coroutines: Fix cases where proxy variables are used [PR94879]

There are several places where the handling of a variable
declaration depends on whether it corresponds to a compiler
temporary, or to some other entity.  We were testing that var
decls were artificial in determining this.  However, proxy vars
are also artificial so that this is not sufficient.  The solution
is to exclude variables with a DECL_VALUE_EXPR as well, since
the value variable will not be a temporary.

gcc/cp/ChangeLog:

2020-04-30  Iain Sandoe  <iain@sandoe.co.uk>

	PR c++/94879
	* coroutines.cc (build_co_await): Account for variables
	with DECL_VALUE_EXPRs.
	(captures_temporary): Likewise.
	(register_awaits): Likewise.

gcc/testsuite/ChangeLog:

2020-04-30  Iain Sandoe  <iain@sandoe.co.uk>

	PR c++/94879
	* g++.dg/coroutines/pr94879-folly-1.C: New test.

gcc/cp/ChangeLog

+2020-04-30  Iain Sandoe  <iain@sandoe.co.uk>
+
+	PR c++/94879
+	* coroutines.cc (build_co_await): Account for variables
+	with DECL_VALUE_EXPRs.
+	(captures_temporary): Likewise.
+	(register_awaits): Likewise.
+
 2020-04-29  Patrick Palka  <ppalka@redhat.com>
 
 	PR c++/94830

gcc/cp/coroutines.cc

@@ -748,7 +748,8 @@ build_co_await (location_t loc, tree a, suspend_point_kind suspend_kind)
   if (INDIRECT_REF_P (e_proxy))
     e_proxy = TREE_OPERAND (e_proxy, 0);
   if (TREE_CODE (e_proxy) == PARM_DECL
-      || (TREE_CODE (e_proxy) == VAR_DECL && !DECL_ARTIFICIAL (e_proxy)))
+      || (VAR_P (e_proxy) && (!DECL_ARTIFICIAL (e_proxy)
+			      || DECL_HAS_VALUE_EXPR_P (e_proxy))))
     e_proxy = o;
   else
     {
@@ -2659,7 +2660,8 @@ captures_temporary (tree *stmt, int *do_subtree, void *d)
 	}
 
       /* This isn't a temporary.  */
-      if ((TREE_CODE (parm) == VAR_DECL && !DECL_ARTIFICIAL (parm))
+      if ((VAR_P (parm)
+	   && (!DECL_ARTIFICIAL (parm) || DECL_HAS_VALUE_EXPR_P (parm)))
 	  || TREE_CODE (parm) == PARM_DECL
 	  || TREE_CODE (parm) == NON_LVALUE_EXPR)
 	continue;
@@ -2742,7 +2744,8 @@ register_awaits (tree *stmt, int *do_subtree ATTRIBUTE_UNUSED, void *d)
   if (INDIRECT_REF_P (aw))
     aw = TREE_OPERAND (aw, 0);
   if (TREE_CODE (aw) == PARM_DECL
-      || (TREE_CODE (aw) == VAR_DECL && !DECL_ARTIFICIAL (aw)))
+      || (VAR_P (aw) && (!DECL_ARTIFICIAL (aw)
+			 || DECL_HAS_VALUE_EXPR_P (aw))))
     ; /* Don't make an additional copy.  */
   else
     {

gcc/testsuite/ChangeLog

+2020-04-30  Iain Sandoe  <iain@sandoe.co.uk>
+
+	PR c++/94879
+	* g++.dg/coroutines/pr94xxx-folly-1.C: New test.
+
 2020-04-30  Marek Polacek  <polacek@redhat.com>
 
 	PR c++/94775

gcc/testsuite/g++.dg/coroutines/pr94879-folly-1.C

+//  { dg-additional-options  "-fpreprocessed -w" }
+
+namespace std {
+template <typename a> a b(a &&);
+template <typename c> struct d { c e; };
+template <typename f, typename> struct coroutine_traits : f {};
+template <typename = void> struct coroutine_handle;
+template <> struct coroutine_handle<> {};
+template <typename> struct coroutine_handle : coroutine_handle<> {};
+struct g {};
+} // namespace std
+
+class h {};
+class i {
+  i(i &&);
+};
+
+namespace ac {
+template <typename> class ad {
+public:
+  bool await_ready();
+  void await_resume();
+  void await_suspend(std::coroutine_handle<>);
+  i ae;
+};
+} // namespace ac
+
+template <typename ab> ac::ad<ab> operator co_await(ab);
+class j {
+  class l {};
+
+public:
+  std::g initial_suspend();
+  l final_suspend();
+};
+class m : public j {
+public:
+  void get_return_object();
+  void unhandled_exception();
+};
+class n {
+public:
+  using promise_type = m;
+};
+std::d<h> k;
+void a() {
+  auto am = k;
+  [&]() -> n { co_await std::b(am.e); };
+}