> what's your take on "Parse, Don't Validate"

Always aspire to that. Translating that to Go conventions, the constructor has to have signature like:

    func NewT() (T, error) {
      ...
    }

Such signatures exist in the stdlib, e.g. https://cs.opensource.google/go/go/+/refs/tags/go1.25.7:src/... although I've met old-hands that were surprised by it.

In larger codebases, I've noticed an emergent phenomenon that usually the T{} itself (bypassing NewT constructor) tends to be unusable anyway, hence the constructor will enforce "parse, don't validate" just well enough. Only very trivial T{} won't have a nilable private field, such as a pointer, func, or chan.

I'd say that "making zero a meaningful value" does not scale well when codebase grows.