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
|
template accept(x) =
static: assert compiles(x)
template reject(x) =
static: assert(not compiles(x))
{.experimental: "notnil".}
type
TRefObj = ref object
x: int
THasNotNils = object of RootObj
a: TRefObj not nil
b: TRefObj not nil
c: TRefObj
THasNotNilsRef = ref THasNotNils
TChoice = enum A, B, C, D, E, F
TBaseHasNotNils = object of THasNotNils
case choice: TChoice
of A:
moreNotNils: THasNotNils
of B:
indirectNotNils: ref THasNotNils
else:
discard
TObj = object
case choice: TChoice
of A:
a: int
of B, C:
bc: int
of D:
d: TRefObj
of E:
e1: TRefObj
e2: int
else:
f: string
TNestedChoices = object
case outerChoice: bool
of true:
truthy: int
else:
case innerChoice: TChoice
of A:
a: int
of B:
b: int
else:
notnil: TRefObj not nil
var x = D
var nilRef: TRefObj
var notNilRef = TRefObj(x: 20)
proc makeHasNotNils: ref THasNotNils =
result.a = TRefObj(x: 10)
result.b = TRefObj(x: 20)
accept TObj()
accept TObj(choice: A)
reject TObj(choice: A, bc: 10) # bc is in the wrong branch
accept TObj(choice: B, bc: 20)
reject TObj(a: 10) # branch selected without providing discriminator
reject TObj(choice: x, a: 10) # the discrimantor must be a compile-time value when a branch is selected
accept TObj(choice: x) # it's OK to use run-time value when a branch is not selected
accept TObj(choice: F, f: "") # match an else clause
reject TObj(f: "") # the discriminator must still be provided for an else clause
reject TObj(a: 10, f: "") # conflicting fields
accept TObj(choice: E, e1: TRefObj(x: 10), e2: 10)
accept THasNotNils(a: notNilRef, b: notNilRef, c: nilRef)
# XXX: the "not nil" logic in the compiler is not strong enough to catch this one yet:
# reject THasNotNils(a: notNilRef, b: nilRef, c: nilRef)
reject THasNotNils(b: notNilRef, c: notNilRef) # there is a missing not nil field
reject THasNotNils() # again, missing fields
accept THasNotNils(a: notNilRef, b: notNilRef) # it's OK to omit a non-mandatory field
# missing not nils in base
reject TBaseHasNotNils()
# once you take care of them, it's ok
accept TBaseHasNotNils(a: notNilRef, b: notNilRef, choice: D)
# this one is tricky!
# it has to be rejected, because choice gets value A by default (0) and this means
# that the THasNotNils field will be active (and it will demand more initialized fields).
reject TBaseHasNotNils(a: notNilRef, b: notNilRef)
# you can select a branch without mandatory fields
accept TBaseHasNotNils(a: notNilRef, b: notNilRef, choice: B)
accept TBaseHasNotNils(a: notNilRef, b: notNilRef, choice: B, indirectNotNils: nil)
# but once you select a branch with mandatory fields, you must specify them
reject TBaseHasNotNils(a: notNilRef, b: notNilRef, choice: A)
reject TBaseHasNotNils(a: notNilRef, b: notNilRef, choice: A, indirectNotNils: nil)
reject TBaseHasNotNils(a: notNilRef, b: notNilRef, choice: A, moreNotNils: THasNotNils())
accept TBaseHasNotNils(a: notNilRef, b: notNilRef, choice: A, moreNotNils: THasNotNils(a: notNilRef, b: notNilRef))
# all rules apply to sub-objects as well
accept TBaseHasNotNils(a: notNilRef, b: notNilRef, choice: B, indirectNotNils: makeHasNotNils())
reject TBaseHasNotNils(a: notNilRef, b: notNilRef, choice: B, indirectNotNils: THasNotNilsRef())
accept TBaseHasNotNils(a: notNilRef, b: notNilRef, choice: B, indirectNotNils: THasNotNilsRef(a: notNilRef, b: notNilRef))
# this will be accepted, because the false outer branch will be taken and the inner A branch
accept TNestedChoices()
# but if we supply a run-time value for the inner branch, the compiler won't be able to prove
# that the notnil field was initialized
reject TNestedChoices(outerChoice: false, innerChoice: x) # XXX: The error message is not very good here
reject TNestedChoices(outerChoice: true, innerChoice: A) # XXX: The error message is not very good here
accept TNestedChoices(outerChoice: false, innerChoice: B)
reject TNestedChoices(outerChoice: false, innerChoice: C)
accept TNestedChoices(outerChoice: false, innerChoice: C, notnil: notNilRef)
reject TNestedChoices(outerChoice: false, innerChoice: C, notnil: nil)
|
