tests/base_ft_detect_variance_constraints.nit

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   4 # you may not use this file except in compliance with the License.
   5 # You may obtain a copy of the License at
   6 #
   7 #     http://www.apache.org/licenses/LICENSE-2.0
   8 #
   9 # Unless required by applicable law or agreed to in writing, software
  10 # distributed under the License is distributed on an "AS IS" BASIS,
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  12 # See the License for the specific language governing permissions and
  13 # limitations under the License.
  14 # Test classes for variance analysis
  15
  16 import end
  17
  18 interface Object
  19 end
  20
  21 # covariant
  22 class A[T]
  23         fun foo: T is abstract
  24 end
  25
  26 # contravariant
  27 class B[T]
  28         fun foo(t: T) is abstract
  29 end
  30
  31 # invariant
  32 class C[T]
  33         fun foo(t: T) is abstract
  34
  35         fun bar: T is abstract
  36 end
  37
  38 # bivariant
  39 class D[T]
  40         fun foo(x: Object) is abstract
  41 end
  42
  43 # bivariant, the contravariant position of this complex expression
  44 # reverse the variance, but contra*bivar = bivar
  45 class E[T]
  46         super D[T]
  47
  48         fun bar(x: E[D[C[T]]]) is abstract
  49 end
  50
  51 # Covariant, the contravariant position reverse the variance,
  52 # and the variance of A[B[T]] is contravariance
  53 class F[T]
  54         super D[T]
  55
  56         fun bar(x: A[B[T]]) is abstract
  57 end
  58
  59 # Can be annotated bivariant
  60 class G[T]
  61         super D[T]
  62
  63         fun bar: A[D[E[T]]] is abstract
  64 end
  65
  66 # invariant
  67 class H[T]
  68         fun bar: A[B[C[T]]] is abstract
  69 end
  70
  71 # Bivariant
  72 class Src[T]
  73         fun bar (x: Dest[T]) is abstract
  74 end
  75
  76 # Bivariant
  77 class Dest[T]
  78         fun bar (x: Src[T]) is abstract
  79 end
  80
  81 # Contravariant
  82 class Src2[T]
  83         super B[T]
  84
  85         fun bar(x: Src[B[T]]) is abstract
  86 end
  87
  88 # Bivariant
  89 class Cycle2[T]
  90         fun foo(x: Cycle2[T]): Cycle2[T] is abstract
  91 end
  92
  93 # Bivariant
  94 class Cycle3[T]
  95         fun foo(x: Cycle2[T]): C[D[T]] is abstract
  96 end