covariance for arrays and sequences
This commit is contained in:
Zahary Karadjov
parent
a802d72452
commit
f4e73344d4
3 changed files with 247 additions and 50 deletions
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@ -1,5 +1,29 @@
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discard """
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cmd: "nim check $file"
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cmd: "nim cpp $file"
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output: '''
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cat
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cat
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dog
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dog
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cat
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cat
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dog
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dog X
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cat
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cat
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dog
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dog
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dog value
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cat value
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dog value
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cat value
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dog
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dog
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dog value
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cat value
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dog 1
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dog 2
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'''
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"""
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template accept(x) =
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@ -8,9 +32,20 @@ template accept(x) =
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template reject(x) =
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static: assert(not compiles(x))
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import macros
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macro skipElse(n: untyped): typed = n[0]
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template acceptWithCovariance(x, otherwise): typed =
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when nimEnableCovariance:
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x
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else:
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reject(x)
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skipElse(otherwise)
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type
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Animal = object of TObject
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x: int
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x: string
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Dog = object of Animal
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y: int
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@ -21,24 +56,94 @@ type
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AnimalRef = ref Animal
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AnimalPtr = ptr Animal
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var dog = new(Dog)
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var cat = new(Cat)
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RefAlias[T] = ref T
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proc wantsRefArray(x: array[2, ref Animal]) = discard
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var dog = new(Dog)
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dog.x = "dog"
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var cat = new(Cat)
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cat.x = "cat"
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proc makeDerivedRef(x: string): ref Dog =
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new(result)
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result.x = x
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proc makeDerived(x: string): Dog =
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result.x = x
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var covariantSeq = @[makeDerivedRef("dog 1"), makeDerivedRef("dog 2")]
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var nonCovariantSeq = @[makeDerived("dog 1"), makeDerived("dog 2")]
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var covariantArr = [makeDerivedRef("dog 1"), makeDerivedRef("dog 2")]
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var nonCovariantArr = [makeDerived("dog 1"), makeDerived("dog 2")]
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proc wantsCovariantSeq1(s: seq[ref Animal]) =
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for a in s: echo a.x
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proc wantsCovariantSeq2(s: seq[AnimalRef]) =
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for a in s: echo a.x
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proc wantsCovariantSeq3(s: seq[RefAlias[Animal]]) =
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for a in s: echo a.x
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proc wantsCovariantOperArray(s: openarray[ref Animal]) =
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for a in s: echo a.x
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proc modifiesCovariantOperArray(s: var openarray[ref Animal]) =
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for a in s: echo a.x
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proc modifiesDerivedOperArray(s: var openarray[ref Dog]) =
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for a in s: echo a.x
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proc wantsNonCovariantOperArray(s: openarray[Animal]) =
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for a in s: echo a.x
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proc wantsCovariantArray(s: array[2, ref Animal]) =
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for a in s: echo a.x
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proc wantsNonCovariantSeq(s: seq[Animal]) =
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for a in s: echo a.x
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proc wantsNonCovariantArray(s: array[2, Animal]) =
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for a in s: echo a.x
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proc modifiesCovariantSeq(s: var seq[ref Animal]) =
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for a in s: echo a.x
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proc modifiesCovariantArray(s: var array[2, ref Animal]) =
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for a in s: echo a.x
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proc modifiesCovariantSeq(s: ptr seq[ref Animal]) =
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for a in s[]: echo a.x
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proc modifiesCovariantArray(s: ptr array[2, ref Animal]) =
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for a in s[]: echo a.x
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proc modifiesDerivedSeq(s: var seq[ref Dog]) =
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for a in s: echo a.x
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proc modifiesDerivedArray(s: var array[2, ref Dog]) =
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for a in s: echo a.x
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proc modifiesDerivedSeq(s: ptr seq[ref Dog]) =
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for a in s[]: echo a.x
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proc modifiesDerivedArray(s: ptr array[2, ref Dog]) =
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for a in s[]: echo a.x
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accept:
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wantsRefArray([AnimalRef(dog), AnimalRef(dog)])
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wantsRefArray([AnimalRef(cat), AnimalRef(dog)])
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wantsRefArray([AnimalRef(cat), dog])
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wantsCovariantArray([AnimalRef(dog), AnimalRef(dog)])
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wantsCovariantArray([AnimalRef(cat), AnimalRef(dog)])
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wantsCovariantArray([AnimalRef(cat), dog])
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# there is a special rule that detects the base
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# type of polymorphic arrays
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wantsRefArray([cat, dog])
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wantsCovariantArray([cat, dog])
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reject:
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# But the current lack of covariance kicks in
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# when we try to pass a derived type array
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wantsRefArray([cat, cat])
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acceptWithCovariance:
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wantsCovariantArray([cat, cat])
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else:
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echo "cat"
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echo "cat"
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var animalRefArray: array[2, ref Animal]
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@ -46,15 +151,21 @@ accept:
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animalRefArray = [AnimalRef(dog), AnimalRef(dog)]
