[Bug c++/95711] New: namespace alias fails inside coroutine

[alejandromagic at hotmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95711

            Bug ID: 95711
           Summary: namespace alias fails inside coroutine
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: alejandromagic at hotmail dot com
  Target Milestone: ---

Created attachment 48743
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=48743&action=edit
Preprocessed file

The following codes triggers a "Compiler internal Error":
namespace A
{

}
generator<int> parse()
{
    namespace B = A;
    co_yield 1;
}

Where generator<T> is just any generator implementation I've tried (I don't
think it have nothing to do with its actual implementation anyway, so I'm
providing the simplest working generator in the attached files). It essentially
happens when any namespace alias is defined inside a lambda. As an attachment I
provide the preprocessed file, although I guess the source should be enough (I
only #include coroutine for obvious reasons).

The command used to compile is:
gcc -v -save-temps --std=c++20 -fcoroutines main.cpp

The system is:
Linux parrot 4.14.0-parrot13-amd64 #1 SMP Parrot 4.14.13-1parrot13 (2018-01-21)
x86_64 GNU/Linux

The output of the compiler (in case it is needed):


Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/local/libexec/gcc/x86_64-pc-linux-gnu/11.0.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../gcc/configure --disable-multilib
--enable-languages=c,c++,go
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 11.0.0 20200507 (experimental) (GCC) 
COLLECT_GCC_OPTIONS='-v' '-save-temps' '-std=c++2a' '-fcoroutines'
'-mtune=generic' '-march=x86-64'
 /usr/local/libexec/gcc/x86_64-pc-linux-gnu/11.0.0/cc1plus -E -quiet -v
-imultiarch x86_64-linux-gnu -D_GNU_SOURCE main.cpp -mtune=generic
-march=x86-64 -std=c++2a -fcoroutines -fpch-preprocess -o main.ii
ignoring nonexistent directory "/usr/local/include/x86_64-linux-gnu"
ignoring nonexistent directory
"/usr/local/lib/gcc/x86_64-pc-linux-gnu/11.0.0/../../../../x86_64-pc-linux-gnu/include"
#include "..." search starts here:
#include <...> search starts here:
 /usr/local/lib/gcc/x86_64-pc-linux-gnu/11.0.0/../../../../include/c++/11.0.0

/usr/local/lib/gcc/x86_64-pc-linux-gnu/11.0.0/../../../../include/c++/11.0.0/x86_64-pc-linux-gnu

/usr/local/lib/gcc/x86_64-pc-linux-gnu/11.0.0/../../../../include/c++/11.0.0/backward
 /usr/local/lib/gcc/x86_64-pc-linux-gnu/11.0.0/include
 /usr/local/include
 /usr/local/lib/gcc/x86_64-pc-linux-gnu/11.0.0/include-fixed
 /usr/include/x86_64-linux-gnu
 /usr/include
End of search list.
COLLECT_GCC_OPTIONS='-v' '-save-temps' '-std=c++2a' '-fcoroutines'
'-mtune=generic' '-march=x86-64'
 /usr/local/libexec/gcc/x86_64-pc-linux-gnu/11.0.0/cc1plus -fpreprocessed
main.ii -quiet -dumpbase main.cpp -mtune=generic -march=x86-64 -auxbase main
-std=c++2a -version -fcoroutines -o main.s
GNU C++17 (GCC) version 11.0.0 20200507 (experimental) (x86_64-pc-linux-gnu)
        compiled by GNU C version 11.0.0 20200507 (experimental), GMP version
6.2.0, MPFR version 4.0.2, MPC version 1.1.0, isl version none
GGC heuristics: --param ggc-min-expand=30 --param ggc-min-heapsize=4096
GNU C++17 (GCC) version 11.0.0 20200507 (experimental) (x86_64-pc-linux-gnu)
        compiled by GNU C version 11.0.0 20200507 (experimental), GMP version
6.2.0, MPFR version 4.0.2, MPC version 1.1.0, isl version none
GGC heuristics: --param ggc-min-expand=30 --param ggc-min-heapsize=4096
Compiler executable checksum: 879e7d5007757f82203f25a489026164
main.cpp: In function ‘generator<int> parse()’:
main.cpp:60:1: internal compiler error: tree check: expected var_decl or
parm_decl or result_decl, have namespace_decl in register_local_var_uses, at
cp/coroutines.cc:3440
   60 | }
      | ^
0x7df6ea tree_check_failed(tree_node const*, char const*, int, char const*,
...)
        ../../gcc/gcc/tree.c:9731
0x61a5d5 tree_check3(tree_node*, char const*, int, char const*, tree_code,
tree_code, tree_code)
        ../../gcc/gcc/tree.h:3334
0x61a5d5 register_local_var_uses
        ../../gcc/gcc/cp/coroutines.cc:3440
0x12ab9fa walk_tree_1(tree_node**, tree_node* (*)(tree_node**, int*, void*),
void*, hash_set<tree_node*, false, default_hash_traits<tree_node*> >*,
tree_node* (*)(tree_node**, int*, tree_node* (*)(tree_node**, int*, void*),
void*, hash_set<tree_node*, false, default_hash_traits<tree_node*> >*))
        ../../gcc/gcc/tree.c:12001
0x8e44e6 morph_fn_to_coro(tree_node*, tree_node**, tree_node**)
        ../../gcc/gcc/cp/coroutines.cc:3815
0x92ebf1 finish_function(bool)
        ../../gcc/gcc/cp/decl.c:16921
0x9d8427 cp_parser_function_definition_after_declarator
        ../../gcc/gcc/cp/parser.c:29013
0x9d9409 cp_parser_function_definition_from_specifiers_and_declarator
        ../../gcc/gcc/cp/parser.c:28926
0x9d9409 cp_parser_init_declarator
        ../../gcc/gcc/cp/parser.c:20675
0x9ba1d2 cp_parser_simple_declaration
        ../../gcc/gcc/cp/parser.c:13739
0x9e33d2 cp_parser_declaration
        ../../gcc/gcc/cp/parser.c:13438
0x9e3b5a cp_parser_translation_unit
        ../../gcc/gcc/cp/parser.c:4734
0x9e3b5a c_parse_file()
        ../../gcc/gcc/cp/parser.c:43989
0xaf965b c_common_parse_file()
        ../../gcc/gcc/c-family/c-opts.c:1190
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <https://gcc.gnu.org/bugs/> for instructions.