From f9b2e92040f52739585a9036a72c2b8fa3576013 Mon Sep 17 00:00:00 2001
From: Antonio Sanchez <cantonios@google.com>
Date: Fri, 29 Oct 2021 09:28:11 -0700
Subject: [PATCH] Remove bad "take" impl that causes g++-11 crash.

For some reason, having `take<n, numeric_list<T>>` for `n > 0` causes
g++-11 to ICE with
```
sorry, unimplemented: unexpected AST of kind nontype_argument_pack
```
It does work with other versions of gcc, and with clang.
I filed a GCC bug
[here](https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102999).

Technically we should never actually run into this case, since you
can't take n > 0 elements from an empty list.  Commenting it out
allows our Eigen tests to pass.


(cherry picked from commit 8f8c2ba2fe19c6c2e47bbe2fbaf87594642e523d)
---
 unsupported/Eigen/CXX11/src/util/CXX11Meta.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/unsupported/Eigen/CXX11/src/util/CXX11Meta.h b/unsupported/Eigen/CXX11/src/util/CXX11Meta.h
index 149ceaff0..f662dee5b 100644
--- a/unsupported/Eigen/CXX11/src/util/CXX11Meta.h
+++ b/unsupported/Eigen/CXX11/src/util/CXX11Meta.h
@@ -81,7 +81,8 @@ template<typename a, typename... as>        struct take<0, type_list<a, as...>>
 template<>                                  struct take<0, type_list<>>         { typedef type_list<> type; };
 
 template<typename T, int n, T a, T... as> struct take<n, numeric_list<T, a, as...>> : concat<numeric_list<T, a>, typename take<n-1, numeric_list<T, as...>>::type> {};
-template<typename T, int n>               struct take<n, numeric_list<T>>           { typedef numeric_list<T> type; };
+// XXX The following breaks in gcc-11, and is invalid anyways.
+// template<typename T, int n>               struct take<n, numeric_list<T>>           { typedef numeric_list<T> type; };
 template<typename T, T a, T... as>        struct take<0, numeric_list<T, a, as...>> { typedef numeric_list<T> type; };
 template<typename T>                      struct take<0, numeric_list<T>>           { typedef numeric_list<T> type; };