Fix a TensorFlow module error.

Fix a "expression too complex" error in Gradients.swift.

Author: dan-zheng

stdlib/public/TensorFlow/Gradients.swift

@@ -344,8 +344,9 @@ func _vjpPow<T : TensorFlowFloatingPoint>(
 ) -> (Tensor<T>, (Tensor<T>) -> (Tensor<T>, Tensor<T>)) {
   let value = pow(x, y)
   return (value, { v in
-    ((v * y * pow(x, y-1)).unbroadcast(like: x),
-     (v * log(x) * value).unbroadcast(like: y))
+    let dfdx = v * y * pow(x, y-1)
+    let dfdy = v * log(x) * value
+    return (dfdx.unbroadcast(like: x), dfdy.unbroadcast(like: y))
   })
 }
 

stdlib/public/TensorFlow/Ops.swift

@@ -1923,7 +1923,7 @@ internal extension Tensor.IndexPath {
   @inlinable
   init(_ ranges: [TensorRange]) {
     precondition(!ranges.isEmpty, "The tensor range collection cannot be empty.")
-    precondition(ranges.count { $0 == TensorRange.ellipsis } < 2,
+    precondition(ranges.count(where: { $0 == TensorRange.ellipsis }) < 2,
                  "Only one ellipsis is allowed per tensor range collection.")
 
     var begin = [Int32](repeating: 0, count: ranges.count)