particular, don't complain about unused variables that have dependent
type until instantiation time, so that we can look at the type of the
variable. Moreover, only complain about unused variables that have
neither a user-declared constructor nor a non-trivial destructor.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@103362 91177308-0d34-0410-b5e6-96231b3b80d8
Douglas Gregor