PR c++/66297, DR 1684 - literal class and constexpr member fns

	* constexpr.c (is_valid_constexpr_fn): Only complain about
	non-literal enclosing class in C++11.
	* class.c (finalize_literal_type_property): Likewise.

From-SVN: r247813

gcc/cp/ChangeLog

+2017-05-09  Jason Merrill  <jason@redhat.com>
+
+	PR c++/66297, DR 1684 - literal class and constexpr member fns
+	* constexpr.c (is_valid_constexpr_fn): Only complain about
+	non-literal enclosing class in C++11.
+	* class.c (finalize_literal_type_property): Likewise.
+
 2017-05-09  Paolo Carlini  <paolo.carlini@oracle.com>
 
 	PR c++/80186

gcc/cp/class.c

@@ -5757,7 +5757,9 @@ finalize_literal_type_property (tree t)
 	   && !TYPE_HAS_CONSTEXPR_CTOR (t))
     CLASSTYPE_LITERAL_P (t) = false;
 
-  if (!CLASSTYPE_LITERAL_P (t))
+  /* C++14 DR 1684 removed this restriction.  */
+  if (cxx_dialect < cxx14
+      && !CLASSTYPE_LITERAL_P (t) && !LAMBDA_TYPE_P (t))
     for (fn = TYPE_METHODS (t); fn; fn = DECL_CHAIN (fn))
       if (DECL_DECLARED_CONSTEXPR_P (fn)
 	  && TREE_CODE (fn) != TEMPLATE_DECL
@@ -5765,12 +5767,11 @@ finalize_literal_type_property (tree t)
 	  && !DECL_CONSTRUCTOR_P (fn))
 	{
 	  DECL_DECLARED_CONSTEXPR_P (fn) = false;
-	  if (!DECL_GENERATED_P (fn) && !LAMBDA_TYPE_P (t))
-	    {
-	      error ("enclosing class of constexpr non-static member "
-		     "function %q+#D is not a literal type", fn);
-	      explain_non_literal_class (t);
-	    }
+	  if (!DECL_GENERATED_P (fn)
+	      && pedwarn (DECL_SOURCE_LOCATION (fn), OPT_Wpedantic,
+			  "enclosing class of constexpr non-static member "
+			  "function %q+#D is not a literal type", fn))
+	    explain_non_literal_class (t);
 	}
 }
 

gcc/cp/constexpr.c

@@ -210,16 +210,17 @@ is_valid_constexpr_fn (tree fun, bool complain)
 	    }
 	}
 
-      if (DECL_NONSTATIC_MEMBER_FUNCTION_P (fun)
+      /* C++14 DR 1684 removed this restriction.  */
+      if (cxx_dialect < cxx14
+	  && DECL_NONSTATIC_MEMBER_FUNCTION_P (fun)
 	  && !CLASSTYPE_LITERAL_P (DECL_CONTEXT (fun)))
 	{
 	  ret = false;
-	  if (complain)
-	    {
-	      error ("enclosing class of constexpr non-static member "
-		     "function %q+#D is not a literal type", fun);
-	      explain_non_literal_class (DECL_CONTEXT (fun));
-	    }
+	  if (complain
+	      && pedwarn (DECL_SOURCE_LOCATION (fun), OPT_Wpedantic,
+			  "enclosing class of constexpr non-static member "
+			  "function %q+#D is not a literal type", fun))
+	    explain_non_literal_class (DECL_CONTEXT (fun));
 	}
     }
   else if (CLASSTYPE_VBASECLASSES (DECL_CONTEXT (fun)))

gcc/testsuite/g++.dg/cpp0x/constexpr-data1.C

@@ -36,7 +36,7 @@ class debug_flag
 {
 public:
    explicit debug_flag(bool);
-   constexpr bool is_on(); // { dg-error "enclosing class .* not a literal type" }
+   constexpr bool is_on(); // { dg-error "enclosing class .* not a literal type" "" { target c++11_only } }
 private:
    bool flag;
 };

gcc/testsuite/g++.dg/cpp0x/constexpr-diag1.C

@@ -5,7 +5,7 @@ template <class T>
 struct A
 {
   T t;
-  constexpr int f() const { return 42; } // { dg-error "enclosing class" }
+  constexpr int f() const { return 42; } // { dg-error "enclosing class" "" { target c++11_only } }
 };
 
 struct B { B(); operator int(); };
@@ -13,7 +13,7 @@ struct B { B(); operator int(); };
 constexpr A<int> ai = { 42 };
 constexpr int i = ai.f();
 
-constexpr int b = A<B>().f();	// { dg-error "non-constexpr function" }
+constexpr int b = A<B>().f();	// { dg-error "" }
 
 template <class T>
 constexpr int f (T t) { return 42; } // { dg-error "parameter" }

gcc/testsuite/g++.dg/cpp0x/constexpr-diag3.C

@@ -16,7 +16,7 @@ int main()
 struct complex 			// { dg-message "no constexpr constructor" }
 {
   complex(double r, double i) : re(r), im(i) { }
-  constexpr double real() const { return re; } // { dg-error "not a literal type" }
+  constexpr double real() const { return re; } // { dg-error "not a literal type" "" { target c++11_only } }
   double imag() const { return im; }
 
 private:
@@ -25,7 +25,7 @@ private:
 };
 
 constexpr complex co1(0, 1);	   // { dg-error "not literal" }
-constexpr double dd2 = co1.real(); // { dg-error "non-constexpr function" }
+constexpr double dd2 = co1.real(); // { dg-error "" }
 
 // --------------------
 

gcc/testsuite/g++.dg/cpp0x/constexpr-memfn1.C

@@ -13,6 +13,6 @@ constexpr X X::g(X x) { return x; }
 struct Y
 {
   Y() { }
-  constexpr Y f(Y y);		// { dg-error "not a literal type" }
+  constexpr Y f(Y y) {}		// { dg-error "constexpr" }
   static constexpr Y g(Y y) {}	// { dg-error "constexpr" }
 };

gcc/testsuite/g++.dg/cpp0x/constexpr-neg1.C

@@ -45,7 +45,7 @@ constexpr int g(int x, int n) {
 class debug_flag {
 public:
   explicit debug_flag(bool);
-  constexpr bool is_on();	// { dg-error "not a literal type" } debug_flag not literal type
+  constexpr bool is_on(); // { dg-error "not a literal type" "" { target c++11_only } } debug_flag not literal type
 private:
   bool flag;
 };

gcc/testsuite/g++.dg/cpp1y/constexpr-dr1684.C

+// DR 1684
+// { dg-do compile { target c++11 } }
+
+struct A {
+  A(int);
+  constexpr int foo() { return 0; } // { dg-error "literal" "" { target c++11_only } }
+};