🐛 Resolve DUE Servo pulse issue (#24305)

Co-authored-by: sjasonsmith <20053467+sjasonsmith@users.noreply.github.com>
Co-authored-by: Scott Lahteine <thinkyhead@users.noreply.github.com>

Marlin/src/core/serial.cpp

@@ -72,8 +72,8 @@ void serial_print_P(PGM_P str) {
   while (const char c = pgm_read_byte(str++)) SERIAL_CHAR(c);
 }
 
-void serial_echo_start()  { static PGMSTR(echomagic, "echo:"); serial_print_P(echomagic); }
-void serial_error_start() { static PGMSTR(errormagic, "Error:"); serial_print_P(errormagic); }
+void serial_echo_start()  { serial_print(F("echo:")); }
+void serial_error_start() { serial_print(F("Error:")); }
 
 void serial_spaces(uint8_t count) { count *= (PROPORTIONAL_FONT_RATIO); while (count--) SERIAL_CHAR(' '); }
 

Marlin/src/core/types.h

@@ -99,8 +99,8 @@ struct Flags {
   void set(const int n)                    { b |=  (bits_t)_BV(n); }
   void clear(const int n)                  { b &= ~(bits_t)_BV(n); }
   bool test(const int n) const             { return TEST(b, n); }
-  bool operator[](const int n)             { return test(n); }
-  bool operator[](const int n) const       { return test(n); }
+  const bool operator[](const int n)       { return test(n); }
+  const bool operator[](const int n) const { return test(n); }
   int size() const                         { return sizeof(b); }
 };
 
@@ -113,8 +113,8 @@ struct Flags<1> {
   void set(const int)                     { b = true; }
   void clear(const int)                   { b = false; }
   bool test(const int) const              { return b; }
-  bool operator[](const int)              { return b; }
-  bool operator[](const int) const        { return b; }
+  bool& operator[](const int)             { return b; }
+  bool  operator[](const int) const       { return b; }
   int size() const                        { return sizeof(b); }
 };