https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101670
Bug ID: 101670
Summary: Internal compiler error with concepts
Product: gcc
Version: 11.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: fchelnokov at gmail dot com
Target Milestone: ---
```
#include <type_traits>
template <typename T, typename V = void, auto = []{}> constexpr bool
is_incomplete = true;
template <typename T> constexpr bool is_incomplete<T,
std::enable_if_t<sizeof(T)>> = false;
template <typename T> concept Incomplete = is_incomplete<T>;
template <Incomplete> struct S {};
struct A;
S<A> s1;
```
https://gcc.godbolt.org/z/McPf9v8s3
In substitution of 'template<class> requires Incomplete<
<template-parameter-1-1> > struct S [with <template-parameter-1-1> = A]':
<source>:10:4: required from here
<source>:6:44: internal compiler error: in unify, at cp/pt.c:24165
6 | template <typename T> concept Incomplete = is_incomplete<T>;
| ^~~~~~~~~~~~~~~~
0x1d80e09 internal_error(char const*, ...)
???:0
0x7311fd fancy_abort(char const*, int, char const*)
???:0
0x9c9a26 most_specialized_partial_spec(tree_node*, int)
???:0
0x9caad5 instantiate_template(tree_node*, tree_node*, int)
???:0
0x9cb9d5 finish_template_variable(tree_node*, int)
???:0
0x9cbb56 lookup_and_finish_template_variable(tree_node*, tree_node*, int)
???:0
0x7b9d5a constraints_satisfied_p(tree_node*, tree_node*)
???:0
0x9a6c10 lookup_template_class(tree_node*, tree_node*, tree_node*, tree_node*,
int, int)
???:0
0x9ff09d finish_template_type(tree_node*, tree_node*, int)
???:0
0x95f1c5 c_parse_file()
???:0
0xae2a62 c_common_parse_file()
???:0
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
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