[C++ PATCH] Fix implicit assignment operators with anonymous aggregates

[Jakub Jelinek <jakub at redhat dot com>]

Hi!

The testcase below results in error (and it did not in g++ 2.95.x), while I
think it is completely valid. It B does not have a trivial assignment
operator, everything compiles fine (A's assignment operator ends up
immediate call to build (MODIFY_EXPR, ...)). The problem is that
fixup_anonymous_aggr removes the assignment operator method, but
build_modify_expr requires it, so it dies on anonymous union's operator= not
being accessible.
This patch fixes it (bootstrapped on i386, no regressions), another approach
might be not to delete the artificial operator= of anonymous aggregates.
For anonymous unions both should IMHO work right, I'm not sure about
anonymous structures:
I don't think we disallow anonymous structure's members to have explicit
operator=, which won't be called now (well, g++ will either error or simply
pretend there are none) nor with the patch below (g++ will pretend there are
none) - to fix that either fixup_anonymous_aggr would have to keep implicit
operator= or do_build_assign_ref would have to build_modify_expr for each of
anonymous structure's fields.

2001-03-20  Jakub Jelinek  <jakub@redhat.com>

	* method.c (do_build_assign_ref): Don't use build_modify_expr for
	anonymous aggregates, since they don't have assignment operator
	method.

	* g++.old-deja/g++.other/anon8.C: New test.

--- gcc/cp/method.c.jj	Tue Mar 20 13:45:06 2001
+++ gcc/cp/method.c	Tue Mar 20 13:55:01 2001
@@ -703,7 +703,11 @@ do_build_assign_ref (fndecl)
 	                build_qualified_type (TREE_TYPE (field), cvquals),
 	                init, field);
 
-	  finish_expr_stmt (build_modify_expr (comp, NOP_EXPR, init));
+	  if (DECL_NAME (field))
+	    finish_expr_stmt (build_modify_expr (comp, NOP_EXPR, init));
+	  else
+	    finish_expr_stmt (build (MODIFY_EXPR, TREE_TYPE (comp), comp,
+				     init));
 	}
     }
   finish_return_stmt (current_class_ref);
--- gcc/testsuite/g++.old-deja/g++.other/anon8.C.jj	Mon Mar 19 17:13:30 2001
+++ gcc/testsuite/g++.old-deja/g++.other/anon8.C	Tue Mar 20 17:01:57 2001
@@ -0,0 +1,22 @@
+// Build don't link:
+
+struct B
+{
+  int a;
+  B & operator= (const B &);
+};
+
+struct A
+{
+  union {
+    int a;
+  };
+  B b;
+};
+
+A x;
+
+void foo (const A &y)
+{
+  x = y;
+}

	Jakub