[C++ PATCH] Error on shadowing a parameter by anon union member in the same scope (PR c++/72707)

[Jakub Jelinek]

Hi!

DECL_ANON_UNION_VAR_P vars are DECL_ARTIFICIAL, but we still to diagnose
them if they shadow something.  The DECL_ARTIFICIAL (x) check has been
missing in older gcc releases, so we diagnosed that properly.

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2016-12-20  Jakub Jelinek  <ja...@redhat.com>

        PR c++/72707
        * name-lookup.c (pushdecl_maybe_friend_1): Do check shadowing of
        artificial x if it is an anonymous union variable.

        * g++.dg/warn/Wshadow-12.C: New test.

--- gcc/cp/name-lookup.c.jj     2016-11-30 08:57:21.000000000 +0100
+++ gcc/cp/name-lookup.c        2016-12-20 14:42:35.482232062 +0100
@@ -1111,8 +1111,10 @@ pushdecl_maybe_friend_1 (tree x, bool is
                                || TREE_CODE (x) == TYPE_DECL)))
                    /* Don't check for internally generated vars unless
                       it's an implicit typedef (see create_implicit_typedef
-                      in decl.c).  */
-                  && (!DECL_ARTIFICIAL (x) || DECL_IMPLICIT_TYPEDEF_P (x)))
+                      in decl.c) or anonymous union variable.  */
+                  && (!DECL_ARTIFICIAL (x)
+                      || DECL_IMPLICIT_TYPEDEF_P (x)
+                      || (VAR_P (x) && DECL_ANON_UNION_VAR_P (x))))
            {
              bool nowarn = false;
 
--- gcc/testsuite/g++.dg/warn/Wshadow-12.C.jj   2016-12-20 14:41:28.083114644 
+0100
+++ gcc/testsuite/g++.dg/warn/Wshadow-12.C      2016-12-20 14:40:19.000000000 
+0100
@@ -0,0 +1,9 @@
+// PR c++/72707
+// { dg-do compile }
+
+void
+foo (double x)
+{
+  union { int x; };    // { dg-error "shadows a parameter" }
+  x = 0;
+}

        Jakub