Re: [PATCH 2/2] c++: remove lookup_template_class's entering_scope flag

[Patrick Palka <ppalka@redhat.com>]

On Fri, 2 Feb 2024, Patrick Palka wrote:

> Bootstrapped and regtested on x86_64-pc-linux, does this look like
> an improvement?  This is not a bugfix and barely related to the previous
> patch, but the previous patch's new use of entering_scope=true motivated
> me to submit this patch since it seems like a nice simplification.

Ping, now that stage 1 is open.

> 
> -- >8 --
> 
> lookup_template_class's entering_scope flag controls whether to prefer
> returning the primary template type A<T> instead of the corresponding
> implicit instantiation A<T>.  When we want to set this flag as part of
> substitution, we need to use tsubst_aggr_type which also takes the flag,
> but this separate entry point to substitution turned out to be subtly
> problematic because it doesn't reuse typedefs like tsubst does, which
> r13-4729-gbe124477b38a71 fixed in a way that respects the flag after the
> fact, by adjusting the entering_scope=false result of
> lookup_template_class as if entering_scope=true was passed.
> 
> But if that's possible then it means lookup_template_class's the
> entering_scope flag is not necessary after all -- we can just do the
> after-the-fact adjustment everywhere that we currently pass
> entering_scope=true to it and tsubst_aggr_type.
> 
> To that end, this patch replaces this flag with an adjustment function
> adjust_type_for_entering_scope, to be used whereever we currently need
> the entering_scope=true behavior.  This means we can also get rid of
> tsubst_aggr_type, since the only reason we needed this entry point
> was to be able to pass entering_scope=true to lookup_template_class.
> 
> gcc/cp/ChangeLog:
> 
> 	* coroutines.cc (instantiate_coro_traits): Adjust call to
> 	lookup_template_class.
> 	(instantiate_coro_handle_for_promise_type): Likewise.
> 	* cp-tree.h (adjust_type_for_entering_scope): Declare.
> 	(lookup_template_class): Adjust declaration.
> 	* decl.cc (make_typename_type): Adjust call to
> 	lookup_template_class. Likewise.
> 	(get_tuple_size): Likewise.
> 	(get_tuple_element_type): Likewise.
> 	* pt.cc (adjust_type_for_entering_scope): Define.
> 	(lookup_template_class): Remove entering_scope parameter.
> 	Replace tsubst_aggr_type call with tsubst followed by
> 	adjust_type_for_entering_scope.
> 	(tsubst_aggr_type): Remove.
> 	(tsubst_aggr_type_1): Inline into tsubst.
> 	(tsubst_function_decl): Replace tsubst_aggr_type call
> 	with tsubst followed by adjust_type_for_entering_scope.
> 	(tsubst_template_decl): Likewise.
> 	(tsubst_decl): Likewise.
> 	(tsubst) <case RECORD_TYPE, UNION_TYPE, ENUMERAL_TYPE>:
> 	Inlined from tsubst_aggr_type_1.
> 	<case BOUND_TEMPLATE_TEMPLATE_PARM>: Adjust calls to
> 	lookup_template_class.
> 	<case TYPENAME_TYPE>: Replace tsubst_aggr_type call with
> 	tsubst tsubst_scope followed by adjust_type_for_entering_scope.
> 	<case UNBOUND_CLASS_TEMPLATE>: Replace tsubst_aggr_type
> 	call with tsubst followed by adjust_type_for_entering_scope.
> 	Increment processing_template_decl when substituting the
> 	context.
> 	(tsubst_baselink): Replace tsubst_aggr_type call with tsubst
> 	followed by adjust_type_for_entering_scope.
> 	(tsubst_expr) <case FIELD_DECL>: Replace tsubst_aggr_type
> 	call with tsubst followed by adjust_type_for_entering_scope.
> 	<case TEMPLATE_DECL>: Likewise.
> 	(instantiate_template): Likewise.
> 	(resolve_typename_type): Adjust lookup_template_class call
> 	and call adjust_type_for_entering_scope afterward.
