
{
storage = ()
{
mixin("const(Storage) newStorage = { ",
Storage.memberName!T, ": value",
" };");
return newStorage;
}();
tag = tid;
}
}
}
else
{
@disable this(const(T) value) const;
}
static if (isCopyable!(immutable(T)))
{
static if (IndexOf!(immutable(T), Map!(ImmutableOf, Types)) == tid)
{
/// ditto
this(immutable(T) value) immutable
{
storage = ()
{
mixin("immutable(Storage) newStorage = { ",
Storage.memberName!T, ": value",
" };");
return newStorage;
}();
tag = tid;
}
}
}
else
{
@disable this(immutable(T) value) immutable;
}
}
static if (anySatisfy!(hasElaborateCopyConstructor, Types))
{
static if
(
allSatisfy!(isCopyable, Map!(InoutOf, Types))
&& !anySatisfy!(hasPostblit, Map!(InoutOf, Types))
)
{
/// Constructs a `SumType` that's a copy of another `SumType`.
this(ref inout(SumType) other) inout
{
storage = other.match!((ref value) {
alias OtherTypes = Map!(InoutOf, Types);
enum tid = IndexOf!(typeof(value), OtherTypes);
alias T = Types[tid];
mixin("inout(Storage) newStorage = { ",
Storage.memberName!T, ": value",
" };");
return newStorage;
});
tag = other.tag;
}
}
else
{
static if (allSatisfy!(isCopyable, Types))
{
/// ditto
this(ref SumType other)
{
storage = other.match!((ref value) {
alias T = typeof(value);
mixin("Storage newStorage = { ",
Storage.memberName!T, ": value",
" };");
return newStorage;
});
tag = other.tag;
}
}
else
{
@disable this(ref SumType other);
}
static if (allSatisfy!(isCopyable, Map!(ConstOf, Types)))
{
/// ditto
this(ref const(SumType) other) const
{
storage = other.match!((ref value) {
alias OtherTypes = Map!(ConstOf, Types);
enum tid = IndexOf!(typeof(value), OtherTypes);
alias T = Types[tid];
mixin("const(Storage) newStorage = { ",
Storage.memberName!T, ": value",
" };");
return newStorage;
});
tag = other.tag;
}
}
else
{
@disable this(ref const(SumType) other) const;
}
static if (allSatisfy!(isCopyable, Map!(ImmutableOf, Types)))
{
/// ditto
this(ref immutable(SumType) other) immutable
{
storage = other.match!((ref value) {
alias OtherTypes = Map!(ImmutableOf, Types);
enum tid = IndexOf!(typeof(value), OtherTypes);
alias T = Types[tid];
mixin("immutable(Storage) newStorage = { ",
Storage.memberName!T, ": value",
" };");
return newStorage;
});
tag = other.tag;
}
}
else
{
@disable this(ref immutable(SumType) other) immutable;
}
}
}
version (SumTypeNoDefaultCtor)
{
@disable this();
}
// Workaround for https://issues.dlang.org/show_bug.cgi?id=21399
version (StdDdoc)
{
// Dummy type to stand in for loop variable
private struct T;
/**
* Assigns a value to a `SumType`.
*
* Assigning to a `SumType` is `@system` if any of the
* `SumType`'s members contain pointers or references, since
* those members may be reachable through external references,
* and overwriting them could therefore lead to memory
* corruption.
*
* An individual assignment can be `@trusted` if the caller can
* guarantee that there are no outstanding references to $(I any)
* of the `SumType`'s members when the assignment occurs.
*/
ref SumType opAssign(T rhs);
}
static foreach (tid, T; Types)
{
static if (isAssignableTo!T)
{
/**
* Assigns a value to a `SumType`.
*
* Assigning to a `SumType` is `@system` if any of the `SumType`'s
* $(I other) members contain pointers or references, since those
* members may be reachable through external references, and
* overwriting them could therefore lead to memory corruption.
*
* An individual assignment can be `@trusted` if the caller can
* guarantee that, when the assignment occurs, there are no
* outstanding references to any such members.
