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# ==========================================================================================
# https://www.gnu.org/software/autoconf-archive/ax_cxx_template_qualified_return_type.html
# ==========================================================================================
#
# SYNOPSIS
#
# AX_CXX_TEMPLATE_QUALIFIED_RETURN_TYPE
#
# DESCRIPTION
#
# If the compiler supports template-qualified return types, define
# HAVE_TEMPLATE_QUALIFIED_RETURN_TYPE.
#
# LICENSE
#
# Copyright (c) 2008 Todd Veldhuizen
# Copyright (c) 2008 Luc Maisonobe <luc@spaceroots.org>
#
# Copying and distribution of this file, with or without modification, are
# permitted in any medium without royalty provided the copyright notice
# and this notice are preserved. This file is offered as-is, without any
# warranty.
#serial 8
AU_ALIAS([AC_CXX_TEMPLATE_QUALIFIED_RETURN_TYPE], [AX_CXX_TEMPLATE_QUALIFIED_RETURN_TYPE])
AC_DEFUN([AX_CXX_TEMPLATE_QUALIFIED_RETURN_TYPE],
[AC_CACHE_CHECK(whether the compiler supports template-qualified return types,
ax_cv_cxx_template_qualified_return_type,
[AC_REQUIRE([AX_CXX_TYPENAME])
AC_LANG_PUSH([C++])
AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
#ifndef HAVE_TYPENAME
#define typename
#endif
template<class X, class Y> struct promote_trait { typedef X T; };
template<> struct promote_trait<int, float> { typedef float T; };
template<class T> class A { public : A () {} };
template<class X, class Y>
A<typename promote_trait<X,Y>::T> operator+ (const A<X>&, const A<Y>&)
{ return A<typename promote_trait<X,Y>::T>(); }
]], [[A<int> x; A<float> y; A<float> z = x + y; return 0;]])],
[ax_cv_cxx_template_qualified_return_type=yes], [ax_cv_cxx_template_qualified_return_type=no])
AC_LANG_POP([C++])
])
if test "$ax_cv_cxx_template_qualified_return_type" = yes; then
AC_DEFINE(HAVE_TEMPLATE_QUALIFIED_RETURN_TYPE,,
[define if the compiler supports template-qualified return types])
fi
])
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