> 	(listify): Adjust lookup_template_class call.
> 	(alias_ctad_tweaks): Likewise.
> 	* semantics.cc (finish_template_type): Adjust lookup_template_class
> 	call and maybe call adjust_type_for_entering_scope afterward.
> ---
>  gcc/cp/coroutines.cc |   4 +-
>  gcc/cp/cp-tree.h     |   3 +-
>  gcc/cp/decl.cc       |   4 +-
>  gcc/cp/pt.cc         | 212 +++++++++++++++++--------------------------
>  gcc/cp/semantics.cc  |   4 +-
>  5 files changed, 91 insertions(+), 136 deletions(-)
> 
> diff --git a/gcc/cp/coroutines.cc b/gcc/cp/coroutines.cc
> index 3194c911e8c..8dab173d5cb 100644
> --- a/gcc/cp/coroutines.cc
> +++ b/gcc/cp/coroutines.cc
> @@ -353,7 +353,7 @@ instantiate_coro_traits (tree fndecl, location_t kw)
>    tree traits_class
>      = lookup_template_class (coro_traits_templ, targ,
>  			     /*in_decl=*/NULL_TREE, /*context=*/NULL_TREE,
> -			     /*entering scope=*/false, tf_warning_or_error);
> +			     tf_warning_or_error);
>  
>    if (traits_class == error_mark_node)
>      {
> @@ -400,7 +400,7 @@ instantiate_coro_handle_for_promise_type (location_t kw, tree promise_type)
>      = lookup_template_class (coro_handle_identifier, targ,
>  			     /* in_decl=*/NULL_TREE,
>  			     /* context=*/std_node,
> -			     /* entering scope=*/false, tf_warning_or_error);
> +			     tf_warning_or_error);
>  
>    if (handle_type == error_mark_node)
>      {
> diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
> index 969c7239c97..4f73a7c84b6 100644
> --- a/gcc/cp/cp-tree.h
> +++ b/gcc/cp/cp-tree.h
> @@ -7506,8 +7506,9 @@ extern tree push_template_decl			(tree, bool is_friend = false);
>  extern tree add_inherited_template_parms	(tree, tree);
>  extern void template_parm_level_and_index	(tree, int*, int*);
>  extern bool redeclare_class_template		(tree, tree, tree);
> +extern tree adjust_type_for_entering_scope	(tree);
>  extern tree lookup_template_class		(tree, tree, tree, tree,
> -						 int, tsubst_flags_t);
> +						 tsubst_flags_t);
>  extern tree lookup_template_function		(tree, tree);
>  extern tree lookup_template_variable		(tree, tree, tsubst_flags_t);
>  extern bool uses_template_parms			(tree);
> diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
> index 3e41fd4fa31..8149aab5781 100644
> --- a/gcc/cp/decl.cc
> +++ b/gcc/cp/decl.cc
> @@ -4569,7 +4569,6 @@ make_typename_type (tree context, tree name, enum tag_types tag_type,
>      {
>        t = lookup_template_class (t, TREE_OPERAND (fullname, 1),
>  				 NULL_TREE, context,
> -				 /*entering_scope=*/0,
>  				 complain | tf_user);
>        if (t == error_mark_node)
>  	return error_mark_node;
> @@ -9163,7 +9162,7 @@ get_tuple_size (tree type)
>    tree inst = lookup_template_class (tuple_size_identifier, args,
>  				     /*in_decl*/NULL_TREE,
>  				     /*context*/std_node,
> -				     /*entering_scope*/false, tf_none);
> +				     tf_none);
>    inst = complete_type (inst);
>    if (inst == error_mark_node
>        || !COMPLETE_TYPE_P (inst)
> @@ -9192,7 +9191,6 @@ get_tuple_element_type (tree type, unsigned i)
>    tree inst = lookup_template_class (tuple_element_identifier, args,
