Constants and iota

Canonical guidance

• constants are evaluated at compile time
• untyped constants have more flexibility until context gives them a type
• iota is just the const-spec index inside one const block

Use when

• reviewing enum-like declarations
• checking representability or overflow at compile time
• explaining why a constant assignment compiles or fails

Avoid

• treating constants like mutable values
• assuming iota continues across separate const blocks
• relying on implicit narrowing without checking representability

Preferred pattern

type Level uint8

const (
	Debug Level = iota
	Info
	Warn
	Error
)

Anti-pattern

• using iota in long opaque const blocks where the actual values are hard to audit

Explanation: This is tempting because it is terse, but opaque const blocks make versioning and review harder than explicit values or short grouped declarations.

Why

• many surprising compile errors around numbers come from constant semantics rather than variable semantics