https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119379
Bug ID: 119379
Summary: [15 regression] ICE on CTAD for alias template with
type constraint
Product: gcc
Version: 15.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: cmingyi01 at gmail dot com
Target Milestone: ---
The following C++20 code causes an ICE in trunk.
```c++
template <class, class>
concept C = true;
template <class T, class U>
struct pair {
constexpr pair(T, U) {}
};
template <class T>
struct S {
template <C<T> U>
using P = pair<T, U>;
};
S<int>::P p{42, ""};
```
Output:
```
<source>:15:19: internal compiler error: same canonical type node for different
types 'S<int>::P<U>' and 'pair<int, U>'
15 | S<int>::P p{42, ""};
| ^
0x2913db5 diagnostic_context::diagnostic_impl(rich_location*,
diagnostic_metadata const*, diagnostic_option_id, char const*, __va_list_tag
(*) [1], diagnostic_t)
???:0
0x292add6 internal_error(char const*, ...)
???:0
0xdb0fd5 comptypes(tree_node*, tree_node*, int)
???:0
0xd0d882 do_auto_deduction(tree_node*, tree_node*, tree_node*, int,
auto_deduction_context, tree_node*, int, tree_node*)
???:0
0xbc423a cp_finish_decl(tree_node*, tree_node*, bool, tree_node*, int,
cp_decomp*)
???:0
0xcee07b c_parse_file()
???:0
0xe4f519 c_common_parse_file()
???:0
```
The latest Clang and MSVC accept this code. (Compiler Explorer's MSVC is not up
to date.)
See https://compiler-explorer.com/z/PT73bh3qd.
