C++ PATCH for c++/78908, template operators and bit-fields

[Jason Merrill]

In this testcase, in a template we were building a non-dependent
version of a COMPONENT_REF with a lowered bit-field type but without
the FIELD_DECL.  We should use the declared type.

Tested x86_64-pc-linux-gnu, applying to trunk.

commit 631e8a030d0c8eebb0800943e41ffbdc38ba7eec
Author: Jason Merrill <ja...@redhat.com>
Date:   Fri Feb 10 15:08:06 2017 -0500

            PR c++/78908 - template ops and bitfields
            * tree.c (build_min_non_dep): Use unlowered_expr_type.

diff --git a/gcc/cp/tree.c b/gcc/cp/tree.c
index 785dfaf..56c4bba 100644
--- a/gcc/cp/tree.c
+++ b/gcc/cp/tree.c
@@ -2884,7 +2884,7 @@ build_min_non_dep (enum tree_code code, tree non_dep, ...)
 
   t = make_node (code);
   length = TREE_CODE_LENGTH (code);
-  TREE_TYPE (t) = TREE_TYPE (non_dep);
+  TREE_TYPE (t) = unlowered_expr_type (non_dep);
   TREE_SIDE_EFFECTS (t) = TREE_SIDE_EFFECTS (non_dep);
 
   for (i = 0; i < length; i++)
diff --git a/gcc/testsuite/g++.dg/template/bitfield3.C 
b/gcc/testsuite/g++.dg/template/bitfield3.C
new file mode 100644
index 0000000..8f11255
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/bitfield3.C
@@ -0,0 +1,20 @@
+// PR c++/78908
+
+struct A { int a : 1; };
+struct F { int foo (A const &); };
+template <typename> struct O : F { int foo (A const &); };
+struct S {} b;
+template <typename L, typename T> int operator<< (L, T) { return (T) 123; }
+template <typename T> int O<T>::foo (A const &x) { return b << x.a; }
+
+int
+main ()
+{
+  A a = { 0 };
+  O<int> o;
+  if (o.foo (a) != 123)
+    __builtin_abort ();
+  signed char d = 2;
+  if ((b << d) != 123)
+    __builtin_abort ();
+}