From 73159ace3d84b3cf01a126d6edefde196cceb621 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Martin=20Ho=C5=99e=C5=88ovsk=C3=BD?=
 <martin.horenovsky@gmail.com>
Date: Thu, 9 Feb 2017 12:57:01 +0100
Subject: [PATCH] REQUIRE_THROWS_AS now catches exception by const&

Prevents some warnings caused by catching complex types by value.

Closes #542
---
 CMakeLists.txt                         |  1 +
 include/internal/catch_capture.hpp     |  3 +-
 include/internal/catch_type_traits.hpp | 47 ++++++++++++++++++++++++++
 projects/SelfTest/CompilationTests.cpp | 18 ++++++++++
 4 files changed, 68 insertions(+), 1 deletion(-)
 create mode 100644 include/internal/catch_type_traits.hpp

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 6fe4e4e2..e9a00c2d 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -195,6 +195,7 @@ set(INTERNAL_HEADERS
         ${HEADER_DIR}/internal/catch_tostring.h
         ${HEADER_DIR}/internal/catch_tostring.hpp
         ${HEADER_DIR}/internal/catch_totals.hpp
+        ${HEADER_DIR}/internal/catch_type_traits.hpp
         ${HEADER_DIR}/internal/catch_version.h
         ${HEADER_DIR}/internal/catch_version.hpp
         ${HEADER_DIR}/internal/catch_wildcard_pattern.hpp
diff --git a/include/internal/catch_capture.hpp b/include/internal/catch_capture.hpp
index ae10f58a..8abc536b 100644
--- a/include/internal/catch_capture.hpp
+++ b/include/internal/catch_capture.hpp
@@ -16,6 +16,7 @@
 #include "catch_tostring.h"
 #include "catch_interfaces_runner.h"
 #include "catch_compiler_capabilities.h"
+#include "catch_type_traits.hpp"
 
 
 ///////////////////////////////////////////////////////////////////////////////
@@ -93,7 +94,7 @@
                 static_cast<void>(expr); \
                 __catchResult.captureResult( Catch::ResultWas::DidntThrowException ); \
             } \
-            catch( exceptionType ) { \
+            catch( Catch::add_const<Catch::add_lvalue_reference<exceptionType>::type>::type ) { \
                 __catchResult.captureResult( Catch::ResultWas::Ok ); \
             } \
             catch( ... ) { \
diff --git a/include/internal/catch_type_traits.hpp b/include/internal/catch_type_traits.hpp
new file mode 100644
index 00000000..9be89162
--- /dev/null
+++ b/include/internal/catch_type_traits.hpp
@@ -0,0 +1,47 @@
+/*
+ *  Created by Martin on 08/02/2017.
+ *
+ *  Distributed under the Boost Software License, Version 1.0. (See accompanying
+ *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+ */
+#ifndef TWOBLUECUBES_CATCH_TYPE_TRAITS_HPP_INCLUDED
+#define TWOBLUECUBES_CATCH_TYPE_TRAITS_HPP_INCLUDED
+
+#if defined(CATCH_CONFIG_CPP11_TYPE_TRAITS)
+#include <type_traits>
+#endif
+
+
+namespace Catch {
+
+#if defined(CATCH_CONFIG_CPP11_TYPE_TRAITS)
+
+     template <typename T>
+     using add_lvalue_reference = std::add_lvalue_reference<T>;
+
+     template <typename T>
+     using add_const = std::add_const<T>;
+
+#else
+
+    template <typename T>
+    struct add_const { 
+        typedef const T type;
+    };
+
+    template <typename T>
+    struct add_lvalue_reference {
+        typedef T& type;
+    };
+    template <typename T>
+    struct add_lvalue_reference<T&> {
+        typedef T& type;
+    };
+    // No && overload, because that is C++11, in which case we have
+    // proper type_traits implementation from the standard library
+
+#endif
+
+}
+
+#endif // TWOBLUECUBES_CATCH_TYPE_TRAITS_HPP_INCLUDED
diff --git a/projects/SelfTest/CompilationTests.cpp b/projects/SelfTest/CompilationTests.cpp
index f12372bf..635c62c8 100644
--- a/projects/SelfTest/CompilationTests.cpp
+++ b/projects/SelfTest/CompilationTests.cpp
@@ -22,3 +22,21 @@ TEST_CASE("#809") {
     foo f; f.i = 42;
     REQUIRE(42 == f);
 }
+
+// ------------------------------------------------------------------
+// REQUIRE_THROWS_AS was changed to catch exceptions by const&
+// using type traits. This means that this should compile cleanly
+
+// Provides indirection to prevent unreachable-code warnings
+void throws_int(bool b) {
+    if (b) {
+        throw 1;
+    }
+}
+
+TEST_CASE("#542") {
+    CHECK_THROWS_AS(throws_int(true), int);
+    CHECK_THROWS_AS(throws_int(true), int&);
+    CHECK_THROWS_AS(throws_int(true), const int);
+    CHECK_THROWS_AS(throws_int(true), const int&);
+}