[stdlib] @available attributes for startIndex/endIndex on ranges

Author: Max Moiseev

stdlib/public/core/ClosedRange.swift

@@ -401,3 +401,14 @@ public func ... <
   return CountableClosedRange(uncheckedBounds: (lower: minimum, upper: maximum))
 }
 
+extension ClosedRange {
+  @available(*, unavailable, renamed: "lowerBound")
+  public var startIndex: Bound {
+    Builtin.unreachable()
+  }
+
+  @available(*, unavailable, renamed: "upperBound")
+  public var endIndex: Bound {
+    Builtin.unreachable()
+  }
+}

stdlib/public/core/Range.swift.gyb

@@ -589,3 +589,15 @@ public func ..< <
 // swift-3-indexing-model: this is not really a proper rename
 @available(*, unavailable, renamed: "IndexingIterator")
 public struct RangeGenerator<Bound> {}
+
+extension Range {
+  @available(*, unavailable, renamed: "lowerBound")
+  public var startIndex: Bound {
+    Builtin.unreachable()
+  }
+
+  @available(*, unavailable, renamed: "upperBound")
+  public var endIndex: Bound {
+    Builtin.unreachable()
+  }
+}