*/
ref SumType opAssign(T rhs)
{
import core.lifetime : forward;
import std.traits : hasIndirections, hasNested;
import std.meta : AliasSeq, Or = templateOr;
alias OtherTypes =
AliasSeq!(Types[0 .. tid], Types[tid + 1 .. $]);
enum unsafeToOverwrite =
anySatisfy!(Or!(hasIndirections, hasNested), OtherTypes);
static if (unsafeToOverwrite)
{
cast(void) () @system {}();
}
this.match!destroyIfOwner;
mixin("Storage newStorage = { ",
Storage.memberName!T, ": forward!rhs",
" };");
storage = newStorage;
tag = tid;
return this;
}
}
}
static if (allSatisfy!(isAssignableTo, Types))
{
static if (allSatisfy!(isCopyable, Types))
{
/**
* Copies the value from another `SumType` into this one.
*
* See the value-assignment overload for details on `@safe`ty.
*
* Copy assignment is `@disable`d if any of `Types` is non-copyable.
*/
ref SumType opAssign(ref SumType rhs)
{
rhs.match!((ref value) { this = value; });
return this;
}
}
else
{
@disable ref SumType opAssign(ref SumType rhs);
}
/**
* Moves the value from another `SumType` into this one.
*
* See the value-assignment overload for details on `@safe`ty.
*/
ref SumType opAssign(SumType rhs)
{
import core.lifetime : move;
rhs.match!((ref value) { this = move(value); });
return this;
}
}
/**
* Compares two `SumType`s for equality.
*
* Two `SumType`s are equal if they are the same kind of `SumType`, they
* contain values of the same type, and those values are equal.
*/
bool opEquals(this This, Rhs)(auto ref Rhs rhs)
if (!is(CommonType!(This, Rhs) == void))
{
static if (is(This == Rhs))
{
return AliasSeq!(this, rhs).match!((ref value, ref rhsValue) {
static if (is(typeof(value) == typeof(rhsValue)))
{
return value == rhsValue;
}
else
{
return false;
}
});
}
else
{
alias CommonSumType = CommonType!(This, Rhs);
return cast(CommonSumType) this == cast(CommonSumType) rhs;
}
}
// Workaround for https://issues.dlang.org/show_bug.cgi?id=19407
static if (__traits(compiles, anySatisfy!(hasElaborateDestructor, Types)))
{
// If possible, include the destructor only when it's needed
private enum includeDtor = anySatisfy!(hasElaborateDestructor, Types);
}
else
{
// If we can't tell, always include it, even when it does nothing
private enum includeDtor = true;
}
static if (includeDtor)
{
/// Calls the destructor of the `SumType`'s current value.
~this()
{
this.match!destroyIfOwner;
}
}
invariant
{
this.match!((ref value) {
static if (is(typeof(value) == class))
{
if (value !is null)
{
assert(value);
}
}
else static if (is(typeof(value) == struct))
{
assert(&value);
}
});
}
// Workaround for https://issues.dlang.org/show_bug.cgi?id=21400
version (StdDdoc)
{
/**
* Returns a string representation of the `SumType`'s current value.
*
* Not available when compiled with `-betterC`.
*/
string toString(this This)();
/**
* Handles formatted writing of the `SumType`'s current value.
*
* Not available when compiled with `-betterC`.
*
* Params:
* sink = Output range to write to.
* fmt = Format specifier to use.
*
* See_Also: $(REF formatValue, std,format)
*/
void toString(this This, Sink, Char)(ref Sink sink, const ref FormatSpec!Char fmt);
}
version (D_BetterC) {} else
/**
* Returns a string representation of the `SumType`'s current value.
*
* Not available when compiled with `-betterC`.
*/
string toString(this This)()
{
import std.conv : to;
return this.match!(to!string);
}
version (D_BetterC) {} else
/**
* Handles formatted writing of the `SumType`'s current value.
*
* Not available when compiled with `-betterC`.
*
* Params:
* sink = Output range to write to.
* fmt = Format specifier to use.
