Hi,

We didn’t quite have time to push this through before the 10.1
deadline, but (since it’s a correctness issue) it should be applied
to the branch too.

tested on x86_64-darwin, linux
OK for master?
10.2 after some bake time?
thanks
Iain

=======

It was agreed amongst the implementors that the correct
interpretation of the standard is that lambda closure pointers
should be treated in the same manner as class object pointers.

gcc/cp/ChangeLog:

        * coroutines.cc (instantiate_coro_traits): Pass a reference
        to lambda closure objects to traits instantiation.
        (morph_fn_to_coro): Likewise for promise parameter
        preview and allocator lookup.
---
 gcc/cp/coroutines.cc | 19 +++++--------------
 1 file changed, 5 insertions(+), 14 deletions(-)

diff --git a/gcc/cp/coroutines.cc b/gcc/cp/coroutines.cc
index b79e2c66b70..6e3f03bdb0d 100644
--- a/gcc/cp/coroutines.cc
+++ b/gcc/cp/coroutines.cc
@@ -304,8 +304,8 @@ instantiate_coro_traits (tree fndecl, location_t kw)
 
   while (arg_node != NULL_TREE && !VOID_TYPE_P (TREE_VALUE (arg_node)))
     {
-      /* See PR94807, as to why we must exclude lambda here.  */
-      if (is_this_parameter (arg) && !lambda_p)
+      if (is_this_parameter (arg)
+         || (lambda_p && DECL_NAME (arg) == closure_identifier))
        {
          /* We pass a reference to *this to the param preview.  */
          tree ct = TREE_TYPE (TREE_TYPE (arg));
@@ -3793,13 +3793,8 @@ morph_fn_to_coro (tree orig, tree *resumer, tree 
*destroyer)
            parm.frame_type = actual_type;
 
          parm.this_ptr = is_this_parameter (arg);
-         /* See PR94807.  When a lambda is in a template instantiation, the
-            closure object is named 'this' instead of '__closure'.  */
          if (lambda_p)
-           {
-             parm.lambda_cobj = DECL_NAME (arg) == closure_identifier;
-             gcc_checking_assert (!parm.this_ptr);
-           }
+           parm.lambda_cobj = DECL_NAME (arg) == closure_identifier;
          else
            parm.lambda_cobj = false;
 
@@ -3953,9 +3948,7 @@ morph_fn_to_coro (tree orig, tree *resumer, tree 
*destroyer)
        {
          param_info *parm_i = param_uses->get (arg);
          gcc_checking_assert (parm_i);
-         if (parm_i->lambda_cobj)
-           vec_safe_push (args, arg);
-         else if (parm_i->this_ptr)
+         if (parm_i->this_ptr || parm_i->lambda_cobj)
            {
              /* We pass a reference to *this to the allocator lookup.  */
              tree tt = TREE_TYPE (TREE_TYPE (arg));
@@ -4159,9 +4152,7 @@ morph_fn_to_coro (tree orig, tree *resumer, tree 
*destroyer)
 
          /* Add this to the promise CTOR arguments list, accounting for
             refs and special handling for method this ptr.  */
-         if (parm.lambda_cobj)
-           vec_safe_push (promise_args, arg);
-         else if (parm.this_ptr)
+         if (parm.this_ptr || parm.lambda_cobj)
            {
              /* We pass a reference to *this to the param preview.  */
              tree tt = TREE_TYPE (arg);
-- 
2.24.1

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