From e9eb0323c5c00a358bbda4cb453c95bae68657d5 Mon Sep 17 00:00:00 2001
From: Emil Dotchevski <emildotchevski@gmail.com>
Date: Tue, 8 Dec 2020 14:36:26 -0800
Subject: [PATCH] Issue #16

---
 include/boost/leaf.hpp        |  2 --
 include/boost/leaf/error.hpp  |  2 --
 test/BOOST_LEAF_AUTO_test.cpp | 18 +++++++++++++++++-
 3 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/include/boost/leaf.hpp b/include/boost/leaf.hpp
index fa59d66..b56aa08 100644
--- a/include/boost/leaf.hpp
+++ b/include/boost/leaf.hpp
@@ -1002,7 +1002,6 @@ namespace boost { namespace leaf {
 #define BOOST_LEAF_TMP BOOST_LEAF_TOKEN_PASTE2(boost_leaf_tmp_, __LINE__)
 
 #define BOOST_LEAF_ASSIGN(v,r)\
-    static_assert(::boost::leaf::is_result_type<typename std::decay<decltype(r)>::type>::value, "The BOOST_LEAF_ASSIGN macro requires a result type as the second argument");\
     auto && BOOST_LEAF_TMP = r;\
     if( !BOOST_LEAF_TMP )\
         return BOOST_LEAF_TMP.error();\
@@ -1012,7 +1011,6 @@ namespace boost { namespace leaf {
     BOOST_LEAF_ASSIGN(auto v, r)
 
 #define BOOST_LEAF_CHECK(r)\
-    static_assert(::boost::leaf::is_result_type<typename std::decay<decltype(r)>::type>::value, "BOOST_LEAF_CHECK requires a result type");\
     auto && BOOST_LEAF_TMP = r;\
     if( BOOST_LEAF_TMP )\
         ;\
diff --git a/include/boost/leaf/error.hpp b/include/boost/leaf/error.hpp
index c6cde7d..9d18e08 100644
--- a/include/boost/leaf/error.hpp
+++ b/include/boost/leaf/error.hpp
@@ -33,7 +33,6 @@
 #define BOOST_LEAF_TMP BOOST_LEAF_TOKEN_PASTE2(boost_leaf_tmp_, __LINE__)
 
 #define BOOST_LEAF_ASSIGN(v,r)\
-    static_assert(::boost::leaf::is_result_type<typename std::decay<decltype(r)>::type>::value, "The BOOST_LEAF_ASSIGN macro requires a result type as the second argument");\
     auto && BOOST_LEAF_TMP = r;\
     if( !BOOST_LEAF_TMP )\
         return BOOST_LEAF_TMP.error();\
@@ -43,7 +42,6 @@
     BOOST_LEAF_ASSIGN(auto v, r)
 
 #define BOOST_LEAF_CHECK(r)\
-    static_assert(::boost::leaf::is_result_type<typename std::decay<decltype(r)>::type>::value, "BOOST_LEAF_CHECK requires a result type");\
     auto && BOOST_LEAF_TMP = r;\
     if( BOOST_LEAF_TMP )\
         ;\
diff --git a/test/BOOST_LEAF_AUTO_test.cpp b/test/BOOST_LEAF_AUTO_test.cpp
index 21e14a5..bda6072 100644
--- a/test/BOOST_LEAF_AUTO_test.cpp
+++ b/test/BOOST_LEAF_AUTO_test.cpp
@@ -34,10 +34,26 @@ leaf::result<value> f2()
 #endif
 }
 
+template <class Lambda>
+leaf::result<value> f2_lambda( Lambda )
+{
+    BOOST_LEAF_AUTO(a, f1());
+#if BOOST_WORKAROUND( BOOST_GCC, < 50000 ) || BOOST_WORKAROUND( BOOST_CLANG, <= 30800 )
+    return std::move(a); // Older compilers are confused, but...
+#else
+    return a; // ...this doesn't need to be return std::move(a);
+#endif
+}
+
 leaf::result<value> f3()
 {
     BOOST_LEAF_AUTO(a, f2());
-    BOOST_LEAF_AUTO(b, f2()); // Invoking the macro twice in the same scope, testing the temp name generation
+
+    // Invoking the macro twice in the same scope, testing the temp name
+    // generation. Also making sure we can pass a lambda (See
+    // https://github.com/boostorg/leaf/issues/16).
+    BOOST_LEAF_AUTO(b, f2_lambda([]{}));
+
     return value { a.x + b.x };
 }