OverloadCandidate::getNumParams - silence static analyzer getAs<FunctionProtoType> null dereference warning. NFCI.

The static analyzer is warning about a potential null dereference, but we should be able to use castAs<FunctionProtoType> directly and if not assert will fire for us.

Also replaces an auto to make the type more obvious.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@373665 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed