From 3b139ae51a52382d4a86764d7b44e1c3d2eb3eca Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Martin=20Ho=C5=99e=C5=88ovsk=C3=BD?=
 <martin.horenovsky@gmail.com>
Date: Sat, 5 Nov 2022 00:42:09 +0100
Subject: [PATCH] Decomposer checks for 0 when assuming an int arg was 0
 literal

---
 src/catch2/internal/catch_decomposer.hpp      | 15 ++++++-
 .../IntrospectiveTests/Details.tests.cpp      | 43 +++++++++++++++++++
 2 files changed, 56 insertions(+), 2 deletions(-)

diff --git a/src/catch2/internal/catch_decomposer.hpp b/src/catch2/internal/catch_decomposer.hpp
index ab563701..3448803f 100644
--- a/src/catch2/internal/catch_decomposer.hpp
+++ b/src/catch2/internal/catch_decomposer.hpp
@@ -12,6 +12,7 @@
 #include <catch2/internal/catch_stringref.hpp>
 #include <catch2/internal/catch_meta.hpp>
 #include <catch2/internal/catch_compare_traits.hpp>
+#include <catch2/internal/catch_test_failure_exception.hpp>
 
 #include <type_traits>
 #include <iosfwd>
@@ -196,6 +197,9 @@ namespace Catch {
                          int> = 0>                                             \
     friend auto operator op( ExprLhs&& lhs, RhsT rhs )                         \
         ->BinaryExpr<LhsT, RhsT> {                                             \
+        if ( rhs != 0 ) {                                                      \
+            throw_test_failure_exception();                                    \
+        }                                                                      \
         return {                                                               \
             static_cast<bool>( lhs.m_lhs op 0 ), lhs.m_lhs, #op##_sr, rhs };   \
     }                                                                          \
@@ -210,6 +214,9 @@ namespace Catch {
                          int> = 0>                                             \
     friend auto operator op( ExprLhs&& lhs, RhsT rhs )                         \
         ->BinaryExpr<LhsT, RhsT> {                                             \
+        if ( lhs.m_lhs != 0 ) {                                                \
+            throw_test_failure_exception();                                    \
+        }                                                                      \
         return { static_cast<bool>( 0 op rhs ), lhs.m_lhs, #op##_sr, rhs };    \
     }
         CATCH_INTERNAL_DEFINE_EXPRESSION_EQUALITY_OPERATOR( eq, == )
@@ -247,7 +254,9 @@ namespace Catch {
                          int> = 0>                                             \
     friend auto operator op( ExprLhs&& lhs, RhsT rhs )                         \
         ->BinaryExpr<LhsT, RhsT> {                                             \
-        /* TODO: do we want to assert that Rhs is 0? */                        \
+        if ( rhs != 0 ) {                                                      \
+            throw_test_failure_exception();                                    \
+        }                                                                      \
         return {                                                               \
             static_cast<bool>( lhs.m_lhs op 0 ), lhs.m_lhs, #op##_sr, rhs };   \
     }                                                                          \
@@ -259,7 +268,9 @@ namespace Catch {
                          int> = 0>                                             \
     friend auto operator op( ExprLhs&& lhs, RhsT rhs )                         \
         ->BinaryExpr<LhsT, RhsT> {                                             \
-        /* TODO: do we want to assert that lhs is 0? */                        \
+        if ( lhs.m_lhs != 0 ) {                                                \
+            throw_test_failure_exception();                                    \
+        }                                                                      \
         return { static_cast<bool>( 0 op rhs ), lhs.m_lhs, #op##_sr, rhs };    \
     }
 
diff --git a/tests/SelfTest/IntrospectiveTests/Details.tests.cpp b/tests/SelfTest/IntrospectiveTests/Details.tests.cpp
index 8a87dc24..a5a43926 100644
--- a/tests/SelfTest/IntrospectiveTests/Details.tests.cpp
+++ b/tests/SelfTest/IntrospectiveTests/Details.tests.cpp
@@ -11,6 +11,8 @@
 #include <catch2/internal/catch_case_insensitive_comparisons.hpp>
 #include <catch2/internal/catch_optional.hpp>
 
+#include <helpers/type_with_lit_0_comparisons.hpp>
+
 #if defined(_MSC_VER)
 #pragma warning(push)
 #pragma warning(disable:4702) // unreachable code in the macro expansions
@@ -86,3 +88,44 @@ TEST_CASE("Optional comparison ops", "[optional][approvals]") {
         REQUIRE_FALSE( a != b );
     }
 }
+
+TEST_CASE( "Decomposer checks that the argument is 0 when handling "
+           "only-0-comparable types",
+           "[decomposition][approvals]" ) {
+    TypeWithLit0Comparisons t{};
+
+    CATCH_INTERNAL_START_WARNINGS_SUPPRESSION
+    CATCH_INTERNAL_SUPPRESS_PARENTHESES_WARNINGS
+
+    REQUIRE_THROWS( Catch::Decomposer{} <= t == 42 );
+    REQUIRE_THROWS( Catch::Decomposer{} <= 42 == t );
+    REQUIRE_NOTHROW( Catch::Decomposer{} <= t == 0 );
+    REQUIRE_NOTHROW( Catch::Decomposer{} <= 0 == t );
+
+    REQUIRE_THROWS( Catch::Decomposer{} <= t != 42 );
+    REQUIRE_THROWS( Catch::Decomposer{} <= 42 != t );
+    REQUIRE_NOTHROW( Catch::Decomposer{} <= t != 0 );
+    REQUIRE_NOTHROW( Catch::Decomposer{} <= 0 != t );
+
+    REQUIRE_THROWS( Catch::Decomposer{} <= t < 42 );
+    REQUIRE_THROWS( Catch::Decomposer{} <= 42 < t );
+    REQUIRE_NOTHROW( Catch::Decomposer{} <= t < 0 );
+    REQUIRE_NOTHROW( Catch::Decomposer{} <= 0 < t );
+
+    REQUIRE_THROWS( Catch::Decomposer{} <= t <= 42 );
+    REQUIRE_THROWS( Catch::Decomposer{} <= 42 <= t );
+    REQUIRE_NOTHROW( Catch::Decomposer{} <= t <= 0 );
+    REQUIRE_NOTHROW( Catch::Decomposer{} <= 0 <= t );
+
+    REQUIRE_THROWS( Catch::Decomposer{} <= t > 42 );
+    REQUIRE_THROWS( Catch::Decomposer{} <= 42 > t );
+    REQUIRE_NOTHROW( Catch::Decomposer{} <= t > 0 );
+    REQUIRE_NOTHROW( Catch::Decomposer{} <= 0 > t );
+
+    REQUIRE_THROWS( Catch::Decomposer{} <= t >= 42 );
+    REQUIRE_THROWS( Catch::Decomposer{} <= 42 >= t );
+    REQUIRE_NOTHROW( Catch::Decomposer{} <= t >= 0 );
+    REQUIRE_NOTHROW( Catch::Decomposer{} <= 0 >= t );
+
+    CATCH_INTERNAL_STOP_WARNINGS_SUPPRESSION
+}