Merge pull request #27051 from gottesmm/pr-e2c4cb6f4381f6d58f10ec9729cadfb4407574df

[opt-transform-range] Do not assume that Range::iterator exists.

Author: gottesmm

include/swift/Basic/STLExtras.h

@@ -611,7 +611,7 @@ makeOptionalTransformIterator(Iterator current, Iterator end,
 
 /// A range filtered and transformed by the optional transform.
 template <typename Range, typename OptionalTransform,
-          typename Iterator = typename Range::iterator>
+          typename Iterator = decltype(std::declval<Range>().begin())>
 class OptionalTransformRange {
 
   Iterator First, Last;