It's reasonable to have multiple values for a given constant, as the example in the command documentation states:

For example, given this snippet,

    package painkiller

    type Pill int

    const (
    	Placebo Pill = iota
    	Aspirin
    	Ibuprofen
    	Paracetamol
    	Acetaminophen = Paracetamol
    )

I think it would be a mistake, a category error, to have stringer become a diagnostic and analysis tool. It blurs its purpose, which is just to make it easy to print names of constants, not to check the correctness of your program.

If you want this sort of constant checking, that should be a separate tool that runs independent of stringer.