From: Jason Merrill <jason@redhat.com>
Date: Thu, 28 May 2020 04:35:56 +0000 (-0400)
Subject: c++: Immediately deduce auto member [PR94926].
X-Git-Tag: basepoints/gcc-12~7554
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=7b599b9f9a1e036ff75a4daa06ac7036c6ebbe01;p=thirdparty%2Fgcc.git

c++: Immediately deduce auto member [PR94926].

In r9-297 I was trying to be more flexible and treat static data members of
class templates more like variable templates, where the type need not be
determined until the variable is instantiated, but I suppose that in a class
the types of all the non-template members need to be determined at the time
of class instantiation.

gcc/cp/ChangeLog:

	PR c++/94926
	* decl.c (cp_finish_decl): Revert r9-297 change.
	(check_static_variable_definition): Likewise.
	* constexpr.c (ensure_literal_type_for_constexpr_object): Likewise.
	* pt.c (instantiate_decl): Return early on type error.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp1z/pr86648.C: Expect error.
	* g++.dg/cpp1z/static2.C: Expect error.
	* g++.dg/cpp0x/nsdmi16.C: New test.
---

diff --git a/gcc/cp/constexpr.c b/gcc/cp/constexpr.c
index 4e441ac8d2fa..4b1f92f989cf 100644
--- a/gcc/cp/constexpr.c
+++ b/gcc/cp/constexpr.c
@@ -96,8 +96,6 @@ ensure_literal_type_for_constexpr_object (tree decl)
       if (CLASS_TYPE_P (stype) && !COMPLETE_TYPE_P (complete_type (stype)))
 	/* Don't complain here, we'll complain about incompleteness
 	   when we try to initialize the variable.  */;
-      else if (type_uses_auto (type))
-	/* We don't know the actual type yet.  */;
       else if (!literal_type_p (type))
 	{
 	  if (DECL_DECLARED_CONSTEXPR_P (decl))
diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index 56571e395708..b0de90630d7c 100644
--- a/gcc/cp/decl.c
+++ b/gcc/cp/decl.c
@@ -7467,18 +7467,24 @@ cp_finish_decl (tree decl, tree init, bool init_const_expr_p,
       && (DECL_INITIAL (decl) || init))
     DECL_INITIALIZED_IN_CLASS_P (decl) = 1;
 
-  /* Do auto deduction unless decl is a function or an uninstantiated
-     template specialization.  */
   if (TREE_CODE (decl) != FUNCTION_DECL
-      && !(init == NULL_TREE
-	   && DECL_LANG_SPECIFIC (decl)
-	   && DECL_TEMPLATE_INSTANTIATION (decl)
-	   && !DECL_TEMPLATE_INSTANTIATED (decl))
       && (auto_node = type_uses_auto (type)))
     {
       tree d_init;
       if (init == NULL_TREE)
-	gcc_assert (CLASS_PLACEHOLDER_TEMPLATE (auto_node));
+	{
+	  if (DECL_LANG_SPECIFIC (decl)
+	      && DECL_TEMPLATE_INSTANTIATION (decl)
+	      && !DECL_TEMPLATE_INSTANTIATED (decl))
+	    {
+	      /* init is null because we're deferring instantiating the
+		 initializer until we need it.  Well, we need it now.  */
+	      instantiate_decl (decl, /*defer_ok*/true, /*expl*/false);
+	      return;
+	    }
+
+	  gcc_assert (CLASS_PLACEHOLDER_TEMPLATE (auto_node));
+	}
       d_init = init;
       if (d_init)
 	{
@@ -10171,7 +10177,6 @@ check_static_variable_definition (tree decl, tree type)
      in check_initializer.  Similarly for inline static data members.  */
   else if (DECL_P (decl)
       && (DECL_DECLARED_CONSTEXPR_P (decl)
-	  || undeduced_auto_decl (decl)
 	  || DECL_VAR_DECLARED_INLINE_P (decl)))
     ;
   else if (cxx_dialect >= cxx11 && !INTEGRAL_OR_ENUMERATION_TYPE_P (type))
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 4d9651acee65..90dafff3aa70 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -25293,6 +25293,7 @@ instantiate_decl (tree d, bool defer_ok, bool expl_inst_class_mem_p)
     d = DECL_CLONED_FUNCTION (d);
 
   if (DECL_TEMPLATE_INSTANTIATED (d)
+      || TREE_TYPE (d) == error_mark_node
       || (TREE_CODE (d) == FUNCTION_DECL
 	  && DECL_DEFAULTED_FN (d) && DECL_INITIAL (d))
       || DECL_TEMPLATE_SPECIALIZATION (d))
diff --git a/gcc/testsuite/g++.dg/cpp0x/nsdmi16.C b/gcc/testsuite/g++.dg/cpp0x/nsdmi16.C
new file mode 100644
index 000000000000..07bc198e6916
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/nsdmi16.C
@@ -0,0 +1,11 @@
+// PR c++/94926
+// { dg-do compile { target c++11 } }
+
+template<typename>
+struct A {
+    static auto self_reference = A{}; // { dg-error "incomplete" }
+};
+
+int main() {
+    A<void>{};
+}
diff --git a/gcc/testsuite/g++.dg/cpp1z/pr86648.C b/gcc/testsuite/g++.dg/cpp1z/pr86648.C
index 20ee4c8c0d44..58c611c985fc 100644
--- a/gcc/testsuite/g++.dg/cpp1z/pr86648.C
+++ b/gcc/testsuite/g++.dg/cpp1z/pr86648.C
@@ -1,5 +1,7 @@
 // { dg-do compile { target c++17 } }
 
 template <typename> class A;
-template <class T> struct B { static A a{T::a}; };
+template <class T> struct B {
+  static A a{T::a};		// { dg-error "int" }
+};
 void foo () { B<int> a; }
diff --git a/gcc/testsuite/g++.dg/cpp1z/static2.C b/gcc/testsuite/g++.dg/cpp1z/static2.C
index 9462e0355c86..5d93a0e7242b 100644
--- a/gcc/testsuite/g++.dg/cpp1z/static2.C
+++ b/gcc/testsuite/g++.dg/cpp1z/static2.C
@@ -3,7 +3,7 @@
 template <class T>
 struct A
 {
-  static constexpr auto x = T::x;
+  static constexpr auto x = T::x; // { dg-error "incomplete" }
 };
 
 struct B;