>  				     /*in_decl*/NULL_TREE,
>  				     /*context*/std_node,
> -				     /*entering_scope*/false,
>  				     tf_warning_or_error);
>    return make_typename_type (inst, type_identifier,
>  			     none_type, tf_warning_or_error);
> diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
> index 17ecd4b9c5a..baf9b0e6fda 100644
> --- a/gcc/cp/pt.cc
> +++ b/gcc/cp/pt.cc
> @@ -185,8 +185,6 @@ static int unify_pack_expansion (tree, tree, tree,
>  static tree copy_template_args (tree);
>  static tree tsubst_template_parms (tree, tree, tsubst_flags_t);
>  static void tsubst_each_template_parm_constraints (tree, tree, tsubst_flags_t);
> -static tree tsubst_aggr_type (tree, tree, tsubst_flags_t, tree, int);
> -static tree tsubst_aggr_type_1 (tree, tree, tsubst_flags_t, tree, int);
>  static tree tsubst_arg_types (tree, tree, tree, tsubst_flags_t, tree);
>  static tree tsubst_function_type (tree, tree, tsubst_flags_t, tree);
>  static bool check_specialization_scope (void);
> @@ -9873,6 +9871,24 @@ maybe_get_template_decl_from_type_decl (tree decl)
>      ? CLASSTYPE_TI_TEMPLATE (TREE_TYPE (decl)) : decl;
>  }
>  
> +/* If TYPE is the generic implicit instantiation A<T>, return the primary
> +   template type A<T> (which is suitable for entering into e.g. for name
> +   lookup), otherwise return TYPE.  */
> +
> +tree
> +adjust_type_for_entering_scope (tree type)
> +{
> +  if (CLASS_TYPE_P (type)
> +      && dependent_type_p (type)
> +      && TYPE_TEMPLATE_INFO (type)
> +      /* We detect the generic implicit instantiation A<T> by inspecting
> +	 TYPE_CANONICAL, which lookup_template_class sets to the primary
> +	 template type A<T>.  */
> +      && TYPE_CANONICAL (type) == TREE_TYPE (TYPE_TI_TEMPLATE (type)))
> +    type = TYPE_CANONICAL (type);
> +  return type;
> +}
> +
>  /* Given an IDENTIFIER_NODE (or type TEMPLATE_DECL) and a chain of
>     parameters, find the desired type.
>  
> @@ -9881,9 +9897,6 @@ maybe_get_template_decl_from_type_decl (tree decl)
>     IN_DECL, if non-NULL, is the template declaration we are trying to
>     instantiate.
>  
> -   If ENTERING_SCOPE is nonzero, we are about to enter the scope of
> -   the class we are looking up.
> -
>     Issue error and warning messages under control of COMPLAIN.
>  
>     If the template class is really a local class in a template
> @@ -9899,7 +9912,7 @@ maybe_get_template_decl_from_type_decl (tree decl)
>  
>  tree
>  lookup_template_class (tree d1, tree arglist, tree in_decl, tree context,
> -		       int entering_scope, tsubst_flags_t complain)
> +		       tsubst_flags_t complain)
>  {
>    auto_timevar tv (TV_TEMPLATE_INST);
>  
> @@ -10085,9 +10098,10 @@ lookup_template_class (tree d1, tree arglist, tree in_decl, tree context,
>  	   template <class T> class C { void f(C<T>); }
>  
>  	 the `C<T>' is just the same as `C'.  Outside of the
> -	 class, however, such a reference is an instantiation.  */
> -      if (entering_scope
> -	  || !PRIMARY_TEMPLATE_P (gen_tmpl)
> +	 class, however, such a reference is an instantiation.
