Add a challenge for variadic generics (#76)

challenges/advanced-variadic-generics/question.py

@@ -0,0 +1,21 @@
+"""
+TODO:
+
+Define an `Array` type that supports element-wise addition of arrays with identical dimensions and types.
+"""
+
+
+class Array:
+    def __add__(self, other):
+        ...
+
+
+## End of your code ##
+from typing import assert_type
+
+a: Array[float, int] = Array()
+b: Array[float, int] = Array()
+assert_type(a + b, Array[float, int])
+
+c: Array[float, int, str] = Array()
+assert_type(a + c, Array[float, int, str])  # expect-type-error

challenges/advanced-variadic-generics/solution.py

@@ -0,0 +1,26 @@
+"""
+TODO:
+
+Define an `Array` type that supports element-wise addition of arrays with identical dimensions and types.
+"""
+
+from typing import Generic, TypeVar, TypeVarTuple, assert_type
+
+T = TypeVar("T")
+Ts = TypeVarTuple("Ts")
+
+
+class Array(Generic[*Ts]):
+    def __add__(self, other: "Array[*Ts]") -> "Array[*Ts]":
+        ...
+
+
+## End of your code ##
+from typing import assert_type
+
+a: Array[float, int] = Array()
+b: Array[float, int] = Array()
+assert_type(a + b, Array[float, int])
+
+c: Array[float, int, str] = Array()
+assert_type(a + c, Array[float, int, str])  # expect-type-error

challenges/advanced-variadic-generics/solution2.py

@@ -0,0 +1,23 @@
+"""
+TODO:
+
+Define an `Array` type that supports element-wise addition of arrays with identical dimensions and types.
+"""
+
+from typing import assert_type
+
+
+class Array[*Ts]:
+    def __add__(self, other: "Array[*Ts]") -> "Array[*Ts]":
+        ...
+
+
+## End of your code ##
+from typing import assert_type
+
+a: Array[float, int] = Array()
+b: Array[float, int] = Array()
+assert_type(a + b, Array[float, int])
+
+c: Array[float, int, str] = Array()
+assert_type(a + c, Array[float, int, str])  # expect-type-error