ValueFlow: Fix for if/else valueflow analysis

lib/valueflow.cpp

@@ -1043,6 +1043,11 @@ static void execute(const Token *expr,
             execute(expr->astOperand2(), programMemory, result, error);
     }
 
+    else if (expr->str() == "!") {
+        execute(expr->astOperand1(), programMemory, result, error);
+        *result = !(*result);
+    }
+
     else
         *error = true;
 }

test/testvalueflow.cpp

@@ -708,6 +708,13 @@ private:
                "}";
         ASSERT_EQUALS(false, testValueOfX(code, 4U, 0));
 
+        code = "void f() {\n"
+               "    int x = 0;\n"
+               "    if (!x) {}\n"
+               "    else { y = x; }\n"
+               "}";
+        ASSERT_EQUALS(false, testValueOfX(code, 4U, 0));
+
         // multivariables
         code = "void f(int a) {\n"
                "    int x = a;\n"