> +	 One can use adjust_type_for_entering_scope to make
> +	 this adjustment as needed.  */
> +      if (!PRIMARY_TEMPLATE_P (gen_tmpl)
>  	  || currently_open_class (template_type))
>  	{
>  	  tree tinfo = TYPE_TEMPLATE_INFO (template_type);
> @@ -10154,8 +10168,8 @@ lookup_template_class (tree d1, tree arglist, tree in_decl, tree context,
>  	    context = DECL_CONTEXT (templ);
>  	  else
>  	    {
> -	      context = tsubst_aggr_type (context, arglist,
> -					  complain, in_decl, true);
> +	      context = tsubst (context, arglist, complain, in_decl);
> +	      context = adjust_type_for_entering_scope (context);
>  	      /* Try completing the enclosing context if it's not already so.  */
>  	      if (context != error_mark_node
>  		  && !COMPLETE_TYPE_P (context))
> @@ -14091,94 +14105,6 @@ tsubst_each_template_parm_constraints (tree parms, tree args,
>    --processing_template_decl;
>  }
>  
> -/* Substitute the ARGS into the indicated aggregate (or enumeration)
> -   type T.  If T is not an aggregate or enumeration type, it is
> -   handled as if by tsubst.  IN_DECL is as for tsubst.  If
> -   ENTERING_SCOPE is nonzero, T is the context for a template which
> -   we are presently tsubst'ing.  Return the substituted value.  */
> -
> -static tree
> -tsubst_aggr_type (tree t,
> -		  tree args,
> -		  tsubst_flags_t complain,
> -		  tree in_decl,
> -		  int entering_scope)
> -{
> -  if (t == NULL_TREE)
> -    return NULL_TREE;
> -
> -  /* Handle typedefs via tsubst so that they get consistently reused.  */
> -  if (typedef_variant_p (t))
> -    {
> -      t = tsubst (t, args, complain, in_decl);
> -      if (t == error_mark_node)
> -	return error_mark_node;
> -
> -      /* The effect of entering_scope is that for a dependent specialization
> -	 A<T>, lookup_template_class prefers to return A's primary template
> -	 type instead of the implicit instantiation.  So when entering_scope,
> -	 we mirror this behavior by inspecting TYPE_CANONICAL appropriately,
> -	 taking advantage of the fact that lookup_template_class links the two
> -	 types by setting TYPE_CANONICAL of the latter to the former.  */
> -      if (entering_scope
> -	  && CLASS_TYPE_P (t)
> -	  && dependent_type_p (t)
> -	  && TYPE_TEMPLATE_INFO (t)
> -	  && TYPE_CANONICAL (t) == TREE_TYPE (TYPE_TI_TEMPLATE (t)))
> -	t = TYPE_CANONICAL (t);
> -
> -      return t;
> -    }
> -
> -  switch (TREE_CODE (t))
> -    {
> -      case RECORD_TYPE:
> -      case ENUMERAL_TYPE:
> -      case UNION_TYPE:
> -	return tsubst_aggr_type_1 (t, args, complain, in_decl, entering_scope);
> -
> -      default:
> -	return tsubst (t, args, complain, in_decl);
> -    }
> -}
> -
> -/* The part of tsubst_aggr_type that's shared with the RECORD_, UNION_
> -   and ENUMERAL_TYPE cases of tsubst.  */
> -
> -static tree
> -tsubst_aggr_type_1 (tree t,
> -		    tree args,
> -		    tsubst_flags_t complain,
> -		    tree in_decl,
> -		    int entering_scope)
> -{
> -  if (TYPE_TEMPLATE_INFO (t) && uses_template_parms (t))
> -    {
> -      complain &= ~tf_qualifying_scope;
> -
> -      /* Figure out what arguments are appropriate for the
> -	 type we are trying to find.  For example, given:
> -
> -	   template <class T> struct S;
