Adding a cpp file to library (not included) causes "not declared in this scope"

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6

full error, verbose mode, attempted compile INO file which does not include Function_Lib.cpp

blah blah blah, all good

Compiling library "SAMD_PORT-master"
"C:\\Users\\Robert\\Documents\\ArduinoData\\packages\\arduino\\tools\\arm-none-eabi-gcc\\7-2017q4/bin/arm-none-eabi-g++" -mcpu=cortex-m0plus -mthumb -c -g -Os -std=gnu++11 -ffunction-sections -fdata-sections -fno-threadsafe-statics -nostdlib --param max-inline-insns-single=500 -fno-rtti -fno-exceptions -MMD -DF_CPU=48000000L -DARDUINO=10813 -DARDUINO_SAMD_MKRWIFI1010 -DARDUINO_ARCH_SAMD -DUSE_ARDUINO_MKR_PIN_LAYOUT -D__SAMD21G18A__ -DUSB_VID=0x2341 -DUSB_PID=0x8054 -DUSBCON "-DUSB_MANUFACTURER=\"Arduino LLC\"" "-DUSB_PRODUCT=\"Arduino MKR WiFi 1010\"" -DUSE_BQ24195L_PMIC "-IC:\\Users\\Robert\\Documents\\ArduinoData\\packages\\arduino\\tools\\CMSIS\\4.5.0/CMSIS/Include/" "-IC:\\Users\\Robert\\Documents\\ArduinoData\\packages\\arduino\\tools\\CMSIS-Atmel\\1.2.0/CMSIS/Device/ATMEL/" "-IC:\\Users\\Robert\\Documents\\ArduinoData\\packages\\arduino\\hardware\\samd\\1.8.10\\cores\\arduino/api/deprecated" "-IC:\\Users\\Robert\\Documents\\ArduinoData\\packages\\arduino\\hardware\\samd\\1.8.10\\cores\\arduino" "-IC:\\Users\\Robert\\Documents\\ArduinoData\\packages\\arduino\\hardware\\samd\\1.8.10\\variants\\mkrwifi1010" "-IC:\\Program Files\\WindowsApps\\ArduinoLLC.ArduinoIDE_1.8.42.0_x86__mdqgnx93n4wtt\\libraries\\SD\\src" "-IC:\\Users\\Robert\\Documents\\Arduino\\libraries\\Time" "-IC:\\Users\\Robert\\Documents\\Arduino\\libraries\\ad5940lib-master" "-IC:\\Users\\Robert\\Documents\\Arduino\\libraries\\SAMD_PORT-master" "-IC:\\Users\\Robert\\Documents\\Arduino\\libraries\\RTCZero\\src" "-IC:\\Users\\Robert\\Documents\\Arduino\\libraries\\FlashStorage-master\\src" "-IC:\\Users\\Robert\\Documents\\Arduino\\libraries\\Arduino_Low_Power\\src" "-IC:\\Users\\Robert\\Documents\\ArduinoData\\packages\\arduino\\hardware\\samd\\1.8.10\\libraries\\SPI" "-IC:\\Users\\Robert\\Documents\\ArduinoData\\packages\\arduino\\hardware\\samd\\1.8.10\\libraries\\Wire" "C:\\Users\\Robert\\Documents\\Arduino\\libraries\\SAMD_PORT-master\\Functions_Lib.cpp" -o "C:\\Users\\Robert\\AppData\\Local\\Temp\\arduino_build_233470\\libraries\\SAMD_PORT-master\\Functions_Lib.cpp.o"
In file included from C:\Users\Robert\Documents\ArduinoData\packages\arduino\hardware\samd\1.8.10\libraries\Wire/Wire.h:24:0,
                 from C:\Users\Robert\Documents\Arduino\libraries\SAMD_PORT-master\Functions_Lib.cpp:11:
C:\Users\Robert\Documents\Arduino\libraries\SAMD_PORT-master\Functions_Lib.cpp: In function 'void displayPowerState()':
C:\Users\Robert\Documents\ArduinoData\packages\arduino\hardware\samd\1.8.10\variants\mkrwifi1010/variant.h:223:39: error: 'SerialUSB' was not declared in this scope
   #define Serial                      SerialUSB
                                       ^
C:\Users\Robert\Documents\Arduino\libraries\SAMD_PORT-master\Functions_Lib.cpp:31:7: note: in expansion of macro 'Serial'
       Serial.println("Battery Not Charging.");
       ^~~~~~
C:\Users\Robert\Documents\ArduinoData\packages\arduino\hardware\samd\1.8.10\variants\mkrwifi1010/variant.h:223:39: note: suggested alternative: 'Serial2'
   #define Serial                      SerialUSB
                                       ^
C:\Users\Robert\Documents\Arduino\libraries\SAMD_PORT-master\Functions_Lib.cpp:31:7: note: in expansion of macro 'Serial'
       Serial.println("Battery Not Charging.");
       ^~~~~~
Using library SD at version 1.2.4 in folder: C:\Program Files\WindowsApps\ArduinoLLC.ArduinoIDE_1.8.42.0_x86__mdqgnx93n4wtt\libraries\SD 
Using library Time at version 1.6 in folder: C:\Users\Robert\Documents\Arduino\libraries\Time 
Using library ad5940lib-master in folder: C:\Users\Robert\Documents\Arduino\libraries\ad5940lib-master (legacy)
Using library SAMD_PORT-master in folder: C:\Users\Robert\Documents\Arduino\libraries\SAMD_PORT-master (legacy)
Using library RTCZero at version 1.6.0 in folder: C:\Users\Robert\Documents\Arduino\libraries\RTCZero 
Using library FlashStorage-master at version 1.0.0 in folder: C:\Users\Robert\Documents\Arduino\libraries\FlashStorage-master 
Using library Arduino_Low_Power at version 1.2.2 in folder: C:\Users\Robert\Documents\Arduino\libraries\Arduino_Low_Power 
Using library SPI at version 1.0 in folder: C:\Users\Robert\Documents\ArduinoData\packages\arduino\hardware\samd\1.8.10\libraries\SPI 
Using library Wire at version 1.0 in folder: C:\Users\Robert\Documents\ArduinoData\packages\arduino\hardware\samd\1.8.10\libraries\Wire 
exit status 1
Error compiling for board Arduino MKR WiFi 1010.