The attached file includes <stdbool.h>, and contains these lines ...

   my_bool =  true &&  false;
   my_bool =  !!(true && false);

Why does the MISRA-C:2004 checker emit diagnostic 10.1/R for this code?

In C, logical expressions are of type "int;" even "true" and "false" are just macros that are integer constants of type "int." The test case assigns these expressions to an object of type "bool," which is just a macro for type _Bool, which, as you've probably seen in the header file, is declared as "unsigned char." You can remove the warning by casting your logical expressions to "unsigned char" before assigning them to "bool" variables:

my_bool = (unsigned char)(true && false);
my_bool = (unsigned char)!!(true && false);

Strangely, neither "bool" nor "_Bool" works as a substitute. I suspect this is a deficiency in the MISRA-C:2004 checking, which naturally does not have a special case for C99 boolean types. That is, cast or no cast, I agree MISRA-C:2004 should not warn here at all, but I'm not surprised it does; this is beyond the original scope of MISRA-C:2004's capacity.