*
* See_Also: $(REF formatValue, std,format)
*/
void toString(this This, Sink, Char)(ref Sink sink, const ref FormatSpec!Char fmt)
{
import std.format.write : formatValue;
this.match!((ref value) {
formatValue(sink, value, fmt);
});
}
static if (allSatisfy!(isHashable, Map!(ConstOf, Types)))
{
// Workaround for https://issues.dlang.org/show_bug.cgi?id=21400
version (StdDdoc)
{
/**
* Returns the hash of the `SumType`'s current value.
*
* Not available when compiled with `-betterC`.
*/
size_t toHash() const;
}
// Workaround for https://issues.dlang.org/show_bug.cgi?id=20095
version (D_BetterC) {} else
/**
* Returns the hash of the `SumType`'s current value.
*
* Not available when compiled with `-betterC`.
*/
size_t toHash() const
{
return this.match!hashOf;
}
}
}
// Construction
@safe unittest
{
alias MySum = SumType!(int, float);
MySum x = MySum(42);
MySum y = MySum(3.14);
}
// Assignment
@safe unittest
{
alias MySum = SumType!(int, float);
MySum x = MySum(42);
x = 3.14;
}
// Self assignment
@safe unittest
{
alias MySum = SumType!(int, float);
MySum x = MySum(42);
MySum y = MySum(3.14);
y = x;
}
// Equality
@safe unittest
{
alias MySum = SumType!(int, float);
assert(MySum(123) == MySum(123));
assert(MySum(123) != MySum(456));
assert(MySum(123) != MySum(123.0));
assert(MySum(123) != MySum(456.0));
}
// Equality of differently-qualified SumTypes
// Disabled in BetterC due to use of dynamic arrays
version (D_BetterC) {} else
@safe unittest
{
alias SumA = SumType!(int, float);
alias SumB = SumType!(const(int[]), int[]);
alias SumC = SumType!(int[], const(int[]));
int[] ma = [1, 2, 3];
const(int[]) ca = [1, 2, 3];
assert(const(SumA)(123) == SumA(123));
assert(const(SumB)(ma[]) == SumB(ca[]));
assert(const(SumC)(ma[]) == SumC(ca[]));
}
// Imported types
@safe unittest
{
import std.typecons : Tuple;
alias MySum = SumType!(Tuple!(int, int));
}
// const and immutable types
@safe unittest
{
alias MySum = SumType!(const(int[]), immutable(float[]));
}
// Recursive types
@safe unittest
{
alias MySum = SumType!(This*);
assert(is(MySum.Types[0] == MySum*));
}
// Allowed types
@safe unittest
{
import std.meta : AliasSeq;
alias MySum = SumType!(int, float, This*);
assert(is(MySum.Types == AliasSeq!(int, float, MySum*)));
}
// Types with destructors and postblits
@system unittest
{
int copies;
static struct Test
{
bool initialized = false;
int* copiesPtr;
this(this) { (*copiesPtr)++; }
~this() { if (initialized) (*copiesPtr)--; }
}
alias MySum = SumType!(int, Test);
Test t = Test(true, &copies);
{
MySum x = t;
assert(copies == 1);
}
assert(copies == 0);
{
MySum x = 456;
assert(copies == 0);
}
assert(copies == 0);
{
MySum x = t;
assert(copies == 1);
x = 456;
assert(copies == 0);
}
{
MySum x = 456;
assert(copies == 0);
x = t;
assert(copies == 1);
}
{
MySum x = t;
MySum y = x;
assert(copies == 2);
}
{
MySum x = t;
MySum y;
y = x;
assert(copies == 2);
}
}
// Doesn't destroy reference types
// Disabled in BetterC due to use of classes
version (D_BetterC) {} else
@system unittest
{
bool destroyed;
class C
{
~this()
{
destroyed = true;
}
}
struct S
{
~this() {}
}
alias MySum = SumType!(S, C);
C c = new C();
{
MySum x = c;
destroyed = false;
}
assert(!destroyed);
{
MySum x = c;
destroyed = false;
x = S();
assert(!destroyed);
}
}
// Types with @disable this()
@safe unittest
{
static struct NoInit
{
@disable this();
}
alias MySum = SumType!(NoInit, int);
assert(!__traits(compiles, MySum()));
auto _ = MySum(42);
}