Hi, everyone.

I have a concern about the formal example in [module.context] p7

//Translation unit #1:

export module stuff;
export template<typename T, typename U> void foo(T, U u) { auto v = u; }
export template<typename T, typename U> void bar(T, U u) { auto v = *u; }  

//Translation unit #2:

export module M1;
import "defn.h";        // provides struct X {};
import stuff;
export template<typename T> void f(T t) {
  X x;
  foo(t, x);
}

// Translation unit #3:

export module M2;
import "decl.h";        // provides struct X; (not a definition)
import stuff;
export template<typename T> void g(T t) {
  X *x;
  bar(t, x);
}

// Translation unit #4:

import M1;
import M2;
void test() {
  f(0);
  g(0);
}

For f(0), the comment says that

the instantiation context of foo<int, X> comprises

the point at the end of translation unit #1,
the point at the end of translation unit #2, and
the point of the call to f(0),

I can understand the first point, because of this rule

During the implicit instantiation of a template whose point of instantiation is specified as that of an enclosing specialization ([temp.point]), the instantiation context is the union of the instantiation context of the enclosing specialization and, if the template is defined in a module interface unit of a module M and the point of instantiation is not in a module interface unit of M, the point at the end of the declaration-seq of the primary module interface unit of M (prior to the private-module-fragment, if any).

However, I cannot figure out the remaining points, especially the second one. How to interpret such two points? Which bullet says the instantiation context of "enclosing specialization" of `f` can comprise the end of `TU2`? According to [module.context#5], the point of instantiation of `f<0>` should either immediately follow the definition of function `test` or at the end of "TU4", which could be the instantiation context of "foo<int,X>", except that there is no rule in [module.context] specifies that the end of "TU2" is a point. Appreciate for answers.