As reported in PR46111, implicit instantiation of a deduction guide
causes us to have an elaborated type as the parameter, rather than the
dependent type.
After review and feedback from @rsmith, this patch solves this problem
by wrapping the value in an uninstantiated typedef/type-alias that is
instantiated when required later.
Retaining the location information here would be good too. (You already have that location info in InnerTLB.) I think there might even be a convenience TypeSourceInfo -> TypeSourceInfo transform you can invoke here.