Change decomposition to use operator<< instead of operator->*, issue #14

This enables the use of *, /, %, + and - at the LHS of expressions used in assertion macros, e.g. EXPECT( 1 + 2 == 3 )

See also discussion at
- Catch commit: Use <= operator instead of ->* for decomposer,
  catchorg/Catch2@8cc1108 and issues mentioned there:
- Catch issue #359, catchorg/Catch2#359
- Catch issue #393, catchorg/Catch2#393
- Catch issue #247, catchorg/Catch2#247

lest.hpp

@@ -32,6 +32,7 @@
 #include <cstddef>
 
 #ifdef __clang__
+# pragma clang diagnostic ignored "-Woverloaded-shift-op-parentheses"
 # pragma clang diagnostic ignored "-Wunused-comparison"
 # pragma clang diagnostic ignored "-Wunused-value"
 #elif defined __GNUC__
@@ -211,7 +212,7 @@
 #define lest_UNIQUE2( name, line ) lest_UNIQUE3( name, line )
 #define lest_UNIQUE3( name, line ) name ## line
 
-#define lest_DECOMPOSE( expr ) ( lest::expression_decomposer()->* expr )
+#define lest_DECOMPOSE( expr ) ( lest::expression_decomposer() << expr )
 
 #define lest_FUNCTION  lest_UNIQUE(__lest_function__  )
 #define lest_REGISTRAR lest_UNIQUE(__lest_registrar__ )
@@ -699,7 +700,7 @@ struct expression_lhs
 struct expression_decomposer
 {
     template <typename L>
-    expression_lhs<L const &> operator->* ( L const & operand )
+    expression_lhs<L const &> operator<< ( L const & operand )
     {
         return expression_lhs<L const &>( operand );
     }

lest_cpp03.hpp

@@ -28,6 +28,7 @@
 #include <ctime>
 
 #ifdef __clang__
+# pragma clang diagnostic ignored "-Woverloaded-shift-op-parentheses"
 # pragma clang diagnostic ignored "-Wunused-value"
 #elif defined __GNUC__
 # pragma GCC   diagnostic ignored "-Wunused-value"
@@ -266,7 +267,7 @@ namespace lest
     } \
     while ( lest::is_false() )
 
-#define lest_DECOMPOSE( expr ) ( lest::expression_decomposer()->* expr )
+#define lest_DECOMPOSE( expr ) ( lest::expression_decomposer() << expr )
 
 #define lest_UNIQUE(  name       ) lest_UNIQUE2( name, __LINE__ )
 #define lest_UNIQUE2( name, line ) lest_UNIQUE3( name, line )
@@ -561,7 +562,7 @@ struct expression_lhs
 struct expression_decomposer
 {
     template <typename L>
-    expression_lhs<L const &> operator->* ( L const & operand )
+    expression_lhs<L const &> operator<< ( L const & operand )
     {
         return expression_lhs<L const &>( operand );
     }

lest_decompose.hpp

@@ -21,6 +21,7 @@
 #include <cstddef>
 
 #ifdef __clang__
+# pragma clang diagnostic ignored "-Woverloaded-shift-op-parentheses"
 # pragma clang diagnostic ignored "-Wunused-comparison"
 # pragma clang diagnostic ignored "-Wunused-value"
 #elif defined __GNUC__
@@ -76,7 +77,7 @@
         throw lest::expected{ lest_LOCATION, #expr, lest::of_type( #excpt ) }; \
     } while ( lest::is_false() )
 
-#define lest_DECOMPOSE( expr ) ( lest::expression_decomposer()->* expr )
+#define lest_DECOMPOSE( expr ) ( lest::expression_decomposer() << expr )
 
 #define lest_LOCATION lest::location{__FILE__, __LINE__}
 
@@ -297,7 +298,7 @@ struct expression_lhs
 struct expression_decomposer
 {
     template <typename L>
-    expression_lhs<L const &> operator->* ( L const & operand )
+    expression_lhs<L const &> operator<< ( L const & operand )
     {
         return expression_lhs<L const &>( operand );
     }

test/test_lest.cpp

@@ -204,6 +204,24 @@ const lest::test specification[] =
         EXPECT_NOT( a >  b );
     },
 
+    CASE( "Expect expression RHS can use *, / %, +, -" )
+    {
+        EXPECT( 7 == 1 * 7 );
+        EXPECT( 7 == 7 / 1 );
+        EXPECT( 0 == 7 % 1 );
+        EXPECT( 7 == 1 + 6 );
+        EXPECT( 7 == 8 - 1 );
+    },
+
+    CASE( "Expect expression LHS can use *, / %, +, -" )
+    {
+        EXPECT( 1 * 7 == 7 );
+        EXPECT( 7 / 1 == 7 );
+        EXPECT( 7 % 1 == 0 );
+        EXPECT( 1 + 6 == 7 );
+        EXPECT( 8 - 1 == 7 );
+    },
+
     CASE( "Function run() returns the right failure count" )
     {
         test pass  [] = {{ CASE( "P"  ) { EXPECT( 1==1 ); } }};

test/test_lest_cpp03.cpp

@@ -202,6 +202,24 @@ CASE( "Expect succeeds for string comparation" )
     EXPECT_NOT( a >  b );
 }
 
+CASE( "Expect expression RHS can use *, / %, +, -" )
+{
+    EXPECT( 7 == 1 * 7 );
+    EXPECT( 7 == 7 / 1 );
+    EXPECT( 0 == 7 % 1 );
+    EXPECT( 7 == 1 + 6 );
+    EXPECT( 7 == 8 - 1 );
+}
+
+CASE( "Expect expression LHS can use *, / %, +, -" )
+{
+    EXPECT( 1 * 7 == 7 );
+    EXPECT( 7 / 1 == 7 );
+    EXPECT( 7 % 1 == 0 );
+    EXPECT( 1 + 6 == 7 );
+    EXPECT( 8 - 1 == 7 );
+}
+
 CASE( "Function run() returns the right failure count" )
 {
     struct f { static void pass(env & $) { EXPECT( 1==1 ); }

test/test_lest_decompose.cpp

@@ -206,6 +206,24 @@ const lest::test specification[] =
         EXPECT( 1 == run( fail_6, os ) );
     },
 
+    CASE( "Expect expression RHS can use *, / %, +, -" )
+    {
+        EXPECT( 7 == 1 * 7 );
+        EXPECT( 7 == 7 / 1 );
+        EXPECT( 0 == 7 % 1 );
+        EXPECT( 7 == 1 + 6 );
+        EXPECT( 7 == 8 - 1 );
+    },
+
+    CASE( "Expect expression LHS can use *, / %, +, -" )
+    {
+        EXPECT( 1 * 7 == 7 );
+        EXPECT( 7 / 1 == 7 );
+        EXPECT( 7 % 1 == 0 );
+        EXPECT( 1 + 6 == 7 );
+        EXPECT( 8 - 1 == 7 );
+    },
+
     CASE( "Function run() returns the right failure count" )
     {
         test pass  [] = {{ CASE( "P"  ) { EXPECT( 1==1 ); } }};