If a global function exists like this:

bool equals(char[] a, char[] b){
  return a == b;
}

It is possible to use it like this:
char[] str1 = ...;
char[] str2 = ...;

str1.equals( str2 ); // compiles OK

But if this is used from within a class that also has a method with the
name "equals" the syntax above does not work any more:

class A {
  bool equals( Object o ){ ... }
  void foo (){
    bool res = str1.equals(str2); // compile error
      // equals(Object) does not
      // match parameter types (char[],char[])

    bool res2 = .equals(str1,str2); // compile OK
  }
}

The compile error should not happen, because in case of str1.equals(.. only the methods of type(str1) and global functions should be looked at.