> -	   template <class T, class U> void f(T, U) { S<U> su; }
> -
> -	 and supposing that we are instantiating f<int, double>,
> -	 then our ARGS will be {int, double}, but, when looking up
> -	 S we only want {double}.  */
> -      tree argvec = tsubst_template_args (TYPE_TI_ARGS (t), args,
> -					  complain, in_decl);
> -      if (argvec == error_mark_node)
> -	return error_mark_node;
> -
> -      tree r = lookup_template_class (t, argvec, in_decl, NULL_TREE,
> -				      entering_scope, complain);
> -      return cp_build_qualified_type (r, cp_type_quals (t), complain);
> -    }
> -  else
> -    /* This is not a template type, so there's nothing to do.  */
> -    return t;
> -}
> -
>  /* Map from a FUNCTION_DECL to a vec of default argument instantiations,
>     indexed in reverse order of the parameters.  */
>  
> @@ -14544,8 +14470,10 @@ tsubst_function_decl (tree t, tree args, tsubst_flags_t complain,
>      lambda_fntype = static_fn_type (lambda_fntype);
>  
>    if (member && !closure)
> -    ctx = tsubst_aggr_type (ctx, args,
> -			    complain, t, /*entering_scope=*/1);
> +    {
> +      ctx = tsubst (ctx, args, complain, t);
> +      ctx = adjust_type_for_entering_scope (ctx);
> +    }
>  
>    tree type = (lambda_fntype ? lambda_fntype
>  	       : tsubst (TREE_TYPE (t), args,
> @@ -14938,8 +14866,10 @@ tsubst_template_decl (tree t, tree args, tsubst_flags_t complain,
>  	  inner = TREE_TYPE (inner);
>  	}
>        if (class_p)
> -	inner = tsubst_aggr_type (inner, args, complain,
> -				  in_decl, /*entering*/1);
> +	{
> +	  inner = tsubst (inner, args, complain, in_decl);
> +	  inner = adjust_type_for_entering_scope (inner);
> +	}
>        else
>  	inner = tsubst_decl (inner, args, complain, /*use_spec_table=*/false);
>      }
> @@ -15443,9 +15373,8 @@ tsubst_decl (tree t, tree args, tsubst_flags_t complain,
>  	    local_p = false;
>  	    if (DECL_CLASS_SCOPE_P (t))
>  	      {
> -		ctx = tsubst_aggr_type (ctx, args,
> -					complain,
> -					in_decl, /*entering_scope=*/1);
> +		ctx = tsubst (ctx, args, complain, in_decl);
> +		ctx = adjust_type_for_entering_scope (ctx);
>  		if (DECL_SELF_REFERENCE_P (t))
>  		  /* The context and type of an injected-class-name are
>  		     the same, so we don't need to substitute both.  */
> @@ -16241,8 +16170,31 @@ tsubst (tree t, tree args, tsubst_flags_t complain, tree in_decl)
>        /* Fall through.  */
>      case UNION_TYPE:
>      case ENUMERAL_TYPE:
> -      return tsubst_aggr_type_1 (t, args, complain, in_decl,
> -				 /*entering_scope=*/0);
> +      if (TYPE_TEMPLATE_INFO (t) && uses_template_parms (t))
> +	{
> +	  complain &= ~tf_qualifying_scope;
> +
> +	  /* Figure out what arguments are appropriate for the
> +	     type we are trying to find.  For example, given:
> +
> +	       template <class T> struct S;
> +	       template <class T, class U> void f(T, U) { S<U> su; }
> +
> +	     and supposing that we are instantiating f<int, double>,
> +	     then our ARGS will be {int, double}, but, when looking up
> +	     S we only want {double}.  */
> +	  tree argvec = tsubst_template_args (TYPE_TI_ARGS (t), args,
> +					      complain, in_decl);
> +	  if (argvec == error_mark_node)
> +	    return error_mark_node;
> +
