P0490R0 GB 20: decomposition declaration should commit to tuple interpretation early

	P0490R0 GB 20: decomposition declaration should commit to tuple
	interpretation early
	* decl.c (get_tuple_size): Make static.  If inst is error_mark_node
	or non-complete type, return NULL_TREE, otherwise if
	lookup_qualified_name fails or doesn't fold into INTEGER_CST, return
	error_mark_node.
	(get_tuple_element_type, get_tuple_decomp_init): Make static.
	(cp_finish_decomp): Pass LOC to get_tuple_size.  If it returns
	error_mark_node, complain and fail.

	* g++.dg/cpp1z/decomp10.C (f1): Adjust expected diagnostics.

From-SVN: r243724

gcc/cp/ChangeLog

+2016-12-15  Jakub Jelinek  <jakub@redhat.com>
+
+	P0490R0 GB 20: decomposition declaration should commit to tuple
+	interpretation early
+	* decl.c (get_tuple_size): Make static.  If inst is error_mark_node
+	or non-complete type, return NULL_TREE, otherwise if
+	lookup_qualified_name fails or doesn't fold into INTEGER_CST, return
+	error_mark_node.
+	(get_tuple_element_type, get_tuple_decomp_init): Make static.
+	(cp_finish_decomp): Pass LOC to get_tuple_size.  If it returns
+	error_mark_node, complain and fail.
+
 2016-12-15  Nathan Sidwell  <nathan@acm.org>
 
 	PR c++/77585

gcc/cp/decl.c

@@ -7259,7 +7259,7 @@ find_decomp_class_base (location_t loc, tree type, tree ret)
 
 /* Return std::tuple_size<TYPE>::value.  */
 
-tree
+static tree
 get_tuple_size (tree type)
 {
   tree args = make_tree_vec (1);
@@ -7268,6 +7268,9 @@ get_tuple_size (tree type)
 				     /*in_decl*/NULL_TREE,
 				     /*context*/std_node,
 				     /*entering_scope*/false, tf_none);
+  inst = complete_type (inst);
+  if (inst == error_mark_node || !COMPLETE_TYPE_P (inst))
+    return NULL_TREE;
   tree val = lookup_qualified_name (inst, get_identifier ("value"),
 				    /*type*/false, /*complain*/false);
   if (TREE_CODE (val) == VAR_DECL || TREE_CODE (val) == CONST_DECL)
@@ -7275,12 +7278,12 @@ get_tuple_size (tree type)
   if (TREE_CODE (val) == INTEGER_CST)
     return val;
   else
-    return NULL_TREE;
+    return error_mark_node;
 }
 
 /* Return std::tuple_element<I,TYPE>::type.  */
 
-tree
+static tree
 get_tuple_element_type (tree type, unsigned i)
 {
   tree args = make_tree_vec (2);
@@ -7297,7 +7300,7 @@ get_tuple_element_type (tree type, unsigned i)
 
 /* Return e.get<i>() or get<i>(e).  */
 
-tree
+static tree
 get_tuple_decomp_init (tree decl, unsigned i)
 {
   tree get_id = get_identifier ("get");
@@ -7342,6 +7345,7 @@ store_decomp_type (tree v, tree t)
     decomp_type_table = hash_map<tree,tree>::create_ggc (13);
   decomp_type_table->put (v, t);
 }
+
 tree
 lookup_decomp_type (tree v)
 {
@@ -7502,6 +7506,12 @@ cp_finish_decomp (tree decl, tree first, unsigned int count)
     }
   else if (tree tsize = get_tuple_size (type))
     {
+      if (tsize == error_mark_node)
+	{
+	  error_at (loc, "%<std::tuple_size<%T>::value%> is not an integral "
+			 "constant expression", type);
+	  goto error_out;
+	}
       eltscnt = tree_to_uhwi (tsize);
       if (count != eltscnt)
 	goto cnt_mismatch;

gcc/testsuite/ChangeLog

+2016-12-15  Jakub Jelinek  <jakub@redhat.com>
+
+	P0490R0 GB 20: decomposition declaration should commit to tuple
+	interpretation early
+	* g++.dg/cpp1z/decomp10.C (f1): Adjust expected diagnostics.
+
 2016-12-15  Nathan Sidwell  <nathan@acm.org>
 
 	PR c++/77585

gcc/testsuite/g++.dg/cpp1z/decomp10.C

@@ -7,7 +7,7 @@ namespace std {
 
 struct A1 { int i,j; } a1;
 template<> struct std::tuple_size<A1> {  };
-void f1() { auto [ x ] = a1; }	// { dg-error "decomposes into 2" }
+void f1() { auto [ x ] = a1; }	// { dg-error "is not an integral constant expression" }
 
 struct A2 { int i,j; } a2;
 template<> struct std::tuple_size<A2> { enum { value = 5 }; };