re PR c++/78931 (ICE on C++17 structured bindings from struct with reference member)

	PR c++/78931
	* decl.c (cp_finish_decomp): Remove probe variable, if tt is
	REFERENCE_REF_P, set tt to its operand.

	* g++.dg/cpp1z/decomp19.C: New test.

From-SVN: r244113

gcc/cp/ChangeLog

 2017-01-05  Jakub Jelinek  <jakub@redhat.com>
 
+	PR c++/78931
+	* decl.c (cp_finish_decomp): Remove probe variable, if tt is
+	REFERENCE_REF_P, set tt to its operand.
+
 	PR c++/78890
 	* class.c (check_field_decls): Diagnose REFERENCE_TYPE fields in
 	unions even for C++11 and later.

gcc/cp/decl.c

@@ -7593,10 +7593,9 @@ cp_finish_decomp (tree decl, tree first, unsigned int count)
 	else
 	  {
 	    tree tt = finish_non_static_data_member (field, t, NULL_TREE);
-	    tree probe = tt;
-	    if (REFERENCE_REF_P (probe))
-	      probe = TREE_OPERAND (probe, 0);
-	    TREE_TYPE (v[i]) = TREE_TYPE (probe);
+	    if (REFERENCE_REF_P (tt))
+	      tt = TREE_OPERAND (tt, 0);
+	    TREE_TYPE (v[i]) = TREE_TYPE (tt);
 	    layout_decl (v[i], 0);
 	    SET_DECL_VALUE_EXPR (v[i], tt);
 	    DECL_HAS_VALUE_EXPR_P (v[i]) = 1;

gcc/testsuite/ChangeLog

 2017-01-05  Jakub Jelinek  <jakub@redhat.com>
 
+	PR c++/78931
+	* g++.dg/cpp1z/decomp19.C: New test.
+
 	PR c++/78890
 	* g++.dg/init/ref14.C: Expect error even in C++11 and later.
 	* g++.dg/init/union1.C: Likewise.

gcc/testsuite/g++.dg/cpp1z/decomp19.C

+// PR c++/78931
+// { dg-do run { target c++11 } }
+// { dg-options "" }
+
+int
+main ()
+{
+  int x = 99;
+  struct S { int &x; };
+  S s{x};
+  auto [p] = s;		// { dg-warning "decomposition declaration only available with" "" { target c++14_down } }
+  return p - 99;
+}