Backported fixes

Fix tuple casting #16113
Be even more careful when combining argument and info in computeAsSeenFrom #16070
Be still more careful when computing denotations of class parameters #16112

Contributors

Thank you to all the contributors who made this release possible 🎉

According to git shortlog -sn --no-merges 3.2.1-RC2..3.2.1-RC3 these are:

     4  Martin Odersky
     2  Paweł Marks