Per [basic.lookup.classref]p3, in an expression of the form p->~type-name, the

type-name is looked up in the context of the complete postfix-expression. Don't
forget to pass the scope into this lookup when the type-name is a template-id;
it might name an alias template which can't be found within the class itself.

Bug spotted by Johannes Schaub on #llvm.

llvm-svn: 168011