[Bug c++/95728] New: [11 Regression] tree check: expected tree_list, have error_mark in tsubst_copy_and_build, at cp/pt.c:19594

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95728

            Bug ID: 95728
           Summary: [11 Regression] tree check: expected tree_list, have
                    error_mark in tsubst_copy_and_build, at cp/pt.c:19594
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Keywords: ice-on-invalid-code
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: redi at gcc dot gnu.org
                CC: jason at gcc dot gnu.org
  Target Milestone: ---

The code below is invalid (attempting to cast const T* to void*) but dies with
an ICE since r11-423:

    PR c++/93286 - ICE with __is_constructible and variadic template.

    My GCC 10 patch for 93286 fixed the missing piece in tsubst's handling of
    lists vs. that in tsubst_copy_and_build, but it would be better to share
the
    code between them.

template<typename T>
  void
  construct(T* p)
  { ::new(static_cast<void*>(p)) T; }

template<typename T>
void
f(const T* t)
{
  construct(t);
}

int main()
{
  int i[1];
  f(i);
}


ice.cc: In instantiation of 'void construct(T*) [with T = const int]':
ice.cc:10:12:   required from 'void f(const T*) [with T = int]'
ice.cc:16:6:   required from here
ice.cc:4:11: error: invalid 'static_cast' from type 'const int*' to type
'void*'
    4 |   { ::new(static_cast<void*>(p)) T; }
      |           ^~~~~~~~~~~~~~~~~~~~~
ice.cc:4:5: internal compiler error: tree check: expected tree_list, have
error_mark in tsubst_copy_and_build, at cp/pt.c:19640
    4 |   { ::new(static_cast<void*>(p)) T; }
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
0x81ac46 tree_check_failed(tree_node const*, char const*, int, char const*,
...)
        /home/jwakely/src/gcc/gcc/gcc/tree.c:9685
0x67d317 tree_check(tree_node*, char const*, int, char const*, tree_code)
        /home/jwakely/src/gcc/gcc/gcc/tree.h:3301
0x67d317 tsubst_copy_and_build(tree_node*, tree_node*, int, tree_node*, bool,
bool)
        /home/jwakely/src/gcc/gcc/gcc/cp/pt.c:19640
0xa91287 tsubst_expr(tree_node*, tree_node*, int, tree_node*, bool)
        /home/jwakely/src/gcc/gcc/gcc/cp/pt.c:18772
0xa93ab7 tsubst_expr(tree_node*, tree_node*, int, tree_node*, bool)
        /home/jwakely/src/gcc/gcc/gcc/cp/pt.c:17879
0xa92db1 tsubst_expr(tree_node*, tree_node*, int, tree_node*, bool)
        /home/jwakely/src/gcc/gcc/gcc/cp/pt.c:18173
0xa90ba1 tsubst_expr(tree_node*, tree_node*, int, tree_node*, bool)
        /home/jwakely/src/gcc/gcc/gcc/cp/pt.c:17834
0xa90ba1 instantiate_decl(tree_node*, bool, bool)
        /home/jwakely/src/gcc/gcc/gcc/cp/pt.c:25653
0xac281b instantiate_pending_templates(int)
        /home/jwakely/src/gcc/gcc/gcc/cp/pt.c:25769
0x9cb4e0 c_parse_final_cleanups()
        /home/jwakely/src/gcc/gcc/gcc/cp/decl2.c:4899
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