Re: [PATCH] c++: make finish non_static_data_member SFINAE friendly [PR105351]

[Jason Merrill via Gcc-patches]

On 5/3/22 13:40, Patrick Palka wrote:

Here, since finish_non_static_data_member isn't SFINAE friendly, we
incorrectly emit an error during overload resolution:

sfinae33.C: In substitution of ‘template<class T> A<T::value> f() [with T = B]’:
sfinae33.C:11:7:   required from here
sfinae33.C:5:31: error: invalid use of non-static data member ‘B::value’
     5 | template<class T> A<T::value> f();
       |                               ^

This patch fixes this by making the function SFINAE friendly in the
usual way: give it a complain parameter, check it before emitting an
error, and pass it through appropriately.

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

OK.

        PR c++/105351

gcc/cp/ChangeLog:

        * cp-tree.h (finish_non_static_data_member): Add defaulted
        complain parameter.
        * pt.cc (tsubst_copy_and_build): Pass complain to
        finish_non_static_data_member.
        * semantics.cc (finish_non_static_data_member): Respect complain
        parameter.
        (finish_qualified_id_expr): Pass complain to
        finish_non_static_data_member.

gcc/testsuite/ChangeLog:

        * g++.dg/template/sfinae33.C: New test.
---
  gcc/cp/cp-tree.h                         |  3 ++-
  gcc/cp/pt.cc                             |  3 ++-
  gcc/cp/semantics.cc                      | 27 ++++++++++++++----------
  gcc/testsuite/g++.dg/template/sfinae33.C | 12 +++++++++++
  4 files changed, 32 insertions(+), 13 deletions(-)
  create mode 100644 gcc/testsuite/g++.dg/template/sfinae33.C

diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index 72177999968..b29e60ee52f 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -7615,7 +7615,8 @@ inline tree force_paren_expr_uneval               (tree t)
  { return force_paren_expr (t, true); }
  extern tree maybe_undo_parenthesized_ref      (tree);
  extern tree maybe_strip_ref_conversion                (tree);
-extern tree finish_non_static_data_member       (tree, tree, tree);
+extern tree finish_non_static_data_member       (tree, tree, tree,
+                                                tsubst_flags_t = 
tf_warning_or_error);
  extern tree begin_stmt_expr                   (void);
  extern tree finish_stmt_expr_expr             (tree, tree);
  extern tree finish_stmt_expr                  (tree, bool);
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 81c3c598c71..f96f8e31885 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -21059,7 +21059,8 @@ tsubst_copy_and_build (tree t,
          }
        else if (TREE_CODE (member) == FIELD_DECL)
          {
-           r = finish_non_static_data_member (member, object, NULL_TREE);
+           r = finish_non_static_data_member (member, object, NULL_TREE,
+                                              complain);
            if (TREE_CODE (r) == COMPONENT_REF)
              REF_PARENTHESIZED_P (r) = REF_PARENTHESIZED_P (t);
            RETURN (r);
diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
index 377f61113c0..bfb737f665b 100644
--- a/gcc/cp/semantics.cc
+++ b/gcc/cp/semantics.cc
@@ -2141,7 +2141,8 @@ finish_parenthesized_expr (cp_expr expr)
     preceded by `.' or `->'.  */

tree

-finish_non_static_data_member (tree decl, tree object, tree qualifying_scope)
+finish_non_static_data_member (tree decl, tree object, tree qualifying_scope,
+                              tsubst_flags_t complain /* = tf_warning_or_error 
*/)
  {
    gcc_assert (TREE_CODE (decl) == FIELD_DECL);
    bool try_omp_private = !object && omp_private_member_map;
@@ -2172,12 +2173,15 @@ finish_non_static_data_member (tree decl, tree object, 
tree qualifying_scope)
    if (is_dummy_object (object) && cp_unevaluated_operand == 0
        && (!processing_template_decl || !current_class_ref))
      {
-      if (current_function_decl
-         && DECL_STATIC_FUNCTION_P (current_function_decl))
-       error ("invalid use of member %qD in static member function", decl);
-      else
-       error ("invalid use of non-static data member %qD", decl);
-      inform (DECL_SOURCE_LOCATION (decl), "declared here");
+      if (complain & tf_error)
+       {
+         if (current_function_decl
+             && DECL_STATIC_FUNCTION_P (current_function_decl))
+           error ("invalid use of member %qD in static member function", decl);
+         else
+           error ("invalid use of non-static data member %qD", decl);
+         inform (DECL_SOURCE_LOCATION (decl), "declared here");
+       }

return error_mark_node;

      }
@@ -2219,8 +2223,9 @@ finish_non_static_data_member (tree decl, tree object, 
tree qualifying_scope)
      {
        tree access_type = TREE_TYPE (object);

- perform_or_defer_access_check (TYPE_BINFO (access_type), decl,

-                                    decl, tf_warning_or_error);
+      if (!perform_or_defer_access_check (TYPE_BINFO (access_type), decl,
+                                         decl, complain))
+       return error_mark_node;

/* If the data member was named `C::M', convert `*this' to `C'

         first.  */
@@ -2234,7 +2239,7 @@ finish_non_static_data_member (tree decl, tree object, 
tree qualifying_scope)
        ret = build_class_member_access_expr (object, decl,
                                            /*access_path=*/NULL_TREE,
                                            /*preserve_reference=*/false,
-                                           tf_warning_or_error);
+                                           complain);
      }
    if (try_omp_private)
      {
@@ -2396,7 +2401,7 @@ finish_qualified_id_expr (tree qualifying_class,
      {
        push_deferring_access_checks (dk_no_check);
        expr = finish_non_static_data_member (expr, NULL_TREE,
-                                           qualifying_class);
+                                           qualifying_class, complain);
        pop_deferring_access_checks ();
      }
    else if (BASELINK_P (expr))
diff --git a/gcc/testsuite/g++.dg/template/sfinae33.C 
b/gcc/testsuite/g++.dg/template/sfinae33.C
new file mode 100644
index 00000000000..cb9d4982211
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/sfinae33.C
@@ -0,0 +1,12 @@
+// PR c++/105351
+
+template<int> struct A;
+
+template<class T> A<T::value> f();
+template<class T> void f();
+
+struct B { int value; };
+
+int main() {
+  f<B>();
+}