c++: Clean up previous change [PR41437]

The previous patch mostly avoided making any changes that had no
functional impact, such as adjusting now-outdated comments and
performing renamings.  Such changes have been consolidated to this
followup patch for easier review.

The main change here is that we now reuse struct deferred_access_check
as the element type of the vector TI_TYPEDEFS_NEEDING_ACCESS_CHECKING
(now renamed to TI_DEFERRED_ACCESS_CHECKS, since it may contain any kind
of access check).

gcc/cp/ChangeLog:

	PR c++/41437
	PR c++/47346
	* cp-tree.h (qualified_typedef_usage_s): Delete.
	(qualified_typedef_usage_t): Delete.
	(deferred_access_check): Move up in file.
	(tree_template_info::typedefs_needing_access_checking): Delete.
	(tree_template_info::deferred_access_checks): New field.
	(TI_TYPEDEFS_NEEDING_ACCESS_CHECKING): Rename to ...
	(TI_DEFERRED_ACCESS_CHECKS): ... this, and adjust accordingly.
	* pt.c (perform_typedefs_access_check): Rename to ...
	(perform_instantiation_time_access_checks): ... this, and adjust
	accordingly.  Remove unnecessary tree tests.
	(instantiate_class_template_1): Adjust accordingly.
	(instantiate_decl): Likewise.
	* semantics.c (enforce_access): Likewise.

gcc/cp/cp-tree.h

@@ -1449,27 +1449,6 @@ struct GTY (()) tree_lambda_expr
   int discriminator;
 };
 
-/* A (typedef,context,usage location) triplet.
-   It represents a typedef used through a
-   context at a given source location.
-   e.g.
-   struct foo {
-     typedef int myint;
-   };
-
-   struct bar {
-    foo::myint v; // #1<-- this location.
-   };
-
-   In bar, the triplet will be (myint, foo, #1).
-   */
-struct GTY(()) qualified_typedef_usage_s {
-  tree typedef_decl;
-  tree context;
-  location_t locus;
-};
-typedef struct qualified_typedef_usage_s qualified_typedef_usage_t;
-
 /* Non-zero if this template specialization has access violations that
    should be rechecked when the function is instantiated outside argument
    deduction.  */
@@ -1489,11 +1468,24 @@ typedef struct qualified_typedef_usage_s qualified_typedef_usage_t;
 #define TINFO_VAR_DECLARED_CONSTINIT(NODE) \
   (TREE_LANG_FLAG_2 (TEMPLATE_INFO_CHECK (NODE)))
 
+/* The representation of a deferred access check.  */
+
+struct GTY(()) deferred_access_check {
+  /* The base class in which the declaration is referenced. */
+  tree binfo;
+  /* The declaration whose access must be checked.  */
+  tree decl;
+  /* The declaration that should be used in the error message.  */
+  tree diag_decl;
+  /* The location of this access.  */
+  location_t loc;
+};
+
 struct GTY(()) tree_template_info {
   struct tree_base base;
   tree tmpl;
   tree args;
-  vec<qualified_typedef_usage_t, va_gc> *typedefs_needing_access_checking;
+  vec<deferred_access_check, va_gc> *deferred_access_checks;
 };
 
 // Constraint information for a C++ declaration. Constraint information is
@@ -3532,14 +3524,15 @@ struct GTY(()) lang_decl {
   ? int_cst_value (NON_DEFAULT_TEMPLATE_ARGS_COUNT (NODE)) \
   : TREE_VEC_LENGTH (INNERMOST_TEMPLATE_ARGS (NODE))
 #endif
-/* The list of typedefs - used in the template - that need
-   access checking at template instantiation time.
+
+/* The list of access checks that were deferred during parsing
+   which need to be performed at template instantiation time.
 
    FIXME this should be associated with the TEMPLATE_DECL, not the
    TEMPLATE_INFO.  */
-#define TI_TYPEDEFS_NEEDING_ACCESS_CHECKING(NODE) \
+#define TI_DEFERRED_ACCESS_CHECKS(NODE) \
   ((struct tree_template_info*)TEMPLATE_INFO_CHECK \
-     (NODE))->typedefs_needing_access_checking
+     (NODE))->deferred_access_checks
 
 /* We use TREE_VECs to hold template arguments.  If there is only one
    level of template arguments, then the TREE_VEC contains the
@@ -7090,19 +7083,6 @@ extern int shared_member_p			(tree);
 extern bool any_dependent_bases_p (tree = current_nonlambda_class_type ());
 extern bool maybe_check_overriding_exception_spec (tree, tree);
 
-/* The representation of a deferred access check.  */
-
-struct GTY(()) deferred_access_check {
-  /* The base class in which the declaration is referenced. */
-  tree binfo;
-  /* The declaration whose access must be checked.  */
-  tree decl;
-  /* The declaration that should be used in the error message.  */
-  tree diag_decl;
-  /* The location of this access.  */
-  location_t loc;
-};
-
 /* in semantics.c */
 extern void push_deferring_access_checks	(deferring_kind);
 extern void resume_deferring_access_checks	(void);

gcc/cp/pt.c

@@ -215,7 +215,7 @@ static bool any_template_arguments_need_structural_equality_p (tree);
 static bool dependent_type_p_r (tree);
 static tree tsubst_copy	(tree, tree, tsubst_flags_t, tree);
 static tree tsubst_decl (tree, tree, tsubst_flags_t);
-static void perform_typedefs_access_check (tree tmpl, tree targs);
+static void perform_instantiation_time_access_checks (tree, tree);
 static tree listify (tree);
 static tree listify_autos (tree, tree);
 static tree tsubst_template_parm (tree, tree, tsubst_flags_t);
@@ -11512,46 +11512,38 @@ apply_late_template_attributes (tree *decl_p, tree attributes, int attr_flags,
     }
 }
 
