[PATCH] c++: implicitly_declare_fn and access checks [PR113908]

[Patrick Palka <ppalka@redhat.com>]

Bootstrapped and regtested on x86_64-pc-linux-gnu, are one of
both of these fixes OK for trunk?

-- >8 --

Here during ahead of time checking of the non-dependent new-expr we
synthesize B's copy constructor, which should be defined as deleted
due to A's inaccessible copy constructor.  But enforce_access incorrectly
decides to defer the (silent) access check for A::A(const A&) during
synthesization since current_template_parms is still set (before r14-557
it checked processing_template_decl which got cleared from
implicitly_declare_fn), which leads to the access check leaking out to
the template context that needed the synthesization.

This patch narrowly fixes this regression in two sufficient ways:

1. Clear current_template_parms alongside processing_template_decl
   in implicitly_declare_fn so that it's more independent of context.
2. Don't defer a silent access check when in a template context,
   since such deferred checks will be replayed noisily at instantiation
   time which may not be what the caller intended.  We need to adjust
   cp_parser_make_typename_type since otherwise the diagnostic for
   typedef22.C regresses because cp_parser_invalid_type_name otherwise
   will emit "invalid combination of multiple type-specifiers" for what
   is an inaccessible qualified-id.

	PR c++/113908

gcc/cp/ChangeLog:

	* method.cc (implicitly_declare_fn): Clear current_template_parms
	alongside processing_template_decl.
	* parser.cc (cp_parser_make_typename_type): Temporarily defer
	access checks around the tf_none call to make_typename_type.
	* semantics.cc (enforce_access): Don't defer silent access
	checks from a template context.

gcc/testsuite/ChangeLog:

	* g++.dg/template/non-dependent31.C: New test.
---
 gcc/cp/method.cc                               |  8 +++++++-
 gcc/cp/parser.cc                               |  2 ++
 gcc/cp/semantics.cc                            |  1 +
 .../g++.dg/template/non-dependent31.C          | 18 ++++++++++++++++++
 4 files changed, 28 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/g++.dg/template/non-dependent31.C

diff --git a/gcc/cp/method.cc b/gcc/cp/method.cc
index 957496d3e18..17d42143299 100644
--- a/gcc/cp/method.cc
+++ b/gcc/cp/method.cc
@@ -3088,6 +3088,7 @@ implicitly_declare_fn (special_function_kind kind, tree type,
   tree this_parm;
   tree name;
   HOST_WIDE_INT saved_processing_template_decl;
+  tree saved_current_template_parms;
   bool deleted_p = false;
   bool constexpr_p = false;
   tree inherited_ctor = (kind == sfk_inheriting_constructor
@@ -3132,6 +3133,10 @@ implicitly_declare_fn (special_function_kind kind, tree type,
      when not in a template.  */
   saved_processing_template_decl = processing_template_decl;
   processing_template_decl = 0;
+  /* Also clear CURRENT_TEMPLATE_PARMS so enforce_access immediately checks
+     access even in a template context.  */
+  saved_current_template_parms = current_template_parms;
+  current_template_parms = NULL_TREE;
 
   type = TYPE_MAIN_VARIANT (type);
 
@@ -3341,8 +3346,9 @@ implicitly_declare_fn (special_function_kind kind, tree type,
         set_constraints (fn, new_ci);
       }
 
-  /* Restore PROCESSING_TEMPLATE_DECL.  */
+  /* Restore PROCESSING_TEMPLATE_DECL and CURRENT_TEMPLATE_PARMS.  */
   processing_template_decl = saved_processing_template_decl;
+  current_template_parms = saved_current_template_parms;
 
   if (inherited_ctor && TREE_CODE (inherited_ctor) == TEMPLATE_DECL)
     fn = add_inherited_template_parms (fn, inherited_ctor);
diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc
index c4292c49ce2..29120995449 100644
--- a/gcc/cp/parser.cc
+++ b/gcc/cp/parser.cc
@@ -4350,8 +4350,10 @@ cp_parser_make_typename_type (cp_parser *parser, tree id,
   tree result;
   if (identifier_p (id))
     {
+      push_deferring_access_checks (dk_deferred);
       result = make_typename_type (parser->scope, id, typename_type,
 				   /*complain=*/tf_none);
+      pop_to_parent_deferring_access_checks ();
       if (result == error_mark_node)
 	cp_parser_diagnose_invalid_type_name (parser, id, id_location);
       return result;
diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
index 3299e270446..0a18eaf9c2e 100644
--- a/gcc/cp/semantics.cc
+++ b/gcc/cp/semantics.cc
@@ -346,6 +346,7 @@ enforce_access (tree basetype_path, tree decl, tree diag_decl,
 
   tree cs = current_scope ();
   if (in_template_context
+      && (complain & tf_error)
       && (CLASS_TYPE_P (cs) || TREE_CODE (cs) == FUNCTION_DECL))
     if (tree template_info = get_template_info (cs))
       {
diff --git a/gcc/testsuite/g++.dg/template/non-dependent31.C b/gcc/testsuite/g++.dg/template/non-dependent31.C
new file mode 100644
index 00000000000..3fa68f40fe1
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/non-dependent31.C
@@ -0,0 +1,18 @@
+// PR c++/113908
+// { dg-do compile { target c++11 } }
+
+struct A {
+  A();
+private:
+  A(const A&);
+};
+
+struct B {
+  A a;
+
+  template<class T>
+  static void f() { new B(); }
+};
+
+template void B::f<int>();
+static_assert(!__is_constructible(B, const B&), "");
-- 
2.44.0.rc0.46.g2996f11c1d