Hi,

In [expr.const] p.154:

---------------------------------------------------------------
An immediate function is a function or constructor that is
— declared with the consteval specifier, or
— an immediate-escalating function F whose function body contains an
immediate-escalating expression E such that E ’s innermost enclosing non-block
scope is F ’s function parameter scope.

example 9

consteval int id(int i) { return i; }

constexpr char id(char c) { return c; }

template<class T>
   constexpr int f(T t) {
   return t + id(t);
}

auto a = &f<char>; // OK, f<char> is not an immediate function

auto b = &f<int>; // error: f<int> is an immediate function
---------------------------------------------------------------

The immediate-escalating function 'f' function parameter scope does not contain
an immediate-escalating expression. The 'f' instantiation declarations are: 'int
f(int t)' and 'int f(char t)'. What is wrong ?