invocation_of_non_function

'{0}' isn't a function.

The analyzer produces this diagnostic when it finds a function invocation, but the name of the function being invoked is defined to be something other than a function.

The following code produces this diagnostic because Binary is the name of a function type, not a function:

typedef Binary = int Function(int, int);

int f() {
  return Binary(1, 2);
}

Replace the name with the name of a function.