[llvm-bugs] [Bug 49702] New: ICE when binding template template arguments with constrained NTTPs

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=49702

            Bug ID: 49702
           Summary: ICE when binding template template arguments with
                    constrained NTTPs
           Product: clang
           Version: unspecified
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: C++2a
          Assignee: unassignedclangbugs at nondot.org
          Reporter: omer.rosler at gmail.com
                CC: blitzrakete at gmail.com, erik.pilkington at gmail.com,
                    llvm-bugs at lists.llvm.org, richard-llvm at metafoo.co.uk

The following snippet:

```c++
template<typename T>
concept C = true;

template<template<C auto...> typename Templ>
struct template_ {};

template<C auto... Args>
struct template_binder
{
    template<template<C auto...> typename Templ>
    using templ = Templ<Args...>;
};

using T = template_<template_binder<>::template templ>;

```

Live demo: https://godbolt.org/z/7KExM4dh4

What is interesting is that removing the concept eliminates the ICE,
but clang rejects the code in this case (which is wrong).

Also,
gcc rejects the code as well (which is wrong).

MSVC accepts the code.

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