PR18876: The special-case rule that ignores the destruction of a top-level

temporary in a decltype expression only applies if that temporary was created
by a function call, not by a function-style cast or other flavour of
expression.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@201542 91177308-0d34-0410-b5e6-96231b3b80d8