re PR c++/57437 (C++11: mutable lambdas)

	PR c++/57437
	* typeck.c (check_return_expr): Lambda proxies aren't eligible
	for nrv or return by move.

From-SVN: r200843

gcc/cp/ChangeLog

 2013-07-09  Jason Merrill  <jason@redhat.com>
 
+	PR c++/57437
+	* typeck.c (check_return_expr): Lambda proxies aren't eligible
+	for nrv or return by move.
+
 	PR c++/57532
 	* parser.c (cp_parser_ref_qualifier_opt): Don't tentatively parse
 	a ref-qualifier in C++98 mode.

gcc/cp/typeck.c

@@ -8399,7 +8399,8 @@ check_return_expr (tree retval, bool *no_warning)
      && VAR_P (retval)
      && DECL_CONTEXT (retval) == current_function_decl
      && ! TREE_STATIC (retval)
-     && ! DECL_ANON_UNION_VAR_P (retval)
+     /* And not a lambda or anonymous union proxy.  */
+     && !DECL_HAS_VALUE_EXPR_P (retval)
      && (DECL_ALIGN (retval) <= DECL_ALIGN (result))
      /* The cv-unqualified type of the returned value must be the
         same as the cv-unqualified return type of the
@@ -8444,7 +8445,7 @@ check_return_expr (tree retval, bool *no_warning)
          Note that these conditions are similar to, but not as strict as,
 	 the conditions for the named return value optimization.  */
       if ((cxx_dialect != cxx98)
-          && (VAR_P (retval)
+          && ((VAR_P (retval) && !DECL_HAS_VALUE_EXPR_P (retval))
 	      || TREE_CODE (retval) == PARM_DECL)
 	  && DECL_CONTEXT (retval) == current_function_decl
 	  && !TREE_STATIC (retval)

gcc/testsuite/g++.dg/cpp0x/lambda/lambda-return1.C

+// PR c++/57437
+// { dg-require-effective-target c++11 }
+
+struct A {
+  int i;
+
+  A(): i(42) {}
+  A(const A&) = default;
+  A(A&& a): i(a.i) { a.i = 0; }
+};
+
+int main()
+{
+  A x;
+
+  auto y = [x] () mutable {
+    x.i++;
+    return x;
+  };
+
+  if (y().i != 43)
+    __builtin_abort ();
+
+  if (y().i != 44)
+    __builtin_abort ();
+}