coroutines: Fix missing dereference (PR94319).

Fix a typo.

gcc/cp/ChangeLog:

2020-03-25  Iain Sandoe  <iain@sandoe.co.uk>

	PR c++/94319
	* coroutines.cc (captures_temporary): Fix a missing dereference.

gcc/cp/ChangeLog

+2020-03-25  Iain Sandoe  <iain@sandoe.co.uk>
+
+	PR c++/94319
+	* coroutines.cc (captures_temporary): Fix a missing dereference.
+
 2020-03-24  Marek Polacek  <polacek@redhat.com>
 
 	PR c++/94190 - wrong no post-decrement operator error in template.

gcc/cp/coroutines.cc

@@ -2651,7 +2651,7 @@ captures_temporary (tree *stmt, int *do_subtree, void *d)
     }
   /* As far as it's necessary, we've walked the subtrees of the call
      expr.  */
-  do_subtree = 0;
+  *do_subtree = 0;
   return NULL_TREE;
 }