re PR c++/52748 ([C++11] N3276 changes to decltype)

	N3276
	PR c++/52748
	* cp-tree.h (tsubst_flags): Add tf_decltype.
	* call.c (build_cxx_call): Don't build a temporary if it's set.
	(build_over_call): Make sure it's only passed to build_cxx_call.
	* parser.c (cp_parser_primary_expression): Add decltype_p parm.
	(cp_parser_unary_expression): Likewise.
	(cp_parser_cast_expression): Likewise.
	(cp_parser_binary_expression): Likewise.
	(cp_parser_assignment_expression): Likewise.
	(cp_parser_postfix_expression): Likewise.  Pass tf_decltype.
	(cp_parser_explicit_instantiation): Add decltype_p.  Force a
	temporary for a call on the LHS of a comma.
	(cp_parser_decltype): Pass true to decltype_p parms.
	* pt.c (tsubst) [DECLTYPE_TYPE]: Pass tf_decltype.
	(tsubst_copy_and_build): Pass tf_decltype down only for
	CALL_EXPR and the RHS of COMPOUND_EXPR.
	* tree.c (build_cplus_new): Call complete_type_or_maybe_complain.

From-SVN: r196736

gcc/cp/ChangeLog

 2013-03-16  Jason Merrill  <jason@redhat.com>
 
+	N3276
+	PR c++/52748
+	* cp-tree.h (tsubst_flags): Add tf_decltype.
+	* call.c (build_cxx_call): Don't build a temporary if it's set.
+	(build_over_call): Make sure it's only passed to build_cxx_call.
+	* parser.c (cp_parser_primary_expression): Add decltype_p parm.
+	(cp_parser_unary_expression): Likewise.
+	(cp_parser_cast_expression): Likewise.
+	(cp_parser_binary_expression): Likewise.
+	(cp_parser_assignment_expression): Likewise.
+	(cp_parser_postfix_expression): Likewise.  Pass tf_decltype.
+	(cp_parser_explicit_instantiation): Add decltype_p.  Force a
+	temporary for a call on the LHS of a comma.
+	(cp_parser_decltype): Pass true to decltype_p parms.
+	* pt.c (tsubst) [DECLTYPE_TYPE]: Pass tf_decltype.
+	(tsubst_copy_and_build): Pass tf_decltype down only for
+	CALL_EXPR and the RHS of COMPOUND_EXPR.
+	* tree.c (build_cplus_new): Call complete_type_or_maybe_complain.
+
 	* cp-tree.h (abstract_class_use): New enum.
 	* typeck2.c (pending_abstract_type): Add use field.
 	(abstract_virtuals_error_sfinae): Add overloads taking

gcc/cp/call.c

@@ -6693,6 +6693,10 @@ build_over_call (struct z_candidate *cand, int flags, tsubst_flags_t complain)
       /* else continue to get conversion error.  */
     }
 
+  /* N3276 magic doesn't apply to nested calls.  */
+  int decltype_flag = (complain & tf_decltype);
+  complain &= ~tf_decltype;
+
   /* Find maximum size of vector to hold converted arguments.  */
   parmlen = list_length (parm);
   nargs = vec_safe_length (args) + (first_arg != NULL_TREE ? 1 : 0);
@@ -7064,7 +7068,7 @@ build_over_call (struct z_candidate *cand, int flags, tsubst_flags_t complain)
 	return error_mark_node;
     }
 
-  return build_cxx_call (fn, nargs, argarray, complain);
+  return build_cxx_call (fn, nargs, argarray, complain|decltype_flag);
 }
 
 /* Build and return a call to FN, using NARGS arguments in ARGARRAY.
@@ -7106,12 +7110,20 @@ build_cxx_call (tree fn, int nargs, tree *argarray,
   if (VOID_TYPE_P (TREE_TYPE (fn)))
     return fn;
 
-  fn = require_complete_type_sfinae (fn, complain);
-  if (fn == error_mark_node)
-    return error_mark_node;
+  /* 5.2.2/11: If a function call is a prvalue of object type: if the
+     function call is either the operand of a decltype-specifier or the
+     right operand of a comma operator that is the operand of a
+     decltype-specifier, a temporary object is not introduced for the
+     prvalue. The type of the prvalue may be incomplete.  */
+  if (!(complain & tf_decltype))
+    {
+      fn = require_complete_type_sfinae (fn, complain);
+      if (fn == error_mark_node)
+	return error_mark_node;
 