> +	  tree r = lookup_template_class (t, argvec, in_decl, NULL_TREE,
> +					  complain);
> +	  return cp_build_qualified_type (r, cp_type_quals (t), complain);
> +	}
> +      else
> +	/* This is not a template type, so there's nothing to do.  */
> +	return t;
>  
>      case ERROR_MARK:
>      case IDENTIFIER_NODE:
> @@ -16424,7 +16376,6 @@ tsubst (tree t, tree args, tsubst_flags_t complain, tree in_decl)
>  		r = lookup_template_class (arg,
>  					   argvec, in_decl,
>  					   DECL_CONTEXT (arg),
> -					    /*entering_scope=*/0,
>  					   complain);
>  		return cp_build_qualified_type
>  		  (r, cp_type_quals (t) | cp_type_quals (r), complain);
> @@ -16516,7 +16467,7 @@ tsubst (tree t, tree args, tsubst_flags_t complain, tree in_decl)
>  	      if (argvec == error_mark_node)
>  		return error_mark_node;
>  	      r = lookup_template_class (tmpl, argvec, in_decl, NULL_TREE,
> -					 /*entering_scope=*/false, complain);
> +					 complain);
>  	      r = cp_build_qualified_type (r, cp_type_quals (t), complain);
>  	      break;
>  	    }
> @@ -16771,9 +16722,10 @@ tsubst (tree t, tree args, tsubst_flags_t complain, tree in_decl)
>  	    ctx = TREE_VEC_ELT (ctx, 0);
>  	  }
>  	else
> -	  ctx = tsubst_aggr_type (ctx, args,
> -				  complain | tf_qualifying_scope,
> -				  in_decl, /*entering_scope=*/1);
> +	  {
> +	    ctx = tsubst_scope (ctx, args, complain, in_decl);
> +	    ctx = adjust_type_for_entering_scope (ctx);
> +	  }
>  	if (ctx == error_mark_node)
>  	  return error_mark_node;
>  
> @@ -16846,8 +16798,10 @@ tsubst (tree t, tree args, tsubst_flags_t complain, tree in_decl)
>  
>      case UNBOUND_CLASS_TEMPLATE:
>        {
> -	tree ctx = tsubst_aggr_type (TYPE_CONTEXT (t), args, complain,
> -				     in_decl, /*entering_scope=*/1);
> +	++processing_template_decl;
> +	tree ctx = tsubst (TYPE_CONTEXT (t), args, complain, in_decl);
> +	ctx = adjust_type_for_entering_scope (ctx);
> +	--processing_template_decl;
>  	tree name = TYPE_IDENTIFIER (t);
>  	tree parm_list = DECL_TEMPLATE_PARMS (TYPE_NAME (t));
>  
> @@ -17065,8 +17019,8 @@ tsubst_baselink (tree baselink, tree object_type,
>  {
>    bool qualified_p = BASELINK_QUALIFIED_P (baselink);
>    tree qualifying_scope = BINFO_TYPE (BASELINK_ACCESS_BINFO (baselink));
> -  qualifying_scope = tsubst_aggr_type (qualifying_scope, args, complain, in_decl,
> -				       /*entering_scope=*/true);
> +  qualifying_scope = tsubst (qualifying_scope, args, complain, in_decl);
> +  qualifying_scope = adjust_type_for_entering_scope (qualifying_scope);
>  
>    tree optype = BASELINK_OPTYPE (baselink);
>    optype = tsubst (optype, args, complain, in_decl);
> @@ -21451,9 +21405,7 @@ tsubst_expr (tree t, tree args, tsubst_flags_t complain, tree in_decl)
>  
>  	   When we instantiate f<7>::S::g(), say, lookup_name is not
>  	   clever enough to find f<7>::a.  */
> -	enum_type
> -	  = tsubst_aggr_type (DECL_CONTEXT (t), args, complain, in_decl,
> -			      /*entering_scope=*/0);
> +	enum_type = tsubst (DECL_CONTEXT (t), args, complain, in_decl);
>  
>  	for (v = TYPE_VALUES (enum_type);
>  	     v != NULL_TREE;
> @@ -21473,8 +21425,8 @@ tsubst_expr (tree t, tree args, tsubst_flags_t complain, tree in_decl)
>  	{
>  	  tree ctx;
>  
> -	  ctx = tsubst_aggr_type (DECL_CONTEXT (t), args, complain, in_decl,
