[bugfix] Fix two bugs in TransformedRangeView and TransformedRangeIterator

• Properly forward r-value references of functions to enable move-construction for function stored in TransformedRangeView where possible.
• Fix and test operator-> in TransformedRangeIterator. For transformations returning l-value references, the operator did a copy, such that it->foo() and (*it).foo() act on different objects. The fix is to correctly forward the l-value reference to the proxy-object returned by operator->.

added bug label

While looking at !1386 I noticed the two bugs. Whatever we decide in !1386, these should be fixed.

@simon Since you already looked at this code: Can you review the bugfix? Getting this working correctly with references and copies at the same time is a little delicate.

I had already started with most of the changes you also have added here. So, looks quiet fine to me.

added 2 commits

• de38fa63 - [bugfix] Fix operator-> for non-proxy TransformedRangeIterator
• ef56d403 - [test] Add check for TransformedRangeIterator::operator->

Compare with previous version

resolved all threads

resolved all threads

enabled an automatic merge when the pipeline for ef56d403 succeeds

merged

mentioned in commit b71d7bf3