-  if (MAYBE_CLASS_TYPE_P (TREE_TYPE (fn)))
-    fn = build_cplus_new (TREE_TYPE (fn), fn, complain);
+      if (MAYBE_CLASS_TYPE_P (TREE_TYPE (fn)))
+	fn = build_cplus_new (TREE_TYPE (fn), fn, complain);
+    }
   return convert_from_reference (fn);
 }
 

gcc/cp/cp-tree.h

@@ -4203,6 +4203,9 @@ enum tsubst_flags {
 				    conversion might be permissible,
 				    not actually performing the
 				    conversion.  */
+  tf_decltype = 1 << 7,          /* We are the operand of decltype.
+				    Used to implement the special rules
+				    for calls in decltype (5.2.2/11).  */
   tf_partial = 1 << 8,		 /* Doing initial explicit argument
 				    substitution in fn_type_unification.  */
   /* Convenient substitution flags combinations.  */

gcc/cp/pt.c

@@ -11781,7 +11781,7 @@ tsubst (tree t, tree args, tsubst_flags_t complain, tree in_decl)
 	++c_inhibit_evaluation_warnings;
 
 	type = tsubst_expr (DECLTYPE_TYPE_EXPR (t), args,
-			    complain, in_decl,
+			    complain|tf_decltype, in_decl,
 			    /*integral_constant_expression_p=*/false);
 
 	--cp_unevaluated_operand;
@@ -13417,6 +13417,12 @@ tsubst_copy_and_build (tree t,
   if (EXPR_HAS_LOCATION (t))
     input_location = EXPR_LOCATION (t);
 
+  /* N3276 decltype magic only applies to calls at the top level or on the
+     right side of a comma.  */
+  if (TREE_CODE (t) != CALL_EXPR
+      && TREE_CODE (t) != COMPOUND_EXPR)
+    complain &= ~tf_decltype;
+
   switch (TREE_CODE (t))
     {
     case USING_DECL:
@@ -13848,10 +13854,16 @@ tsubst_copy_and_build (tree t,
 	complain));
 
     case COMPOUND_EXPR:
-      RETURN (build_x_compound_expr (EXPR_LOCATION (t),
-				    RECUR (TREE_OPERAND (t, 0)),
-				    RECUR (TREE_OPERAND (t, 1)),
-                                    complain));
+      {
+	tree op0 = tsubst_copy_and_build (TREE_OPERAND (t, 0), args,
+					  complain & ~tf_decltype, in_decl,
+					  /*function_p=*/false,
+					  integral_constant_expression_p);
+	RETURN (build_x_compound_expr (EXPR_LOCATION (t),
+				       op0,
+				       RECUR (TREE_OPERAND (t, 1)),
+				       complain));
+      }
 
     case CALL_EXPR:
       {
@@ -13862,6 +13874,10 @@ tsubst_copy_and_build (tree t,
 	bool koenig_p;
 	tree ret;
 
+	/* Don't pass tf_decltype down to subexpressions.  */
+	tsubst_flags_t decltype_flag = (complain & tf_decltype);
+	complain &= ~tf_decltype;
+
 	function = CALL_EXPR_FN (t);
 	/* When we parsed the expression,  we determined whether or
 	   not Koenig lookup should be performed.  */
@@ -14028,6 +14044,9 @@ tsubst_copy_and_build (tree t,
 	if (DECL_P (function))
 	  mark_used (function);
 
+	/* Put back tf_decltype for the actual call.  */
+	complain |= decltype_flag;
+
 	if (TREE_CODE (function) == OFFSET_REF)
 	  ret = build_offset_ref_call_from_tree (function, &call_args,
 						 complain);

gcc/cp/tree.c

@@ -469,6 +469,9 @@ build_cplus_new (tree type, tree init, tsubst_flags_t complain)
   tree rval = build_aggr_init_expr (type, init);
   tree slot;
 
+  if (!complete_type_or_maybe_complain (type, init, complain))
+    return error_mark_node;
+
   /* Make sure that we're not trying to create an instance of an
      abstract class.  */
   if (abstract_virtuals_error_sfinae (NULL_TREE, type, complain))

gcc/testsuite/g++.dg/cpp0x/decltype-call1.C

+// PR c++/52748
+// N3276
+// { dg-do compile { target c++11 } }
+
+struct A;			// { dg-error "forward declaration" }
+A f();
+
+decltype(f()) g1();		 // OK
+decltype(((f()))) g2b();	 // OK
+decltype(42,f()) g3();		 // OK
+decltype(42,45,f()) g3b();	 // OK
+decltype(42,45,(f())) g3c();	 // OK
+decltype(42,((45,(f())))) g3c(); // OK
+
+decltype(f(),42) g4();		 // { dg-error "" }
+decltype(45,f(),42) g4b();	 // { dg-error "" }
+
+class B
+{
+  ~B();				// { dg-error "private" }
+public:
+  int i;
+  void operator[](int);
+};
+B h();
+
+void i(const B&);
+
+decltype(h()) g5a();		// OK
+decltype(h().i) g5();		// { dg-error "" }
+decltype(h()[0]) g6();		// { dg-error "" }
+decltype(i(h())) g7();		// { dg-error "" }