On 5/27/22 12:43, Marek Polacek wrote:
On Fri, May 27, 2022 at 11:52:12AM -0400, Jason Merrill wrote:
On 5/26/22 20:33, Marek Polacek wrote:
As discussed here:
<https://gcc.gnu.org/pipermail/gcc-patches/2021-February/564629.html>,
type_dependent_expression_p should not be called with a type argument.

I promised I'd add an assert so here it is.  One place needed adjusting,
the comment explains why.

Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?

        PR c++/99080

gcc/cp/ChangeLog:

        * pt.cc (type_dependent_expression_p): Assert !TYPE_P.
        * semantics.cc (finish_id_expression_1): Don't call
        type_dependent_expression_p for a type.
---
   gcc/cp/pt.cc        | 2 ++
   gcc/cp/semantics.cc | 4 +++-
   2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 24bbe2f4060..89156cb88b4 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -27727,6 +27727,8 @@ type_dependent_expression_p (tree expression)
     if (expression == NULL_TREE || expression == error_mark_node)
       return false;
+  gcc_checking_assert (!TYPE_P (expression));
+
     STRIP_ANY_LOCATION_WRAPPER (expression);
     /* An unresolved name is always dependent.  */
diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
index cd7a2818feb..7f8502f49b0 100644
--- a/gcc/cp/semantics.cc
+++ b/gcc/cp/semantics.cc
@@ -4141,7 +4141,9 @@ finish_id_expression_1 (tree id_expression,
       }
     else
       {
-      bool dependent_p = type_dependent_expression_p (decl);
+      /* DECL could be e.g. UNBOUND_CLASS_TEMPLATE which is a type which
+        t_d_e_p doesn't accept.  */
+      bool dependent_p = !TYPE_P (decl) && type_dependent_expression_p (decl);

Maybe instead we could handle UNBOUND_CLASS_TEMPLATE at a higher level in
the function, like with an 'else if' before this 'else'?

Maybe, but I think I'd have to duplicate (parts of) this block:
  4227       else if (scope)
  4228         {
  4229           if (TREE_CODE (decl) == SCOPE_REF)
  4230             {
  4231               gcc_assert (same_type_p (scope, TREE_OPERAND (decl, 0)));
  4232               decl = TREE_OPERAND (decl, 1);
  4233             }
  4234
  4235           decl = (adjust_result_of_qualified_name_lookup
  4236                   (decl, scope, current_nonlambda_class_type()));
  4237
  4238           cp_warn_deprecated_use_scopes (scope);
  4239
  4240           if (TYPE_P (scope))
  4241             decl = finish_qualified_id_expr (scope,
  4242                                              decl,
  4243                                              done,
  4244                                              address_p,
  4245                                              template_p,
  4246                                              template_arg_p,
  4247                                              tf_warning_or_error);
  4248           else
  4249             decl = convert_from_reference (decl);
  4250         }

Would that be acceptable?  Can't do

   else if (TREE_CODE (decl) == UNBOUND_CLASS_TEMPLATE)
     {
       gcc_checking_assert (scope);
       *idk = CP_ID_KIND_QUALIFIED;
       goto do_scope;
     }
because that will complain about skipping the initialization of dependent_p.

Here's a patch with the partial duplication, which passes dg.exp:

-- >8 --
As discussed here:
<https://gcc.gnu.org/pipermail/gcc-patches/2021-February/564629.html>,
type_dependent_expression_p should not be called with a type argument.

I promised I'd add an assert so here it is.  One place needed adjusting.

        PR c++/99080

gcc/cp/ChangeLog:

        * pt.cc (type_dependent_expression_p): Assert !TYPE_P.
        * semantics.cc (finish_id_expression_1): Handle UNBOUND_CLASS_TEMPLATE
        specifically.
---
  gcc/cp/pt.cc        |  2 ++
  gcc/cp/semantics.cc | 11 +++++++++++
  2 files changed, 13 insertions(+)

diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 24bbe2f4060..89156cb88b4 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -27727,6 +27727,8 @@ type_dependent_expression_p (tree expression)
    if (expression == NULL_TREE || expression == error_mark_node)
      return false;
+ gcc_checking_assert (!TYPE_P (expression));
+
    STRIP_ANY_LOCATION_WRAPPER (expression);
/* An unresolved name is always dependent. */
diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
index cdc91a38e25..f62b0a4a736 100644
--- a/gcc/cp/semantics.cc
+++ b/gcc/cp/semantics.cc
@@ -4139,6 +4139,17 @@ finish_id_expression_1 (tree id_expression,
        }
        return r;
      }
+  else if (TREE_CODE (decl) == UNBOUND_CLASS_TEMPLATE)
+    {
+      gcc_checking_assert (scope);
+      *idk = CP_ID_KIND_QUALIFIED;
+      decl = (adjust_result_of_qualified_name_lookup
+             (decl, scope, current_nonlambda_class_type()));

This call should have no effect, it only affects BASELINKs. OK without this statement.

+      cp_warn_deprecated_use_scopes (scope);
+      decl = finish_qualified_id_expr (scope, decl, done, address_p,
+                                      template_p, template_arg_p,
+                                      tf_warning_or_error);
+    }
    else
      {
        bool dependent_p = type_dependent_expression_p (decl);

base-commit: d822f4bbd714c6595f70cc68888dcebecfb6662d

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