Re: [PATCH] c++: current inst name lookup within noexcept-spec [PR122668]

[Jason Merrill]

On 11/18/25 3:27 AM, Patrick Palka wrote:

Bootstrapped and regtested on x86_64-pc-linux-gnu, does this
look OK for trunk/15?

OK.

-- >8 --

Since we don't implement deferred noexcept-spec parsing of a friend
declaration, the r15-2117 change to diagnose name lookup failure for
the current instantiation ahead of time needs to compensate by
suppressing the name lookup failure in this case.

        PR c++/122668
        PR c++/114764

gcc/cp/ChangeLog:

        * pt.cc (dependentish_scope_p): Return true for the current
        instantiation from within an immediately parsed noexcept-spec.

gcc/testsuite/ChangeLog:

        * g++.dg/cpp0x/noexcept91.C: New test.
---
  gcc/cp/pt.cc                            | 10 +++++++++-
  gcc/testsuite/g++.dg/cpp0x/noexcept91.C | 15 +++++++++++++++
  2 files changed, 24 insertions(+), 1 deletion(-)
  create mode 100644 gcc/testsuite/g++.dg/cpp0x/noexcept91.C

diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index b7cb807d8daa..f132f8b39d24 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -29057,7 +29057,15 @@ dependent_scope_p (tree scope)
  bool
  dependentish_scope_p (tree scope)
  {
-  return dependent_scope_p (scope) || any_dependent_bases_p (scope);
+  return dependent_scope_p (scope) || any_dependent_bases_p (scope)
+    /* A noexcept-spec is a complete-class context, so this should never hold.
+       But since we don't implement deferred noexcept-spec parsing of a friend
+       declaration (PR114764) we compensate by treating the scope as dependent
+       in this case to avoid bogus name lookup failures (PR122668).  */
+    || (cp_noexcept_operand
+       && CLASS_TYPE_P (scope)
+       && TYPE_BEING_DEFINED (scope)
+       && dependent_type_p (scope));
  }

/* T is a SCOPE_REF. Return whether it represents a non-static member of

diff --git a/gcc/testsuite/g++.dg/cpp0x/noexcept91.C 
b/gcc/testsuite/g++.dg/cpp0x/noexcept91.C
new file mode 100644
index 000000000000..590dfa6162a3
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/noexcept91.C
@@ -0,0 +1,15 @@
+// PR c++/122668
+// { dg-do compile { target c++11 } }
+
+template<class T>
+struct A {
+  friend void f1(A& a) noexcept(noexcept(a.g(0))) { }
+  friend void f2(A& a) noexcept(noexcept(A::g(0))) { }
+  static void g(int) noexcept;
+};
+
+int main() {
+  A<int> a;
+  static_assert(noexcept(f1(a)), "");
+  static_assert(noexcept(f2(a)), "");
+}