-/* Perform (or defer) access check for typedefs that were referenced
-   from within the template TMPL code.
-   This is a subroutine of instantiate_decl and instantiate_class_template.
-   TMPL is the template to consider and TARGS is the list of arguments of
-   that template.  */
+/* The template TMPL is being instantiated with the template arguments TARGS.
+   Perform the access checks that we deferred when parsing the template.  */
 
 static void
-perform_typedefs_access_check (tree tmpl, tree targs)
+perform_instantiation_time_access_checks (tree tmpl, tree targs)
 {
   unsigned i;
-  qualified_typedef_usage_t *iter;
+  deferred_access_check *chk;
 
-  if (!tmpl
-      || (!CLASS_TYPE_P (tmpl)
-	  && TREE_CODE (tmpl) != FUNCTION_DECL))
+  if (!CLASS_TYPE_P (tmpl) && TREE_CODE (tmpl) != FUNCTION_DECL)
     return;
 
-  if (vec<qualified_typedef_usage_t, va_gc> *tdefs
-      = TI_TYPEDEFS_NEEDING_ACCESS_CHECKING (get_template_info (tmpl)))
-    FOR_EACH_VEC_ELT (*tdefs, i, iter)
+  if (vec<deferred_access_check, va_gc> *access_checks
+      = TI_DEFERRED_ACCESS_CHECKS (get_template_info (tmpl)))
+    FOR_EACH_VEC_ELT (*access_checks, i, chk)
       {
-	tree type_decl = iter->typedef_decl;
-	tree type_scope = iter->context;
+	tree decl = chk->decl;
+	tree diag_decl = chk->diag_decl;
+	tree type_scope = TREE_TYPE (chk->binfo);
 
-	if (!type_decl || !type_scope || !CLASS_TYPE_P (type_scope))
-	  continue;
-
-	if (uses_template_parms (type_decl)
-	    || (TREE_CODE (type_decl) == FIELD_DECL
-		&& uses_template_parms (DECL_CONTEXT (type_decl))))
-	  type_decl = tsubst_copy (type_decl, targs, tf_error, NULL_TREE);
+	if (uses_template_parms (decl)
+	    || (TREE_CODE (decl) == FIELD_DECL
+		&& uses_template_parms (DECL_CONTEXT (decl))))
+	  decl = tsubst_copy (decl, targs, tf_error, NULL_TREE);
 	if (uses_template_parms (type_scope))
 	  type_scope = tsubst (type_scope, targs, tf_error, NULL_TREE);
 
 	/* Make access check error messages point to the location
 	   of the use of the typedef.  */
-	iloc_sentinel ils (iter->locus);
+	iloc_sentinel ils (chk->loc);
 	perform_or_defer_access_check (TYPE_BINFO (type_scope),
-				       type_decl, type_decl,
-				       tf_warning_or_error);
+				       decl, diag_decl, tf_warning_or_error);
       }
 }
 
@@ -12080,11 +12072,7 @@ instantiate_class_template_1 (tree type)
      definitions or default arguments, of the class member functions,
      member classes, static data members and member templates....  */
 
-  /* Some typedefs referenced from within the template code need to be access
-     checked at template instantiation time, i.e now. These types were
-     added to the template at parsing time. Let's get those and perform
-     the access checks then.  */
-  perform_typedefs_access_check (pattern, args);
+  perform_instantiation_time_access_checks (pattern, args);
   perform_deferred_access_checks (tf_warning_or_error);
   pop_nested_class ();
   maximum_field_alignment = saved_maximum_field_alignment;
@@ -25631,12 +25619,8 @@ instantiate_decl (tree d, bool defer_ok, bool expl_inst_class_mem_p)
       else
 	start_preparsed_function (d, NULL_TREE, SF_PRE_PARSED);
 
-      /* Some typedefs referenced from within the template code need to be
-	 access checked at template instantiation time, i.e now. These
-	 types were added to the template at parsing time. Let's get those
-	 and perform the access checks then.  */
-      perform_typedefs_access_check (DECL_TEMPLATE_RESULT (td),
-				     args);
+      perform_instantiation_time_access_checks (DECL_TEMPLATE_RESULT (td),
+						args);
 
       /* Create substitution entries for the parameters.  */
       register_parameter_specializations (code_pattern, d);

gcc/cp/semantics.c

@@ -295,12 +295,12 @@ enforce_access (tree basetype_path, tree decl, tree diag_decl,
 	  return true;
 
 	/* Defer this access check until instantiation time.  */
-	qualified_typedef_usage_t typedef_usage;
-	typedef_usage.typedef_decl = decl;
-	typedef_usage.context = TREE_TYPE (basetype_path);
-	typedef_usage.locus = input_location;
-	vec_safe_push (TI_TYPEDEFS_NEEDING_ACCESS_CHECKING (template_info),
-		       typedef_usage);
+	deferred_access_check access_check;
+	access_check.binfo = basetype_path;
+	access_check.decl = decl;
+	access_check.diag_decl = diag_decl;
+	access_check.loc = input_location;
+	vec_safe_push (TI_DEFERRED_ACCESS_CHECKS (template_info), access_check);
 	return true;
       }