> -				  /*entering_scope=*/1);
> +	  ctx = tsubst (DECL_CONTEXT (t), args, complain, in_decl);
> +	  ctx = adjust_type_for_entering_scope (ctx);
>  	  if (ctx != DECL_CONTEXT (t))
>  	    {
>  	      tree r = lookup_field (ctx, DECL_NAME (t), 0, false);
> @@ -21517,8 +21469,8 @@ tsubst_expr (tree t, tree args, tsubst_flags_t complain, tree in_decl)
>  	     TEMPLATE_DECL with `D<T>' as its DECL_CONTEXT.  Now we
>  	     have to substitute this with one having context `D<int>'.  */
>  
> -	  tree context = tsubst_aggr_type (DECL_CONTEXT (t), args, complain,
> -					   in_decl, /*entering_scope=*/true);
> +	  tree context = tsubst (DECL_CONTEXT (t), args, complain, in_decl);
> +	  context = adjust_type_for_entering_scope (context);
>  	  RETURN (lookup_field (context, DECL_NAME(t), 0, false));
>  	}
>        else
> @@ -22060,8 +22012,10 @@ instantiate_template (tree tmpl, tree orig_args, tsubst_flags_t complain)
>  	   already non-dependent, then we might as well use it.  */
>  	ctx = DECL_CONTEXT (tmpl);
>        else
> -	ctx = tsubst_aggr_type (DECL_CONTEXT (gen_tmpl), targ_ptr,
> -				complain, gen_tmpl, true);
> +	{
> +	  ctx = tsubst (DECL_CONTEXT (gen_tmpl), targ_ptr, complain, gen_tmpl);
> +	  ctx = adjust_type_for_entering_scope (ctx);
> +	}
>        push_nested_class (ctx);
>      }
>  
> @@ -29214,8 +29168,8 @@ resolve_typename_type (tree type, bool only_current_p)
>        tree args = TREE_OPERAND (fullname, 1);
>        /* Instantiate the template.  */
>        result = lookup_template_class (tmpl, args, NULL_TREE, NULL_TREE,
> -				      /*entering_scope=*/true,
>  				      tf_error | tf_user);
> +      result = adjust_type_for_entering_scope (result);
>        if (result == error_mark_node)
>  	result = NULL_TREE;
>      }
> @@ -29443,7 +29397,7 @@ listify (tree arg)
>    TREE_VEC_ELT (argvec, 0) = arg;
>  
>    return lookup_template_class (std_init_list, argvec, NULL_TREE,
> -				NULL_TREE, 0, tf_warning_or_error);
> +				NULL_TREE, tf_warning_or_error);
>  }
>  
>  /* Replace auto in TYPE with std::initializer_list<auto>.  */
> @@ -30389,7 +30343,7 @@ alias_ctad_tweaks (tree tmpl, tree uguides)
>  	    fprime = copy_decl (fprime);
>  	  tree fntype = TREE_TYPE (fprime);
>  	  ret = lookup_template_class (TPARMS_PRIMARY_TEMPLATE (atparms), targs,
> -				       in_decl, NULL_TREE, false, complain);
> +				       in_decl, NULL_TREE, complain);
>  	  fntype = build_function_type (ret, TYPE_ARG_TYPES (fntype));
>  	  TREE_TYPE (fprime) = fntype;
>  	  if (TREE_CODE (fprime) == TEMPLATE_DECL)
> diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
> index 3299e270446..cea819db221 100644
> --- a/gcc/cp/semantics.cc
> +++ b/gcc/cp/semantics.cc
> @@ -3946,8 +3946,10 @@ finish_template_type (tree name, tree args, int entering_scope)
>    tree type;
>  
>    type = lookup_template_class (name, args,
> -				NULL_TREE, NULL_TREE, entering_scope,
> +				NULL_TREE, NULL_TREE,
>  				tf_warning_or_error | tf_user);
> +  if (entering_scope)
> +    type = adjust_type_for_entering_scope (type);
>  
>    /* If we might be entering the scope of a partial specialization,
>       find the one with the right constraints.  */
> -- 
> 2.43.0.493.gbc7ee2e5e1
> 
>