[Bug c++/86836] internal compiler error on structured bindings with shadow parameter on templated function

["jakub at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86836

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jason at gcc dot gnu.org

--- Comment #6 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
I've tried to defer the assert until after cp_finish_decl:
--- pt.c.jj1    2018-07-31 23:57:23.000000000 +0200
+++ pt.c        2018-08-03 11:11:41.384454435 +0200
@@ -16555,10 +16555,7 @@ tsubst_decomp_names (tree decl, tree pat
        decl2 = DECL_CHAIN (decl2))
     {
       if (TREE_TYPE (decl2) == error_mark_node && *cnt == 0)
-       {
-         gcc_assert (errorcount);
-         return error_mark_node;
-       }
+       return error_mark_node;
       (*cnt)++;
       gcc_assert (DECL_DECOMP_BASE (decl2) == pattern_decl);
       gcc_assert (DECL_HAS_VALUE_EXPR_P (decl2));
@@ -16572,7 +16569,6 @@ tsubst_decomp_names (tree decl, tree pat
        DECL_TEMPLATE_INSTANTIATED (decl3) = 1;
       else
        {
-         gcc_assert (errorcount);
          decl = error_mark_node;
          continue;
        }
@@ -16582,10 +16578,7 @@ tsubst_decomp_names (tree decl, tree pat
       else if (decl != error_mark_node
               && DECL_CHAIN (decl3) != prev
               && decl != prev)
-       {
-         gcc_assert (errorcount);
-         decl = error_mark_node;
-       }
+       decl = error_mark_node;
       else
        prev = decl3;
     }
@@ -16770,6 +16763,8 @@ tsubst_expr (tree t, tree args, tsubst_f
                        cp_finish_decl (decl, init, const_init, NULL_TREE, 0);
                        if (ndecl != error_mark_node)
                          cp_finish_decomp (ndecl, first, cnt);
+                       else
+                         gcc_assert (errorcount);
                      }
                    else
                      cp_finish_decl (decl, init, const_init, NULL_TREE, 0);
@@ -16813,9 +16808,13 @@ tsubst_expr (tree t, tree args, tsubst_f
        tree decomp_first = NULL_TREE;
        unsigned decomp_cnt = 0;
        if (VAR_P (decl) && DECL_DECOMPOSITION_P (decl))
-         decl = tsubst_decomp_names (decl, RANGE_FOR_DECL (t), args,
-                                     complain, in_decl,
-                                     &decomp_first, &decomp_cnt);
+         {
+           decl = tsubst_decomp_names (decl, RANGE_FOR_DECL (t), args,
+                                       complain, in_decl,
+                                       &decomp_first, &decomp_cnt);
+           if (decl == error_mark_node)
+             gcc_assert (errorcount);
+         }

        if (processing_template_decl)
          {

but that doesn't help, the bug isn't diagnosed in this case either.
For some reason, the orig decomp VAR_DECL is tsubsted to the PARM_DECL rather
than a new VAR_DECL representing the structured binding id, and thus also
cp_finish_decl succeeds.  Giving up here.