[Bug c++/107276] New: ICE Deducting return type from ill-formed structured binding name

[Bug c++/107276] New: ICE Deducting return type from ill-formed structured binding name

[johelegp at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107276

            Bug ID: 107276
           Summary: ICE Deducting return type from ill-formed structured
                    binding name
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Keywords: ice-on-invalid-code
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: johelegp at gmail dot com
                CC: johelegp at gmail dot com
  Target Milestone: ---

See https://compiler-explorer.com/z/6MqKTjKd7.

```C++
auto f(auto x) {
  auto [y] = x;
  return y;
}
int i = f(0);
```

```
<source>: In instantiation of 'auto f(auto:1) [with auto:1 = int]':
<source>:5:10:   required from here
<source>:2:8: error: cannot decompose non-array non-class type 'int'
    2 |   auto [y] = x;
      |        ^~~
<source>:3:10: internal compiler error: tree check: expected non_lvalue_expr or
static_cast_expr, have error_mark in set_implicit_rvalue_p, at
cp/cp-tree.h:8688
    3 |   return y;
      |          ^
0x236ef7e internal_error(char const*, ...)
        ???:0
0x95b166 tree_check_failed(tree_node const*, char const*, int, char const*,
...)
        ???:0
0xc9d1ca do_auto_deduction(tree_node*, tree_node*, tree_node*, int,
auto_deduction_context, tree_node*, int)
        ???:0
0xd4e054 check_return_expr(tree_node*, bool*)
        ???:0
0xcf39f3 finish_return_stmt(tree_node*)
        ???:0
0xcad9e6 instantiate_decl(tree_node*, bool, bool)
        ???:0
0xb8e015 maybe_instantiate_decl(tree_node*)
        ???:0
0xb8fa9e mark_used(tree_node*, int)
        ???:0
0xad275e build_new_function_call(tree_node*, vec<tree_node*, va_gc,
vl_embed>**, int)
        ???:0
0xcf93c8 finish_call_expr(tree_node*, vec<tree_node*, va_gc, vl_embed>**, bool,
bool, int)
        ???:0
0xc806a7 c_parse_file()
        ???:0
0xdbdef9 c_common_parse_file()
        ???:0
Please submit a full bug report, with preprocessed source (by using
-freport-bug).
Please include the complete backtrace with any bug report.
See <https://gcc.gnu.org/bugs/> for instructions.
Compiler returned: 1
```

[Bug c++/107276] ICE Deducing return type from ill-formed structured binding name

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107276

Martin Liška <marxin at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2022-10-17
             Status|UNCONFIRMED                 |WAITING
     Ever confirmed|0                           |1
                 CC|                            |marxin at gcc dot gnu.org

--- Comment #1 from Martin Liška <marxin at gcc dot gnu.org> ---
Can't reproduce the ICE.

[Bug c++/107276] ICE Deducing return type from ill-formed structured binding name

[johelegp at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107276

--- Comment #2 from Johel Ernesto Guerrero Peña <johelegp at gmail dot com> ---
I just compiled GCC and it still ICEs:

```cli
$ ../root/gcc/bin/g++ --version
g++ (GCC) 13.0.0 20221019 (experimental)
Copyright (C) 2022 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

$ cat x.cpp 
auto f(auto x) {
  auto [y] = x;
  return y;
}
int i = f(0);
$ ../root/gcc/bin/g++ -std=c++23 -c x.cpp 
x.cpp: In instantiation of ‘auto f(auto:1) [with auto:1 = int]’:
x.cpp:5:10:   required from here
x.cpp:2:8: error: cannot decompose non-array non-class type ‘int’
    2 |   auto [y] = x;
      |        ^~~
x.cpp:3:10: internal compiler error: tree check: expected non_lvalue_expr or
static_cast_expr, have error_mark in set_implicit_rvalue_p, at
cp/cp-tree.h:8689
    3 |   return y;
      |          ^
0x22ea70c internal_error(char const*, ...)
        ???:0
0x8e3b63 tree_check_failed(tree_node const*, char const*, int, char const*,
...)
        ???:0
0xbb8768 do_auto_deduction(tree_node*, tree_node*, tree_node*, int,
auto_deduction_context, tree_node*, int)
        ???:0
0xc6d039 check_return_expr(tree_node*, bool*)
        ???:0
0xc101f3 finish_return_stmt(tree_node*)
        ???:0
0xbee0a3 instantiate_decl(tree_node*, bool, bool)
        ???:0
0xa9b5f5 maybe_instantiate_decl(tree_node*)
        ???:0
0xa9cfa0 mark_used(tree_node*, int)
        ???:0
0x9dcd4b build_new_function_call(tree_node*, vec<tree_node*, va_gc,
vl_embed>**, int)
        ???:0
0xc16768 finish_call_expr(tree_node*, vec<tree_node*, va_gc, vl_embed>**, bool,
bool, int)
        ???:0
0xb9949b c_parse_file()
        ???:0
0xcde1f1 c_common_parse_file()
        ???:0
Please submit a full bug report, with preprocessed source (by using
-freport-bug).
Please include the complete backtrace with any bug report.
See <https://bugs.archlinux.org/> for instructions.
```

