https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123688
Bug ID: 123688
Summary: [14/15/16 Regression] ICE in
template_heads_equivalent_p (tree check: expected
template_decl, have template_template_parm) during
mangling of lambda with requirements
Product: gcc
Version: 16.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: jirehguo at tju dot edu.cn
Target Milestone: ---
Compiler Explorer: https://godbolt.org/z/n8Phfx1qf
The following c++ code crash gcc trunk with -std=c++20 flag.
Goes back to 14.1 with checking.
Code:
```cpp
template <int D>
struct S_Base {
static constexpr int D_val = D;
};
template <typename T>
struct S_Derived : S_Base<T::value> {
using S_Base<T::value>::D_val;
};
template <class, class> class C
{
};
template <template<class,class=int> class C, class T> void g(C<T> c)
{
struct Config;
auto constrained_func = []() requires (S_Derived<Config>::D_val > 0) {};
}
int main()
{
C<int,int> c;
g(c);
}
```
Stack dump:
```
<source>: In instantiation of 'struct S_Derived<g<C, int>(C<int,
int>)::Config>':
required from 'g<C, int>(C<int, int>)::<lambda()>'
<source>:15:63:
15 | auto constrained_func = []() requires (S_Derived<Config>::D_val >
0) {};
| ^~~~~
required from 'void g(C<T>) [with C = C; T = int]'
<source>:15:29:
15 | auto constrained_func = []() requires (S_Derived<Config>::D_val >
0) {};
|
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
required from here
<source>:20:4:
20 | g(c);
| ~^~~
<source>:6:8: error: incomplete type 'g<C, int>(C<int, int>)::Config' used in
nested name specifier
6 | struct S_Derived : S_Base<T::value> {
| ^~~~~~~~~
<source>:7:29: error: incomplete type 'g<C, int>(C<int, int>)::Config' used in
nested name specifier
7 | using S_Base<T::value>::D_val;
| ^~~~~
<source>:15:29: internal compiler error: tree check: expected template_decl,
have template_template_parm in template_heads_equivalent_p, at cp/pt.cc:3548
15 | auto constrained_func = []() requires (S_Derived<Config>::D_val >
0) {};
| ^
0x2950b58 diagnostics::context::diagnostic_impl(rich_location*,
diagnostics::metadata const*, diagnostics::option_id, char const*,
__va_list_tag (*) [1], diagnostics::kind)
???:0
0x294591b internal_error(char const*, ...)
???:0
0xa2350f tree_check_failed(tree_node const*, char const*, int, char const*,
...)
???:0
0xc80cc9 mangle_decl(tree_node*)
???:0
0x18c3645 decl_assembler_name(tree_node*)
???:0
0xfca176 symbol_table::finalize_compilation_unit()
???: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
```
