--assign expression
Class A {
	man(a:C):Int { 
         a<-1          --incompatible types
	};

	man1():Int {
         let a:C, b:Bool  in
            {
            a<-1; b<-1;  --incompatible types
            }
	};
};

Class B {
	r:Int;
	man2():Int {
            a<-1  --unknown a
	};
	man3():Int {
         {
         r <- t; --unknown t
	 q<-u; --unkwon q and u
         }
	};
	man4():Bool { 
            r<-1  --incompatible ret type
	};
};

class C inherits D {
   man1():Object {
     {
     a<- true;   --invalid type
     b<-1;     --invalid type
     let b:Int in
         b<-1;  --valid type

     } 
   };
};

class D {
   a:Int;
   b:Bool;
   c:Cool; --wrong type
   md1():Object {
   let f:F <- 1 in
       b <- f+1
   };
   md2():C {
       b <- (b <- (c+1))
   };

   md3():C {
       b <- c
   };

   md4():Int {
       c
   };

   md5():Int {
       c <- b
   };
};