<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/86606>86606</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            Template lambda mixing up types in some template contexts
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            new issue
      </td>
    </tr>

    <tr>
      <th>Assignees</th>
      <td>
      </td>
    </tr>

    <tr>
      <th>Reporter</th>
      <td>
          joshuamaiche
      </td>
    </tr>
</table>

<pre>
    Apologies for the slightly convoluted repro; the behavior seems to manifest when only certain templates are at play.

**main.cpp**
```
#include <type_traits>

template <typename... Ts>
struct TypeList
{
    template <typename T>
 static constexpr bool Contains()
    {
        return (std::is_same_v<T, Ts> || ...);
    }

    template <auto checker>
    using evaluate_on_all_t =
 std::integral_constant<bool,
            (checker.template operator()<Ts>() || ...)>;

    // Works fine
    template <typename T>
    static constexpr bool overlaps_v =
 evaluate_on_all_t<
            []<typename U>(){return T::template Contains<U>();}
        >::value;

    // Fails to compile
 template <typename T>
    using overlaps_t =
 evaluate_on_all_t<
            []<typename U>(){return T::template Contains<U>();}
        >;
};

using MyTypeList = TypeList<float, int>;
constexpr bool TypeListOverlap_v = MyTypeList::overlaps_v<TypeList<int, bool>>; // Works fine
using TypeListOverlap_t = MyTypeList::overlaps_t<TypeList<int, bool>>; // Fails to compile

int main()
{}
```

The relevant parts here are `overlaps_v` and `overlaps_t`. Both use a template lambda to evaluate if a TypeList `T` contains any relevant types. In the case of `overlaps_v`, a template constexpr variable, `T` is correctly interpreted as being a TypeList, and compiles. However, in the case of `overlaps_t`, a template alias, the compiler seems to get confused, and thinks `T` refers to the individual variadic types of the TypeList. Note that the lambdas are identical; the main difference seems to be whether a constexpr variable or an alias is being used.

**Console**
```
>clang++ -std=c++20 main.cpp
main.cpp:28:37: error: type 'float' cannot be used prior to '::' because it has no members
            []<typename U>(){return T::template Contains<U>();}
                                    ^
main.cpp:15:31: note: in instantiation of function template specialization 'TypeList<float, int>::(anonymous
      class)::operator()<float>' requested here
 (checker.template operator()<Ts>() || ...)>;
 ^
main.cpp:27:9: note: in instantiation of template type alias 'evaluate_on_all_t' requested here
        evaluate_on_all_t<
 ^
main.cpp:33:36: note: in instantiation of template class 'TypeList<float, int>' requested here
constexpr bool TypeListOverlap_v = MyTypeList::overlaps_v<TypeList<int, bool>>; // Works fine
 ^
main.cpp:28:37: error: type 'int' cannot be used prior to '::' because it has no members
            []<typename U>(){return T::template Contains<U>();}
 ^
main.cpp:15:31: note: in instantiation of function template specialization 'TypeList<float, int>::(anonymous
 class)::operator()<int>' requested here
            (checker.template operator()<Ts>() || ...)>;
 ^
main.cpp:27:9: note: in instantiation of template type alias 'evaluate_on_all_t' requested here
        evaluate_on_all_t<
 ^
main.cpp:33:36: note: in instantiation of template class 'TypeList<float, int>' requested here
constexpr bool TypeListOverlap_v = MyTypeList::overlaps_v<TypeList<int, bool>>; // Works fine
 ^
main.cpp:28:37: error: type 'int' cannot be used prior to '::' because it has no members
            []<typename U>(){return T::template Contains<U>();}
 ^
main.cpp:15:31: note: in instantiation of function template specialization 'TypeList<int, bool>::(anonymous
 class)::operator()<int>' requested here
            (checker.template operator()<Ts>() || ...)>;
 ^
main.cpp:27:9: note: in instantiation of template type alias 'evaluate_on_all_t' requested here
        evaluate_on_all_t<
 ^
main.cpp:21:37: note: in instantiation of template class 'TypeList<int, bool>' requested here
            []<typename U>(){return T::template Contains<U>();}
                                    ^
main.cpp:33:48: note: in instantiation of static data member 'TypeList<float, int>::overlaps_v<TypeList<int, bool>>'
      requested here
constexpr bool TypeListOverlap_v = MyTypeList::overlaps_v<TypeList<int, bool>>; // Works fine
 ^
main.cpp:28:37: error: type 'bool' cannot be used prior to '::' because it has no members
            []<typename U>(){return T::template Contains<U>();}
                                    ^
main.cpp:15:31: note: in instantiation of function template specialization 'TypeList<int, bool>::(anonymous
      class)::operator()<bool>' requested here
 (checker.template operator()<Ts>() || ...)>;
 ^
main.cpp:27:9: note: in instantiation of template type alias 'evaluate_on_all_t' requested here
        evaluate_on_all_t<
 ^
main.cpp:21:37: note: in instantiation of template class 'TypeList<int, bool>' requested here
            []<typename U>(){return T::template Contains<U>();}
                                    ^
main.cpp:33:48: note: in instantiation of static data member 'TypeList<float, int>::overlaps_v<TypeList<int, bool>>'
      requested here
constexpr bool TypeListOverlap_v = MyTypeList::overlaps_v<TypeList<int, bool>>; // Works fine
                                               ^
4 errors generated.
```

**version**
```
>clang++ --version
clang version 16.0.5
Target: i686-pc-windows-msvc
Thread model: posix
```
</pre>
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