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## todo publish the `isCyclic` when it's mature.
proc isCyclic(t: typedesc): bool {.magic: "TypeTrait".} =
## Returns true if the type can potentially form a cyclic type
template cyclicYes(x: typed) =
doAssert isCyclic(x)
template cyclicNo(x: typed) =
doAssert not isCyclic(x)
# atomic types are not cyclic
cyclicNo(int)
cyclicNo(float)
cyclicNo(string)
cyclicNo(char)
cyclicNo(void)
type
Object = object
Ref = ref object
cyclicNo(Object)
cyclicNo(Ref)
type
Data1 = ref object
Data2 = ref object
id: Data1
cyclicNo(Data2)
type
Cyclone = ref object
data: Cyclone
Alias = Cyclone
Acyclic {.acyclic.} = ref object
data: Acyclic
LinkedNode = object
next: ref LinkedNode
LinkedNodeWithCursor = object
next {.cursor.} : ref LinkedNodeWithCursor
cyclicYes(Cyclone)
cyclicYes(Alias)
cyclicNo(seq[Cyclone])
cyclicNo((Cyclone, ))
cyclicNo(Acyclic)
cyclicYes(LinkedNode)
cyclicNo(LinkedNodeWithCursor) # cursor doesn't increase rc, cannot form a cycle
type
ObjectWithoutCycles = object
data: seq[ObjectWithoutCycles]
cyclicNo(ObjectWithoutCycles)
block:
type
Try = object
id: Best
Best = object
name: ref Try
Best2 = ref Best
cyclicYes(Best)
cyclicYes(Try)
cyclicNo(Best2)
type
Base = object
data: ref seq[Base]
Base2 = ref Base
cyclicYes(Base)
cyclicNo(Base2)
type
Base3 = ref object
id: Base3
Base4 = object
id: ref Base4
cyclicYes(Base3)
cyclicYes(Base4)
cyclicYes(ref Base4)
block:
type Cyclic2 = object
x: ref (Cyclic2, int)
cyclicYes (Cyclic2, int)
cyclicYes (ref (Cyclic2, int))
block:
type
myseq[T] = object
data: ptr UncheckedArray[T]
Node = ref object
kids: myseq[Node]
cyclicNo(Node)
block:
type
myseq[T] = object
data: ptr UncheckedArray[T]
Node = ref object
kids: myseq[Node]
proc `=trace`(x: var myseq[Node]; env: pointer) = discard
cyclicYes(Node)
block:
type
Foo = object
id: ptr ref Foo
cyclicNo(Foo)
block:
type
InheritableObj = object of RootObj
InheritableRef = ref object of RootObj
cyclicYes(InheritableObj)
cyclicYes(InheritableRef)
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