Re: [PATCH] c++: constrained partial spec type context [PR111890]

[Jason Merrill]

On 7/11/24 1:08 PM, Patrick Palka wrote:

Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
trunk/14?

OK.

-- >8 --

maybe_new_partial_specialization wasn't propagating TYPE_CONTEXT when
creating a new class type corresponding to a constrained partial spec,
which do_friend relies on via template_class_depth to distinguish a
template friend from a non-template friend, and so in the below testcase
we were incorrectly instantiating the non-template operator+ as if it
were a template leading to an ICE.

        PR c++/111890

gcc/cp/ChangeLog:

        * pt.cc (maybe_new_partial_specialization): Propagate TYPE_CONTEXT to
        the newly created partial specialization.

gcc/testsuite/ChangeLog:

        * g++.dg/cpp2a/concepts-partial-spec15.C: New test.
---
  gcc/cp/pt.cc                                  |  1 +
  .../g++.dg/cpp2a/concepts-partial-spec15.C    | 20 +++++++++++++++++++
  2 files changed, 21 insertions(+)
  create mode 100644 gcc/testsuite/g++.dg/cpp2a/concepts-partial-spec15.C

diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index a382dce8788..314b0be4f19 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -992,6 +992,7 @@ maybe_new_partial_specialization (tree& type)
        tree t = make_class_type (TREE_CODE (type));
        CLASSTYPE_DECLARED_CLASS (t) = CLASSTYPE_DECLARED_CLASS (type);
        SET_TYPE_TEMPLATE_INFO (t, build_template_info (tmpl, args));
+      TYPE_CONTEXT (t) = TYPE_CONTEXT (type);

/* We only need a separate type node for storing the definition of this

         partial specialization; uses of S<T*> are unconstrained, so all are
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-partial-spec15.C 
b/gcc/testsuite/g++.dg/cpp2a/concepts-partial-spec15.C
new file mode 100644
index 00000000000..ad01a390fef
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-partial-spec15.C
@@ -0,0 +1,20 @@
+// PR c++/111890
+// { dg-do compile { target c++20 } }
+
+template<class>
+struct A {
+  template<class T>
+  struct B { };
+
+  template<class T> requires T::value
+  struct B<T> { };
+
+  template<class T> requires (sizeof(T) == sizeof(int))
+  struct B<T> {
+    friend void operator+(B&, int) { }
+  };
+};
+
+void f(A<int>::B<int> b) {
+  b + 0;
+}