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animalRefArray = [AnimalRef(cat), dog]
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reject:
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acceptWithCovariance:
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animalRefArray = [dog, dog]
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wantsCovariantArray animalRefArray
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else:
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echo "dog"
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echo "dog"
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accept:
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var animal: AnimalRef = dog
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animal = cat
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var vdog: Dog
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vdog.x = "dog value"
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var vcat: Cat
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vcat.x = "cat value"
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reject:
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vcat = vdog
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@ -79,22 +190,93 @@ accept:
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proc wantsRefSeq(x: seq[AnimalRef]) = discard
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accept:
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wantsRefSeq(@[AnimalRef(dog), AnimalRef(dog)])
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wantsRefSeq(@[AnimalRef(cat), AnimalRef(dog)])
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wantsRefSeq(@[AnimalRef(cat), dog])
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wantsRefSeq(@[cat, dog])
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wantsCovariantSeq1(@[AnimalRef(dog), AnimalRef(dog)])
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wantsCovariantSeq1(@[AnimalRef(cat), AnimalRef(dog)])
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wantsCovariantSeq1(@[AnimalRef(cat), dog])
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wantsCovariantSeq1(@[cat, dog])
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reject:
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wantsRefSeq(@[cat, cat])
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wantsCovariantSeq2(@[AnimalRef(dog), AnimalRef(dog)])
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wantsCovariantSeq2(@[AnimalRef(cat), AnimalRef(dog)])
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wantsCovariantSeq2(@[AnimalRef(cat), dog])
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wantsCovariantSeq2(@[cat, dog])
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wantsCovariantSeq3(@[AnimalRef(dog), AnimalRef(dog)])
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wantsCovariantSeq3(@[AnimalRef(cat), AnimalRef(dog)])
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wantsCovariantSeq3(@[AnimalRef(cat), dog])
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wantsCovariantSeq3(@[cat, dog])
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wantsCovariantOperArray([cat, dog])
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acceptWithCovariance:
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wantsCovariantSeq1(@[cat, cat])
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wantsCovariantSeq2(@[dog, makeDerivedRef("dog X")])
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# XXX: wantsCovariantSeq3(@[cat, cat])
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wantsCovariantOperArray(@[cat, cat])
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wantsCovariantOperArray([dog, dog])
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else:
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echo "cat"
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echo "cat"
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echo "dog"
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echo "dog X"
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echo "cat"
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echo "cat"
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echo "dog"
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echo "dog"
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var dogRefs = @[dog, dog]
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var dogRefsArray = [dog, dog]
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var animalRefs = @[dog, cat]
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accept:
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modifiesDerivedArray(dogRefsArray)
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modifiesDerivedSeq(dogRefs)
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reject modifiesCovariantSeq(dogRefs)
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reject modifiesCovariantSeq(addr(dogRefs))
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reject modifiesCovariantSeq(dogRefs.addr)
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reject modifiesCovariantArray([dog, dog])
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reject modifiesCovariantArray(dogRefsArray)
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reject modifiesCovariantArray(addr(dogRefsArray))
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reject modifiesCovariantArray(dogRefsArray.addr)
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var dogValues = @[vdog, vdog]
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var dogValuesArray = [vdog, vdog]
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var animalValues = @[Animal(vdog), Animal(vcat)]
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var animalValuesArray = [Animal(vdog), Animal(vcat)]
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wantsNonCovariantSeq animalValues
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wantsNonCovariantArray animalValuesArray
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reject wantsNonCovariantSeq(dogRefs)
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reject modifiesCovariantOperArray(dogRefs)
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reject wantsNonCovariantArray(dogRefsArray)
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reject wantsNonCovariantSeq(dogValues)
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reject wantsNonCovariantArray(dogValuesArray)
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reject modifiesValueArray()
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modifiesDerivedOperArray dogRefs
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reject modifiesDerivedOperArray(dogValues)
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reject modifiesDerivedOperArray(animalRefs)
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wantsNonCovariantOperArray animalValues
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reject wantsNonCovariantOperArray(animalRefs)
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reject wantsNonCovariantOperArray(dogRefs)
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reject wantsNonCovariantOperArray(dogValues)
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var animalRefSeq: seq[ref Animal]
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accept:
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animalRefArray = [AnimalRef(dog), AnimalRef(dog)]
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animalRefArray = [AnimalRef(cat), dog]
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animalRefSeq = @[AnimalRef(dog), AnimalRef(dog)]
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animalRefSeq = @[AnimalRef(cat), dog]
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reject:
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animalRefArray = [dog, dog]
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acceptWithCovariance:
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animalRefSeq = @[makeDerivedRef("dog 1"), makeDerivedRef("dog 2")]
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wantsCovariantSeq1(animalRefSeq)
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else:
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echo "dog 1"
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echo "dog 2"
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var pdog: ptr Dog
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var pcat: ptr Cat
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@ -116,17 +298,6 @@ proc wantsVarPointer2(x: var AnimalPtr) =
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reject wantsVarPointer1(pdog)
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reject wantsVarPointer2(pcat)
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proc usesVarRefSeq(x: var seq[AnimalRef]) = discard
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proc usesVarRefArray(x: var array[2, AnimalRef]) = discard
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reject:
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var catsSeq = @[cat, cat]
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usesVarRefSeq catsSeq
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reject:
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var catsArray = [cat, cat]
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usesVarRefArray catsArray
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# covariance may be allowed for certain extern types
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{.emit: """
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@ -178,9 +349,6 @@ var
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reject: ptrPtrDog = ptrPtrAnimal
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type
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RefAlias[T] = ref T
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# Try to break the rules by introducing some tricky
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# double indirection types:
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var
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