The predefined X "Y" may not be redeclared.
where X is the type of the shelf, Y its name.
or The shelf X "Y" has already been declared as type Z in the same
or Local X "Y" is already declared in the current scope.
or Global X "Y" is already declared.
Compilation continues but no compiled source code file will be saved.
The predefined shelves (the ones
starting with a '#') may never be declared.
Unless the program is using heralded names, two variables of
different types may not be declared in the same scope (either both
global, or both at the same level as a local). With version 5.4, a
global variable may not be declared more than once.