the function cant be assign to parameter flutter
If the right-hand side should be assigned to something else, such as a local variable, then change the left-hand side:
void f() {}
void g() {
var x = () {};
print(x);
}
If the intent is to change the implementation of the function, then define a function-valued variable instead of a function:
void Function() f = () {};
void g() {
f = () {};
}
//please go through
https://dart.dev/tools/diagnostic-messages#assignment_to_function