[Bug c++/107276] ICE Deducing return type from ill-formed structured binding name since r13-2905-g772d532e0ba1e4b2

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107276

Martin Liška <marxin at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|ICE Deducing return type    |ICE Deducing return type
                   |from ill-formed structured  |from ill-formed structured
                   |binding name                |binding name since
                   |                            |r13-2905-g772d532e0ba1e4b2
             Status|WAITING                     |NEW
                 CC|                            |mpolacek at gcc dot gnu.org

--- Comment #3 from Martin Liška <marxin at gcc dot gnu.org> ---
Now I can reproduce it, started with r13-2905-g772d532e0ba1e4b2.

[Bug c++/107276] ICE Deducing return type from ill-formed structured binding name since r13-2905-g772d532e0ba1e4b2

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107276

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Assignee|unassigned at gcc dot gnu.org      |mpolacek at gcc dot gnu.org
             Status|NEW                         |ASSIGNED

--- Comment #4 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Mine.

[Bug c++/107276] ICE Deducing return type from ill-formed structured binding name since r13-2905-g772d532e0ba1e4b2

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107276

--- Comment #5 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The trunk branch has been updated by Marek Polacek <mpolacek@gcc.gnu.org>:

https://gcc.gnu.org/g:f7d8ccfda2d5c90dac97b1a3ede8b10391a3cc40

commit r13-3462-gf7d8ccfda2d5c90dac97b1a3ede8b10391a3cc40
Author: Marek Polacek <polacek@redhat.com>
Date:   Thu Oct 20 15:55:28 2022 -0400

    c++: ICE with invalid structured bindings [PR107276]

    This test ICEs in C++23 because we reach the new code in do_auto_deduction:

    30468   if (cxx_dialect >= cxx23
    30469       && context == adc_return_type
    30470       && (!AUTO_IS_DECLTYPE (auto_node)
    30471           || !unparenthesized_id_or_class_member_access_p (init))
    30472       && (r = treat_lvalue_as_rvalue_p (maybe_undo_parenthesized_ref
(init),
    30473                                         /*return*/true)))

    where 'init' is "VIEW_CONVERT_EXPR<<<< error >>>>(y)", and then the move
    in treat_lvalue_as_rvalue_p returns error_mark_node whereupon
    set_implicit_rvalue_p crashes.

    I don't think such V_C_Es are useful so let's not create them.  But that
    won't fix the ICE so I'm checking the return value of move.  A structured
    bindings decl can have an error type, that is set in cp_finish_decomp:

     8908           TREE_TYPE (first) = error_mark_node;

    therefore I think treat_lvalue_as_rvalue_p just needs to cope.

            PR c++/107276

    gcc/cp/ChangeLog:

            * typeck.cc (treat_lvalue_as_rvalue_p): Check the return value of
move.

    gcc/ChangeLog:

            * tree.cc (maybe_wrap_with_location): Don't create a location
wrapper
            when the type is erroneous.

    gcc/testsuite/ChangeLog:

            * g++.dg/cpp2a/decomp4.C: New test.

[Bug c++/107276] ICE Deducing return type from ill-formed structured binding name since r13-2905-g772d532e0ba1e4b2

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107276

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED

--- Comment #6 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Fixed.