re PR c++/85210 (ICE with broken structured binding in template)

	PR c++/85210
	* pt.c (tsubst_decomp_names): Return error_mark_node and assert
	errorcount is set if tsubst doesn't return a VAR_DECL.

	* g++.dg/cpp1z/decomp42.C: New test.

From-SVN: r259181

gcc/cp/ChangeLog

+2018-04-06  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c++/85210
+	* pt.c (tsubst_decomp_names): Return error_mark_node and assert
+	errorcount is set if tsubst doesn't return a VAR_DECL.
+
 2018-04-06  David Malcolm  <dmalcolm@redhat.com>
 
 	PR c++/85021

gcc/cp/pt.c

@@ -16235,6 +16235,12 @@ tsubst_decomp_names (tree decl, tree pattern_decl, tree args,
       DECL_HAS_VALUE_EXPR_P (decl2) = 1;
       if (VAR_P (decl3))
 	DECL_TEMPLATE_INSTANTIATED (decl3) = 1;
+      else
+	{
+	  gcc_assert (errorcount);
+	  decl = error_mark_node;
+	  continue;
+	}
       maybe_push_decl (decl3);
       if (error_operand_p (decl3))
 	decl = error_mark_node;

gcc/testsuite/ChangeLog

+2018-04-06  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c++/85210
+	* g++.dg/cpp1z/decomp42.C: New test.
+
 2018-04-06  David Malcolm  <dmalcolm@redhat.com>
 
 	PR c++/85021

gcc/testsuite/g++.dg/cpp1z/decomp42.C

+// PR c++/85210
+// { dg-do compile { target c++11 } }
+// { dg-options "" }
+
+struct A { int i; };
+
+template <int>
+void
+foo (int j)
+{
+  auto [j] = A{j};	// { dg-error "shadows a parameter" }
+}			// { dg-warning "structured bindings only available with" "" { target c++14_down } .-1 }
+
+void
+bar ()
+{
+  foo<0> (0);
+}