[Bug c++/126759] New: ICE in tsubst_expr, at cp/pt.cc:22938

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126759

            Bug ID: 126759
           Summary: ICE in tsubst_expr, at cp/pt.cc:22938
           Product: gcc
           Version: 16.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: gcc at maxmitti dot at
  Target Milestone: ---

Created attachment 65283
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=65283&action=edit
Preprocesesd soure code

The following code produces an ICE:

template <int v>
struct c{};

template <typename T>
concept a = requires (T v) { c<v>{}; };

template <typename T>
concept b = requires (T w) { c<w>{}; };

void foo()
{
        b<int>;
}



With the following output:

$ g++ -save-temps -v test.cpp

g built-in specs.
COLLECT_GCC=g++
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-pc-linux-gnu/16/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../gcc/configure
--enable-languages=ada,c,c++,d,fortran,go,lto,m2,objc,obj-c++,rust,cobol
--enable-bootstrap --prefix=/usr --libdir=/usr/lib --libexecdir=/usr/lib
--mandir=/usr/share/man --infodir=/usr/share/info
--with-bugurl=https://gitlab.archlinux.org/archlinux/packaging/packages/gcc/-/issues
--with-build-config=bootstrap-lto --with-gcc-major-version-only
--with-linker-hash-style=gnu --with-system-zlib --enable-cet=auto
--enable-checking=release --enable-clocale=gnu --enable-default-pie
--enable-default-ssp --enable-gnu-indirect-function --enable-gnu-unique-object
--enable-libstdcxx-backtrace --enable-link-serialization=1
--enable-linker-build-id --enable-lto --enable-multilib --enable-plugin
--enable-shared --enable-threads=posix --disable-fixincludes --disable-libssp
--disable-libstdcxx-pch --disable-werror
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 16.1.1 20260728 (GCC) 
COLLECT_GCC_OPTIONS='-save-temps' '-v' '-shared-libgcc' '-mtune=generic'
'-march=x86-64' '-dumpdir' 'a-'
 /usr/lib/gcc/x86_64-pc-linux-gnu/16/cc1plus -E -quiet -v -D_GNU_SOURCE
test.cpp -mtune=generic -march=x86-64 -fpch-preprocess -o a-test.ii
ignoring nonexistent directory
"/usr/lib/gcc/x86_64-pc-linux-gnu/16/include-fixed"
ignoring nonexistent directory
"/usr/lib/gcc/x86_64-pc-linux-gnu/16/../../../../x86_64-pc-linux-gnu/include"
#include "..." search starts here:
#include <...> search starts here:
 /usr/lib/gcc/x86_64-pc-linux-gnu/16/../../../../include/c++/16

/usr/lib/gcc/x86_64-pc-linux-gnu/16/../../../../include/c++/16/x86_64-pc-linux-gnu
 /usr/lib/gcc/x86_64-pc-linux-gnu/16/../../../../include/c++/16/backward
 /usr/lib/gcc/x86_64-pc-linux-gnu/16/include
 /usr/local/include
 /usr/include
End of search list.
COLLECT_GCC_OPTIONS='-save-temps' '-v' '-shared-libgcc' '-mtune=generic'
'-march=x86-64' '-dumpdir' 'a-'
 /usr/lib/gcc/x86_64-pc-linux-gnu/16/cc1plus -fpreprocessed a-test.ii -quiet
-dumpdir a- -dumpbase test.cpp -dumpbase-ext .cpp -mtune=generic -march=x86-64
-version -o a-test.s
GNU C++20 (GCC) version 16.1.1 20260728 (x86_64-pc-linux-gnu)
        compiled by GNU C version 16.1.1 20260728, GMP version 6.3.0, MPFR
version 4.2.2, MPC version 1.4.1, isl version isl-0.28-GMP

GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
Compiler executable checksum: 92a285fc5382abf8eb3acadb63c2d94b
test.cpp: In function ‘void foo()’:
test.cpp:8:30: internal compiler error: in tsubst_expr, at cp/pt.cc:22935
    8 | concept b = requires (T w) { c<w>{}; };
      |                              ^~~~~~
0x2815a98 diagnostics::context::diagnostic_impl(rich_location*,
diagnostics::metadata const*, diagnostics::option_id, char const*,
__va_list_tag (*) [1], diagnostics::kind)
        ???:0
0x28180a7 internal_error(char const*, ...)
        ???:0
0x737a7f fancy_abort(char const*, int, char const*)
        ???:0
0x964f71 tsubst_template_arg(tree_node*, tree_node*, int, tree_node*)
        ???:0
0x970a47 tsubst_template_args(tree_node*, tree_node*, int, tree_node*)
        ???:0
0x976671 tsubst(tree_node*, tree_node*, int, tree_node*)
        ???:0
0x7b9b73 evaluate_concept_check(tree_node*)
        ???:0
0x7ce227 convert_to_void(tree_node*, impl_conv_void, int)
        ???:0
0x9cb8be finish_expr_stmt(tree_node*)
        ???:0
0xaa51c0 c_common_parse_file()
        ???:0
/usr/lib/gcc/x86_64-pc-linux-gnu/16/cc1plus -fpreprocessed a-test.ii -quiet
-dumpdir a- -dumpbase test.cpp -dumpbase-ext .cpp -mtune=generic -march=x86-64
-version -o a-test.s
Please submit a full bug report, with preprocessed source (by using
-freport-bug).
Please include the complete backtrace with any bug report.
See <https://gitlab.archlinux.org/archlinux/packaging/packages/gcc/-/issues>
for instructions.



Multiple versions are affected: 14.3, 14.4, 15.1, 15.2, 15.3, 16.1, 16.2 and
trunk
All tested on godbolt.org: https://godbolt.org/z/hEEdjj163