Revert "use sizeof(expr) for unevaluated syntax check"

Using sizeof(expr) can trigger a compile-time error,
"lambda expressions are not allowed in an unevaluated context", when passing
expression containing lambda, like a std algorithm. This error is considered
a standard defect, as it is meant to prevent lambdas in decltype
or templates, but not in sizeof.

This reverts commit 227598af47.

include/internal/catch_capture.hpp

@@ -40,7 +40,8 @@
             __catchResult.useActiveException( resultDisposition ); \
         } \
         INTERNAL_CATCH_REACT( __catchResult ) \
-    } while( Catch::alwaysFalse( sizeof(expr) ) ) // expr here is never evaluated at runtime but it forces the compiler to give it a look
+    } while( Catch::isTrue( false && static_cast<bool>( !!(expr) ) ) ) // expr here is never evaluated at runtime but it forces the compiler to give it a look
+    // The double negation silences MSVC's C4800 warning, the static_cast forces short-circuit evaluation if the type has overloaded &&.
 
 ///////////////////////////////////////////////////////////////////////////////
 #define INTERNAL_CATCH_IF( expr, resultDisposition, macroName ) \

include/internal/catch_common.h

@@ -119,8 +119,9 @@ namespace Catch {
     std::ostream& operator << ( std::ostream& os, SourceLineInfo const& info );
 
     // This is just here to avoid compiler warnings with macro constants and boolean literals
-    inline bool alwaysTrue( std::size_t = 0 ) { return true; }
+    inline bool isTrue( bool value ){ return value; }
-    inline bool alwaysFalse( std::size_t = 0 ) { return false; }
+    inline bool alwaysTrue() { return true; }
+    inline bool alwaysFalse() { return false; }
 
     void throwLogicError( std::string const& message, SourceLineInfo const& locationInfo );