In [temp.deduct.funcaddr] p1, [temp.deduct.conv] p1, [temp.deduct.partial] p8, and [temp.deduct.decl] p1, they all have a similar wording like:

The deduction is then done as described in [temp.deduct.type].

However, [temp.deduct.call] lacks wording like this. We want the following rules

If type deduction cannot be done for any P/A pair, or if for any pair the deduction leads to more than one possible set of deduced values, or if different pairs yield different deduced values, or if any template argument remains neither deduced nor explicitly specified, template argument deduction fails.

and

If a template parameter is used only in non-deduced contexts and is not explicitly specified, template argument deduction fails.

that are defined in [temp.deduct.type] apply to these cases

template<class T>
void fun(T,T){}

fun(0,0.f); // deduction fail

template<class T, class U>
void show(T, typename U::type){}

show(0,0); // deduction fail

Add the following rule in [temp.deduct.call] p4, by saying

The deduction is done as described in [temp.deduct.type].